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Polyester Porcessing and Troubleshooting Guide

1. Part Runner Min Runner Thickness Length Diameter Inches Inches Inches 0 020 0 060 Up to 2 0 0625 0 020 0 060 Over 2 0 125 0 060 0 150 Up to 4 0 125 0 060 0 150 Over 4 0 1875 0 150 0 250 Up to 4 0 250 0 150 0 250 Over 4 0 3125 Generous radii should be provided in the runner system where the sprue joins the runner On multiple cavity molds with primary and secondary runners the primary runner should extend beyond the intersection of the secondary runner in order to provide a cold slug well for the runner flow front This length should be at least equal to the basic runner diameter D See Figure 2 1 Runner length should be kept at a minimum Parts requiring close dimensional control in multi cavity molds should have balanced runner systems Close tolerance parts should not be designed into family mold layouts Gates Various types of gates used in injection molds are shown in Figures 2 2A 2 2B and 2 3 gt 0 D Cold Slug elbere o Figure 2 1 Balanced Runner and Cavity Layout 2 1 Ce J SPRUE A simple design for single cavity molds SIDE or EDGE A simple design for multicavity and symmetry on circular shapes molds Suitable for medium and thick sections Suitable for thick sections L d e C PIN 3 plate tool Used to minimize finishing RESTRICTED or PIN Provides simple degating where edge gating is undesirable and for automatic and fini
2. Ticona Celanex Vandar Impet and Riteflex Thermoplastic Polyesters Processing and Troubleshooting Guide PE 6 Typical Injection Molding Parameters Molding Parameter Celanex Vandar Impet Riteflex Mold Temperature C F Melt Temperature C F 38 121 100 250 227 260 440 500 38 121 100 250 238 282 460 540 110 121 230 250 271 299 520 570 24 93 75 200 171 266 340 510 Screw Speed rom 60 125 60 125 60 125 60 125 Back Pressure psi 0 50 0 100 0 25 0 100 Injection Speed Fast Medium to Fast Medium to Fast Fast Injection Pressure Low to Medium Low to High As Needed Low to Medium Cushion Inches 0 125 0 125 0 125 0 125 0 250 Barrel Settings C F Feed Zone 232 249 450 480 232 254 450 490 260 271 500 520 154 243 310 470 Center Zone 238 254 460 490 238 260 460 500 271 277 520 530 171 249 340 480 Front Zone 243 260 470 500 243 266 470 510 277 282 530 540 171 254 340 490 Nozzle 249 260 480 500 249 271 480 520 277 288 530 550 171 260 340 500 For parameters specific to Celanex 16 series grades refer to Table 3 2 Chapter 3 For parameters specific to Vandar Grades 6000 AB100 AB875 and 9114 see Table 3 3 Chapter 3 Typical Extrusion Processing Parameter
3. Equipment For maximum resistance to abrasion and corrosion extruder screws breaker plates screens adapters and dies should all be made of corrosion resistant metals Extruder Barrel Standard extruders having barrel length to diameter ratios equal to or greater than those shown in Table 5 1 are recommended for processing polyesters Higher L D ratios provide a more homogeneous melt and higher output rate for a given extruder size Screw Design Screw designs should have a compression ratio between 3 1 and 4 1 the ratio between the feed zone channel depth and the metering zone channel depth As shown in Figure 5 1 the feed zone screw depth should be approximately 0 400 inch deep while the metering zone screw depth should gradually reduce to approximately 0 100 inch Table 5 1 Barrel Length to Diameter Ratios Product L D Ratios Celanex 30 1 Vandar 30 1 Impet 30 1 Riteflex 20 1 Feed Section Transition Section Metering Section FER SS SEE ean Screw depth 0 400 inch Screw depth 0 100 inch Figure 5 1 Typical Screw Design 5 1 Recommended lengths of the feed transition and metering zones each representing a percentage of the total screw length are shown in Table 5 2 Table 5 2 Typical Lengths of Feed Transition and Metering Zones Zone Distribution Transition Product Feed Metering Celanex Vandar 33
4. 238 260 460 500 243 266 470 510 Nozzle 249 260 480 500 249 271 480 520 277 282 530 540 277 288 530 550 For parameters specific to Celanex 16 series grades see Table 3 2 page 3 2 For parameters specific to Vandar Grade 6000 AB100 AB875 and 9114 see Table 3 3 page 3 4 171 254 340 490 171 260 340 500 3 1 Table 3 2 Molding Conditions for Celanex Polyester Celanex Grades All Other Celanex Grades 38 121 100 250 Molding Parameter Mold Temperature C F 3116 3216 3316 66 93 150 200 Melt Temperature C F 238 249 460 480 238 260 460 500 Screw Speed rom 60 125 60 125 Back Pressure psi 0 25 0 50 Injection Speed fast fast Injection Pressure psi Cushion Inches as needed to fill mold 0 125 low to medium 0 125 Barrel Settings C 9F Feed Zone 238 249 460 480 232 249 450 480 Center Zone 243 254 470 490 238 254 460 490 Front Zone 243 254 470 490 243 260 470 500 Nozzle 249 260 480 500 249 260 480 500 Celanex Thermoplastic Polyester Molding Conditions Table 3 2 contains recommended molding conditions for all grades of Celanex thermoplastic polyester Drying Requirements Celanex resins should be dried to a moisture level equal to or less than 0 02 before injection molding Refer
5. E Dried together with the virgin resin before molding Note Celanex thermoplastic polyester grades 2016 3116 3126 3216 3226 and 3316 have been approved by Underwriters Labs for regrind usage up to 50 The UL94 V 0 rating is retained with part thicknesses as small as 0 75 mm 0 030 inch Drying Resins It is extremely important to thoroughly dry virgin and regrind material and minimize exposure to ambient air before molding parts High moisture levels can M Cause processing problems M Create surface imperfections including voids B Degrade the material causing significant reduction of mechanical properties Drying Equipment Because of the importance of properly dried polymer we strongly recommend using dehumidifying hopper dryers such as the unit shown in Figure 2 10 Hot air ovens should not be used because E Trays filled to a depth of more than 1 to 1 5 inches can cause inadequate drying E Drying time is extended because of poor heat transfer E Different materials being dried in the same oven can be inadvertently mixed causing contamination If hot air ovens are absolutely necessary they should be used following the above precautions as long as the recommended moisture level is reached See Table 2 7 on pg 2 13 2 11 1 Vacuum Loader 2 Drying Hopper 3 Filter 4 Process Air Blower 5 Desiccant Cartridge 6 Dehumidified Air Reheater 7 Regeneration Blower 8 Regenerat
