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(Buch): 978-3-446

1. Stichwortverzeichnis Gregory A Campbell Mark A Spalding Analyzing and Troubleshooting Single Screw Extruders ISBN Buch 978 3 446 41371 9 ISBN E Book 978 3 446 43266 6 For further information and order see http www hanser fachbuch de 978 3 446 41371 9 or contact your bookseller Carl Hanser Verlag M nchen Author A Abrantes 1 7 141 705 706 708 712 713 Adams 97 98 99 100 102 Agassant 255 Agur 132 173 279 281 Alemanskin 336 Allen 53 255 Alotaibi 118 Altinkaynak 119 121 152 195 197 200 212 213 445 447 574 587 601 695 Anderson 368 369 370 371 372 373 Angel 374 Anolick 662 Arcer 24 51 68 70 101 Armeniades 368 Armstrong 76 Avenas 255 Averous 25 Avgousti 228 B Baba 200 226 Baer 32 Baird 132 146 147 149 Baker 377 663 Balch 257 Balke 495 Bar 486 Barlow 438 440 Barr 6 199 225 255 365 366 367 400 419 536 575 626 635 639 641 643 645 Beagan 332 Benkreira 333 346 347 374 523 Berghaus 174 Bernhardt 303 Berry 107 Biesenberger 662 Bigio 337 353 498 515 662 Billham 379 Bird 76 261 Black 332 333 Blackson 486 Bohn 157 Bokis 667 671 Bomma 338 Booy 256 Boussinesq 255 744 Boyd 353 Bozzelli 238 374 Bremner 377 Brittin 374 523 Brizzolara 662 Brown 661 671 Broyer 92 139 142 Bruin 257 Bruker 257 258 Buchelli 667 671 Buck 649 Bullwinkel 11 132 146 147 200 201 203 205
2. 418 419 453 ager 408 aillefer 278 223 361 625 663 allouk 254 255 256 272 292 297 aloney 671 672 alvern 261 293 294 295 304 anas Zloczower 329 336 365 araschin 661 arshall 446 arshek 421 atsuoka 257 cClelland 119 cCullough 124 125 390 409 567 599 605 CKelvey 254 255 256 272 292 297 303 388 cManus 53 cNally 332 379 eijer 174 176 177 200 203 334 368 369 370 3 1 372 373 eister 98 enges 176 177 178 194 erz 94 etzner 287 iaw 257 Middleman 83 255 297 302 303 Mihara 377 663 Miller 133 Moffat 346 Mohr 254 255 256 257 297 Mokhtarian 337 Mol 715 134 137 138 140 143 151 Molnar 199 Mondcai 199 Moore 124 332 Morgan 479 499 Morrison 76 81 83 688 690 Mount 119 121 192 227 419 442 572 592 Moysey 141 143 144 145 146 Murakami 125 Murphy 332 379 Myers 365 366 367 421 427 639 641 643 645 652 N Nagarajan 118 Naguib 126 Naumovitz 237 545 Nazrisdoust 279 657 Nelb 119 518 695 Nichols 388 634 Nomura 200 203 Norden 365 367 Noriega 174 177 178 O Ober 24 51 68 70 101 Ogando 537 Oka 125 Okamoto 26 Osswald 174 177 178 Ostwald 103 Ottino 334 P Pan 778 Paquet 24 Park C B 126 Park S 126 Parnaby 112 Patal 3 4 Patterson 119 180 181 518 695 Paul 116 333 Pavlicek 442 447 Pearson 199 204 221 257 Peiffer 178 Penlidis 53 Penumadu 17 140 141 151 171 705 706
3. 708 712 713 Perdikoulias 442 492 634 Pessoa 661 671 Peters 365 367 368 369 370 Phal 479 Pham 447 467 548 595 Pinto 256 Pittman 255 Platt 411 Platzer 661 Plumley 640 Pocius 332 Potente 178 179 194 277 388 389 596 Powell 377 378 657 663 Powers 119 131 154 158 225 237 330 365 367 466 541 545 574 737 Prausnitz 671 672 Prentice 7 2 Prettyman 645 646 Psarreas 53 Puhalla 421 Pukhanszky 33 51 Q Qiu 12 R Rabinowitsch 84 Rahim 118 Ramanathan 492 661 671 Ramesh 702 Raphael 368 Rashid 255 Rasmussen 102 Reber 175 Redwine 700 Reeder 371 Rehg 492 Reski 388 Reuschle 486 Robinson 287 Rodriguez 24 26 27 28 37 42 51 53 59 68 69 70 78 79 83 97 101 Rokudai 377 663 Rom Roginski 495 Ronaghan 176 Rotem 257 Rowell 171 254 255 256 267 304 306 Rubens 24 Rudin 377 663 S Salamon 332 365 367 Sandall 314 Sastrohartono 257 Sato 125 Saucier 76 93 Savargaonkar 485 Saxton 254 Scheirs 485 Author 767 Schellenberg 34 Schlafi 133 Schneider 115 116 138 140 142 143 150 Sch ppner 179 353 Schreiber 377 663 Schrenk 492 Schultz 437 440 Schulze 116 Schwank 332 379 Schwedes 7 6 Scorah 53 Sebastian 228 578 662 Semmekrot 365 Sergent 255 Sernas 257 258 Serrano 365 367 Shales 333 346 347 Shanker 492 Shapiro 199 204 221 Sheth 614 634 Shinnar 257 Shinya 200 203 Shishido 701 Sickl
4. Transient process data were col lected for an extruder with a downstream gear pump as shown in Fig 12 4 For this case the control algorithm was controlling the speed of the screw such that the inlet pressure to the pump was maintained at 8 MPa Although the variation in screw speed was not excessive at 67 1 5 rpm the variation in motor current seemed quite high at 540 90 A At about 16 minutes into the run the extruder was switched from automatic to manual screw control the screw speed was held constant at 67 rpm As shown by the data in Fig 12 5 the motor current variation was unchanged indicating that the screw speed control algorithm was not induc ing the variation in the motor current During the period that the screw speed was held constant the pressure to the inlet of the pump slowly increased as shown in Fig 12 6 This pressure was increasing because the screw was operating at a speed that delivered a rate slightly higher than that needed by the pump When the con trol was placed back into automatic mode the screw speed was decreased initially to compensate for the higher than desired inlet pressure This type of analysis is recommended when minor levels of flow surging are observed with a process where the screw speed is controlled from the inlet pressure of a gear pump 550 12 Flow Surging 90 800 i l i Motor Current E 85 i t 750 Sg lt 80 700 g i 2 i E o 75 l l H 650 o z o l
5. 10 Numerical calculations and a Maddock solidification experiment confirmed that the midsection of the extruder was operating partially filled Thus a small 10 C increase in the first barrel zone tem perature was enough to cause the extruder to go from operating as a stable process producing high quality product to one that was unstable with reduced rates and having a product with unacceptable product dimensions Numerous other experi ments had shown that the first barrel zone temperature needed for stable extru sion depended on the screw speed and the temperature of the feed resin Moreover the processor indicated that flow surging was experienced for some extruders at zone T1 barrel temperatures as low as 148 C 555 556 12 Flow Surging 25 180 20 c 170 8 Oo S 45 5 g 3 160 3 8 10 E E lz ld N i ea Wh dili all M 0 140 30 40 50 60 80 90 100 Time minutes Figure 12 10 Barrel pressures and temperatures for the 38 1 mm diameter extruder operating at azone 1 barrel temperature condition that caused the extruder to flow surge The temperature profiles are in red while the pressures are black Based on the data collected the Maddock solidification experiment and the numerical calculations the problem was diagnosed as poor solids conveying from improper temperatures in the section Slight differences between extruders such as the axial and radial position of the zone T1 thermocouple barrel zone contro
6. 138 140 143 151 Darus 486 David 365 367 Davis 174 177 178 646 Dealy 76 93 100 101 Degee 25 deGroot 700 Dekker 228 Dennis 333 Derezinski 112 167 442 446 454 729 Devellian 368 de Waele 703 Dey 662 Dhib 53 Donovan 199 Dontula 11 13 139 140 141 151 205 222 258 259 263 269 270 279 304 705 706 707 708 709 712 Dooley 71 119 124 160 164 203 257 279 351 352 447 451 461 498 515 636 637 638 640 641 Dray 355 626 649 Dubois 25 Duvdevani 194 199 203 208 446 Dyer 257 E Eccher 257 Edmondson 446 Edwards 333 346 347 Effen 596 Eirich 700 Elbirli 200 218 226 258 Elemans 332 376 El Kindi 377 663 Embirucu 667 671 Epacher 33 57 Erwin 337 353 Esseghir 257 258 365 367 F Fan 614 634 Fasano 371 Felton 11 205 222 250 258 259 304 Fenner 199 256 257 388 446 451 454 541 542 666 Ferry 77 102 Finlayson 11 254 255 256 267 304 306 Fogarty D 680 Fogarty J 680 Fogler 408 Fontan 53 Fox 100 101 Franjione 661 671 Frankland 161 596 650 651 Franzkoch 176 177 178 Fraser 258 Frencham 28 46 Fritz 25 Fujiki 377 663 Fujiyoshi 26 Fukase 200 203 Furches 374 G Gailus 353 Galaktionov 368 369 370 Gale 329 332 365 Gao 235 Garcia Meitin 486 Germano 248 Geyer 626 Ghosh 333 Giles 192 419 442 Gilette 132 146 147 Gilmor 495 Gleissle 96 Gogos 69 102 103 124 228 294 302 36
7. 222 250 251 252 253 259 260 263 297 298 299 300 301 304 Butler 119 192 484 485 C Calidonio 495 Call 661 671 Calland 634 Camesasca 336 Campbell 71 13 97 98 99 100 102 117 118 132 139 140 141 146 147 149 151 171 200 201 203 204 205 222 250 251 252 253 258 259 260 263 269 270 279 287 297 298 299 300 301 304 317 318 319 338 445 657 705 706 707 708 709 712 713 Canedo 374 Carley 254 255 256 272 292 388 391 481 Carlson 11 205 222 279 317 318 319 657 Carnahan 28 46 Carreau 104 255 Gengel 750 Ceraso 332 Chang 257 333 Chella 334 Chempath 338 Chen 25 144 349 498 501 Author Cheng 11 205 222 250 251 252 253 259 260 263 297 298 299 300 301 302 304 Cheung 32 Chiruvella 258 Cho 119 121 212 213 333 Christiano 176 632 Christie 408 Chum 24 32 Chung 6 119 121 199 212 213 227 235 255 353 375 377 378 388 389 400 419 536 542 572 575 592 626 635 657 663 Cieslinski 27 Clap 257 Clarke 379 Clegg 377 663 Cleven 332 Cohen 4 51 68 70 101 119 121 124 189 194 196 227 376 533 572 695 Collias 132 Conant 16 Conner 498 515 Connor 337 Costa 661 671 Cox 94 446 451 454 541 542 Coyle 258 Crabtree 119 121 152 195 197 200 212 442 445 447 574 587 601 695 Crawford 116 Cross 104 Cubberly 757 Curtiss 76 D Dai 363 Darnell 175 134 137
8. 356 358 362 466 491 495 497 512 514 518 521 527 529 degree of crystallinity 38 dehydrohalogenate 50 depolymerize 50 design 454 629 design defect 512 deterministic chaos 338 devolatilization 364 662 die swell 72 dilatant 65 direct compounding 379 direct current 436 discharge 350 discharge pressure increases 157 discharge pressures 154 164 227 252 274 376 387 402 409 467 595 606 608 discharge temperature 227 297 302 317 318 319 375 401 409 442 445 451 542 593 597 598 608 609 614 628 648 discharge tip 459 dispersed 339 dispersive 177 331 598 dispersive mixer 334 359 377 dispersive mixing 333 360 dissipation energy 36 58 67 205 211 212 222 297 300 304 305 306 307 621 676 distributive melt mixing 645 distributive mixing 178 333 362 DM2 high performance screw 235 524 633 645 646 647 double bond 57 Double Wave screws 614 622 633 downstream equipment 422 drag flow 11 254 255 drag force 600 dried properly 574 drier 500 drive shank 459 drying air 499 DSB I 632 DSB IIl 632 dual cavity screen 479 dust 477 dust seal 429 430 dye 343 dynamic friction 567 600 dynamic mixers 364 E Eagle mixing tip 646 elastic 73 elastic deformation 63 64 electrical component 409 electronic filters 433 elongate 348 elongation 347 elongational flow 334 elongation rate 333 encapsulate 237 energy balance 207 316 439 e
