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Perspex - Design Guide & Technical Manual

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1. Chemical Concentration Resistance Exposure Time Notes Acetic acid 10 S 5 years 100 U 1 day Badly swollen Glacial U 3 days Dissolved Acetone 100 U 1 day Dissolved Alchols n butyl U 1 year Crazing and disintegration Ethyl 10 A 1 year Slight attack 50 A 1 year Slight attack 100 U 1 year Slight swelling and softening Isopropyl 10 A 1 year Crazing 50 A 1 year Crazing 100 A 1 year Attacked Methyl 10 A 1 year Slight attack 50 A 168 days Swollen 100 U 168 days Swollen weight increase Ammonia 0 880 sol 5 1 year Amyl acetate U 28 days Dissolved Aniline U 7 days Dissolved Aviation fuel 100 octane A 168 days Slight crazing Benzaldehyde U 7 days Dissolved Benzene U 10 days Dissolved Calcium chloride Saturated sol 5 3 days Slight attack Carbon tetrachloride U 84 days Dissolving Chloroform U 1 day Dissolved Chlorine 2 in water A 5 years Surface crazing and attack Chromic acid 10 S 5 years Stained Saturated sol U 1 year Dissolving Citric acid Saturated sol S 5 years Dibutyl phthalate A 2 years Surface crazed Dioctyl phthalage A 2 years Slight attack Dibutyl sebacate A 2 years Slight attack Diethyl ether U 168 days Swollen amp Soft Ethylene glycol S 5 years Ethylene dichloride U 1 day Dissolved Ethyl acetate U 3 days Dissolved Epichlorydrin U 1 day Dissolved Formaldehyde 40 S 5 years Formic acid 10 S 5 years 90 U 7 days 38 Design Guide Part 3 Technical amp Performance Properti
2. Perspex l pe ay theplasticsnop co uk E g TIa Amphitheatre made using Perspex Fro Potential Performance Perspex Design Guide Potential Performance Perspex www theplasticshop co uk 2 Design Guide Table of Contents Introduction Outstanding Properties of Perspex Part 1 Fabrication Engineering design data Thermal and moisture expansion Masking protection Storage Preparing for fabrication Cleaning Proprietary acrylic polishes Machining Cutting Tools Sawing Scribe Breaking Laser Cutting Laser Engraving Drilling Screwing and Tapping Turning Spindle Moulding Routing Finishing Sanding Power Buffing Diamond Polishing Flame Polishing Hand Polishing Thermoforming Pre drying Heating Shrinkage Cooling Thermoforming of Colours Methods of Thermoforming Single Curvature Thermoforming Tubes Local Bending Vacuum Forming Moulds Cementing Fixing and Sealing Cementing Lamination Face to Face Bonding Edge Bonding Bonding to other Substrates Fixing Methods Sealing Printing Painting and Surface Decoration Screen Printing Spray painting and Hot foil Stamping Self adhesive vinyl films Stress in Acrylic Sheet Annealing Normalising Safety Recycling A A A A A 2A 2 QO o N AD i amp bQ N S2 ak cak ark dax Garcia EO NS SS S SS S S amp amp amp amp A AA AA A AA A AA AA O IS amp S s i i D ON o 0S 68 o a a w S
3. The term luminance is used to describe the measured brightness of a point on a surface when viewed in a given direction Of the various photometric concepts luminance is the one which is most relevant to the design of an illuminated sign In the following paragraphs the concept of luminance and its applications are described in practical terms For the purpose of considering glare in relation to luminance it is best to consider luminance as brightness in the simple sense The degree of glare caused by a sign depends on many other factors as well as its brightness These include its size colour its position relative to the direction from which it is seen the brightness of its surroundings and the age and maintenance of the sign A sign mounted in a well lit city street will appear less bright than the same sign seen in the darkness of the countryside The sign must therefore be bright enough to command attention but not so bright as to cause annoyance to local residents or distract the attention of motorists To decide on the very complex problem of how bright a sign should be in any particular location reference should be made to a report entitled Technical Report No 5 Brightness of Illuminated Advertisements copies of which can be obtained from the Institution of Lighting Engineers www theilp org uk The luminance of any internally illuminated sign or fascia is determined by five factors 1 Light source th
4. cell cast acrylic sheet contains stresses introduced during the casting process and under normal circumstances these have no effect on the behaviour of the final article If however components are being machined to very close tolerances it is advisable to remove these casting stresses by the process called normalising By heating Perspex above its glass transition temperature the stresses are relaxed giving rise to a uniform shrinkage of approximately 2 Normalised Perspex is therefore said to be fully Cooling rate from between 105 110 C to room stress relieved and fully shrunk The normalising temperature not greater than 4 C hour Minimum process consists of a closely controlled temperature cooling time 21 hrs Maximum allowable differential and time cycle depending on the sheet thickness between material and ambient temperature at time The sheet to be normalised is heated to 140 C in of removal from oven is 7 C an air circulating oven and held there until it has been heated uniformly It is then allowed to cool The treatment conditions especially for thick sheet down slowly to avoid the reintroduction of thermal and block are quite critical and stresses Table 3 gives typical normalising cycles for cast Perspex Table 3 Typical normalising cycles for cast Perspex sheet amp block Thickness Cycle Heating to Holding at Cooling to Holding at mm 140 C 140 C 105 110 C 105
5. 110 C Hour Min Hour Min Hour Min Hour Min 3 30 50 30 30 4 30 1 30 30 50 5 30 1 30 30 50 6 30 1 40 30 50 8 1 00 2 15 1 00 1 30 10 1 00 3 00 1 00 1 30 12 1 00 3 45 1 00 1 50 13 1 00 3 45 1 00 1 50 15 1 00 4 15 2 00 2 00 20 1 30 5 30 3 30 3 00 25 1 39 Z7 00 3 30 3 30 30 1 45 8 30 4 45 4 00 35 2 00 9 45 5 00 5 00 40 2 30 11 15 5 30 5 45 45 2 30 12 30 6 30 6 30 50 3 00 14 00 7 00 7 00 55 3 00 15 30 7 00 7 45 60 3 30 16 45 8 30 8 30 NOTES 1 Assuming room temperature 20 C 2 Take the actual sheet thickness 3 For sheet thicknesses significantly different to those above either calculate the appropriate cycle or use that given for the next larger thickness 21 Design Guide Part 1 Fabrication Potential Performance Perspex www theplasticshop co uk 1 7 Safety Handling and machining Flammability Perspex is a hard material Sharp edges can cause All Perspex grades are combustible and if ignited cuts and chips can damage eyes Appropriate will continue to burn Little smoke is evolved when personal protective equipment should be worn as Perspex sheet burns Perspex burns similar to sharp edges can cause cuts and chips can cause hardwood and Perspex cast sheet does not form eye damage molten droplets Thermoforming Users of Perspex are recommended to consult When using presses or rams for thermoforming it the appropriate Lucite International MSDS which is imperative that adequate safety devices are in is obtain
6. accurate work especially where a high degree of finish is required diamond tipped tools are particularly suitable for machining Perspex 1 1 2 Sawing For small jobs Perspex may be cut with fine toothed hand saws such as fret saws and hack saws The work must be securely fixed and only light pressure applied Powered saws with blades having alternative teeth bevelled as for aluminium are particularly recommended for sawing Perspex as are band saws jigsaws and fret saws The recommended conditions for sawing Perspex are given in Table 2 Figure 1 gives details of the recommended type of TCT circular saw blade suitable for cutting Perspex sheets Saw Type Optimum Blade Optimum Saw Pitch Recommendation Speed approx Sheet Thickness Teeth cm Bandsaw 1500m min Up to 3mm 6 8 Keep saw guides as close 3 13mm 4 5 together as possible to Over 13mm 1 5 2 prevent blade twisting Circular saw 3000m min All 0 8 1 6 See Figure 1 carbide tipped thicknesses Jigsaw fretsaw Non critical Up to 6mm 5 6 Allow blade to stop before withdrawing from saw cut Fig 1a Fig 1b Fig 1c 15 Clearance angle Typical diameter 200 250mm Width 2 3mm Figure 1 A tungsten carbide tipped saw blade suitable for cutting Perspex Rake angle 0 5 Potential Performance Perspex www theplasticshop co uk Bevelled tooth 7 Design Guide 1 1 3 Scribe Breaking Perspex up to 4mm thick may be conveniently cut in a straigh
7. are colour of tints and hues available to precise colour balanced on a full sized light box to ensure matching batch to batch consistency and stringent uniformity of illuminated colour If this is not manufacturing controls There are however several possible thickness measurements should be taken factors which do affect how the colour of the sign at the butt edges and the panels aligned to give as is perceived near uniform thickness as possible across the butt joints to ensure colour uniformity before any fret 2 6 1 Thickness Tolerance cutting or cementing Cast acrylic sheet has a manufacturing thickness tolerance which can reveal some variation in 2 6 2 Surface Finish colour by transmitted light at opposite ends of the When using Perspex Frost Silk Satin or tolerance This effect inherent in the cell casting Impressions reflected colours will be slightly lighter manufacturing process can therefore reveal slight as a result of the light scattering effect of the changes in hue between certain dark colours such textured surface as greens and blues even though the thickness difference may only be fractions of a millimetre Such slight differences in transmitted colour are most noticeable when two fascia panels are cut from different sheets and butted up together 33 Design Guide Potential Performance Perspex www theplasticshop co uk Part 3 Technical amp Performance Properties Part 3 Technical