6. Impet Riteflex 50 Feed zone length should comprise at least 25 of the total screw length A long and gradual transition section of at least 25 is also recommended since sharp or short transition sections can cause high barrel pressures and higher melt temperatures due to high shear especially at higher speeds Length of the metering zone and the screw depth are Critical in maintaining optimum control of melt temperature and output consistency Too long or shallow a metering zone increases the melt temperature due to shear while short and deep metering zones can result in pressure fluctuations surging and nonuniform output A typical polyethylene type screw design meets the requirements for processing polyesters Screws designed for nylon where the transition zone is of proper length have also been successful Breaker Plate and Screens Screens usually 80 100 mesh are recommended for processing Celanex Vandar and Riteflex polyesters Screens are used to protect the die from being damaged by foreign matter and to increase back pressure especially when mixing fillers or pigments A breaker plate usually incorporated at the end of the screw is used to support the screens Dies Dies must be streamlined having no areas where material can be trapped or hung up Thermoplastic materials exposed to high temperatures for prolonged periods degrade and contaminate subsequent extruded product Processing Proced
7. 4 Melt Temperature i i 3 4 Mold Temperature N i 3 4 Injection and Holding Pressure i i 3 4 Injection Speed r i 3 5 Cycle Time f r f f 3 5 Back Pressure and Screw Speed B B 3 5 Startup i 3 5 Shutdown f 3 5 Impet Polyester Molding Conditions f 3 6 Drying Requirements i i i i i 3 6 Mold Temperature i 3 6 Riteflex Polyester Molding Conditions i i i 3 7 Drying Requirements i i 3 7 Mold Temperature i i i 3 7 Injection and Holding Pressure i i 3 7 Injection Speed i f 3 7 Screw Speed and Cushion f 3 7 Shutdown f f 3 7 Chapter 4 Troubleshooting Injection Molding Introduction i 4 1 Troubleshooting Guide i i i 4 1 Chapter 5 Processing Extrusion General i f i i 5 1 Safety and Health Information f 5 1 Drying Requirements i 5 1 Equipment 5 1 Extruder Barrel A i j 5 1 Screw Design i 5 1 Breaker Plate and Screens i i 5 2 Dies i i f f 5 2 Processing Procedures f i 5 2 Startup i 5 2 Purging and Shutdown i f i 5 2 Wire Coating f i 5 4 Cooling Trough 1 B 5 4 Tube E
8. Material bridging in transition section Barrel temperature too low Change to screw with longer feed section Raise temperature in rear zone Raise temperature settings Compression ratio of screw too low Increase back pressure Change screw Watt density in heater too low Increase wattage Change heater bands Cold spots in extruder sections Roll too hot Get more heat to area along barrel extension to die neck Check thermocouples and controllers for accuracy Insulate exposed areas to prevent heat loss Reduce roll temperature Material too hot Reduce melt temperature Inspect functioning of controller heaters and thermocouples 6 4 NOTICE TO USERS To the best of our knowledge the information contained in this publication is accurate however we do not assume any liability whatsoever for the accuracy and completeness of such information Further the analysis techniques included in this publication are often simplifications and therefore approximate in nature More vigorous analysis techniques and or prototype testing are strongly recommended to verify satisfactory part performance Anyone intending to rely on such recommendation or to use any equipment processing technique or material mentioned in this publication should satisfy themselves that they can meet all applicable safety and health standards It is the sole responsibili
9. Molding Conditions Table 3 3 contains recommended molding conditions for all grades of Vandar alloys Drying Requirements Vandar alloys should be dried to a moisture level equal to or less than 0 02 before injection molding Refer to pages 2 11 through 2 13 for more information on drying Melt Temperature For unreinforced grades 6000 8929 9056 and 9116 preferred melt temperatures are M 260 282 C 500 540 F for grade 6000 Do not exceed 293 C 560 F B 238 266 C 460 510 F for grades 8929 9056 and 9116 Do not exceed 271 C 520 F E For other grades of Vandar alloys see Table 3 3 Mold Temperature To maximize impact strength of parts made of Vandar alloys use mold temperatures below 49 C 120 F Table 3 3 Molding Conditions for Vandar Alloys Mold temperatures for glass filled grades can be higher up to 93 C 200 F Injection and Holding Pressure Because of ease of flow grades 8929 9056 and 9116 require only moderate injection pressures typically in the range of 50 75 of machine maximum Unreinforced grades 2100 2500 4602Z 6000 and glass filled grades 4316 4612R 4632Z 4662Z require higher injection pressures Holding pressures are typically in the range of 60 80 of the injection pressures Since Vandar alloys crystallize rapidly holding pressures and holding time are dependent on part thickness Very thin walled parts may require only moderate holding pressur
10. applications Polyester resin is extremely fluid in the melt state and therefore flows well in a mold However rapid crystallization imposes limitations on how far the resin will flow in filling a mold Among the process variables that influence flow are melt temperature mold temperature injection pressure and composition Wall thickness also influences resin flow Thicker sections allow for larger flow than thinner sections Figure 2 4 shows the influence of wall thickness on flow Mold Shrinkage As with all other crystalline resins the mold shrinkage of polyester is anisotropic Shrinkage in the direction of material flow is always less than in the transverse direction Injection Pressure Flow Inches w Mold Temp 66 C 150 F Melt Temp 249 C 480 F 0 020 040 060 080 Thickness Inches Figure 2 4 Flow vs Wall Thickness for Celanex 3300 Variables that significantly affect part shrinkage during molding include B Melt mold temperatures BW Injection pressure E Flow direction gate runner design and size E Part or wall thickness and size E Presence low shrinkage or absence high shrinkage of fibrous reinforcements To accurately design molds it is strongly recommended that the mold design engineer determine shrinkage of the actual part by using prototype tooling before making the final tool Measurements of the material to be used should be made on p