9. 580 ead length 8 321 438 607 609 eakage flow 306 eathery 529 edge 575 evels of gloss 515 ight scattering 62 iquid additives 364 iquid injection 360 ocal high temperature 521 ocal pressure 217 og normal distribution 98 oss modulus 93 ow compression ratio 517 owest cost provider 465 ow pressure separator 661 671 672 ow viscosities 374 ubricating oil 419 429 M addock melting mechanism 799 200 addock mixer 333 509 632 addock solidification 110 addock solidification experiments 193 216 217 351 418 453 magnetic collection 482 ark Houwink Sakurada equation 70 mass rate 206 masterbatches 374 375 523 material degradation 547 mathematical models 200 maximum torque 425 426 Maxwell fluid 75 measurement noise 548 measuring instruments 416 melt conveying channels 227 melt density 125 126 melted mass 156 melt fed extruders 279 657 melt film 348 628 melt film interface 348 melt film thickness 214 melt filtration 478 melt flow index 94 melt infiltration 2 7 234 melting 189 351 352 Subject melting abilities 639 melting capacity 592 628 melting flux 121 189 196 347 601 melting mechanism 793 230 melting mixing 374 644 melting process 199 200 237 346 347 351 627 melting rate 121 212 227 442 721 melting section 499 542 547 melt pool 216 217 melt pump 467 melt temperature 318 319 mesh 479 Metal fragments 420 482 metallocene 44 metering sect
10. 619 pellet 146 pelletization 657 pendant groups 37 periodic undercut 680 peroxide 52 53 phase shift 93 physical description 199 pigment 337 374 pineapple mixer 354 pin mixer 354 362 598 plant and equipment 465 plasticate 320 plasticating extruders 507 plasticating screw 536 plastication rate 463 plate rheometer 97 plating 459 plug flow 145 polyacetal 53 polyamides 41 42 polycarbonate 53 polydispersity index 62 polyester 41 53 polyethers 42 polymer fragments 480 polymer viscosity 213 polyolefin 484 polyolefin type gels 480 polyurea 47 polyurethane 41 53 poor housekeeping 477 poorly aligned barrel 425 potential energy barrier 36 power 435 439 440 power factor 438 440 power law index 293 pressure 14 97 567 pressure change 215 482 pressure discharge control unit 146 pressure driven flow 272 pressure drop 487 pressure flow 11 12 254 255 287 410 439 464 pressure flow velocity 267 pressure fluctuation 444 pressure generation 319 pressure gradient 14 216 286 320 387 504 599 604 609 pressure oscillation 566 pressure profile 198 215 547 pressure rating 433 pressure sensors 427 432 557 pressure swing 555 pressure transducers 546 pressure variation 558 pressurization extruder 658 primary extruder 675 process data 390 554 584 processing aids 662 process stability 444 process temperatures 542 544 production efficiency 466 production rates 465 producti
11. barrel for a screw speed of 60 rpm and a positive downstream pressure gradient OP Oz gt 0 8 for a transducer positioned in a metering section where the resin is completely molten and b for a transducer positioned in a single flighted melting section The pressure profile shown in Fig 12 2 a is for a constant depth metering channel that is completely filled with molten resin a screw speed of 60 rpm and a positive downstream pressure gradient OP Oz gt 0 five rotations are shown The pres sure is the highest at the pushing side of the channel and the lowest at the trailing side of the channel The pressure typically increases nearly linearly with rotation from the trailing side of the channel to the pushing side As the flight tip passes underneath the transducer the pressure decreases quickly to that of the trailing side of the channel Figure 12 2 b shows a similar pressure profile with rotation in a conventional melting section For this case the solid bed extends across about 5056 of the channel The pressure profile is similar to that for the metering channel case except that the pressure gradient in the region over the solid bed is higher than that for the melt pool The width of the molten resin can be estimated by the time fraction that the transducer spends over the melt pool and solid bed 547 548 12 Flow Surging The pressure profiles with rotation shown in Fig 12 2 are ideal In practice the pressure profil
12. conveying for HIPS resin would occur with a feed zone barrel inner surface temperature near 150 C and a screw surface temperature in the feed section no higher than 110 C In practice screw temperatures less than 90 or 100 C are preferred such that melting of the resin does not happen if an emer gency shutdown should occur For the solid state temperature region the shear stress at the interface can be converted to the coefficient of dynamic friction by the following f T P 12 4 where f is the coefficient of dynamic friction 7 is the shear stress at the polymer metal interface and P is the pressure 0 7 MPa in this case 12 7 Case Studies for Extrusion Processes That Flow Surge 0 5 a e7 6cm s o 4 a E OA ng a 15 2 cm s z 4 03 4 4 30 5 cm s o 4 a i 7 kh 027 H M oO D 0 17 0 0 50 100 300 150 200 250 Temperature C Figure 12 17 Shear stress between HIPS resin and a metal surface at a pressure of 0 7 MPa and as a function of temperature and sliding velocity 12 7 4 Flow Surging Due to High Temperatures in the Feed Casing The extruder described in Fig 12 11 on a different occasion started to flow surge but with a slightly different frequency as shown in Figs 12 18 and 12 19 As indi cated in these figures there were short time periods when the discharge pressure and screw speed were stable and the motor current was high During these periods the extruder was operating well but at a reduce
13. cooling water was turned on a temperature change of 44 C As will be presented later in this section solids conveying of HIPS resin becomes difficult or unstable at screw temperatures of about 150 C and higher The temperature of the screw surface was unknown but it likely increased by at least 44 C and possibly approached 150 C 12 7 Case Studies for Extrusion Processes That Flow Surge 1400 pa 1200 Motor Current 320 lt 4000 280 5 d 2 800 240 5 Q 9 o S M i Icootinad 200 gt 2 Cooling On Cooling Cooling On 3 S 400 or m 200 Screw Speed 120 a 80 0 10 20 30 40 50 60 Time minutes Figure 12 15 Screw speed and motor current for the screw cooling experiment 200 40 iCoolin 35 Cooling On Cooling On 30 160 25 20 15 120 Screw Speed 80 Pressure MPa Screw Speed rpm 10 Extruder Discharge 40 Time minutes Figure 12 16 Screw speed pressure at the entry to the first stage meter P1 and discharge pressure for the screw cooling experiment Based on the above data the cause of the extrusion instability was identified as high temperatures on the screw surfaces of the feed section These high surface temperatures caused the coefficients of dynamic friction to increase increasing the retarding forces on the solids at the screw surface Since solids conveying depends on a combination of forwarding forces at the barrel wall and pushing fli
14. is pos sible 13 For gear pump assisted extrusion the extruder control algorithms are set to maintain a constant pressure to the inlet side of the pump The pump is operated at a constant rotational speed and thus it delivers molten polymer at a very steady and controlled rate A schematic of a gear pump assisted extrusion 12 5 Gear Pump Control 549 process is shown in Fig 12 4 If the pressure to the inlet of the pump is less than the set point value then the control system will increase the screw speed of the extruder Conversely if the inlet pressure is too high the control system will decrease the screw speed Thus processes that use a gear pump downstream of an extruder can show large variations in the screw speed in an attempt to compensate for an extruder that is flow surging Hopper Gear N Vent un N aw i j Figure 12 4 Schematic of a two stage extruder with a downstream gear pump A poor control algorithm for the pump can cause some variation in the extruder screw speed causing large variations in the inlet pressure to the pump This type of control induced surging can occur even though the process as designed is inherently stable To determine if the control algorithm is inducing the surging the screw speed of the extruder should be operated in a manual mode and at a constant speed If the controller is inducing the surging placing the process in manual control mode will stabilize the process
15. meter production extruder a proprietary screw design and resin that had pre viously exhibited flow surging and reduced rate The extruder was equipped with three barrel zone heaters with control thermocouples labeled T1 T2 and T3 and two pressure sensors One pressure sensor was located in the midsection zone 2 of the barrel P2 and the other at the end of the barrel near the tip of the screw P3 Both transducers were positioned over the top of the screw such that a pressure variation due to screw rotation would be observed During the trial process data were collected from each sensor at a frequency of once every 10 seconds using a portable data acquisition system For barrel zone temperatures of 150 163 and 174 C for zones T1 through T3 respectively the extruder was operating stably and at rates that were consistent with numerical simulations and it was producing a high quality product Process data for steady state operation are shown in Fig 12 9 for a screw speed of 50 rpm As indicated by this figure the barrel zone temperatures were steady and only small variations occurred for the P2 and P3 pressure sensors Slight pressure variations were expected for this extruder because the sensors were positioned in the barrel and were measuring pressure in different regions of the channel as the screw rotated The pressure patterns are not periodic like those in Fig 12 3 due to the screw speed and acquisition rate used For this case pr
16. stage transition 10 onen rate was 0 0032 First stage meter Zell 8 Vent section 31 9 4 5 The pump ratio was 1 7 Second stage transition 3 5 Second stage meter 12 3 6 Lead length flight width and flight clearance were 203 2 23 9 and 0 20 mm respectively in all sections of the screw A 28 7 mm diameter screw cooling hole was drilled in the shank end of the screw and it extended 3 8 diameters into the feed section The first 2 5 diameters of the screw were inside a water cooled feed casing The specific rotational rate of the first stage metering section was calculated at 20 kg h rpm Hopper Screw N Pa Vent ip Cooling N EIER V V VV VN NEN V EE Pai P Figure 12 11 Schematic of the 203 2 mm diameter extrusion process for HIPS resin 557 558 12 Flow Surging In order to diagnose the problem a data acquisition system was temporarily con nected to the extrusion panel All available sensor outputs were connected in parallel with the acquisition system Electronic data were collected at a frequency of once every 9 s Steady state operation of the extruder is shown by the first 400 minutes in Figs 12 12 12 13 and 12 14 The data for these figures were from the same production run The extruder was running at 2250 kg h and a screw speed of 99 rpm for a specific rate of 22 7 kg h rpm This specific rate is about 14 higher than the specific rotational flow rate calculated for the first stage