8. correctly it must be heated uniformly and cell cast sheet requires slightly more heating than extruded sheet The optimum heating time and temperature will depend on the thickness of the sheet the type of mould being used and the degree of stretching required Fundamental differences exist between the thermoforming of cast and extruded sheet and it is important to understand what these differences are before any work is started in order to achieve the best results For example Perspex Continuous Cast and extruded sheet have lower thermal softening temperatures than cast sheet meaning that they soften more easily and can be stretched with very little force For this reason they are more suitable for vacuum forming than Perspex cell cast sheet Extruded sheet if overheated will start to extend under its own weight if hung in a vertical heating oven and control of heating time and temperature are critical if oven heating is used The heating of extruded sheet on a horizontal oven shelf is not recommended because the hot sheet surface marks easily and can quickly stick to the shelf Infra red heated vacuum forming machines can overcome these difficulties and are the preferred option for thermoforming Perspex extruded sheet Perspex cast sheet is more suited to thermoforming by mechanical press forming where greater force can be applied by clamping and pressing 1 2 1 Pre drying Typically it is not necessary to pre dry Perspex cell cast a
9. cracking cements screen printing ink or exposure to high energy radiation It is therefore important to ensure that only the minimum stress is induced in acrylic sheet when fabricating or thermoforming and that component parts are designed to prevent excessive mechanical loads being applied during service Extruded acrylic sheet has a lower stress level tolerance than cast sheet and particular attention must be given to design parameters when using this material Inherent stress i e moulded in stress can usually be eliminated after moulding or fabrication by an annealing process This is a gentle heat conditioning process that allows the release of stress without crazing to produce a stress free component Annealing should be undertaken whenever fabricated parts are to be cemented or screen printed especially when using extruded acrylic sheet For thermoformed components the annealing temperature should be reduced to within the range of 70 85 C It is advisable to anneal all extruded sheet components before cementing painting or screen printing A rapid annealing cycle which is reliable especially for thin sheets is to pre heat the oven to 80 C anneal for one hour then remove the parts from the oven and allow cooling to room temperature Potential Performance Perspex www theplasticshop co uk 20 Design Guide Part 1 Fabrication Potential Performance Perspex www theplasticshop co uk 1 6 Normalising Perspex
10. from either scrap Perspex or hardwood to prevent splintering the exit hole Under no circumstances should a centre punch be used before drilling Perspex A small pilot hole should be drilled first to locate the drill Coolants are strongly recommended for any deep drilling into Perspex and time must be allowed to remove swarf from the drill at regular intervals ad Hole saws may be used for larger holes greater than 12mm diameter but when drilling large holes in thin extruded sheet especially if it is not possible to support the work cone cut drills have been found to be particularly suitable Potential Performance Perspex www theplasticshop co uk 9 Design Guide 1 1 7 Screwing and Tapping Standard taps and dies may be used for cutting screw threads in Perspex but wherever possible coarse threads are preferred as they are less liable to damage Lubricants are essential water or soluble oil being preferred Threads must not be overstressed and it is not advisable to thread Perspex if frequent dismantling is likely In such conditions threaded metal inserts are recommended 1 1 8 Turning Perspex can be turned on conventional metalworking lathes but it is important to keep the work cool by the use of coolants and ensuring that feed rates are slow Any overheating of the work is likely to lead to localised distortions and a loss of tolerance Crazing may also occur sometime after Correct grinding
11. kept clear of mould surfaces to prevent dust marks especially when moulding clear sheet Mould temperatures should be maintained at between 75 85 C a Pressure assisted press forming Vv Air vents A Compressed air 4 Figure 14 Press forming using air and or vacuum Heating Double sided heating is recommended for all Perspex vacuum forming above 2mm thickness It is difficult to give precise recommendations on heating times and conditions because these vary according to the machine design and the machine supplier may be able to give some information Generally speaking top heaters are typically set for a heat output of 20kW m2 and lower heaters for 8kW mz2 Starting at this level the sheet should be heated carefully and examined regularly until it is ready for shaping Vay Potential Performance Perspex www theplasticshop co uk b Vacuum assisted pressing with cold plunger Y y y Air release valve 4 Vacuum Some trial and error will be needed to reach this stage but it is particularly important not to overheat the sheet and allow it to sag on to the hot lower heater since damage could occur to the machine with the possible risk of fire The use of levelling is advisable by injecting air into the box cavity so supporting the hot sheet during the final heating stages Extruded sheets can absorb moisture which can cause blistering when vacuum forming If moisture blisters occur when vacuum f
12. necessary 1 1 11 Finishing Machined surfaces of Perspex with the exception of laser cutting which many customers will leave as a finished edge are usually matt unless diamond cutting tools are used Machine marks are best removed by scraping with a sharp blade set at 90 or sanding and then the gloss finish restored by polishing Part 1 Fabrication 1 1 11 1 Sanding Bench mounted or portable sanders may be used as may belt sanders to remove machine marks or saw cut marks from the edge of Perspex Sanding should be carried out dry and only very light pressure applied to prevent softening or melting of the surfaces After any sanding operation it will be necessary to anneal the work if cementing or surface decoration is intended 1 1 11 2 Power buffing Power buffing with rotating calico mops is the traditional polishing technique for Perspex Edges must first be scraped or sanded to remove all machine marks then a mild abrasive buffing soap may be applied Moderate speeds and only very light pressure is needed otherwise overheating will occur 1 1 11 3 Diamond polishing Diamond polishing can be used for straight edges and gives excellent results without the rounded edges often produced by buffing Diamond polishing produces very little stress in the surface 1 1 11 4 Flame polishing Flame polishing is ideal for polishing thin edges of Perspex because it is fast and effective A good routered or scraped
13. of the lathe tool is necessary HSS tool bits are preferred ground to zero rake at the top and 15 20 front rake The fine grain texture of HSS tools ensures a better finish than TCT tools but all cutting surfaces must be kept very sharp Cutting speeds of 90 150m min are typical for turning Perspex but for a first class finish speeds of 15 30m min are recommended Diamond fly cutting is particularly recommended where a good polished finish is required after turning 1 1 9 Spindle Moulding A spindle moulder is a useful machine for the rapid machining of Perspex Cutters designed for woodworking are suitable two bladed cutters being preferred Spindle moulding is carried out dry as swarf is easy to remove 1 1 10 Routing Routing is a common machining operation used on Perspex today Fixed head moving head or portable standard woodworking routers are suitable for Perspex using the same cutter speeds as for wood Double edged cutters are preferred ground and honed with a back clearance angle of about 12 or more Cutters Spindle Speed 6 to 12mm diameter or less ca 24000 RPM gt 12 ca 18000 RPM Routing is usually performed dry but provision must be made to clear all swarf from the work bench and keep the cutter cool A compressed air jet directed at the work piece usually performs this task HSS cutters give better results than TCT cutters although their life will be shorter Regular sharpening is therefore
14. weathering properties and ease of fabrication to produce double gazed units are met In addition certain Perspex grades and thicknesses are accredited to the German Transport Regulations ABG as approved materials for roof lights side and rear windows for vehicles and caravans The prime requirement of these floors is that they must feel rigid to walk across Care should be taken to ensure the floor design meets all local building codes The Table below gives recommendations for Perspex sheet thickness against panel size assuming a loading requirement of 5000 N m2 Table 13 Guideline thicknesses of Perspex required for different areas Panel Size mm x mm Minimum Sheet Thickness To Restrict Deflection to 1 4 Sheet Thickness 300 x 300 8mm 12mm 750 x 750 15mm 20mm 1000 x 1000 20mm 30mm 2000 x 1000 25mm 30mm 1500 x 1500 30mm 35mm The surface hardness of Perspex is usually acceptable for floors and if required the surface gloss can be refurbished by polishing The Perspex floor should be protected against damage arising from contact with a metal or wooden support structure This can be achieved by the use of acrylic compatible glazing rubbers Potential Performance Perspex www theplasticshop co uk 30 Design Guide Potential Performance Perspex www theplasticshop co uk Part 2 Design amp Applications 2 4 Lighting Traditionally a wide range of gloss opal colours have been used in lightin
15. 1 x 3 mm Perspex 26 1 x 6 mm Perspex 32 1 x 8 mm Perspex 34 1 x 12 mm Perspex 35 To maximise the efficiency of double glazing it is important to minimise sound leakage within the glazing profile 2 2 5 Heat Transfer Coefficient amp Thermal Conductivity Table 6 The heat transfer coefficient U value of Perspex and glass windows measured in W m2 C Glazing Option Air Gap Between Panels Heat Loss U Value Glass Perspex 3 mm single pane 5 6 5 2 5 mm single pane 5 5 4 9 3 mm double pane 3mm 4 0 3 6 3 mm double pane 12mm 3 1 2 9 3 mm double pane 20mm 2 9 2 7 Table 7 The thermal conductivity coefficient K value of Perspex and glass Unit Glass Perspex Wm m2 C 1 15 0 189 Potential Performance Perspex www theplasticshop co uk 26 Design Guide 2 2 6 Perspex UV Absorbing amp IR Transmitting Grades In addition to the standard grade of Perspex we also offer UV absorbing and IR transmitting grades Perspex Cell Cast VE and VA absorbing UV Light Perspex VE is available for applications where the minimum transmission of UV light is required e g the glazing of museum exhibits to protect delicate artefacts Perspex VE absorbs 99 99 of all incident UV light below 400nm Perspex VA has been developed for applications requiring extreme resistance to UV light It is therefore the preferred grade for glazing applications in tropical regions It is also suitable for