11. no areas where material can hang up Cone length the distance between the die face and the point where the polyester coats the wire is very important Generally speaking it is between 1 2 and 2 inches and is determined by trial and error Too long a cone may sag and set before drawing is finished while too short a cone can produce pinholes and tearing Before the coated wire enters the water cooling trough it passes through an air cooling gap which is important in shrinking the coating on the wire This governs adhesion of the insulation and should be balanced with the proper cone length to insure the desired integrity of the coating Cooling Trough A water cooling trough is used to reduce the melt temperature and harden the coating The water temperature in the trough is critical Too low water temperatures of 4 16 C 40 60 F will freeze the polyester coating into a semi crystalline or amorphous state Post crystallization of the polyester coating can occur and cause it to take a set on the spool or winding reel A water temperature of 38 54 C 100 130 F reduces post crystallization and eliminates or reduces spool set giving better mechanical properties 5 4 Tube Extrusion Polyester can be readily extruded into tubing up to 0 375 inch 9 5 mm without requiring special equipment Control of the polyester melt temperature is important If too high it can reduce the melt strength causing irregul
12. the order in which they are listed under Riteflex Moisture in material Trapped air Dry material to proper moisture level before use Raise rear barrel temperature e e Use correct screw Use more back pressure Check controllers Degradation of resin due to high tempera tures and or long holdup time Lower temperatures Increase extrusion rate Use correct screw Look for hang ups in extruder and die Check functioning of controller heaters and thermocouples Resin moisture content too high Draw down ratio too high Dry material to proper moisture level before use Reduce draw down ratio Contamination See Contaminated Extrudate Short cone too fast a draw Lengthen cone reduce draw rate Material temperature too low Raise melt or die temperature Poor blends of pigments or fillers Cooling too fast Blend more homogeneously before extrusion Use correct screw Reduce pigment or filter loading Lengthen air gap Slow down extrusion rate Degradation of resin See Bubbles Cone too long cooling too soon before it coats Shorten cone 6 1 Table 6 1 Troubleshooting Guide Extrusion Continued Problem Contaminated extrudate Diameter fluctuates Out of round deformed nonconcentric Typical Cause Poor handling of resin
13. to pages 2 11 through 2 13 for more information on drying Melt Temperature The melt temperature should be 238 260 C 460 500 F Avoid melt temperatures in excess of 271 C 520 F Provide adequate ventilation in the molding area Also keep barrel residence time to a minimum for optimum part properties Mold Temperature Mold temperatures for Celanex polyesters are generally in the 38 121 C 100 250 F range For unfilled resins use 38 66 C 100 150 F For glass reinforced resins use 66 93 C 150 200 F Unlike most other glass reinforced resins Celanex polyester yields a smooth glossy finish even when molded in a relatively cold mold Higher mold temperatures are used to obtain the ultimate in surface gloss and uniformity maximize crystallinity and minimize mold and post mold part shrinkage Low mold temperatures are sometimes used to help prevent sink or warpage Injection and Holding Pressure Because of its ease of flow Celanex polyesters require only moderate injection pressures typically in the range of 50 75 of machine maximum Holding pressures are typically in the range of 60 80 of the injection pressures Since Celanex polyester crystallizes rapidly holding pressures and holding time are dependent on part thickness Very thin walled parts may require only moderate holding pressure while thick section parts may require high holding pressure and long holding times Inj
14. 6500 0 002 0 005 0 2 0 5 J235 0 004 0 006 0 4 0 6 J600 LW6443R 0 004 0 006 0 4 0 6 6400 6406 0 004 0 006 0 4 0 6 Low Warp Flame Retardant 7305 7316 0 003 0 005 0 3 0 5 7304 7700 0 005 0 007 0 5 0 7 7716 0 002 0 005 0 2 0 5 Data obtained from laboratory test specimens 2 5 Table 2 4 Shrinkage Vandar Alloys In In Flow Grades Direction Unreinforced General Purpose 2100 2500 4602Z 0 017 0 022 1 7 2 2 6000 0 005 0 009 0 5 0 9 Unreinforced Flame Retardant 8000 0 025 0 028 2 5 2 8 Glass Reinforced 4361 0 002 0 005 0 2 0 5 4612R 0 006 0 008 0 6 0 8 4632Z 0 004 0 006 0 4 0 6 4662Z 0 003 0 005 0 3 0 5 Unreinforced Higher Flexural Modulus 8929 0 015 0 020 1 5 2 0 9056 9114 9116 0 011 0 016 1 1 1 6 9500 0 011 0 016 1 1 1 6 Mineral Reinforced 2122 0 013 0 015 1 3 1 5 Table 2 5 Shrinkage Impet Polyesters In In Flow Grades Direction Glass Reinforced 320R 0 004 0 0070 0 4 0 7 330R 0 001 0 0030 0 1 0 3 340R 0 001 0 0020 0 1 0 2 Mineral Filled 610R 0 005 0 0080 0 5 0 8 630R 0 003 0 0050 0 3 0 5 830R 0 001 0 0030 0 1 0 3 Table 2 6 Shrinkage Riteflex Polyester Elastomers In In Flow Grades Direction 640 0 009 0 011 0 9 1 1 655 0 014 0 016 1 4 1 6 677 0 018 0 022 1 8 2 2 Data obtained from laboratory test specimens 0 125 inch thick R
15. Celanex polyesters purge the machine to remove any other type of plastic previously run Polymers suitable for purging are low or high density polyethylene polypropylene and polystyrene For parts requiring subsequent painting or adhesive application use low molecular weight PBT such as Celanex 1400 to purge the machine When the cylinder is completely free of the material used for purging raise cylinder temperatures to 232 243 C 450 470 F before feeding Celanex polyester into the machine After several shots to clear residual foreign polymer set the desired molding temperatures and start the regular molding on cycle Shutdown For brief shutdown periods 10 15 minutes 1 Lower material temperature to 232 238 C 450 460 F Purge the machine periodically preferably on cycle to prevent excessive residence time in the cylinder For longer shutdown periods 1 Remove the Celanex material from the barrel 2 Turn cylinder heaters off with the nozzle maintained at molding temperature Purge the machine until the material temperature is no higher than 232 C 450 F Then shut down the machine When shutting down a screw machine leave the screw in the forward position If a mass of molten material is left in front of the screw at shutdown restarting the machine will be delayed until the solidified slug of material in front of the screw is remelted 3 3 Vandar Thermoplastic Alloy
16. Corrective Action Protect resin keep clean Celanex e Vandar e Impet Riteflex e Dirty extruder Remove all resins and clean e e e Extruder corrosion Use corrosion resistant parts which contact melted resin e e e Dirty regrind Variation in take off speed Clean extruder Use clean regrind dried to proper moisture level Check tension control Raise pressure on tractor treads Surging Raise screw speed Raise back pressure with screen pack Heat cycles Use variable transformers with time proportioning con trollers Make sure controllers are ON most of the time Too slow a draw rate Reduce cone length Too much tension on sizing plates tube extrusion or sizing die Shorten sizing die length by eliminating a plate or two Use water or water and soap lubricant at sizing die Uneven feed to extruder Check uniformity of extrusion rate cross head pressure Lower temperature at rear barrel Cool throat of hopper Moisture Misshapen die Dry material to proper moisture level before use Replace die Correct guider tip Varying cooling rate Fix depth of water submersion Center the die Coating sets after sagging Lower melt temperature Step up rate of draw down by increasing extruding speed increasing draw down ratio or shortening con