17. 27 507 541 543 554 564 575 583 586 uidelement 348 uid flows 250 ute 356 oaming temperature 674 771 Subject oreign contamination 488 oreign material 477 Four channel Energy Transfer 679 our films 2710 our melt films 204 221 721 our polymer films 209 ragments 234 350 354 357 363 572 592 rame indifference 262 ree helix 250 251 259 ree helix extruder 338 344 ree radicals 44 51 reezing point depression 67 requency 437 ull 3 D equation 393 Fusion screws 235 633 649 G galling 596 gas bubble 483 Gaussian 60 gearboxes 421 435 436 gear mixer 354 360 364 622 667 gear pump 548 557 584 gel analysis 485 gels 484 489 508 600 gel showers 501 geltype 478 generalized Newtonian method 281 282 286 288 general purpose screw 153 geometry 454 glass barrel 250 glass transition temperature 33 36 98 glassy polymers 37 gloss 377 378 gradients 355 gravimetric blending 467 gray parts 516 grinding lathe 458 grooved bore extruders 133 174 179 632 grooved bore liner 176 grooved feed section 178 H halo surface defects 575 handheld thermocouple measurement 4 7 hard facing 419 420 456 596 haze 377 378 heat capacity 123 heat conduction 454 heat flux 148 154 584 heat flux sensors 148 heat of mixing 335 heat soak 425 heat transfer 374 315 heat transfer coefficient 124 313 helical 339 helical channel 248 259 helical coordin
18. 34 op oooocoooocoooooooooooocococooossscdsocotoc T target rate 387 technical solution 4 7 temperature 97 98 297 300 301 303 306 308 315 354 445 temperature calculation 374 temperature control 542 544 553 temperature gradient 154 332 temperature increase 259 314 temperature sensor 148 567 temperature zones 442 tensile strength 61 426 termination 44 45 thermal conductivity 124 thermal expansion 423 424 thermal gradients 332 333 353 363 367 446 514 675 676 thermocouples 432 thixotropy 65 three dimensional numerical method 282 thrust 157 time dependent 72 tools 416 torque 91 157 435 436 592 614 orque balance 138 otal mass flow 15 tracer particle 144 145 trailing flight 145 transfer line 491 567 ransformed frame 267 268 ransformed velocity solutions 267 transient process data 549 570 transition section 206 218 439 441 517 612 721 723 transverse barrier 224 ransverse flow 256 rap 354 364 trial and error design 387 troubleshooting 408 543 roubleshooting a process 546 roubleshooting problems 15 Turbo Screws 680 turbulence 335 Twente mixing ring 365 win screw extruders 7 U Ubbelohde viscometer 68 ultracentrifugation 62 undercut clearance 357 uniform mixing 337 Unimix screw 652 unit operations 665 unmelts 533 unmixed gel 508 unstable process 548 559 571 585 615 unwrapped 248 V value analysis 466 Variable Barrier
19. 5 367 482 578 Golding 667 Gore 255 256 297 Gottgetreu 200 226 Gould 408 465 468 Gramann 174 177 178 Gratch 100 Gregory 355 Griffith 256 257 Grob 495 Grout 368 Gr nschlo 175 178 Guerra 485 Guerrieri 667 671 Guo 388 Gupta 119 121 152 195 197 200 212 213 445 447 574 587 601 695 H Halasz 199 Hall 9 Halley 25 Halmos 199 204 221 Hamielec 53 Han 349 356 629 Hanhart 388 Hara 116 Harrah 175 Harris 26 Hassager 76 Hasson 257 Hattori 26 Headley 492 Heaney 379 Hemsley 486 487 Heniche 371 Hennessey 119 Hiemenz 42 Hiltner 32 Himmelblau 442 Hindmarch 365 Hinton 140 151 158 172 578 705 708 Ho 33 Hoang 53 Hoenig 28 46 Hoffmann 578 Hogan 119 121 212 213 639 643 645 Hong 119 121 212 213 Hook 646 Hovis 479 499 Hrymak 373 Hsieh 33 Hsu 626 Huck 377 663 Hudak 649 Hughes 7 0 116 117 160 171 365 366 367 578 651 705 Hunt 259 298 Hunter 333 Hyun 71 110 112 113 116 117 119 120 121 122 124 131 139 140 142 150 151 152 154 158 160 164 171 172 189 194 196 203 225 227 231 237 257 279 330 Author 351 352 376 392 447 451 461 466 467 498 515 533 541 542 543 545 548 572 574 578 595 598 636 637 638 640 641 695 705 706 708 710 liuta 26 ngen Housz 174 176 177 200 203 ngen Housz 365 367 sayev 3 462 514 sherwood 541 542 to 26 101 J ac
20. 610 667 compression rate 191 192 399 410 414 440 441 520 531 577 compression ratio 197 192 399 404 414 440 520 531 573 577 concentrate 374 500 concentration 337 concentration peaks 343 concrete floor 422 condensation 53 condensation reactions 40 conduction pathway 238 cone 91 cone and plate rheometer 691 contamination defects 477 498 501 513 521 continuous screen changers 479 continuum statics based models 147 control 532 control algorithms 554 control volume 374 316 317 conventional melting 226 conventional screw 349 conveying rate 164 165 convey solids 560 cool 552 cooling coils 675 cooling extruder 597 cooling level 553 cooling water 552 586 cooling water flow 544 core 251 core drag flow 258 core rotation 253 correction factor Fc 393 correction factors 273 290 corrosive 466 cost effective 471 cotton fiber 490 crack 236 420 crammer feeder 615 creep 74 critical molecular weight 62 63 98 critical temperature 593 cross channel flow 264 cross channel velocity 262 265 crosslinked 32 46 48 crosslinked gels 487 493 495 496 cross section 357 curvature 497 curved channels 256 cycle time 533 D data acquisition 558 data acquisition system 417 544 554 565 570 584 decompression section 577 decrease the rate 190 deep channel 278 320 deeper channel 438 deep screw 301 defect 408 529 degradation process 48 degradation products 46 52 237
21. Energy Transfer screws VBET 633 641 vectorial velocities 209 velocity profiles 256 vent diverter 595 617 vent flow 593 619 vinyl polymerization 40 viscoelastic 72 viscoelasticity 58 viscoelastic model 75 viscoelastic properties 73 visco seal 430 669 670 viscosity 57 64 335 375 viscosity average molecular weight 77 viscosity ratio 374 viscous 73 visualization 250 voids 510 Voigt solid 74 volumetric flow rate 271 W water cooling 546 wave screws 235 wear 422 575 weight average molecular weight 58 welded material 467 whirling process 457 wiper flight 356 wiping 687 Subject 777 wire diameter 479 wire shielding 434 worn feed casing 583 worn screw 598 wrong resin 478 Z Ziegler Natta catalyst 44 zone screw temperatures 545
22. HANSER Preface Gregory A Campbell Mark A Spalding Analyzing and Troubleshooting Single Screw Extruders ISBN Buch 978 3 446 41371 9 ISBN E Book 978 3 446 43266 6 For further information and order see http www hanser fachbuch de 978 3 446 41371 9 or contact your bookseller Carl Hanser Verlag M nchen Preface Classically all prior extrusion books are based on barrel rotation physics Litera ture developed over the past 15 years has led to this first book to be published based on the actual physics of the process screw rotation physics After the theo ries and the math models are developed in the first nine chapters the models are then used to solve actual commercial problems in the remainder of the book Realis tic case studies are unique in that they describe the problem as viewed by the plant engineers and provide the actual dimensions of the screws Knowledge is developed using a series of hypotheses that are developed and then tested which allows a series of technical solutions Several actual solutions are proposed with the final results that solve the problem then clearly presented Overall there is not a book on the market with this level of detail and disclosure New knowledge in this book will be highly useful for production engineers technical service engi neers working with customers consultants specializing in troubleshooting and process design and process researchers and designers that are re
23. I o 5 70 i i Screw Speed 600 e i i i 65 Automatic Screw Manual Automatic Screw 550 Control Ti Control Control 60 l 500 0 5 10 15 20 25 30 35 40 Time minutes Figure 12 5 An extrusion process with a downstream gear pump with the screw operating in inlet pressure control and followed by the screw in manual operation constant screw speed The large level of variation in the motor current during constant screw speed control suggests that the extruder process is unstable and the control algorithm is not the root cause for the variation in the motor current o 90 es gt N Pressure Wy ne nV Screw Speed oo oa a N co o Co pa eo Pressure MPa Screw Speed rpm M eo oa o oa Automatic Screw Manual Automatic Screw Control Ti Control Control I O N A Oo o o 0 5 10 15 20 25 30 35 40 Time minutes Figure 12 6 Pressure at the inlet to the gear pump for the data presented in Fig 12 5 The pressure increased during manual control because the flow rate of the extruder was slightly higher than the rate of the pump 12 7 Case Studies for Extrusion Processes That Flow Surge 551 B 12 6 Solids Blocking the Flow Path Compacted solid polymer fragments can block and restrict the flow in a process In order for this to occur two defects typically exist in the process The first defect causes the compacted solid to fragment and flow downstream in the scr
24. Zoller 126 391 Zweifel 133 A abrasive 466 Abrasive purge 494 abrupt reduction 5 2 absorbed water 53 abstracted 52 a cast film 507 active center 43 45 addition polymerization 40 addition reactions 43 agglomerated 500 agglomerates 334 374 air bubbles 530 air cooled zone 546 alignment 421 422 alkyd resin 4 alternating current 436 alternative hypotheses 411 413 amorphous 35 39 amortized 466 amperage 435 analyzing gels 484 anecdotal information 4 3 angular velocity 91 297 300 antioxidants 47 51 52 494 apparent shear rate 83 atactic 34 average channel width 70 average shear rate 274 average shear viscosity 274 axial length 10 446 axial pressure 196 198 504 659 axial pressure profile 216 axial screw temperature 454 B Bagley correction 87 82 baker s fold 336 368 barrel 17 421 445 barrel axis 422 barrel cooling 552 barrel diameter 8 Subject barrel flange 575 barrel heaters 7 barrel length 177 351 barrel rotation 254 297 300 301 307 318 barrel support 422 423 424 barrel temperatures 403 415 442 443 452 611 barrel temperature setting 409 barrel wall 223 452 611 barrel zone temperatures 6 1 Barr Fluxion ring mixer 365 barrier 221 barrier design 626 barrier flight 279 223 224 509 625 barrier flighted 352 barrier flighted screws 507 barrier melting 190 218 415 507 barrier screw 218 223 225 520 521 629 barrier section 224 511 512 barrier sec