16. 3 o 1000 40 amp D mo v j w 5 3mm 1 1 1 D 500 20 3 3 1 1 1 1 0 20 40 60 80 100 120 140 km h 25 62 87 mph 11 27 8 39 m sec Pressure 75 470 920 N m Figure 16 The recommended thicknesses of Perspex for various wind loads when designing for rectangular windows with all edges fully supported Potential Performance Perspex www theplasticshop co uk 24 Design Guide Part 2 Design amp Applications Potential Performance Perspex www theplasticshop co uk 2 2 3 Installation 2 2 3 1 Mounting Details The preferred method of mounting Perspex glazing is between metal frames Aluminium profiles or glazing bars are generally acceptable As a general rule Perspex should be fixed in the frames with rubber profile sections as is the normal glazing practice If preferred flexible mastics may be used and polysulphide sealants have been found to be suitable for this purpose Silicone sealants can be used but as stated earlier it is very important to use rubber profiles or sealants which are known to be compatible with acrylic sheet In the event of any doubt the manufacturer s advice should be sought first When installing glazing in any frame system two critical observations need to be taken into account 1 Thermal expansion clearance 2 Rebate depth 2 2 3 2 Thermal expansion clearance Perspex has a high thermal expansion coefficient compared to trad
17. 8 16 Cream 133 29 Yellow 229 19 Yellow 260 19 Yellow 261 29 Yellow 2252 21 Yellow 2TL1 22 Yellow 2TL2 25 Orange 363 4 Orange 3TL1 18 Red 431 3 Red 433 2 Red 440 3 Red 4403 8 Red 4415 6 Red 4494 lt 1 Red 4TL1 18 Red 4TL2 14 Red 4TL3 15 Green 650 3 Green 692 21 Green 6TL1 8 Green 6TL2 6 Blue 727 5 Blue 743 4 Blue 744 lt 1 Blue 750 2 Blue 751 2 Blue 7033 8 Blue 7TL1 12 Violet 886 4 Grey 9981 8 Black 962 Infra Red transmitting 0 Black 9T30 0 35 Design Guide Part 3 Technical amp Performance Properties 3 1 1 3 Perspex Transparent Colours and Tints Table 16 Light Transmission 380 790 nm Perspex Grade Amber 300 38 Red 4401 8 Brown 504 53 Green 6600 14 Green 6T21 90 Blue 7703 8 Blue 7704 83 3 1 1 4 Perspex Neutrals for glazing Table 17 Perspex Grade Light Transmission 380 790 nm Neutral Grey 901 61 Neutral Grey 9T04 31 Neutral Brown 9T13 54 Neutral Grey 9T20 36 Neutral Grey 9T21 41 Neutral Grey 9T23 14 Neutral Grey 9T38 36 Neutral Grey 9T45 73 Neutral Grey 9T56 46 Neutral Grey 9HO3 14 Neutral Grey 9H04 35 Neutral Grey 9T9A 42 NB 1 Light transmission measurements have been measured on apparatus conforming to ASTM D 1003 Illuminant C Values to Illuminant D65 are virtually identical in most instances 2 All figures quoted are the results of tests on typical s
18. S SQ N w N wnh w N nl n m x zk hk SO SO SO KO SO S QO S S SO 00 N NIN OS OS 0S CI QI C I SS HA Part 2 2 0 2 1 2 2 1 2 2 2 22 3 2 2 3 1 2 2 3 2 2 2 3 3 2 2 4 22 5 2 2 6 2 3 2 3 1 2 3 2 2 3 3 2 3 4 2 3 5 2 3 6 2 4 25 1 2 5 2 25 3 2 5 4 25 9 2 6 1 2 6 2 Part 3 3113 3 1 1 4 3 2 3 3 3 3 1 3 3 2 3 3 3 Potential Performance Perspex www theplasticshop co uk Design amp Applications Perspex Products Perspex Glazing General Glazing Compatible Products Recommended Thickness of Perspex for Windows 23 Installation Mounting Details Thermal Expansion Clearance Rebate Depth Sound Reduction Index Heat Transfer Coefficient amp Thermal Conductivity Perspex UV Absorbing amp IR Transmitting Grades Glazing Applications Roofing Balcony Guards Security Glazing Boat Glazing Vehicle Glazing Flooring Lighting Visual Communications Illumination Luminance Light Transmission Diffusion Factor Light Source Spacing ratio Factors Affecting Perceived Colour Thickness Tolerance Surface Finish Technical And Performace Properties Weathering Light Transmission Properties Of Coloured Sheet Light Transmission Values of 3 mm Perspex Colours Perspex Opals including Perspex Spectrum LED Perspex Solid and Translucent Colours including Spectrum LED Perspex Transparent Colours and Tints Perspex Neutrals for Gl
19. Tensol 12 or Tensol 70 in order to avoid stress crazing This is most critical on line bent joints where EXTRU FIX may be more appropriate 1 3 1 3 Bonding to other Substrates metal wood glass etc The easiest way to bond Perspex to other substrates is by using a cyanocrylate adhesive Bostik 7452 is suggested As well as being useful for bonding small areas of Perspex to Perspex this system is also suitable for attaching fittings to Perspex Where there are high mechanical strength requirements a toughened acrylic adhesive such as EVO tech TA 431 is to be preferred Part 1 Fabrication Potential Performance Perspex www theplasticshop co uk 1 3 2 Fixing methods The use of bolts and screws is not normally recommended for securing Perspex sheet If such methods must be used care must be taken to ensure that adequate allowance is made for thermal expansion and contraction Oversized holes must be drilled and screws must not be over tightened Self locking nuts should be used and the use of cup washers is recommended to assist in spreading loads 1 3 3 Sealing Joints in Perspex and a variety of other materials can be effectively sealed with a suitable acrylic compatible silicone sealant In order to avoid stress crazing the sealant needs to be neutral cure A low modulus type such as Bondflex Low Modulus Silicone Sealant will best accommodate any movement in between the components The B
20. able from your supplier Users of other place to prevent hands being trapped during the materials mentioned in this publication but not operation of the press These should include guards produced by Lucite International are advised to and safety interlocks and all safety fixtures must be obtain Health and Safety information from the maintained in good working order suppliers Ovens should be fitted with fail safe thermal cut out switches to prevent the risk of overheating 1 8 Recycling Perspex acrylic sheet can be fully recycled back to its original monomer For further information on recycling Perspex sheet please contact your Perspex sales office 22 Design Guide Potential Performance Perspex www theplasticshop co uk Part 2 Design amp Applications Part 2 Design amp Applications 2 0 Perspex Products Perspex Cell Cast Acrylic Sheet Cast Perspex is the original cell cast product first produced 80 years ago It offers better optical properties and craze resistance than other acrylic sheet products and hence is often the choice for applications requiring critical visual performance It is available in a very wide range of colours and thicknesses An impact modified grade of cast sheet is also available as is a variety of textured surface products for glazing applications For full details of the products we offer please see our Product Range Perspex CC Continuous Cast Perspex continu
21. amp Performance Properties 3 0 Weathering Most grades of Perspex acrylic sheet have outstanding resistance to outdoor weathering and can be considered amongst the best of all plastics materials Under normal exposure conditions correctly fabricated self coloured signs made from Perspex will not lose mechanical strength over a typical design life of 10 years exposure outdoors in Europe Lucite International offers a 10 year guarantee on the mechanical performance of its standard Perspex acrylic sheets and copies of this document may be obtained from www perspex com During long term exposure outdoors especially in tropical climates all painted surfaces self coloured materials and even natural materials such as stone can be expected to show some colour change with time In terms of the light transmission value for clear Perspex 92 this will not fall below 85 The 10 year guarantee therefore applies to that period of exposure under normal conditions during which any colour change which may occur will remain unnoticed by the casual observer from street level It is important to note that new panels of Perspex installed alongside older panels of the same colour which have been exposed for some time will almost certainly display a difference in colour This is quite normal for most coloured surfaces and cannot be avoided 3 1 Light Transmission Properties Of Coloured Sheet Perspex sheet is produced to th
22. amples and do not constitute a specification 3 The above figures are for typical standard colours and are only a small representation of the Perspex colour range For details of other colours or the procedure for ordering special colours please contact your nearest Perspex sales office 3 2 Food Contact Perspex Cast Acrylic sheet is capable of complying to current EU and American FDA food contact regulations Please note that food contact compliance testing should be carried out on finished articles and not flat sheet samples For further information please contact your Perspex sales office Potential Performance Perspex www theplasticshop co uk 36 Design Guide 3 3 Technical Data 3 3 1 Physical and mechanical properties Part 3 Technical amp Performance Properties Table 18 Shows the typical physical and mechanical properties of Perspex cell cast acrylic sheet Property Test Method Units Values General Properties Density ISO 1183 g cm 3 1 19 Rockwell Hardness ISO 2039 2 M scale 102 Water Absorption ISO 62 0 2 Flammability ISO 11925 2 E Optical Properties Light Transmission ASTM D1003 3 mm gt 92 Refractive Index ISO 489 A 1 49 Thermal Properties Vicat Softening Point ISO 306A C gt 110 Coefficient of Thermal Expansion Linear ASTM D696 x 105 K1 7 7 Maximum Working Temperature C 80 85 Specific Heat ASTM C351 cal g C 0 35 The
23. ard Perspex sheet No significant change in visual appearance or physical performance will take place during ten years outdoors A high gloss hard surface Perspex is one of the hardest thermoplastics and remains aesthetically attractive for much longer than many other plastic sheet products High tensile strength and rigidity Perspex is ideal for applications where surfaces that are resistant to bending or deformation are required Lightweight Perspex is half the weight of an equivalent glass panel and is more easily transported installed and supported Good resistance to impact Perspex is internationally recognised as a safety glazing material meeting the requirements of ANSI Z 97 and BS 6262 Easy to clean The high gloss surface of Perspex makes it easy to clean keeping maintenance costs to a minimum Easily thermoformable Perspex is easy to thermoform with low cost tooling leading to cost effective production Excellent environmental credentials Perspex an efficiently produced non toxic pure material with a long service life Perspex can also be recycled all the way back to the original raw material monomer regardless of colour or aesthetic effect Potential Performance Perspex www theplasticshop co uk 4 Design Guide Part 1 Fabrication Engineering design data Part 1 Fabrication The long term mechanical performance of Perspex will depend on temperature and app