17. Mold temperatures below 93 C 200 F may lead to incomplete crystallization and dimensional changes especially if finished parts are subjected to post mold elevated temperature use 3 6 Riteflex Thermoplastic Polyester Elastomer Molding Conditions Table 3 5 contains recommended molding conditions for all grades of Riteflex polyester elastomer Drying Requirements Riteflex polyester should be dried to a moisture level equal to or less than 0 05 before injection molding Refer to pages 2 11 through 2 13 for more information on drying Mold Temperature Begin at the lower end of the molding temperature range using short shots Injection and Holding Pressure Keep injection pressure low when starting the molding cycle this will produce short shots Gradually increase pressure by 50 100 psi until the cavity fills completely As complete parts are ejected from the mold raise injection pressure approximately 100 psi making sure the material does not flash Injection Speed For all grades of Riteflex polyester elastomers the injection speed of the machine should be ata medium setting Screw Speed and Cushion Screw speed should be 60 125 rpm and the cushion pad should be 0 125 0 250 inch Shutdown When a machine is being shut down from molding Riteflex polyester the nozzle and barrel heaters should be maintained at the molding temperature The machine should be first purged with polyethylene or polypropylen
18. ar wall thickness Too low a melt temperature can result in poor tube finish uneven dimensions and weld lines Use the temperature ranges given in Tables 5 3 through 5 6 as starting points The same type of dies and temperature ranges used in wire coating are used in free extrusion of tubing The extruded tube of resin is pulled through one or more sizing rings which are immersed in the water cooling trough see Figure 5 3 Vacuum Tank A vacuum sizing tank is generally used for tubing 0 50 inch 12 7 mm or larger The vacuum in the water cooling trough causes the tube to expand to the sizing die set to the required outside tube dimensions As before melt and vacuum tank temperatures are most important because polyester is a semi crystalline material with a relatively narrow melt freeze range Haul off Unit Take up Reel Unit Water Trough Sizing Dies Low pressure Air Supply Figure 5 3 Polyester in Tube Extrusion Sheet Extrusion As shown in Figure 5 4 polyester sheeting is extruded with standard equipment including an extruder a sheet die a polishing roll stand pull rolls edge trim knives tension rolls and a winder unit A flex lip coat hanger type die is best suited for sheet extrusion Unlike the T type dies it does not have stagnant areas that allow material to hang up and cause degradation The flex lip must be adjusted to provide a uniform flow across the face of the d
19. bution excessive thermal degradation 50 feed zone 25 transition zone Screw Design 25 metering zone The metering type screw generally recommended for polyester resins is shown in Figure 2 7 The bottom portion of this illustration shows the three major B Compression ratio 3 1 to 4 1 sections of the screw the feed zone transition zone B L D ratio 16 1 to 24 1 Injection Cylinder Feed Hopper Heater Bands Nozzle Nonreturn Flow Valve Assembly Rotating and Reciprocating Screw Screw Piston Shaft Figure 2 6 Single Stage Reciprocating Screw Injection Molding Machine E Overall Length Flight L h gt c Valve ight Lengt Metering Feed Outside Depth y Y Diameter Depth y Transition Zone Metering Zone Figure 2 7 Recommended Metering Screw 2 9 If you have any problems or questions regarding proper screw design contact Product Information Services at 1 800 833 4882 or the manufacturer of your equipment Nozzle A simple free flow type nozzle with an independent heater band temperature controller is recommended Free flowing nozzles require melt compression suck back control on the machine Nonreturn Valves Figures 2 8 and 2 9 show the check ring and internal ball check nonreturn valves used on reciprocating screw injection molding machines These valves are shown in both the plastication and injection cycle
20. d need only be fast enough to retract the screw before the mold opens Generally screw speeds used are in the 25 to 50 rpm range A normal back pressure level should be under 50 psi Startup Before using Vandar alloys purge the machine to remove any other type of plastic previously run Polymers suitable for purging are low or high density polyethylene polypropylene and polystyrene For parts requiring subsequent painting or adhesive application use low molecular weight PBT such as Celanex 1400 to purge the machine When the cylinder is completely free of the material used for purging raise cylinder temperatures to the recommended ranges see Table 3 3 before feeding Vandar alloy into the machine After several shots to clear residual foreign polymer set the desired molding temperatures and start the regular molding on cycle For initial molding start with short shots and increase pressure until filled Then raise the pressure by an additional 100 psi Shutdown For brief shutdown periods 10 15 minutes 1 Ensure that the material temperature is no higher than 232 C 450 F no higher than 215 C 420 F for AB100 AB875 and 9118 Purge the machine periodically preferably on cycle to prevent excessive residence time in the cylinder For longer shutdown periods 1 Remove the Vandar material from the barrel 2 Turn cylinder heaters off with the nozzle maintained at molding temperature Purge the mach
21. e After no more Riteflex polyester elastomer issues from the nozzle the heating cylinder should be completely purged of Riteflex polyester elastomer and the machine may be shut down Table 3 5 Molding Conditions for Riteflex Polyester Elastomer Riteflex Grades Molding Parameter Mold Temperature C F 640 24 52 75 125 655 24 52 75 125 677 38 93 100 200 Melt Temperature C F Screw Speed rpm 182 204 360 400 60 125 221 238 430 460 60 125 238 266 460 510 60 125 Back Pressure psi 0 50 0 50 0 100 Injection Speed fast fast fast Cushion Inches 0 125 0 250 0 125 0 250 0 125 Barrel Settings C F Feed Zone 163 182 325 360 199 216 390 420 232 243 450 470 Center Zone Front Zone 182 204 360 400 216 238 420 460 243 254 470 490 Nozzle 182 199 360 390 182 204 360 400 216 232 420 450 216 238 420 460 238 249 460 480 249 260 480 500 3 7 3 8 Chapter 4 Troubleshooting Injection Molding Introduction Many processing problems are caused by easily corrected conditions such as inadequate resin drying incorrect temperatures and or pressures etc Often solutions to these problems can be found by following the recommendations in Table 4 1 Try them in the order in which they are