25. agments 353 355 603 626 solidification experiment 196 199 solids 350 359 solids blocking 557 solids channel 2 9 221 223 solids conveying 132 134 143 462 542 560 563 576 581 600 603 solids conveying device 146 158 162 solids conveying models 139 705 solids conveying rates 161 solids conveying zone 499 544 solids forwarding angle 136 138 solution viscosity 67 specification of equipment 471 specific energy 396 439 440 specific rate 225 320 321 443 502 532 616 644 specific rotational flow rate 529 SPI guideline 423 spiral channel 429 spiral dam mixers 333 353 354 361 362 526 530 534 535 536 572 573 splay 412 500 513 516 775 Subject splay problem 536 spontaneous mixing 335 ability 443 abilization 47 abilizer 52 abilizers 53 662 able operation 559 agnant regions 223 491 495 512 527 ainless steel 456 anding waves 92 arve fed 604 660 atic mixer 367 368 372 467 atistical analysis 413 eady state temperature 449 ep reactions 40 ereo structure 34 orage modulus 93 rain 74 rain hardening 433 rain rate 64 ratablend 650 ream stripping 665 ress 64 74 91 362 600 ress refinement 377 retching 336 337 339 340 retching rate 333 retch performance 507 riations 336 347 348 363 ripping agent 364 593 662 superposition principle 78 supersaturated 671 surface defects 414 surface flaws 585 surface temperatures 561 564 syndiotactic
26. ashi 257 362 363 Takatani 26 Tang 11 200 201 202 203 204 228 229 445 Tanguy 371 Tanifuji 362 te Riele 71 205 222 250 251 252 253 259 260 263 297 298 299 300 301 304 Thiel 356 393 Thompson 118 141 143 144 145 146 542 632 Tobin 408 Todd 124 125 314 365 367 391 481 578 658 Trumbull 336 545 Tsumashima 69 Tucker 314 Tung 248 295 Tusim 19 Tzoganakis 53 126 492 U Uhl 446 Umeya 116 V Valentinotti 257 Valsamis 374 Van Prooyen 377 van Wunnik 332 376 Van Zuilichem 257 Verbraak 200 Vieira de Melo 661 671 Vlachopoulos 53 132 173 279 281 419 614 634 W Wagner 119 131 175 192 330 419 442 466 578 Wakeman 33 Walia 379 Walker 24 132 Walsh 126 397 Wang 7 13 32 139 140 151 178 200 201 203 205 222 250 251 252 253 258 259 260 263 269 270 279 297 298 299 300 301 304 336 365 Weeks 255 Welsh 6 4 Werling 377 378 657 663 Wheeler 287 349 356 546 629 632 Whissler 287 White 314 333 446 658 Williams 77 102 388 Womer 133 175 431 546 634 649 651 Wong 235 236 Wood Adams 700 101 Woods 332 Wortberg 175 495 X Xie 25 Xue 178 Y Yamamuro 117 140 141 151 171 705 706 708 712 713 Yamashita 363 Yang 662 Yao 362 363 Youngson 119 518 695 Yu 25 365 367 Z Zafar 578 Zamodits 257 Zawisza 119 518 695 Zhang 337 Zhu 53 144 235 236 349 Zitzenbacher 356 393
27. ates 70 helix 250 251 253 259 helix angle 9 helix driven flow 253 helix rotation 253 higher compression 535 higher modulus 475 high performance 627 high performance cooling screw 678 high performance design 400 high performance screw 235 349 519 528 568 high pressure event 428 high pressure separator 661 high quality 525 high rate profile 400 high scrap rate 520 high temperature 586 holes 510 homogenizing 337 335 353 367 602 homogenous polymers 37 hot stage microscope 484 Huggins function 70 humidity level 499 hydraulic back pressure 464 hydrolysis 53 hypothesis 4 7 413 Hyun Spalding model 142 impact properties 67 Improper drying 499 improper labeling 477 incompletely melted polymer 530 incumbent resin 413 induced stresses 236 inefficiencies 440 inert gas 496 inertial terms 262 initiators 44 injectate temperature 463 injection molding 412 462 513 516 517 525 536 inlet pressure 549 584 in line production 332 in plant regrind 466 inside diameter 419 instantaneous rate 464 543 intensification factor 464 interfacial surface area 337 348 368 intrinsic viscosity 67 IR temperature 417 isocyanate 41 42 isotactic 34 K Kelvin solid 74 Kenics mixer 368 KMX mixer 371 knob mixer 354 363 raemer function 70 L abor 465 aboratory frame 268 Lagrangian frame 11 259 and widths 327 arge flight clearance 421 arge radii 520 arge radii screw 164 arger flight clearance
28. ct and decreasing the profitability of the plant Obviously a process that is very steady has the capability of minimizing resin usage and thus maximizing the profitability of the process For a profile process where the dimen sion of the cross section is critical to downstream assembly processes the extreme ends of the rate surges may result in a product that is outside of the specification and some profiles will need to be scrapped or recycled In this chapter numerous case studies along with diagnostic methods are presented for processes that flow surge The additional cost of producing products from a line that is flow surging can be substantial If the flow surge is not too large and the line can be operated the insta bility of mass flow at the die can cost the converter from 5 to 15 added costs in resins The higher resin costs are incurred because the dimensions of the articles are larger or thicker than needed For example if a line is producing sheet for a downstream thermoforming process and it is operating unstably then some ther moformed parts will have an acceptable mass while others will have a higher mass costing the plant more in resin Often the instability occurs only at a high rate while at lower rates the process is stable In this case the plant may miss shipment dates since the line can only be operated at a fraction of its capacity or the plant may incur higher labor costs because the line will need to operate over weeken
29. d production rate During periods of unstable operation the motor current decreased by about 20 the screw speed increased and the discharge pressure became extremely oscillatory Like the pre vious case as the motor current decreased solids conveying decreased causing the controller to increase the speed of the screw During the trial the feed casing to the extruder had an outside surface tempera ture of about 80 C Although not measured the inside cylinder wall of the feed casing for the first 1 5 diameters downstream of the feed opening was considerably hotter These higher temperatures were caused by a combination of frictional heating of the solids on the wall and also by conduction from the first heated zone of the barrel It is estimated that temperatures as high as 170 C occurred in the feed casing As presented in Section 12 7 3 optimal solids conveying will occur when the stress at the polymer metal interface at the barrel is a maximum and for HIPS resin this surface temperature is near 150 C Surface temperatures higher than 150 C in the feed section will reduce conveying and lead to starving of the screw channels and ultimately flow surging Corrosion inside of the cooling chan nels of the feed casing prevented the flow of cooling water Cleaning the cooling channels and adding a larger cooling water recirculation pump reduced the tem perature of the feed casing and eliminated the flow surging problem 563 HANSER
30. drical restriction or die for a power law fluid 4 AQ 0 0 0 1 1 AP 12 1 AP P P P 12 2 Q P Yn or 12 3 Q 15 where n is the power law index Q and P are the rate and discharge pressure at condition 1 and Q and P are the rate and pressure at condition 2 The pressure at the die lip is assumed to be zero For example a 5 variation in the discharge pres sure AP 0 05 for a polymer with a power law index of 0 3 will cause a 16 change in the instantaneous rate AQ 0 16 An instantaneous rate change of this magnitude is unacceptable for most processes The flow relationship with pressure is much more complicated than this for a commercial die but the trend is the same B 12 2 Troubleshooting Flow Surging Processes The analysis and troubleshooting of a process that is flow surging can be a difficult task especially when the line is required to run production The analysis can often be complicated by the operation of equipment downstream from the die For exam ple if a pulling system is not operating at a constant speed then variations in velocity can cause the product to vary in dimension even though the extruder is operating stably Worn components on a calendering roll stack can cause the speed of the rolls to vary or cause the gap between the rolls to change during a revolu tion Both conditions will cause the product to change dimensions in the down stream direction Unit operations d
31. ds In severe cases flow surging can cause the line to be incapable of producing pro duct at any rate Thus in order to produce product at the lowest possible cost the line must be operating stably so that the rate and product quality are maximized 542 12 Flow Surging Processes that flow surge will often cause a higher level of degradation products to occur in the extrudate For these cases the unsteady nature of the flows in the screw channels will tend to break off small levels of degradation products adhering to the screw The degradation products could occur at the flight radii and regions with long residence times and they may not contaminate the extrudate under normal conditions But the unsteady state nature of the flow surge will tend to break them away from the screw surface B 12 1 An Overview of the Common Causes for Flow Surging Improper process temperatures and poor temperature controls are common root causes for flow surging For example solids conveying depends on a balance of the forwarding forces at the barrel wall and the pushing flight and the retarding forces at the screw surface These forces depend mainly on the geometry of the channel and are directly proportional to the coefficient of dynamic friction for temperatures less than the melting or devitrification temperature and on viscous forces for higher temperatures 6 Since the coefficient depends on temperature pressure and velocity 7 surface temperatur
32. e changes for the barrel and screw in the feeding section will strongly affect the performance of the extruder If the surface tempera tures become too different from the optimal values flow surging and loss of spe cific rate will occur If the solids conveying section of the extruder is controlling rate not the metering section as designed then a portion of the screw channel between the sections will be partially filled at the low rate swing of the cycle and most often will be completely filled at the high rate region of the cycle Improper design and operation of the melting section of the screw can lead to extrusion instabilities For example solid bed breakup 3 can cause solids to migrate downstream These solids can wedge into other sections of the screw and cause the extruder to flow surge 2 4 or cause the extrudate to have periodic changes in temperature Periodic changes in discharge temperature will cause some level of flow surging at the die 8 12 1 1 Relationship Between Discharge Pressure and Rate at the Die Dies are shaping devices that operate at a rate that is directly proportional to the upstream pressure Thus if the pressure to the die is not constant then a variable rate will occur at the die opening causing the dimensions of the product to vary Rate surges at the die can be estimated from the pressure surges using the 12 2 Troubleshooting Flow Surging Processes 543 following equations for flow through a cylin