24. aric acid Saturated sol S 5 years Toluene U 7 days Dissolved Trichloroethane U 1 day Dissolved Trichlorethylene U 1 day Dissolved Tricresyl phosphate U 2 years Attacked crazed Water S 5 years White Spirit 5 5 years Slight crazing Xylene U 7 days Dissolved NOTE Chemical resistance tests are difficult to interpret accurately because plastics materials generally may be attacked in several ways The table must therefore be used with discretion and should be supplemented by component tests under actual service conditions Potential Performance Perspex www theplasticshop co uk PERSPEX Available to buy worldwide from theplasticshop co uk Freephone 0800 321 3085 International Phone 44 24 76 588 383 isales theplasticshop co uk www theplasticshop co uk For more details on any of the products featured in this brochure please contact our sales team on 0800 321 3085 Potential Performance Perspex www theplasticshop co uk theplasticshop co uk Lucite Zz International Perspex is a registered trademark of Lucite International a member of the Mitsubishi Rayon Group
25. azing Food Contact Technical Data Physical and Mechanical Properties Reaction to Fire Chemical Resistance 24 24 24 24 25 25 26 27 27 28 28 28 29 29 30 30 30 31 31 31 31 32 32 32 33 3 Design Guide Introduction Perspex acrylic sheet is a most useful material in the workshop because it can be used to make precision engineering components for both domestic and industrial products Typical applications include signs glazing safety screening roof lighting furniture lighting fittings and a great many industrial parts Perspex is manufactured in two forms cast and extruded sheet Perspex cast sheet is available in a wide range of thicknesses and colours including blocks colours and surface patterns Some differences exist between Perspex cast and Perspex XT extruded properties arising from their molecular structure and this can be reflected in their fabrication behaviour These differences are highlighted where appropriate in the handbook Otherwise fabrication behaviour may be assumed to be very similar for both products Outstanding Properties of Perspex Exceptional light transmission with virtually no colour bias even in thick blocks Clear Perspex transmits 92 of all visible light No other product offers better light transmission not even glass Excellent resistance to outdoor weathering We offer a ten year weathering guarantee on the outdoor performance of stand
26. communications and lighting applications 2 5 1 Illumination Lighting an internally illuminated sign made from Perspex acrylic sheet requires careful consideration to achieve maximum visual impact With the wide range of available colours of Perspex sheet and the many different types of light sources it is not possible to present a simple set of rules which assures the most effective results for every individual sign design For most types of sign however the method of lighting is predictable and general guidelines are given in this booklet which will enable the designer to create aesthetic appeal combined with a suitable level of luminance Where a sign is of unusual design it may be necessary to construct an experimental prototype in order to establish the most effective means of illumination For details of light sources electrical gear and additional technical support on lighting design the lamp manufacturer should be consulted Perspex for Displays e Surface Effects Perspex Frost Impressions Silk and Satin e Edge Effects Perspex Fluorescent Vario Metropolitan and Glass Look e Enhanced Chemical Resistance Perspex Forte e Perspex Vision for rear projection Colour Matching Our in house laboratory can match almost any colour as well as guaranteeing batch to batch colour consistency The following sections offer guidance on constructing signs made from Perspex 31 Design Guide 2 5 2 Luminance
27. crylic sheet prior to thermoforming This however is not necessarily the case for Perspex Continuous Cast or extruded sheet where pre drying is generally recommended 1 2 2 Heating When Perspex cast sheet is heated to 140 170 C it becomes flexible and rubber like and can be formed into complex shapes by the application of force such as air pressure or mechanical press clamping If held to that shape and cooled below 90 C it will retain the shape If reheated it will return to its original flat condition Cell Cast Sheet When Perspex extruded sheet is heated to this temperature range it behaves in a similar manner to cast sheet except that it is easier to deform requiring less force and will actually flow rather than stretch Consequently mouldings made from extruded sheet will not return to the flat condition on re heating Figure 4 illustrates the effect of heating on both cast and extruded sheet and as a general rule the preferred thermoforming temperature for cast sheet is 170 C and 155 C for extruded sheet When heating impact modified grades of Perspex it will be noticed that the sheet becomes opaque at the shaping temperature This is perfectly normal and the clarity will return when the shapings reach room temperature Optimum Maximum Oven Degradation Elongation Temperature Point Thermoforming Range Thermoforming Range Figure 4 Heating Perspex transition stages Moisture Melt Blisters Poin
28. cshop co uk Ceramic or Quartz Elements Operating Temperature 400 1000 C 752 1832 F 14 kW m 14 kW m Zi YZ Gres Ges Gps 200 C 200 C 390 C 390 C x Vv A Perspex 165 C 120 C 5mm 330 C 258 C 200 C 390 C SF eS 7 kW m Single Side Heating Double Sided Heating Figure 6 gives details of the heating of Perspex using typical infra red heaters When using infra red heaters the sheet should be When extruded sheet is freely heated it will exhibit heated simultaneously on both sides i e with the rather more shrinkage in the direction of extrusion use of double sided heater platens and very little across the direction of extrusion It is difficult to give precise figures for shrinkage of SAFETY NOTE extruded sheet because this will depend on the Infra red heaters as used on vacuum forming thickness and the heating time As a general rule machines can raise the temperature of the sheet 2mm sheet will shrink slightly more than 5mm sheet very quickly and overheating is possible If the when freely heated typically about 5 surface temperature of Perspex exceeds 200 C degradation will occur leading to decomposition When sheets are clamped cold in a frame prior to and the evolution of flammable decomposition heating the shrinkage is restrained and no allowance gases Initial indications of this for cast sheet are for shrinkage should usually be necessary the appearance of blisters on the surface followed by a crackling sound a
29. d above Extruded BS 476 Pt7 Class 4 all thicknesses United States Cast UL 94 HB Extruded UL 94 HB Perspex cast acrylic sheet burns at a rate similar to that of hard woods but with low smoke evolution Encapsulating the edges of all Perspex sheets into metal glazing profiles greatly reduces the ease of ignition Potential Performance Perspex www theplasticshop co uk 37 Design Guide Potential Performance Perspex www theplasticshop co uk Part 3 Technical amp Performance Properties 3 3 3 Chemical Resistance Perspex has very good resistance to attack by water alkalis aqueous inorganic salt solutions and most common dilute acids It is difficult to generalise about the effects of organic materials on Perspex some liquids have no effect at all some cause swelling crazing or weakening and some dissolve it completely Table 20 gives an indication of the chemical resistance of Perspex cast clear as judged by the visual appearance of samples of dimensions approximately 100 x 12 x 6 mm immersed in typical solutions or liquids at 20 C Table 20 The chemical resistance of Perspex cast clear sheet at 20 C The following symbols have been used in the table S Satisfactory no apparent effect apart from possible staining A Some attack evident swelling or slight crazing U Unsatisfactory the sample has dissolved swollen decomposed etc
30. d thicknesses of Perspex for various wind loads when designing for square windows with all edges fully supported NB The figures for sheet thickness apply to areas bounded by the curves Example of the use of Figure 16 To determine the thickness of Perspex that must be used for a window 1100 x 1520 mm with a wind load of 90km h 380 N m2 determine the point of intersection between wind load line and shorter panel size see the dotted line The recommended thickness is 6 mm NB At the recommended thickness the sheet can deflect under full wind load and it is therefore important to use the appropriate depth of rebate as recommended in Table 4 to ensure the sheet remains firmly fixed in the frame Part 2 Design amp Applications 2 2 2 Recommended thickness of Perspex for Windows The required thickness is dictated by two considerations The first is the desired impact strength and the second is the wind loading which an external window must sustain In most countries statutory requirements or codes of practice exist which specify wind loads for building structures and these must be followed For example in the United Kingdom BS CP3 Chapter V Part 2 is the Code of Practice to be followed when designing windows or glazed structures Figures 15 and 16 give the recommended thicknesses of Perspex for various wind loads 2000 80 12mm E 1500 6 3 8mm 10mm 3 5mm 6mm a 6 6 f FN
31. ded Perspex for barrel vaults where the barrel height is 1 8 span dimension Barrel Span mm Sheet Width 1000mm 2000mm 800 4mm 6mm 1100 5mm 6mm 1400 6mm 8mm 1700 6mm 8mm 2000 8mm 10mm NB 1 All the above calculations have been based on an assumed wind load of 1000 N m2 2 When using impact modified grades the above thicknesses should be increased to the next size Table 12 The recommended thickness of cast and extruded Perspex for flat roofs Roof Span mm Sheet Width 800 1000 1200 800 5mm 6mm 6mm 1400 6mm 8mm 8mm 2000 6mm 8mm 10mm The values for Table 10 assume a snow load of 750 N m2 28 Design Guide Part 2 Design amp Applications Potential Performance Perspex www theplasticshop co uk 2 3 2 Balcony Guards Perspex has been used for balcony guard in fill panels across Europe for over 20 years Typically 6mm and 8mm sheets are used to ensure rigidity and impact strength Following testing approval has been gained to ANSI Z 97 BS 6206 and NFP 01 013 The exceptional weathering performance of Perspex ensures that no significant loss of mechanical properties takes place over a number of years We recommend that infill panels made from Perspex should be supported on all 4 edges to provide sufficient panel rigidity at a minimum sheet thickness In order to reduce the possibility of the infill panel being sprung from its frame the rebate depth should be at least 20mm If only 2 edg