22. e 2 3 Gate and Mold Design Affect Part Strength Gate location should be selected carefully to minimize possible part distortion or adverse effects on part dimensions due to anisotropic shrinkage see Mold Shrinkage page 2 4 For best results the gate should be located so as to achieve balanced flow in all directions and minimum flow length from the gate to the extremities of the part Where this is not possible the gate should be located so that the flow direction is along the axis of the most critical dimension since the mold shrinkage is considerably less in the direction of flow particularly in glass fiber reinforced grades To minimize breakage and reduction in length of the glass fibers in the reinforced grades it is desirable to gate the part in a thick rather than a thin walled section and to incorporate radii where the runner joins the gate This is illustrated in Figure 2 3 Gate size recommendations keyed to part thickness are given in Tables 2 2A and 2 2B 2 3 Table 2 2A Size Recommendations Rectangular Edge Gate for Celanex Impet and Vandar Higher modulus grades Polyesters Part Thickness Gate Dimensions Inches Inches Depth Width Land Length Less than 0 030 To 0 020 To 0 040 0 040 0 030 0 090 0 020 0 060 0 030 0 090 0 040 0 090 0 125 0 060 0 085 0 090 0 130 0 040 0 125 0 250 0 085 0 165 0 130 0 250 0 040 Table 2 2B Size Recommendations Direc
23. e and decreased pressure Try higher and lower mold temperature Increase mold closed time Lower material temperature by Lowering cylinder temperature Decreasing screw rotational speed Lowering back pressure Try differential mold temperatures to counteract warp Jig the part and cool uniformly Check for contamination Brittleness Dry the material before use Check for contamination Lower melt temperature and or residence time Lower material temperature by Lowering cylinder temperature Decreasing screw rotational speed Lowering back pressure Lower mold temperature Raise mold temperature Reduce amount of regrind in feed Delamination Raise temperature of mold and or material Check for and eliminate any contamination Dry the material before use Increase injection speed 4 5 Table 4 1 Troubleshooting Guide Injection Molding Continued Problem and Corrective Action Poor Dimensional Control Celanex Vandar Impet Riteflex Set uniform cycle times Maintain uniform feed and cushion from cycle to cycle Eliminate any shot to shot machine variation Fill the mold as rapidly as possible Check machine s hydraulic and electrical systems for erratic performance Increase gate size Balance cavities for uniform flow Reduce number of cavities in the mold Add vents Check for da
24. e length Cool faster by reducing air gap from die to water trough or by raising output Take up pressure too high Put slack in wire line Lower capstan tension Lengthen cooling so extrudate is set before take up 6 2 Table 6 1 Troubleshooting Guide Extrusion Continued Problem Out of round deformed nonconcentric Continued Out of round buckling or folding Extruder overloading Shrink back Rough finish Typical Cause Die off center Corrective Action Center die Celanex Vandar Impet Riteflex Guider tip too flexible Use shorter guider tip Use bigger tip with same diameter hole e e e Hole in guider tip not small enough for wire diameter Hang up on die face or guider tip Use guider tip with smaller hole Remove imperfections Melt tension varies Make hole in guider tip smaller or center the die Too fast a draw rate Lengthen cone reduce vacuum for slower draw rate short cone Draw down ratio too high Reduce draw down ratio Compared with ratio of guider tip size to wire size ratio of die size to coated wire size is too low Feed section has too deep a flight depth Increase the draw ratio Use screw with shallower feed Use lubricant Rear temperature too low Increase rear temperature Check rear zone thermo couple and controller Wedg
25. e while thick section parts may require high holding pressure and long holding times To maximize toughness of parts molded of Vandar alloys avoid overpacking the material Vandar Grades AB100 21 52 70 125 Molding Parameter Mold Temperature C F 9114 29 52 85 125 AB875 21 52 70 125 6000 38 121 100 250 All Other Grades 38 121 100 250 Melt Temperature C F 199 210 390 410 218 227 425 440 188 216 370 420 260 282 500 540 238 266 450 510 Screw Speed rpm to match cycle 60 125 60 125 Back Pressure psi 0 50 0 100 0 100 Injection Speed Slow Continuous medium to fast fast Injection Pressure psi Start with short shots increase until fill and add 200 psi medium to high medium to high Cushion Inches 0 125 0 250 0 125 0 125 Barrel Settings C F Feed Zone 199 390 204 400 177 199 350 390 243 254 470 490 232 243 450 470 Center Zone 204 400 210 410 185 207 365 405 249 260 480 500 238 249 460 480 Front Zone 210 410 216 420 191 213 375 415 254 266 490 510 243 254 470 490 Nozzle 210 410 216 420 193 216 380 420 260 271 500 520 249 260 480 500 Vandar grades 8929 and 9116 require moderate injection pressure 50 75 of machine capacity Vandar 9114 may require a reverse barrel profile 3 4 Injection Speed Fast fill speed is desirable for the higher modulus Vanda
26. ecrease booster time Adjust feed for constant cushion Decrease injection hold time Increase mold closed time Lower mold temperature Lower cylinder and nozzle temperature Check mold for undercuts and or insufficient draft z Use proper mold release Sticking on the Core Increase injection pressure Increase booster time Increase injection speed Decrease mold closed time E Decrease core temperature 4 8 Table 4 1 Troubleshooting Guide Injection Molding Continued Problem and Corrective Action Sticking on the Core Continued Check mold for undercuts and or insufficient draft Sticking in Sprue Bushing Raise mold temperature Celanex Vandar Impet Riteflex Decrease injection pressure Decrease hold time Decrease injection time Decrease booster time Increase mold closed time Increase mold temperature at sprue bushing Raise nozzle temperature Check sizes and alignment of holes in nozzle and sprue bushing holes in sprue bushing must be larger Check mold and nozzle design Provide more effective sprue puller Weld Lines Increase injection pressure Increase injection forward time Increase injection speed Raise mold temperature Raise material temperature by Raising cylinder temperature Increasing screw rotational speed Increasing back pressure Vent the cavity in the weld area Pr