33. erature range will depend on the resin equipment design placement of the temperature control sensor and rate Thermocouple placement on extruders is not standard and thus they can be positioned at different axial positions for the zones and at different depths into the barrel wall Because of these extruder and process differences barrel tempera tures typically need to be optimized for the machine and application Optimization of barrel temperatures was presented in Section 10 9 Equipment devices that are not functioning properly can cause a process to flow surge For example the feed casing of the extruder is typically cooled with water such that the outside temperature of the casing is about 50 C or less If the cooling water flow is turned off or is not flowing at a high enough rate then the tempera ture of the inside wall of the casing will become too hot to convey solids into the machine As a general rule for most resins the outside temperature of the feed casing will be too hot to touch if the inside wall becomes too hot to convey solids that is at temperatures higher than 50 C At high casing temperatures the rate limiting step of the process is the solids conveying of resin from the casing to the barrel and not the metering channel of the screw Thus the specific rate will decrease and flow surging is very likely to occur For specialty PE resins with very low solid densities the temperature of the feed casing may need to be l
34. es 133 Sikora 175 Singh 371 372 373 Skochdopole 674 Slusarz 632 Small 718 Smith 26 112 133 391 465 468 479 481 499 546 614 634 649 662 Somers 203 351 352 365 367 636 637 638 640 641 651 Spalding 17 110 112 113 116 117 119 120 121 122 124 125 131 139 140 142 150 151 152 154 158 160 164 171 172 180 181 189 194 195 196 197 200 203 204 205 212 213 222 225 227 231 257 279 287 317 318 319 330 336 351 352 365 366 367 376 390 391 392 409 442 445 447 451 461 465 466 468 498 504 515 518 533 541 542 543 567 572 574 578 587 598 599 601 605 636 637 638 639 640 641 643 645 646 651 657 695 705 706 708 710 Squires 14 257 Stangland 119 124 Staples 1 8 Starr 257 Steward 133 546 632 Stewart 261 St John 338 St Louis 545 Stolp 257 Stoughton 479 499 Stowe 132 146 147 Strand 11 139 257 279 447 451 498 515 Street 193 Strub 256 Sugden 578 Sulzer Chemtech 370 371 Author Sumner 365 367 Svabik 634 Swain 336 Sweeney 11 13 205 222 250 258 259 263 269 270 279 304 Swogger 28 32 46 Szeri 231 T Tadmor 8 14 69 102 103 124 131 134 135 138 139 140 142 143 151 194 199 200 201 202 203 205 207 208 211 212 218 222 226 230 235 254 256 257 286 287 294 302 303 306 329 356 375 446 482 541 575 712 722 724 725 726 727 730 750 Takah
35. es contain a level of measurement error and unsteady state behavior Pressure in an actual channel operating at a screw speed of 30 rpm for an ABS resin is shown in Fig 12 3 16 Metering Section N oo Melting Section Pressure MPa gt 100 104 108 112 116 120 Time s Figure 12 3 Measured pressure profiles with rotation for a 63 5 mm diameter extruder running an ABS resin at 30 rpm a conventional single flighted screw and with a positive downstream pressure gradient in the metering section OP Oz gt 0 As shown in Fig 12 3 for the metering channel the highest pressure is at the pushing side of the channel and the lowest is at the trailing side of channel The angular pressure profile in the melting section was typical and very similar to the ideal profile shown in Fig 12 2 because properly operating melting sections have positive pressure gradients in the downstream direction The data in Fig 12 3 clearly shows that a level of measurement noise and unsteady state activity is occurring in the process B 12 5 Gear Pump Control Gear pumps are often positioned between the extruder and the die and they pro vide several processing advantages These advantages include the mitigation of pressure and flow surges from the extruder a decrease in the discharge tempera ture by generating the pressure for the die by the pump instead of the extruder and by decreasing the discharge pressure via the pump a capacity increase
36. ess than 35 C High temperatures on the feed casing can also cause the resin to bridge over the feed opening such that pellet flow to the extruder is severely or completely restricted Flow surging can occur if the temperature of the screw becomes too high in the solids conveying section In general the temperature of the screw in this section needs to be less than the T for amorphous resins or less than the melting tempera ture for semicrystalline resins Small diameter screws will typically operate at feed 12 3 Barrel Zone and Screw Temperature Control zone screw temperatures that are low enough without the need for special cooling For screws 150 mm in diameter and higher the temperature of the screw however can become too hot for optimal solids conveying In these cases the temperature of the screw can be decreased by flowing water into the screw using a rotary union and piping assembly as shown in Fig 12 1 Cool process water flows through the union and into a pipe that extends up to within 10 cm of the end of the cooling hole The water then flows back out of the screw through a section of cast pipe The cast pipe is attached by threads to the screw shank and rotary union The length of the cooling hole and the flow rate of water are used to maintain the screw tempera ture in an optimal range In general the cooling hole is drilled into the screw up to the end of the feed section Two case studies are presented that show flow surgin
37. essure increased at the gear pump inlet the gear pump controller decreased the screw speed back to about 100 rpm causing the extruder to flow surge Flow surging caused the screw speed controller to oscillate about once every 25 minutes As indicated in Fig 12 12 the screw speed controller was able to provide a relatively stable pressure to the pump inlet allowing the process to run at reduced rates The barrel zone temperatures as indicated in Fig 12 14 were extremely oscillatory As indicated in Fig 12 12 the P1 pressure was considerably lower during the period of unstable operation This result indicates that the cause of the problem originated in the first stage of the screw before the first stage metering section At a screw speed of 160 rpm the extruder was still operating at a rate of 2250 kg h but the specific rate decreased to 14 kg h rpm This specific rate is considerably less than the specific rotational flow rate of 20 kg h rpm indicating that the first stage metering section was operating improperly and only partially filled The most likely reason for a partially filled or starved metering section was poor solids con veying from the feed section to the transition section Poor solids conveying was likely due to improper temperature control of the metal surfaces in the feed section of the extruder and screw Barrel feed zone heaters controllers and the feed casing were examined and determined to be operating properly at s
38. essure samples were collected every 8 3 rotations A faster data collection rate would have shown a periodic oscil 12 7 Case Studies for Extrusion Processes That Flow Surge 180 C 170 o 160 Pressure MPa 150 Barrel Temperature 140 Time minutes Figure 12 9 Barrel pressures and temperatures for the 38 1 mm diameter extruder operating stably The temperature profiles are in red while the pressures are black lation of the pressure These data indicate that conditions exist for the stable pro cessing of the resin For a second experiment the extruder was operated at barrel set point tempera tures of 160 163 and 174 C for zones T1 through T3 the zone T1 temperature was increased by 10 C and zones T2 and T3 temperatures were unchanged This increase in the T1 temperature caused the extruder to flow surge and decreased the rate by about 2096 The process data for the unstable conditions are shown in Fig 12 10 As indicated by this figure the pressure for the midbarrel pressure sen sor P2 was zero during the low pressure swing of the cycle indicating that this portion of the channel was operating partially filled or starved Later in the experiment the pressure sensor responses were checked when the pressure was known to be zero in the channels The pressure was measured by the sensors at 1 4 MPa when the pressure was actually zero explaining the offset pressure at the bottom of the pressure cycle in Fig 12
39. et point temperatures typically used for HIPS resin Based on this information the investigation was focused on the temperature control of the screw It was hypothesized that the screw temperature in the feed section was too hot to convey solids effectively to downstream sections of the screw To test this hypothe sis the effect of internal screw cooling was determined during a period when the extruder was operating stably For this period cooling water was flowing to the screw cooling device and the extruder was operating stably and properly at a rate of 2360 kg h and a screw speed of about 104 rpm The metal surface temperatures of the pipes used to flow water into and out of the screw were measured at 29 and 37 C respectively At about 28 minutes into the run the cooling water flow to the screw was turned off as indicated in Figs 12 15 and 12 16 At about 30 minutes the pressure at the end of the first stage transition section P1 started to decrease as shown in Fig 12 16 indicating that solids conveying was significantly reduced Like before the reduced solids flow caused the downstream pressures to decrease and ultimately to cause the extruder to flow surge At about 36 minutes into the run cooling water flow was turned on and within about four minutes the extruder operation became stable as indicated in Figs 12 15 and 12 16 The surface tem perature of the pipe for water flow out of the screw was measured at 81 C just after the