32. e highest quality standards which ensure colour consistency from batch to batch and sheet to sheet Since the colour extends throughout the thickness of the sheet scuff and scratch marks have little effect on the appearance of illuminated colours Most coloured Perspex sheet is produced so that the light transmission decreases with increasing thickness However for those applications where this effect would not be appropriate i e where different sheet thicknesses of a colour may be needed on the same sign Constant Transmission CT colours are available giving the same colour transmission irrespective of sheet thickness CT Colours are identified by the letter T in the colour reference number e g Opal White 1T02 Red 4T17 etc 34 Design Guide Part 3 Technical amp Performance Properties Potential Performance Perspex www theplasticshop co uk 3 1 1 Light Transmission Values of 3mm Perspex Colours 3 1 1 1 Perspex Opals including Perspex Spectrum LED Table 14 Perspex Grade Light Transmission 380 790 nm 028 25 030 67 040 46 050 36 069 9 1212 0 1T04 30 1T21 4 1T67 21 1177 35 1TL1 37 1TL2 51 3 1 1 2 Perspex Solid and Translucent Colours including Spectrum LED Table 15 Perspex Grade Light Transmission 380 790 nm Cream 12
33. e humidity can result in a dimensional increase of 0 3 and due allowance should be made for any possible expansion to avoid distortions occurring in the sign Perspex XT extruded acrylic sheet can exhibit slightly more dimensional change in humid environments due to the lower initial moisture content of extruded sheet The coefficient of linear thermal expansion of thermoplastic materials is greater than that of most other materials and therefore where significant variations in temperature are expected during the service use of the outdoor application an allowance must be made for thermal movement of the material When Perspex sheet is to be used for any outdoor applications adequate allowance must be made for thermal expansion and contraction during the design and construction of the sign In Europe external signs can be subjected to extremes of temperature from 20 C in winter to 30 C in summer a temperature variation of 50 C From many years practical experience it has been found that as a general rule and bearing in mind that darker colours will be more reactive to heat than lighter colours an expansion allowance of 0 5 or 5mm per metre run length on both panel dimensions should be sufficient to accommodate any temperature and humidity variations It is equally important to bear in mind that when fixing Perspex sign panels into frames the rebate depth of the framing must be sufficient not only to accept the expan
34. e support is possible then the thickness of the Perspex sheet should be increased because of the lower flexural strength of the fixing system Also minimum rebate depths should be increased to 35mm to prevent spring out occurring Bolt fixing at the edge of a Perspex sheet should NOT be used as the primary support method without the use of load spreading devices because of problems associated with stress build up and crazing in service Similarly the panel must be fitted on the inside of a support post to ensure that any impact loads bear against metal supports and not the fixing bolts All bolt holes must be drilled oversize and contain Neoprene washers Also a good quality Neoprene gasket should be used between Perspex and any metal 2 3 3 Security Glazing Clear Perspex of the correct thickness can be used as security glazing for protection against projectiles from hand guns and other firearms The superb clarity of Perspex makes it particularly attractive for the protection of prestigious offices banks and other public buildings Perspex may also be used as self supporting structures free from metal framing for added design appeal Perspex can be laminated with other glazing materials e g glass and polycarbonate to produce high specification bullet resistant glazing 2 3 4 Boat Glazing Outstanding weathering performance and its resistance to marine environments are the reasons why Perspex is used t
35. edge is essential for flame polishing Specialised equipment is available otherwise a small blowtorch type gas air flame can be used The technique requires some practice to achieve the desired level of skill Only the slightest impingement of the hottest part of the flame is required rapidly passing the jet across the work Great care must be taken not to ignite the surface and it should be noted that flame polishing can produce highly stressed edges Annealing of the work piece will be necessary if the flame polished edges are to be cemented or decorated Flame polishing can be difficult on certain heavily pigmented colours resulting in a matt finish or discolouration 1 1 11 5 Hand polishing Hand polishing is suitable for the restoration of the original gloss finish after minor surface scratching Deep scratches should first be removed using 600 grade waterproof abrasive paper applied wet with a light circular motion To avoid optical distortions the abraded area should be much larger than the damaged surface to feather the edges Final polishing of the matt abraded area can be carried out using proprietary acrylic polishes Good quality metal polish intended for use on silver plate can be used provided the product has been tested and found to be compatible with Perspex Potential Performance Perspex www theplasticshop co uk 10 Design Guide 1 2 Thermoforming General Part 1 Fabrication To thermoform Perspex
36. eir number type light output colour and position in the sign case 2 Materials the light transmission reflection absorption and diffusion factors of the Perspex grade and thickness used 3 The Sign Case its dimension particularly its depth and the reflection factor of the paint or other finish used on the inside of the case 4 Light Absorption the effect of absorption of light by the lamps and electrical equipment within the case 5 Maintenance the reduction in the light output of the lamps with increasing age and the influence of dust inside the case Part 2 Design amp Applications 2 5 3 Light Transmission Planning authorities often apply a simple formula to assess the brightness of a sign to ensure it conforms to the agreed limits and this requires the light transmittance value of the sign making material The light transmission values of all Opal White grades and most of the popular Perspex sign colours are listed in section 3 1 2 5 4 Diffusion Factor When designing signs made from Perspex sheet consideration must be given to the diffusion factor of the chosen colour A good diffuser when illuminated will scatter direct or transmitted light uniformly in all directions If a material has a diffusion factor of between 0 82 and 0 89 it can be considered to have maximum degree of diffusion All Opal White Perspex sheet grades have excellent diffusion except Opal White 030 which is designed to give
37. es Table 20 Continued The chemical resistance of Perspex cast clear sheet at 20 C Chemical Concentration Resistance Exposure Time Notes Glycerol glycerine S 5 years Hexane S 168 days Slight crazing Hydrochloric acid 10 S 168 days Slight crazing Conc S 168 days Slight crazing Hydrocyanic acid U 1 day Dissolved Hydrofluoric acid Conc U 1 day Swollen amp Soft Hydrogen peroxide 10 vol S 1 year 90 U Mercury S 2 years Methylene chloride dichloromethane U 1 day Dissolved Methyl salicylate U 7 days Dissolved Nitric acid 10 5 1 year Conc U 1 day Swollen Oils transformer S 5 years Staining diesel S 1 year Hazing olive S 5 years Slight crazing paraffin medicinal S 5 years silicones A 1 year Swollen Oxalic acid Saturated sol S 5 years Severe crazing Perchloroethylene U 5 years Severe crazing Phenol Saturated sol U 7 days Dissolved Phosphoric acid 10 S 5 years Conc U 7 days Severe crazing Potassium dichromate 10 S 5 years Slight staining Potassium hydrozide Saturated sol S 168 days Potassium permanganate N 10 sol S 5 years Severe staining Sodium carbonate Saturated sol S 5 years Sodium chlorate Saturated sol S 5 years Sodium hydroxide Saturated sol S 5 years Sodium hypochlorite 10 chlorine sol S 5 years Sulphuric acid 10 S 5 years 30 S 1 year Slight edge attack Conc U 1 day Swollen Tart
38. f the curvature Cloth covered mould Heated Perspex Figure 10 Single curvature thermoforming 15 Design Guide Part 1 Fabrication Potential Performance Perspex www theplasticshop co uk Drape forming is another single curvature thermoforming technique Slightly more force is applied by draping the hot sheet over a mandrel mould and holding it there with several layers of soft mould cloth until it has cooled See Figure 11 Cloth former Figure 11 Drape forming j 1 2 6 2 Tubes Tubes can be made by laying the hot Perspex sheet into a split cylindrical mould and dropping this into a jig to keep it tight Allowance has to be made for thermal contraction and some experimentation may be required to obtain the correct blank size Once shaped the split line may be cemented Heated Perspex Mould in jig Hinged mould Figure 12 illustrates the method and tooling The technique is useful for producing large diameter tubes for display models for example which cannot be conveniently made by extrusion or casting 16 Design Guide 1 2 6 3 Local bending Local bending sometimes referred to as line bending is a very important technique for producing display items point of sale and many more components from Perspex including boxes shelf racks light fittings food trays etc Perspex sheets are softened along a narrow line by a strip heater usually a hot wire When the shaping temperature is reached the sheet