27. ection Speed Fast fill speed is desirable because Celanex polyester solidifies very rapidly once it enters the mold cavity In some cases reduced fill speed can help cure warpage problems induced by orientation of the glass fibers in the material Cycle Time Because Celanex polyester solidifies rapidly cycle times can be extremely short Plunger forward times need only be long enough to deliver the molten charge to the mold and hold the material under pressure until the gate freezes 3 2 The part should be sufficiently set up so that when it is ejected any impact does not cause dents or any other distortions Consequently overall cycle time is a function of part size and wall thickness Generally cycles for Celanex polyester molding vary from as little as 5 seconds for small thin walled parts to 40 45 seconds for large thick walled parts Cycle times over 45 seconds are encountered only in rare instances where molds must be opened closed slowly due to special coring or where inserts must be loaded into the mold Back Pressure and Screw Speed Use low back pressure and minimum screw speed when molding glass fiber reinforced Celanex polyester in a screw machine High back pressures and high screw speeds tend to reduce the length of the glass fibers in the material causing a reduction in physical properties Generally screw speeds should be 25 50 rpm Back pressure should be less than 50 psi Startup Before using
28. erature Ranges for Riteflex Polyester Elastomer and Vandar 9118 and AB100 Impet Grades Parameters 320R 610R All Riteflex Barrel Settings C F Parameters Grades Zone 1 254 271 490 520 Barrel Settings C F Zone 2 254 271 490 520 Zone 1 182 199 360 390 Zone 3 260 282 500 540 Zone 2 188 204 370 400 Zone 4 266 288 510 550 Zone 3 188 204 370 400 Zone 5 266 288 510 550 Zone 4 193 210 380 410 Adapter C F 266 288 510 550 Zone 5 193 210 380 410 Die C F 271 293 520 560 Adapter C F 193 210 380 410 Melt Temperature C F 271 293 520 560 Die C F 199 221 390 430 Melt Temperature C F 199 221 390 430 5 3 Wire Coating In wire coating the extruded tube of polyester forms a cone at the die into which the wire passes The wire is completely coated as it passes through the cross head The draw down ratio is defined as the ratio between the cross sectional area of the tube at the die face to the cross sectional area of the finished coating Draw down ratio for polyesters should be between 6 1 and 10 1 See Figure 5 2 lt LD DOODLE a A i a a a a a Wire lt Draw down ratio A Cross Head Figure 5 2 Polyester in Wire Coating Since streamline design is critical to avoid degradation the die face must have
29. ers made with up to 100 post consumer recycled polyethylene terephthalate PET They possess outstanding physical properties and superior thermal and chemical resistance Impet polyesters are ideal for high performance applications that require toughness rigidity exceptional dimensional stability and excellent electrical properties and have flame retardance ratings of UL94 HB The Impet grades are reinforced with glass fibers or with combinations of mineral glass fibers Table 1 3 lists grades of Impet polyesters and recommended processing methods Table 1 3 Impet Grades and Processing Methods Table 1 2 lists grades of Vandar alloys and Processing Methods recommended processing methods Type of Material Injection and Grade Molding Extrusion Glass Reinforced Table 1 2 Vandar Grades and Processing Methods 320R i Lom 330R Processing Methods 340R Type of Material Injection and Grade Molding Extrusion ees Minera Reinforced Unreinforced General 610R Purpose 2100 630R 3 2500 i 830R 4602Z 6000 Unreinforced and Flame Retardant 8000 Glass Reinforced 361 4612R 4632Z 4662Z AB875 Unreinforced Higher Flexural Modulus 8929 9114 9116 AB100 Mineral Reinforced 2122 Riteflex Thermoplastic Polyester Elastomer Riteflex products are a family of copolyester polymers which combine
30. es a sufficient shot size it forces the screw to retract Injection The screw moves forward seating the check ring which forces the molten polymer through the sprue runners and gates into the cavities of the mold The part conforms to the shape of the mold cavities and the cooled mold helps to solidify the plastic into a solid form The mold opens and the part is ejected usually with the aid of ejection pins A Plastication Feed Hopper Screw Drive On Limit Switches adjustable Oil Feed Hopper Screw Drive Off B Injection Limit Switches A adjustable Oil Figure 2 5 Molding Sequence Single Stage Reciprocating Screw Injection Molding Machine Molding Equipment and metering zone The feed and metering zones both Polyester resins can be processed without difficulty maintain constant root diameters while the transition in different types of screw injection molding machines zone employs an involuted taper For reference purposes a typical single stage reciprocating screw injection molding machine is Since polyester materials are fast cycling a machine shown in Figure 2 6 should have a high plasticating capability to achieve optimum cycle times Some general guidelines are For best results machines should be selected so that accen E Metering zone 3 4 flights the shot weight is in the 5096 range of rated machine capacity This minimizes residence time and prevents W Zone distri
31. hen add a safety factor This can be done by plac ing several parts in the oven and removing them one at a time at predetermined intervals After a cooling time of at least 24 hours the parts are measured and the point at which the dimensions show no further change is the minimum annealing time A rule of thumb annealing time for most polyester resin parts is 1 3 hours in air depending on part thickness It is suggested that the minimum annealing time be determined for a specific part as described above Typical shrinkage encountered in glass fiber reinforced grades during annealing is up to 0 002 inch inch in the flow direction and 0 003 inch inch in the transverse direction This is in addition to the mold shrinkages shown in Tables 2 3 2 6 2 7 Molding Process Because molding is so crucial to producing high quality parts it is essential to understand the process and to select equipment which ensures consistency and efficiency Figure 2 5 illustrates the plastication A and injection B sequences of a single stage reciprocating screw injection molding machine Plastication The hopper feeds dried resin into the barrel The feed section of the screw conveys the resin forward Resin is melted by the heat of the barrel and mechanical shear of the transition zone Molten plastic is then pressurized and conveyed through the metering zone forming a melt pool in front of the screw As the melt pool accumulat