40. ew chan nels The second defect is a restriction in the channel where the fragments are trapped and accumulated As the restriction builds the local pressure just upstream of the restriction will increase while the pressure downstream will decrease As the downstream pressure decreases the pressure and rate at the discharge of the extruder will also decrease The local and high pressure just upstream of the restric tion will cause the melting rate of the fragments to increase temporarily clearing the blockage 2 When the blockage is removed the rate of the process returns to normal until the next solid fragment blocks the restricted region Repeated blocking and clearing of the restricted region creates the flow surging To eliminate surging due to solid blockages the troubleshooter must eliminate the defect that caused the solid bed to break up and must also mitigate the restric tion in the downstream section of the screw It is preferred to correct both defects to permanently eliminate surging from the process B 12 7 Case Studies for Extrusion Processes That Flow Surge Numerous case studies are presented in the next sections that show some common flow surging problems In these case studies the problem is presented in a manner that the troubleshooter would encounter during a trial or information gathering ses sion Incomplete data and erroneous data are often presented to the troubleshooter These data were not included here because inc
41. g processes that had poor temperature cooling on the feed section of the screw Figure 12 1 Diagram showing a rotary union piping assembly for cooling the feed section of a screw Two zone temperature control of the screw has been utilized to mitigate process instabilities in the solids conveying zone and carbonaceous material buildup on the screw root in the melting zone for polyvinylidene chloride PVDC resins 9 Two zone screw temperature control can also be used to control the temperature of the solids conveying zone and energy removal in the metering zone The control device is similar to that shown in Fig 12 1 except that a second rotary union is required for the second fluid and a sealing device 10 is needed to isolate the cooling fluids 12 3 1 Water and Air Cooled Barrel Zones Heating and cooling of the barrel zones is typically done using modules that are equipped with electrical heaters and either water or air cooling These modules are then clamped onto the outside of the barrel Water cooling has the capability of removing more energy from the process and it is well suited for extruders larger 545 546 12 Flow Surging than 150 mm in diameter where the cooling demand is high that is where water flows to the modules for 1096 or more of the time If lower levels of cooling are required however water cooling can create temperature oscillations in the zone For example when the zone becomes too hot the cont
42. ght and retarding forces at the screw root and trailing flight an increase in the retarding forces will cause a reduction in the solids conveying rate The instability appeared to be random due to the complicated interactions of cooling water flow rate and temperature and due to changes in bulk density of the feedstock Several technical solutions were considered to increase the cooling level to the feed section of the screw including increased water flow and the use of chilled water The best technical solution and quickest to implement was to increase the 561 562 12 Flow Surging length of the cooling hole in the screw The length of the cooling hole was increased from 3 8 diameters into the flighted section to 7 diameters up to the end of the feed section After the screw modification the extruder has not experienced instabili ties of this type and the rate has increased to 100 of its maximum potential rate Cooling on the screw and feed casing are often limited by the water pressure at the supply and discharge sides That is if the water pressure on the discharge header is nearly the same as that of the supply side then the water flow rate will be very low due to the lack of a pressure driving force Thus if the driving pres sure for water flow is not available then adequate cooling to the screw and casing may not exist A simple way to test if the cooling water flow is acceptable is to dis connect the discharge water line fro
43. imized the temperature oscillations In order to reduce the cooling level to the barrel zone a metering valve was placed in the water line upstream of the solenoid valve as shown in Fig 12 8 b Now when the controller opens the solenoid valve a much lower quantity of water and thus cooling is available to the barrel zone Prior to this modification the barrel temperatures oscillated 10 C about the set point temperature After the modifica tion the temperature oscillations were reduced to about 3 C and the profitability of the process was improved due to the minimization of resin consumption This temperature control problem occurred due to the implementation of a high performance type screw The original screw was fabricated with a relatively shal low metering channel The shallow channel had a low specific rate and also dissipated a relatively high level of energy The excess energy was easily removed through the barrel wall with the water cooling using the configuration shown in Fig 12 8 a That is the solenoid valve was in the open position enough to main tain cooling while not causing the barrel temperature to undershoot the set point temperature The high performance screw however was designed with a deeper metering section had a considerably higher specific rate and dissipated less energy For this screw less excess energy needed to be conducted through the bar rel wall Since the cooling system was designed for a process w
44. ion 219 259 320 415 438 439 532 micrometer 416 milling lathe 467 milling process 457 misalignment 421 422 mitigating gels 493 mixer 354 356 439 mixing 190 321 330 338 346 347 351 352 353 367 mixing device 355 mixing flight 354 355 356 361 509 mixing quality 376 mixing section 458 Moffat eddies 321 346 497 molecular branching 97 molecular weight 57 58 67 97 98 molecular weight distribution 46 57 58 97 98 molten resin 547 momentum balance 277 motor controls 429 motor current 409 415 431 432 435 576 motor power 592 motors 436 moving boundary 260 moving boundary problem 262 N negative pressure gradient 602 new barrel 521 new screw design 416 Newtonian viscosity 58 62 82 nitrogen inerting 496 673 non Newtonian shear rheology 293 nonorthogonal coordinate transformation 248 nonreturn valve 365 462 521 number average 58 60 numerically 343 numerical method 288 numerical simulation 657 numerical solutions 257 773 Subject O off specification 407 one dimensional melting 228 232 234 operations downstream 543 oscillate 584 oscillating depth 680 oscillation mode 92 osmotic pressure 61 Ostwald viscometer 68 overall stretching 338 oversized in diameter 578 overspeeding 437 oxidation 47 52 53 Oxidized gels 486 Oxygen exclusion 496 P paired flutes 355 parison temperature 620 partially filled 503 518 555 particles 340 payback time
45. ith a high heat flux through the barrel the temperature became very oscillatory when the energy flux was reduced when the high performance screw was implemented 553 554 12 Flow Surging This simple case study shows the importance of verifying the control algorithms before proceeding with a troubleshooting trial Before any testing or equipment modifications are performed it is extremely important to have a deep understand ing of the process and have all process controls and sensors in acceptable opera tion If the sensors and controls are not functioning properly then the troubleshooter may modify the wrong section of the process and obtain little to no improvement in the process 12 7 2 Optimization of Barrel Temperatures for Improved Solids Conveying Numerous complaints were logged by a single processor from several different manufacturing plants on flow surging and reduced rates for a specialty resin The flow surging caused unacceptable variations in the final product In all cases small diameter extruders were used but the operating conditions reported were differ ent in the plants In several of the plants there were some extruders that did not flow surge yet the design of these machines appeared to be identical to those that experienced flow surging It was not apparent why some of the extruders were operating well while others were surging An extrusion trial was performed at the processor s plant using a 38 1 mm dia
46. ko t p M soo o 6 600 5 160 5 a 400 3 120 Screw Speed 200 80 0 0 250 500 750 1000 Time minutes Figure 12 13 Screw speed and motor current for a large diameter extruder running stably and unstably 300 320 250 Extrudate 280 N PIAN 0 P T9 24o pom u en IT 1 74 Ng 8 TAPAS messis 15 76 200 o 9 150 T2 T3 3 E 160 5 P 100 D Screw Speed 120 50 T T T T 80 0 200 400 600 800 1000 Time minutes Figure 12 14 Screw speed extrudate temperature and barrel zone temperatures for a large diameter extruder running stably and unstably At about 410 minutes into the run the extruder started to operate unstably as indicated in Figs 12 12 12 13 and 12 14 The processing change that caused the extruder to go from a stable operation to an unstable one was not known but it could have been due to minor changes in the bulk density of the feedstock or cooling water fluctuations to the screw As indicated by these figures the event started when the P1 pressure decreased slightly causing the rate and the P2 pressure to decrease This decreased pressure transmitted down the extrusion system even tually decreasing the pressure at the inlet to the gear pump To correct for the lower pressure the controller on the gear pump increased the speed of the screw from 99 rpm to about 160 rpm Next the P1 pressure increased due to the higher 560 12 Flow Surging screw speed and higher flow rate as indicated in Fig 12 12 As the pr
47. l amount of barrel cooling At the low temperature portions of the cycle both heating and cooling were off The small amount of excess energy dissi pated in the screw channel was causing the barrel temperature to increase slightly with time When the temperature exceeded 220 C the control algorithm took action and opened the solenoid valve on the water line upstream of the heating and cooling barrel jacket as shown in Fig 12 8 a The controller opened the solenoid valve for the minimum amount of time sending a short burst of water to the zone The water would flash evaporate in the unit and then quickly cool the barrel to about 210 C Since the solenoid was opened for the shortest possible amount of time the level of cooling that was utilized was the minimum It was very obvious that the level of cooling water to this barrel zone was too high for this process The barrel temperature oscillations shown in Fig 12 7 were enough to cause a small variation in the product dimensions Although the variations in the product dimen sions were acceptable the variations did reduce the profitability of the process by causing too much resin to be used in the final product 12 7 Case Studies for Extrusion Processes That Flow Surge Control On Off Solenoid Valves Figure 12 8 Heating and cooling system on the barrel a schematic of the original configuration that created the temperature oscillations in Fig 12 7 and b a better configuration that min