39. g applications however the increasing popularity of LEDs has not only led to the emergence of thinner light boxes with improved energy consumption but also to the use of grades of Perspex providing better diffusion Perspex Crystal Clear Frost S2 000 is an ideal material where maximum light output is required and Perspex Frost S2 1T96 is the optimal material where maximum diffusion is required All of our Frost products have the added advantage of retaining the Frosted surface even after thermoforming 2 5 Visual communications Over the years Perspex has established itself an envious reputation as one of the most creative flexible and eye catching products in the market for corporate imaging signage Point of Sale displays and shop fitting From international companies to smaller specialist outlets Perspex is used to create signs and displays that are long lasting attractive and cost effective Perspex for Signage e Perspex Colours and Opals including Perspex Spectrum LED available in thicknesses from 3mm to 30mm to allow production of signs and letters e Perspex Secret Sign a single sided matt product which appears black when non illuminated and either white red green or blue when the material is back lit e Perspex Duo a dual layer of black and either Gold or Silver which can be engraved to allow the base colour through e Perspex S Lux D Lux and Prismex our patented edge lit lighting technology for
40. gure 2a Breaking along the scribline 1 1 5 Laser Engraving Perspex is easy to engrave using pantographs or CNC engraving machines Laser engraving can also be carried out to give remarkable fine detail on Perspex The use of coolants is generally unnecessary for mechanical engraving other than the use of a compressed air jet directed on to the cutting head to remove swarf and cool the cutter Filling is best carried out using one of the usual setting waxes Paints can be used but it is most important to use those paints intended for use with acrylic sheet and known to be compatible When intending to engrave Perspex and fill with paint especially for outdoor use annealing of the engraved sections before filling is strongly recommended to prevent subsequent crazing Potential Performance Perspex www theplasticshop co uk 8 Design Guide Part 1 Fabrication 1 1 6 Drilling Standard woodworking twist drills can be used for all normal drilling work with Perspex It is advisable to re grind twist drills to give a zero rake Figure 3 demonstrates the preferred cutting angles Slow spiral polished flats 130 a oe A Zero rake Lip angle clearance 12 15 Re ground cutting edge with zero rake ie ground face is perpendicular to surface of Perspex Figure 3 A standard drill 130 with cutting edges re ground for use with Perspex Wherever possible the work should be supported by a back stop made
41. high UV intensity street lighting applications VA can also be a preferred product for picture or artwork glazing applications where maximum UV protection coupled with excellent colour rendition is required Part 2 Design amp Applications Non visible gt lt Visible light Ultra violet Violet Blue Green Yellow Red 100 p Perspex Nr H 47 5 80 Clear 000 a z 7 2 y E 70 rn 60 Silicate 1 Perspex o 50 Glass e j VE Opal 031 2 pouhe gt E 40 Glazing f 5 Perspex a VA Cl ar 004 30 HE gi 2 Hi Perspex 10 Hl VE Clear 003 0 24 200 250 300 350 400 450 500 550 600 650 700 750 Figure 18 Spectral transmittance of 3 mm Perspex Wavelength nanometres cast sheet grades compared with silicate glass Perspex Cell Cast Black 962 transmitting infra red light Perspex Black 962 is a unique product which whilst appearing black to visible light gives excellent transmission in the near IR region 850nm The product finds uses particularly in remote control and infra red monitoring devices 100 AT 962 6MM SP 962 3MM SP Figure 19 Spectral transmittance of Perspex 962 mm 900 1000 1100 Potential Performance Perspex www theplasticshop co uk 27 Design Guide Part 2 Design amp Applications Potential Performance Perspex www theplasticshop co uk 2 3 G
42. high light transmission with only moderate diffusion Most translucent Perspex colours have diffusion factors in excess of 0 80 and can be considered to be good diffusers 2 5 5 Light Source Spacing ratio Uniform luminance of a sign made from Perspex sheet is dependent on the diffusion factor of the Perspex grade and the spacing of the light source whether this be LEDs or lamps Generally if the diffusion factor is over 0 80 a spacing ratio of 1 to 1 5 should prove satisfactory This ratio is calculated as follows Distance between light source centres Light source spacing ratio Distance from light source centre to Perspex sheet If a number of different colours are used in one sign then no fixed rule can be applied to obtain the level and uniformity of luminance required and a prototype should be constructed to confirm the desired effect A prototype sign will also ensure that the correct complementary colour balance will be achieved between the different illuminated colours without any unexpected and unwanted visual colour distortions Potential Performance Perspex www theplasticshop co uk 32 Design Guide Part 2 Design amp Applications Potential Performance Perspex www theplasticshop co uk 2 6 Factors Affecting Perceived Colour Perspex offers the sign maker endless It is therefore strongly recommended that when opportunities with colour from the vast array making fascia signs the cut panels
43. hroughout the world as a high specification boat glazing product A wide range of attractive tints are available in various thicknesses to provide style safety and comfort 29 Design Guide 2 3 5 Vehicle Glazing Since its introduction as a tough and durable product for aircraft glazing Perspex has found many new uses within vehicle glazing not only because of the many attributes listed previously but also because of its good chemical resistance to motor oils and fuels Its ease of fabrication permits Perspex to be manufactured into articles not possible with glass Perspex may easily be refurbished by polishing Typical automotive glazing products made from Perspex include Caravan windows Motor cycle windshields Glider and helicopter glazing Commercial aircraft interior window panels Marine glazing Submarine periscopes Vehicle Registration Plates Car wind deflectors Truck visors Car wind deflectors Vehicle Registration Plates 2 3 6 Flooring Many entertainment buildings e g dance halls and restaurants either interior or exterior use the light transmitting property of Perspex to provide design features Perspex sheets and blocks are used because of their resistance to breakage weathering and scratching Part 2 Design amp Applications Thermoformed acrylic sheet is now almost exclusively used as the glazing for touring caravan windows where all the requirements for light weight safety good
44. in a cool stress free machining temperature 2 Perspex is a brittle material It is therefore important that only light machining cuts are taken and feed rates are kept slow Various coolants can be used including water and water air mists soluble oils and compressed air Soluble oils must be oil in water emulsions and must not contain solvents which may cause stress cracking When machining drilling or cutting Perspex the heat build up can generate stress in the final work piece which can induce stress cracking a phenomenon common to many plastics materials when stressed The risk of crazing can be reduced or eliminated by the simple process of heat annealing and it is strongly recommended that all machined or worked components made from Perspex are annealed Please see section 1 5 for full details of the annealing process Table 2 Conditions for sawing Perspex Part 1 Fabrication 1 1 1 Cutting Tools To achieve a good finish on Perspex all cutting tools must be kept sharp Most hand tools designed for use with wood and soft metals are suitable for use with Perspex except laminate cutters guillotines and blanking dies If necessary these tools can be used with Perspex provided the sheet is heated to at least 50 C Most power tools can be used and HSS tools bits are suitable to achieve a good cut finish For lengthy runs tungsten carbide tipped blades and tool bits are recommended for long life For
45. is bent and clamped or placed in a jig to cool Suitable heaters for local bending work include nichrome wire and electrical heating tapes depending on the radius of curvature needed and thickness of sheet used Perspex heated locally along Figure 13 Cooling jig for locally bent Perspex For a sharp bend the width of the heating zone should be about 4 to 6 times the thickness of the sheet When local bending of long shallow sections some warpage will be noticed along the line of the bend This is always possible with local bending and is very difficult to avoid If warpage is totally unacceptable the only alternatives are full sheet thermoforming or cementing To reduce warpage it is advisable to produce as near to a right angled bend as can be accepted since this will provide extra stiffness to the panel Distortion tends to be greater the more shallow the angle of bend NB Local heating of Perspex especially line bending induces localised stresses in the line bend due to shrinkage along the heated section Stress cracking can occur especially with extruded sheet in the presence of solvents in cements inks or spray paints To minimise the risk of crazing all locally bent components should be annealed after bending Part 1 Fabrication line of ZZ TV Potential Performance Perspex www theplasticshop co uk For sheets thicker than 5mm double sided heating is recommended and although the eq
46. is planned such as vacuum metallization or screen printing it is advisable to wash the sheet surfaces to be decorated with clean fresh water using a chamois leather or soft cloth This has the advantage of removing all traces of static charge from the sheet after removal of the film which might otherwise attract dust For all general purpose cleaning operations Perspex should be washed simply with clean cold water to which a little detergent has been added The use of any solvents such as methylated spirits turpentine white spirit or proprietary window cleaning products is neither necessary nor recommended Chamois leather is suitable for cleaning but cloths must never be used dry Proprietary acrylic polishes Proprietary acrylic polishes are available to restore the surface finish of Perspex glazing in the event of accidental scratches and these products are available from your local Perspex supplier Potential Performance Perspex www theplasticshop co uk 6 Design Guide 1 1 Machining The machining characteristics of Perspex are similar to those of soft brass or hard aluminium but there are two important differences 1 Perspex will soften if heated above 80 C Considerable heat can be generated by machining causing stress so it is therefore very important that heat build up is kept to a minimum The use of coolants during machining is recommended to assist in lubrication removing swarf and to mainta