32. ie Good temperature control across the die face is also necessary The air gap must be as small as possible and the melt bank between the nip rolls must also be very small Too large a melt bank causes stress in the sheeting while too small a melt bank results in nonuniform sheet thickness Polishing Roll Stand Polishing rolls will improve the surface finish of the sheet Normal temperatures of the rolls are as follows M Top Roll 38 77 C 100 170 F Bi Center Roll 38 71 C 100 160 F E Bottom Roll 38 71 C 100 160 F Final roll temperatures and heat transfer are governed mainly by the internal cleanliness of these rollers Edge Trim or Slitting Tension Rolls Take up Unit Polishing Roll Stand Figure 5 4 Polyester Sheet Extrusion 5 6 Troubleshooting Extrusion Chapter 6 Troubleshooting As with injection molding many extrusion processing problems are caused by easily corrected conditions such as inadequate resin drying incorrect temperatures and or pressures etc Often solutions to these problems can be found each problem category Table 6 1 Troubleshooting Guide Extrusion Process Problem Blistering Bubbles Breaks pin holes tears Coatings non adherent Typical Cause Cooling too quickly Corrective Action Slow down cooling rate Celanex e Vandar Impet by following the recommendations in Table 6 1 Try them in
33. ine until the material temperature is no higher than 232 C 450 F Then shut down the machine When shutting down a screw machine leave the screw in the forward position If a mass of molten material is left in front of the screw at shutdown restarting the machine will be delayed until the solidified slug of material in front of the screw is remelted 3 5 Impet Thermoplastic Polyester Molding Conditions Table 3 4 contains recommended molding conditions for all grades of Impet polyester Table 3 4 Molding Conditions for Impet Polyesters Molding Parameter Mold Temperature C F Melt Temperature C F All Impet Grades 110 121 230 250 271 299 520 570 50 75 0 25 Screw Speed rpm Back Pressure psi Injection Speed medium to fast Injection Pressure psi as needed Cushion Inches 0 125 Barrel Settings C F Feed Zone 260 271 500 520 Center Zone 271 277 520 530 Front Zone 277 282 530 540 Nozzle 277 288 530 550 Drying Requirements Impet polyester should be dried to moisture levels below 0 01 before injection molding Refer to pages 2 11 through 2 13 for more information on drying It is extremely critical that moisture levels below 0 01 be maintained before injection molding Therefore it is recommended that a dehumidifying hopper dryer as discussed on page 2 12 be used on the injection molding machine Mold Temperature
34. ing cylinder temperature Decreasing screw rotational speed Lowering back pressure Decrease residual pressure in cylinder by Reducing plunger forward time and or back pressure Increasing decompress time if machine has this control Decrease overall cycle time 4 2 Table 4 1 Troubleshooting Guide Injection Molding Continued Problem and Corrective Action Celanex Vandar Impet Riteflex Nozzle Drool Continued Reduce back pressure Decrease die open time Use nozzle with positive shutoff valve Dry the material before use e Use nozzle with smaller orifice Use reverse taper nozzle or nozzle valve Nozzle Freeze off Insulate nozzle from mold Raise nozzle temperature Decrease cycle time Increase injection pressure g Decrease injection pressure Raise mold temperature Use nozzle with larger orifice Use reverse taper nozzle Burn Marks Decrease injection speed Decrease booster time Decrease injection pressure Improve venting in mold cavity s Change gate position and or increase gate size to alter flow pattern Sticking in Cavities Decrease injection pressure Decrease plunger forward time Raise mold temperature Decrease injection time Decrease injection speed Decrease hold time D
35. ing of pellets between flight land and barrel Wire stretching Raise rear temperature Reduce tension on wire Orientation too great during draw down Contamination Preheat the wire Raise the draw rate shorter cone Reduce draw down ratio Enlarge air gap or lower quench rate Increase die and melt temperatures See Contaminated Extrudate Dirty or poorly finished die Inspect finish on die and tip Look for burrs and remove Melt fracture caused by excessive shear Raise die temperature Widen die opening Lower extrusion rate Increase melt temperature Wrong rate of draw Change cone length Material on die face Clean Wire vibrating Use dampening pads or guides 6 3 Table 6 1 Troubleshooting Guide Extrusion Continued Problem Surging Unmelted pel lets or particles in extrudate Sheet sticking to roll Typical Cause Slipping drive belts Corrective Action Secure belts Celanex e Vandar e Impet Riteflex e Inadequate melt reservoir Use different screw to adjust e e e Slow down screw speed e e Check temperature cycling Make die opening smaller Increase back pressure Material bridging in feed section Check controller in feed zone Reduce rear temperatures Increase cooling in feed throat water
36. ion Heater Figure 2 10 Hopper Dryer Unit Reprinted with permission of Novatec Inc Baltimore MD 2 12 Drying Process Figure 2 10 shows a typical hopper dryer unit A vacuum loader 1 drops resin into the insulated drying hopper 2 on demand Heated dehumidified air enters the drying hopper penetrating the resin and carrying moisture vapor up to the return line outlet Moisture laden air passes through a filter 3 to remove fines or very small particles before the air re enters the desiccant cartridge This filter must be kept clean To save energy the heated air should be recirculated The process air blower 4 forces moisture laden air through on stream desiccant cartridges 5 where moisture is trapped The dehumidified air is then reheated 6 and delivered back to the drying hopper While the desiccant cartridge is on stream removing moisture another cartridge is being regenerated Separate regeneration blowers 7 and heaters 8 are used for that purpose General Drying Guidelines To produce acceptable moisture levels when drying virgin or regrind material in a dehumidifying hopper drier use the guidelines provided in Table 2 7 For drying polyester materials dew points should be maintained between 30 C and 40 C If polymer is to be dried overnight temperatures can be reduced to 102 C 215 F for Celanex Impet and most Vandar polyesters For the very flexible Vandar and R