48. ller tuning screw geometry variations and thermocouple accuracy likely caused con ditions such that some of the extruders flow surged while others did not These minor variations could influence the temperature of the inside barrel wall of the solids conveying section Moreover different rate requirements for different pro ducts required that the extruder be operated at different screw speeds which further complicated the solids conveying problem The problem could have been avoided if plant personnel had optimized the barrel temperatures for each extruder using the technique described in Section 10 9 12 7 3 Flow Surging Due to High Temperatures in the Feed Section of the Screw A severe and random flow surging problem limited the production rate for a large diameter two stage vented extruder If it were not for a gear pump positioned between the extruder and die this extrusion line would not have been operable The surging did however limit the output of the line to about 70 of its potential rate The maximum potential rate is the rate that the extruder can run at high screw speeds and with proper operation The extruder was 203 2 mm in diameter and had a 40 L D barrel A schematic for the extruder and gear pump arrange ment is shown in Fig 12 11 and the screw channel dimensions are provided in 12 7 Case Studies for Extrusion Processes That Flow Surge Table 12 1 The specific rotational flow rate for the first stage metering sectio
49. luding them may mislead the reader The troubleshooter however must be able to separate the actual facts of the process from misleading perceptions In each case study the modifications required to fix the process are detailed along with supporting fundamental information In all cases the rate of the process was limited and the cost to manufacture was high 12 7 1 Poor Barrel Zone Temperature Control A 203 2 mm diameter plasticating extruder was running GPPS resin and dis charging to a specialty downstream process Like most processes the downstream equipment required a nearly steady supply of molten polymer For this case the 552 12 Flow Surging 230 O Set Point Water o Temperature am On 220 a g w Q E w I p 210 s e 200 0 30 60 90 120 150 Time minutes Figure 12 7 Barrel temperature data for a 203 2 mm diameter extruder running GPPS resin and with water cooling on the barrel heating and cooling This extruder was configured with a water cooling capability that was too high for the process barrel zones were electrically heated and water cooled The barrel zone tempera ture is shown in Fig 12 7 The barrel heater for this zone was only used during startup Once the extruder was operating the energy dissipation from the screw to the resin was more than enough to keep the section hot In fact in order to main tain the zone at the set point temperature of 215 C the extruder was operated with a very smal
50. m the header and either flow this water to a drain or the parking lot using a temporary hose The discharge water flow should be high and the temperature should be warm to the touch A permanent arrange ment might consist of a water pump and a rotameter in line upstream of the rotary union attached to the screw To aid in the understanding of this solids conveying problem the coefficient of dynamic friction was measured for the resin as a function of temperature and sliding velocity at a pressure of 0 7 MPa The equipment used to make the measurement is described in Section 4 3 1 and is shown in Fig 4 11 Since the coefficient of dynamic friction is only defined for solid state processes the friction values are reported here as stress at the interface because the stress can be described from ambient temperatures up to processing temperatures The shear stress at the inter face for HIPS resin is shown in Fig 12 17 at a pressure of 0 7 MPa As indicated by this figure the shear stress was nearly constant from ambient temperature up to about 110 C increased to a maximum stress near 150 C and then decreased as the temperature was increased further Optimal performance of the solids conveying section for this resin would be such that the forwarding forces are maximized with metal surface temperatures near 150 C where the stress is a maximum and the retarding forces minimized with metal surface temperatures of 110 C or lower Thus optimal solids
51. metering section indicating that a negative pressure profile exists in the section The negative pressure gradient is expected for a first stage metering section of a vented screw that is operating properly that is the first stage metering section was full of resin To maintain the stability the extruder screw speed was reduced such that the extruder was operating at about 70 of its potential maximum rate That is at screw speeds higher than 99 rpm the extruder was more likely to transi tion from a stable to an unstable operation The barrel pressure at the end of the first stage transition section P1 had variations of about 3 MPa about the average pressure This pressure variation was considerably higher than expected and suggests that the extruder although running stably was on the verge of unstable operation Some of the variation was due to the movement of the flight tip past the sensor Barrel zone temperatures tracked the set point values and were stable 1400 Current Current bab 1200 o o O A 800 Extruder Discharge IAN e Pump Inlet i mm NG 400 200 0 200 400 600 800 1000 Pressure MPa Motor Current Time minutes Figure 12 12 Barrel discharge and pump inlet pressures and motor current for stable and unstable extrusion for a large diameter extruder running HIPS resin 12 7 Case Studies for Extrusion Processes That Flow Surge 559 280 1400 1200 E 240 Motor Current E 1000
52. n was calculated at 20 0 kg h rpm The extruder was fed a mixture of fresh HIPS resin with 30 to 60 recycled ground sheet from a downstream thermoforming process The level of recycle affected the bulk density of the feedstock entering the extruder The HIPS resin had an MFR of 3 9 dg min 230 C 5 0 kg The screw was single flighted and typical of what is used for HIPS resins Screw temperature control was accomplished by flowing cooling water through a rotary union into and out of a hole cut into the feed end of the screw as shown in Fig 12 1 This hole extended 3 8 diameters into the feed section Pressure sensors were positioned in the barrel wall at the end of the first stage transition section P1 at the end of the first stage metering section just before the vent P2 and at the discharge Additional pres sure sensors were positioned at the discharge of the extruder and at the inlet suc tion side to the gear pump A screen filtering system was positioned between these pressure sensors as shown in Fig 12 11 A commercial control scheme adjusted the screw speed to maintain a constant pressure of 9 MPa to the inlet of the gear pump The gear pump was operated at constant speed in order to maintain a constant flow rate of material to the die Table 12 1 Screw Channel Dimensions for a 203 2 mm Diameter Two Stage Vented Screw Running HIPS Resin Depth mm Length diameters Notes Feed section 28 6 7 The compression ratio was First
53. nderstanding operation and troubleshooting of single screw extruders Gregory A Campbell Mark A Spalding The views and opinions expressed in this book are soley those of the authors and contributors These views and opinions do not necessarily reflect the views and opinions of any affiliated individuals companies or trade associations HANSER Sample Pages Gregory A Campbell Mark A Spalding Analyzing and Troubleshooting Single Screw Extruders ISBN Buch 978 3 446 41371 9 ISBN E Book 978 3 446 43266 6 For further information and order see http www hanser fachbuch de 978 3 446 41371 9 or contact your bookseller Carl Hanser Verlag M nchen Flow Surging Flow surging is defined as the oscillatory change in the rate of the extruder while maintaining constant set point conditions Flow surging can originate from many different sources including improper solids conveying melting instabilities flow restrictions and improper control algorithms 1 5 Surging in most cases results in lower production rates higher scrap rates higher resin consumption material degradation and higher labor costs In mild cases flow surging will cause plant personnel to set the product at the low end of the dimension setting at the low rate portion of the surge At the high rate portion of the surge the dimensions of the product will be oversized Oversized products will use more resin than necessary adding cost to the produ
54. nergy dissipation 66 248 256 301 302 303 304 315 354 611 616 energy equation 257 277 energy flux 57 Energy Transfer screws 235 633 engineering design approach 389 enhanced mixing 639 entrained air 195 514 533 entrained gas 191 entrained solid 387 entrapment 477 entropy 336 Subject entropy of mixing 335 entry 536 equipment failures 477 ET Energy Transfer screws 401 518 536 622 626 635 636 638 639 640 678 Eulerian 259 Eulerian reference frame 304 excessive wear 511 existing experimental data 392 exit 536 experience 392 experimental plan 415 exponential 340 extended startup times 70 extended wear 575 extrudate 477 602 extrudate temperature 320 417 623 extruder 339 extruder diameter 388 extrusion trial 554 F acing materials 4 9 ailed 432 ailure 596 Fc correction factor 289 292 FDM 257 277 280 281 eed casing 133 420 421 562 574 575 578 580 eed channel depth 533 eedhopper 132 eed section 439 560 561 586 612 eedstock pellets 238 FEM 257 277 ield weakened 436 ilm interface 347 ines 330 inite difference 257 657 666 inite element 258 it checked 425 ive zone melting model 200 ixed boundary problem 262 ange diameter 583 ash evaporate 552 ight clearance 375 587 598 ight radii 321 496 497 498 499 517 ight starts 8 ight undercuts 476 ight wear 596 ight width 8 ood fed 78 ow channels 457 owrate 297 ow surging 214 2