47. itional glazing materials and allowance within the frames must be made in both directions for thermal expansion and contraction Failure to observe this rule can lead to stresses in the sheet which can cause distortions in the panel and crazing at the edges of the sheet in time An allowance of 5 mm per metre run length should be allowed in both dimensions during installation This figure has been found from long experience to be sufficient for all locations and climates 2 2 3 3 Rebate depth It follows from the above that the rebate depth must be sufficient to allow for the expansion clearance and also the thermal contraction that can take place in winter Rebate depth must also be sufficient to prevent the sheet from being deflected out of the frame in gale force winds Figure 17 shows a typical profile assembly and Table 4 the recommended rebate depth for various panel sizes based on installation at 20 C Figure 17 Mounting details for Perspex glazing Table 4 The recommended rebate depth for glazed Perspex panels in frames Nominal Panel Minimum Rebate Contraction Expansion Total Rebate Size A Depth B Allowance C Allowance D E 1000mm 30mm 5mm 5mm 30mm 2000mm 35mm 10mm 10mm 55mm 3000mm 40mm 15mm 15mm 70mm 25 Design Guide Part 2 Design amp Applications 2 2 4 Sound Reduction Index Table 5 The Sound Reduction Index of Perspex in decibels db Glazing Option Sound Reduction Index db
48. lazing Applications 2 3 1 Roofing The below figures were originally derived from NB It is the installer s responsibility to ensure stress strain studies From experience gained over that the design and construction of any Perspex 20 years it is known that if the minimum cold bend glazing structure complies with the statutory radius is reduced further there is a greater risk of requirements of all local building codes or official sheet crazing in service building control standards Perspex from Lucite has been extensively used as a roofing product in applications such as moulded dome lights and continuous roof lights or barrel vaults Typical sheet thickness recommendations are given below Table 8 The minimum cold bend radius for Perspex barrel vaults in temperate climates Sheet Thickness mm 3 4 5 6 Perspex Cast 600 800 1000 1200 Perspex Extruded 900 1200 1500 1800 Table 9 The recommended thickness of cast and extruded Perspex for barrel vaults where the barrel height is 1 2 span dimension Barrel Span mm Sheet Width 1000mm 2000mm 800 3mm 4mm 1100 4mm 5mm 1400 5mm 5mm 1700 6mm 6mm 2000 6mm 8mm Table 10 The recommended thickness of cast and extruded Perspex for barrel vaults where the barrel height is 1 4 span dimension Barrel Span mm Sheet Width 1000mm 2000mm 800 4mm 5mm 1100 4mm 5mm 1400 5mm 6mm 1700 6mm 8mm 2000 6mm 8mm Table 11 The recommended thickness of cast and extru
49. lied stress and when designing engineering components these considerations must be taken into account Table 1 gives details of the maximum long term and short term design stress levels derived from fracture mechanics studies that can be safely applied to engineering components made from Perspex cast sheet Please refer to the short term physical properties in Technical Appendix section 3 3 1 Table 1 Design data for Perspex cast acrylic sheet at 20 C Property Units Short Term Intermittent Long Term Continuous 6 hours 10 years Tensile strength kgf cm 170 88 unexposed MPa 17 8 6 Ibf in 2500 1250 Tensile strength kgf cm 140 70 exposed MPa 14 7 Ibf in 2000 1000 Modulus kgf cm 2 5 x 104 1 3 x 104 GPa 2 5 1 2 Ibf in 3 6 x 10 1 8 x 105 Poisson s ratio 0 39 0 40 Thermal and moisture expansion Perspex in common with all acrylic materials will expand or contract with temperature change and may be subject to water absorption over long periods of service It is therefore important to consider these inherent characteristics when designing with Perspex to create durable impactful and cost effective signs Acrylic sheet may absorb up to 2 of water over long periods and this absorption can result in dimensional changes in the sign The level of absorption and the dimensional change depends on the relative humidity of the atmosphere and the initial water content of the sheet As a general rule 100 relativ
50. nt when cutting the sheet can give rise to a reduction in opacity into blanks prior to thermoforming For Perspex cast sheet colours the show face is always that surface covered by the printed masking film 12 Design Guide Part 1 Fabrication 1 2 6 Methods of thermoforming Perspex can be thermoformed by a number of simple techniques the most suitable of which will depend on the amount of stretch required to achieve the desired result For blowing domes and similar shapes a blowing table will be needed fitted with toggle clamps and using steels rings to clamp the hot sheet down Figures 7 and 8 illustrate typical basic designs Pressure Working Needle control valve Compressed air in Figure 7 Typical blowing table Figure 8 Toggle clamp Potential Performance Perspex www theplasticshop co uk 14 Design Guide Part 1 Fabrication Potential Performance Perspex www theplasticshop co uk T an Figure 9 illustrates typical clamping designs to hold the hot sheet under the blowing ring using toggle clamps a i e 1 2 6 1 Single curvature thermoforming Because there is virtually no stretching single curvature thermoforming requires very little force Figure 10 shows a typical mould for making motor cycle windscreens The hot Perspex is laid on to the mould covered with several layers of mould cloth to prevent surface marking The sheet then takes up the shape o
51. o ensure that the vinyl film products chosen are suitable for use in contact with Perspex and are formulated for long term outdoor exposure 1 5 Annealing The recommended annealing process for cast Perspex is as follows 1 Place the components in an air circulating oven at room temperature 2 Raise the oven temperature at a rate not exceeding 18 C per hour 3 When the annealing temperature of 90 C is reached maintain the temperature for a 1 hour for up to 3mm thickness b 2 hours for up to 6mm thickness c 4 hours for up to 12mm thickness d 6 hours for up to 20mm thickness 4 Cool to room temperature at a rate not greater than 12 C per hour Part 1 Fabrication 1 4 3 Stress in acrylic sheet Stress is a phenomenon which can affect many materials including acrylic sheet It is produced by the application of force and if excessive can result in total mechanical failure Long before these limits are reached with acrylic sheet the appearance of fine crazing or stress cracking can occur over time which at best is unsightly and at worst can reduce the mechanical properties of the material Stress may be generated by thermoforming at too low a temperature by the application of mechanical force or by the generation of heat during fabrication e g machining and drilling Crazing is induced by the release of stress especially inherent stress brought on by exposure to chemical solvents environmental stress
52. oated continuous cast acrylic sheet manufactured by Mitsubishi Rayon Company MRC using an in line process that offers significant advantages over traditional hard coating methods When allied with the technical strengths of the continuous cast acrylic sheet to which the hard coat is applied the result is a superior product appropriate for a wide range of applications requiring excellent abrasion resistance 23 Design Guide 2 2 General Glazing 2 2 1 Compatible products When installing Perspex glazing panels it is essential to ensure that all ancillary products and materials used in contact with the sheet are fully compatible with acrylic Failure to observe this may result in permanent damage to the Perspex glazing For example rubber sealing strips and profiles should be made from butyl rubber or polysulphide rubber Certain EPDM rubbers can be used as alternatives as can compatible silicone sealants but in all cases it is important to seek the advice of the product supplier before use Plasticised PVC sealing strips should not be used under any circumstances as these are known to cause stress crazing of acrylic sheets 2000 80 12mm 10mm E 8mm z 1500 60 2 p g 6mm 2 4 5mm a 9 ke o 1000 40 D D 3mm o o 2 2 500 20 zi a 0 20 40 60 80 100 120 140 km h 25 62 87 mph 11 27 8 39 m sec Pressure 75 470 920 N m Figure 15 The recommende
53. orming Perspex XT the sheet should be dried before use preferably with the masking film removed At least 24 hours drying time may be required at 75 85 C 18 Design Guide 1 3 Cementing Fixing amp Sealing 1 3 1 Cementing All grades of Perspex can be bonded using acrylic cements A range of Tensol cements and Tensol adhesives is produced and supplied by Bostik Ltd to whom all enquiries should be directed The correct selection of adhesive is vital in order to produce bonds with good strength durability and optical clarity 1 3 1 1 Lamination Face to Face Bonding Two sheets of Perspex from Lucite may be laminated together using the solvent free clear adhesive Tensol 70 from the Bostik range Tensol 70 has excellent optical clarity and good mechanical strength 1 3 1 2 Edge Bonding Solvent welding is the quickest and easiest way of forming edge bonds The best results can be easily and safely achieved when EXTRU FIX Tensol 12 are applied using an EVO PLAS application bottle Features of this system which is intended for indoor applications include good resistance to stress crazing even on line bent sections and high clarity bubble free bonds Filled systems such as Tensol 12 offer slightly better gap filling properties For external applications a highly durable adhesive such as Tensol 70 is required When cementing Perspex XT extruded items great care must be taken when using
54. ostik range of adhesives Cleaning solvents Mirror Adhesive and Anti static Cleaner is available from most Perspex stockists and distributors Alternatively please contact Bostik directly Before cementing the user should study the safety data sheets and ensure that the adhesive is suitable for the intended application 19 Design Guide 1 4 Printing Painting amp Surface Decoration 1 4 1 Screen Printing spray painting and hot foil stamping Perspex can be readily screen printed painted or hot foil stamped Paints and screen inks formulated for use on acrylic sheet must be used and it is strongly recommended that the sheet surfaces are washed before decorating to obtain maximum service life outdoors Screen inks are available for thermoforming and it is important to ensure that any screen inks or paints applied to Perspex have adequate UV stability 1 4 2 Self adhesive vinyl films Coloured designs and letters can be applied to Perspex to make signs using self adhesive vinyl films These products are usually translucent light transmitting films In recent years the use of vinyl films has become extremely popular following the development of small high speed plotting and cutting machines Designs can be quickly scanned or drawn using CAD techniques This method of sign making lends itself well to low cost production of short runs As in the case of screen printing and spray painting it is essential for users t