55. obsen 25 aluria 257 258 anssen 334 enkins 119 231 237 545 695 epson 124 254 313 314 595 Jerome 25 ia 178 in 178 235 236 Johnson 33 368 Jons 492 ung 3 4 uvinall 427 K Kacir 230 Kamal 3 462 514 ang 373 arlbauer 356 393 arwe 257 Kaufman 336 Keum 314 446 hariwala 32 im 7119 121 124 212 213 314 333 336 626 639 643 645 658 Kirkland 6 536 635 Kirkpatrick 119 120 131 150 152 231 542 695 islansky 661 671 lein 8 14 131 134 135 138 139 140 143 151 194 196 199 200 201 202 203 205 207 208 211 212 214 218 222 226 227 234 235 254 256 257 286 287 303 306 356 375 376 446 541 542 551 572 575 596 712 722 724 725 726 727 730 750 lenk 194 Kodjie 485 Koppi 332 oyama 362 363 ramer 124 437 440 546 reith 151 Krohnke 33 51 Kruder 388 614 633 634 uhman 645 646 umari 26 765 766 Author unio 200 203 urata 69 wade 116 L Lacher 218 625 Ladin 126 Lafuente 53 Landel 77 102 Larachi 26 Larson 76 645 646 Laurence 248 295 Lawrence 626 649 LeBlanc 408 Leder 34 Lee 228 349 356 629 Lepore 651 LeRoy 354 355 Liauw 53 Lightfoot 267 Lin 257 Lindt 200 203 218 226 258 333 498 501 Ling 337 Liu 3 25 462 514 596 LiuR 235 236 Liu T 235 236 Lobo 124 Lodge 42 Loshaek 100 Lounsbury 419 M ack 374 acosko 76 80 84 92 97 addock 110 193 194 199 355
56. ownstream from the die must be checked to determine if they are the root cause of the product variation The troubleshooter must be diligent to set a hypothesis and then test the hypothesis If some problem other than the root cause is fixed then the process will continue to flow surge The standard array of diagnostic equipment is required for the troubleshooting of a process that is flow surging These tools include screw measuring devices pyrometers and devices to calibrate sensors in the process These devices are dis cussed in Chapter 10 Often it is very difficult to impossible to determine a cause and effect relationship from process displays that are attached to typical extrusion 544 12 Flow Surging lines However a portable data acquisition system that is capable of collecting pro cess data as a function of time is highly useful in determining the cause and effect relationships between process parameters In all of the cases presented here the extrusion line was either equipped with a data acquisition system or a temporary acquisition system was connected to the machine during the trial B 12 3 Barrel Zone and Screw Temperature Control Improper selection of process temperatures poor temperature control and inopera tive temperature control devices are common causes for flow surging As stated earlier temperatures for the metal surfaces in the solids conveying zone must be within a specific range for an application This temp
57. roller will open the solenoid valve to the water flow line for the shortest possible duration If this minimum amount of water flow is too large then the cooling on the zone can be too much causing the temperature of the zone to undershoot the set point temperature 11 The control scheme will cause the zone temperature to oscillate Variation in tem perature for the barrel zones can affect the rate and discharge temperature The oscillations can be mitigated by installing metering or needle valves in the water flow lines to reduce the water flow rate to the module An in line water filter is typically installed in the cooling line so that the needle valves do not get plugged with particulates Air cooled zone modules do not have the ability to remove as much energy as do water cooled units For processes that only require a low level of cooling air cooled units will provide a more stable control of the temperature Recent innovations in air cooling using high flow fan systems 12 have allowed the replacement of some water cooled systems with less costly and lower maintenance air cooled systems 11 B 12 4 Rotation and Geometry Induced Pressure Oscillations Pressure transducers that are positioned in the barrel can be extremely useful for troubleshooting a process Common positions include midway into the melting sec tion and at the entry to the metering section For two stage screws positioning of a transducer at the entry to the second s
58. sponsible for processes that run at maximum rates and maximum profitability Debugging and troubleshooting single screw extruders is an important skill set for plant engineers since all machines will eventually have a deterioration in their performance or a catastrophic failure Original design performance must be restored as quickly as possible to mitigate production losses With troubleshooting know ledge and a fundamental understanding of the process the performance of the extruder can be restored in a relatively short time minimizing the economic loss to the plant Common root causes and their detection are provided Hypothesis testing is outlined in Chapter 10 and is used throughout the troubleshooting chap ters to identify the root causes Elimination of the root cause is provided by offering the equipment owner several technical solutions allowing the owner to choose the level of risk associated with the process modification Mechanical failures are also common with single screw extruders and the common problems are identified Illustrations are provided with the problems along with many numerical simula tions of the case studies Collectively these instruct the reader on how to deter mine and solve many common extrusion problems About 100 case studies and defects are identified in the book with acceptable technical solutions Lastly we Preface hope that this book provides the information and technology that is required for the u
59. tage metering section provides information on the degree of fill of the stage and provides knowledge on the likelihood of vent flow The pressures measured from these transducers provide three types of infor mation 1 the average pressure in the channel 2 the pressure variation in the angular direction due to the rotating screw and 3 the stability of the process by comparing the pressure oscillations during several screw rotations The pressure in the angular direction is composed of two pressure components 1 a pressure component in the downstream direction OP Oz and 2 the cross channel pres sure gradient OP Ox The shape of the angular pressure profile depends on the magnitudes of the components In order to measure the pressures during rotation high speed data acquisition equipment is required For example a screw that is rotating at a speed of 60 rpm will require a data acquisition frequency of at least 12 4 Rotation and Geometry Induced Pressure Oscillations 20 Hz providing 20 pressure measurements per rotation Typical pressure measure ments for transducers positioned in melting sections and metering sections that are filled with molten resin are shown in Fig 12 2 Pressure Sensor oo o a 2 g 2 o o 2 an Pressure Sensor g Pushing side E g b P oO Trailing side Solid bed Meltpool 0 1 2 3 4 5 Time s Figure 12 2 Typical pressure measurements for transducers positioned in the
60. tion melting model 226 Barrll 630 Barr Ill 630 baseline extrusion process 389 bed thickness 222 belt sander 458 best solution 408 Bingham plastic 65 black carbonized 518 black char 47 black color streaks 525 black degraded resin 527 black specks 53 493 518 631 black streaks 516 520 523 525 blending 330 blister mixers 333 353 359 360 577 667 669 blockage 415 566 572 blocked screens 478 blowing agent 332 364 blow molding 510 619 boiling point increase 67 bottlenecks 597 boxy 250 break 425 breaker plate 478 482 breakup 194 573 Subject bulk density 110 111 239 410 bulk temperature 409 burned out 432 C calibration 432 Campbell Dontula model 143 capillary rheometer 80 687 carbonaceous deposit 637 carbon specks 501 case study 417 casing temperatures 544 Cavity Transfer Mixer 365 ceiling temperature 49 50 change in rate 227 channel curvature 256 channel depth 8 223 chaotic mixing 336 338 339 341 344 Charles Ross amp Son Company 372 Chemineer Incorporated 370 chrome plated 483 chromium 44 circulation channel 687 clean 431 clearance 357 361 419 coefficients of friction 119 445 562 cold screw 425 cold start 425 colligative 67 Colmonoy 456 color masterbatches 374 478 500 523 524 color streaks 354 501 comonomer 39 compaction 110 112 195 complex viscosity 93 component cost 465 composition 333 compounder 604 compounding line
61. ty factor 404 scale down 389 scale up 389 scaling rules 387 388 scrap rates 541 screen packs 478 screw 1 425 431 445 449 452 454 562 screw channels 416 578 screw design 595 screw manufacturer 456 screw modification 460 screw root 450 454 screw rotation 238 253 259 265 270 297 300 318 723 screw rotation analysis 7 screw rotation theory 258 Screw Simulator 719 600 screw speed 401 409 451 533 549 screw surfaces 561 screw temperature 452 453 560 screw wear 419 596 Subject seals 360 secondary extruder 332 674 675 secondary mixers 331 353 second flight 278 selection of equipment 470 semicrystalline 39 sensitivity analysis 393 service life 468 shallow channel 301 438 shaping process 597 shear rate 82 83 84 362 375 shear refinement 377 663 shear strength 426 shear stress 46 82 93 120 334 357 378 shear thinning 82 287 318 shear viscosity 524 sheave ratio 435 short barrel 659 silver spots 529 simple rotational flow 387 simulation 396 401 402 simulation process 391 single flighted screw 526 sinusoidal 97 sled device 416 sleeve rings 365 slide valve 673 sliding interface 119 slip agents 662 slipping 671 SMX static mixer 371 software controls 427 solidbed 112 144 205 217 225 229 231 234 235 348 450 572 573 628 723 solid bed breakup 234 235 349 351 542 solid bed interfaces 270 solid bed reorganizes 2 0 solid fr
62. vity improvement 623 product quality 466 product variation 543 propagation 44 45 proper equipment 464 pseudoplastic 65 pseudoplasticity 92 pump ratio 441 593 purging 493 661 673 pushing flight 223 Q quality control 478 quality of the mixing 349 R radial bearing 422 radicals 52 random flow surging 556 rate 319 409 rate increase 389 617 rate limited 468 591 597 614 rate surge 567 reaction chemistry 40 recirculation flow 92 reclaim pelletizing 617 Recommended Dimensional Guideline for Single Screws 496 501 recrystallize 508 rectangular channel 254 recycle stream 114 477 reduced bulk density 399 reduced rates 554 reduce the cycle time 647 redundant pressure sensors 429 reference frame 261 refurbishment 4 0 460 regrind 238 relaxation time 72 74 relay 432 reorganizing solid bed 203 reorientation 334 344 353 reorienting 362 residence time 250 321 346 499 resin changes 389 resin consumption 553 resin cost 465 541 resin degradation 192 resin deposits 533 resin temperature 672 resistive temperature devices 447 restricted bond angles 335 retrofit 362 reversible reactions 53 Reynolds bearing 237 Rheopexy 65 root causes 411 413 543 567 Ross mixer 368 rotating screw 297 rotation 259 rotational flow 12 122 272 287 410 439 464 568 rotational flow rate 282 287 502 604 620 routine maintenance 4 9 rubbing in 750 rupture disk 427 428 S safe

(Buch): 978-3-446

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