55. ous cast sheet has a very narrow thickness tolerance and is easy to thermoform It is suited to glazing and thermoforming applications requiring improved optical and chemical properties compared to extruded sheet 2 1 Perspex Glazing For many years Perspex acrylic sheet has been used as a glazing material initially for aircraft canopies and then for a wide variety of architectural automotive and industrial applications which take advantage of some of the many outstanding properties of Perspex Exceptional light transmission with no inherent edge colour Clear Perspex transmits 92 of all visible light We offer a ten year weathering guarantee on the outdoor performance of most grades of Perspex sheet No significant change in visual appearance or physical performance will take place during ten years outdoors Low weight and safety Perspex is half the weight of an equivalent glass panel and is five time stronger It is internationally recognized as a safety glazing material meeting the requirements of ANSI Z 97 and BS6262 Perspex XT Extruded Sheet The standard grade of extruded sheet is ideal for general glazing applications and is available in a range of clear opal and tinted grades Perspex extruded IM impact modified grades are also available see later Please refer to our Product Range for full details of the available product range ShinkoLite MR200 ShinkoLite MR200 is a double sided hard c
56. rmal Conductivity Coefficient K Value Wmm C 0 189 Heat Transfer Coefficient U Value W m C 3mm single pane 5 2 5 mm single pane 4 9 Mechanical Properties Tensile strength 5mm min ISO 527 MPa 75 Elongation at Break 5mm min ISO 527 4 Flexural Strength 2mm min ISO 178 MPa 116 Flexural Modulus 2mm min ISO 178 MPa 3210 Impact Strength Charpy unnotched ISO 179 kJ m 12 Poisson s Ratio 0 38 3 3 2 Reaction to Fire Perspex is a combustible material and if ignited will continue to burn Perspex cast acrylic sheet has a combustion rate similar to hard woods but unlike many other plastic materials in the event of a fire Perspex produces no hydrogen cyanide or halogen based toxic gases and very little smoke Perspex extruded sheet has a rate of combustion similar to cast sheet but will eventually produce molten droplets which will continue to burn For full details of the behaviour of Perspex grades to many international fire tests see table 19 Table 19 Fire test performance of Perspex to the more important international fire tests Country Product Type Test Result Class Europe Cast amp ISO 11925 2 E Extruded France Cast NFP 92 307 M4 Extruded NFP 92 307 M4 Germany Cast DIN 4102 B2 Extruded DIN 4102 B2 Holland Cast NEN 6005 Class 3 surface spread of flame Extruded NEN 6006 Class 4 contribution to flashover United Kingdom Cast BS 476 Pt 7 Class 4 under 3 mm Cast BS 476 Pt 7 Class 3 for 3 mm an
57. s the sheet begins to 1 2 4 Cooling decompose After thermoforming Perspex cast sheet should be kept on the mould until the temperature has If blisters or bubbles appear in extruded sheet reached about 60 C Uniformity of cooling is without any indication of decomposition it is important to prevent warpage and stress but more likely that this is due to absorbed moisture mouldings should not be left on the mould too requiring an overnight drying cycle at 75 85 C long otherwise they may contract tightly on to the mould and damage when lifted off 1 2 3 Shrinkage The production processes for cast and extruded 1 2 5 Thermoforming of colours Perspex sheets differ fundamentally and both Certain Perspex colours can change slightly materials will exhibit some shrinkage when heated during the heating process especially if the sheet to thermoforming temperature When cast sheet is overheated It is always important to ensure is heated for example it will shrink such that on that the first surface is always the show face as the cooling again it will be approximately 2 smaller second surface can be slightly duller after heating in both length and breadth with a perceptible It is also important to note that as coloured sheet increase in thickness No further shrinkage will then is stretched during thermoforming there will be an take place on reheating but this initial shrinkage inevitable thinning of the sheet in those areas which must be taken into accou
58. sion clearance but also an equivalent contraction allowance otherwise panels could be blown out of their frames in gale force winds during the winter months Potential Performance Perspex www theplasticshop co uk 5 Design Guide Part 1 Fabrication Masking protection The surfaces of Perspex are covered with a masking film for protection during transport storage and fabrication A thermoformable masking can be applied on request subject to minimum order quantities Storage Perspex sheet must be stored indoors preferably in a cool well ventilated dry room maintained at a reasonably constant temperature lt is recommended to store sheets horizontally It is strongly recommended not to stack pallets so as to create internal stresses and alter the flatness of the sheets Perspex can also be stored vertically in racks no more that 30cm in width to give adequate support and stability It is recommended to avoid storage of the Perspex sheet for more than 6 months Furthermore failure to allow expansion allowances will result in warping of the sheet Preparing for fabrication The masking film can frequently be left in place during fabrication work and all marking out drawn on the film The film must be removed before thermoforming operations Cleaning Surfaces of items made from Perspex should not generally require cleaning until after fabrication and before packaging If however any surface decoration process
59. t Can Occur Potential Performance Perspex www theplasticshop co uk 11 Design Guide Part 1 Fabrication Except when local bending the entire area of Perspex sheet should be uniformly heated and for cast sheet the best equipment for this is an air circulating oven with accurate temperature control Both clear and coloured sheets may be laid on clean horizontal shelves in the oven but when optical quality is paramount sheets should be hung vertically to avoid any surface damage or contamination during heating Suitable hanging clamps can be devised to suspend the sheets along their longest dimension Vertical hanging is also the recommended method for heating extruded sheets in an air circulating oven Heat exchanger j Perspex Matt metal shelves j Figure 5 Air circulating oven Potential Performance Perspex www theplasticshop co uk Figure 5 gives a diagrammatic description of a typical air circulating oven suitable for heating Perspex sheets As an alternative to air oven heating certain infra red heaters can be used to heat Perspex sheet e g quartz and ceramic elements but since these can heat the Perspex surfaces very quickly heaters and heated platens must be designed to give uniform heating under carefully controlled conditions to avoid overheating and degrading the sheet Thermostat 12 Design Guide Part 1 Fabrication Potential Performance Perspex www theplasti
60. t line by deeply scribing one surface several times with a sharp metal scriber clamping the sheet with the scribed line uppermost and pressing sharply down over the edge of a bench See Figures 2 and 2a for details of scribe breaking Fig 2 Part 1 Fabrication Fig 2a OR Figure 2 A Scribe breaking Perspex suitable for cutting Perspex 1 1 4 Laser Cutting Perspex may be laser cut see Figure 3 and very complex and intricate shapes may be cut out using this type of equipment Thicknesses up to 25mm can be cut although some experimentation will be necessary to achieve the optimum quality of edge finish above 12mm Some stress can be generated around the edge of laser cut Perspex and it is important that the laser beam is accurately focussed If cementing or surface decorating up to a laser cut edge it may be found necessary to carry out a short annealing cycle see later to reduce the risk of fine crazing along the edge It may be found preferable to remove the top masking film to improve the edge polishing effect from the laser NB When laser cutting Perspex as with all other materials it is very important to provide adequate ventilation at the cutting head to remove any traces of unpleasant combustion vapour Expert advice should be sought from the machine manufacturers if in any doubt Before laser cutting Perspex please read the safety notes on flammability and combustion products on page 26 Fi
61. uipment can be built in the workshop excellent commercial machines are readily available Figure 18 shows a typical cooling jig for local bending For local bending of thick cast sheet where a sharp radius is required it can sometimes be helpful to machine a V groove along the inside face to approximately half the sheet depth This has the effect of removing material and making it easier to bend into a sharp angle but at the risk of producing a weaker edge Retaining strips f Wood or metal base 1 2 6 4 Vacuum Forming Vacuum forming is a well established process for shaping articles from polymer sheet materials and many commercial computer controlled vacuum forming machines equipped with infra red heating platens are available for high speed production work Perspex extruded sheet is ideally suited to the vacuum forming process because due to its lower melt strength it can be drawn by the relatively low vacuum forces has high extensibility and therefore high definition within the mould Perspex cast sheet requires higher shaping forces and is therefore less suitable for the low pressure vacuum forming process unless the shapes are quite large and simple in design such as a domestic bath 17 Design Guide Part 1 Fabrication 1 2 6 5 Moulds For long production runs and high quality mould detail cast aluminium moulds cored for water cooling are recommended A smooth matt finish is preferred and all dust must be

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