37. iteflex polyesters use 93 C 200 F for overnight drying For best results these moisture levels must be achieved and maintained while processing all polyester products Table 2 7 Drying Guidelines Use dehumidifying dryer Product Type Temperature Drying Time Moisture Level Celanex 121 C 250 F 4 hours less than 0 02 Vandar 107 C 225 F 3 to 4 hours less than 0 02 Vandar 9114 68 C 155 4 hours or overnight less than 0 02 Impet 135 C 275 4 hours less than 0 01 Riteflex 107 C 225 F 4 hours less than 0 05 To successfully dry Vandar 9114 it is critical that the dew point be 30 or lower 2 13 2 14 Chapter 3 Processing Injection Molding General For all polyester products the molder must control processing parameters carefully to produce high quality molded parts The quality of the finished part depends as much on proper processing as it does on part design Chapter 3 contains basic guidelines for injection molding Celanex thermoplastic polyester Vandar thermoplastic alloy Impet thermoplastic polyester and Riteflex thermoplastic polyester elastomer Typical injection molding parameters for each product group are summarized in Table 3 1 This is followed by more specific molding information on the various grades within each product group When molding an unfamiliar grade or if problems arise during processing that cannot be corrected using the tr
38. lass Reinforced Flame Retardant 3112 2 3116 3210 2 3216 3310 2 3316 Table 1 1 Celanex Grades and Processing Methods Continued Processing Methods Type of Material and Grade High Impact 1632Z Injection Molding Extrusion 1642Z 1662Z 4202 4300 4302 4305 306 Good Surface Finish 5200 2 5300 2 7862Z Low Warp General Purpose J235 J600 LW2333R LW6443R LW6362R LW7345R 6400 2 6406 6407 6500 Low Warp Flame Retardant 7304 7305 316 7700 2 Vandar Thermoplastic Alloys Vandar products are thermoplastic polyester alloys possessing Bi Outstanding ductility and stiffness combined with the excellent chemical and environmental resistance properties of polyesters B High impact strength at ambient and low temperatures The unreinforced and higher flexibility grades possess high impact with a flexibility between that of thermoplastics and elastomers Unfilled Vandar 8000 has a flammability rating of UL94 V 0 as low as 0 85 mm 0 033 in part thickness The remainder of the Vandar products are rated UL94 HB Vandar alloys are also available in grades formulated with glass fiber and minerals Filled grades improve modulus and strength while maintaining excellent toughness Impet Thermoplastic Polyesters Impet products are thermoplastic polyest
39. listed under each problem category Table 4 1 Troubleshooting Guide Injection Molding Problem and Corrective Action Short Shots Poor Surface Finish Increase feed Adjustments should be moderate and the machine should be allowed to line out before any further adjustments are made Check that the machine is operating within the parameters recommended for the specific grade of resin For example stock melt temperature should be confirmed on air shots collected at typical cycle times Celanex Vandar Impet Riteflex Increase injection pressure Use booster and maximum ram speed Decrease cushion Raise cylinder temperature Raise mold temperature Increase overall cycle time Check shot size vs rated machine shot capacity if shot size exceeds 75 of rated styrene shot capacity move to larger machine Increase size of sprue runners gates Increase injection time Increase injection speed Increase decrease feed to maintain proper cushion Check cavity vents for blockage Increase booster time Increase screw speed unfilled grades only Increase back pressure unfilled grades only Use lubricated resin Flashing Lower material temperature by Lowering cylinder temperature Decreasing screw rotational speed Lowering back pressure Decrease injection pressure Decrease overall cycle time Decrease plunger forward time Check mold closu
40. maged check ring 4 6 Processing Extrusion Chapter 5 General Chapter 5 contains basic processing guidelines for extruding Celanex thermoplastic polyesters Vandar thermoplastic alloys Impet thermoplastic polyesters and Riteflex thermoplastic polyester elastomers When extruding an unfamiliar grade or if problems arise during processing that cannot be corrected using the troubleshooting guide in Chapter 6 contact your local Ticona representative or call Product Infor mation Services at 1 800 833 4882 Safety and Health Information Before starting the extrusion process obtain and read the appropriate polyester Material Safety Data Sheet MSDS for detailed safety and health information They may be obtained by calling Customer Services at 1 800 526 4960 Use process controls work practices and protective measures described in the MSDS sheets to control workplace exposure to dust volatiles etc Drying Requirements Celanex Vandar Impet and Riteflex polyesters must be dried to proper moisture levels before extruding Refer to pages 2 11 through 2 13 for more information on drying It is extremely critical that moisture levels below 0 01 be maintained before extruding Impet polyester Therefore it is recommended that a dehumidifying hopper dryer as discussed on page 2 13 be used on the extruding machine For drying polyesters dewpoints should be maintained between 30 C and 40 C
41. many desirable features of thermoset rubbers with the processing ease of engineering plastics These products are tough tear resistant resist flex fatigue and perform over a broad temperature span Riteflex elastomers are resistant to many chemicals including acids and bases common solvents oils and greases They are also abrasion resistant The harder versions exhibit enhanced heat and chemical resistance while the softer materials possess good low temperature mechanical properties Table 1 4 lists grades of Riteflex elastomers and recommended processing methods Table 1 4 Riteflex Grades and Processing Methods Processing Methods Type of Material Injection and Grade Molding Extrusion 635 640 647 655 663 677 i The last 2 digits denote the Shore D hardness e g Grade 640 has a Shore D hardness of 40 Chapter 2 Mold Design Equipment Selection and Preprocessing Mold Design The Ticona family of engineering thermoplastic polyester resins may be successfully molded in conventional two and three plate molds stack molds and in a wide variety of hot runner and insulated runner molds Conventional Runners Full round runners are recommended and trapezoidal are second best Rectangular or half round runners may also be used but they are less efficient Suggested sizes for full round runners are provided in Table 2 1 Table 2 1 Runner Size Recommendation
42. n 5 2 Table 5 3 Typical Extrusion Temperature Ranges for Celanex Polyester Celanex Grades 1602Z 2002 2002 2 2002 3 Parameters 2012 2 2016 3112 2 3116 1600A 1700A 2001 Barrel Settings C F Zone 1 232 249 450 480 243 271 470 520 Zone 2 232 249 450 480 249 271 480 520 Zone 3 232 249 450 480 249 271 480 520 Zone 4 238 254 460 490 249 271 480 520 Zone 5 238 254 460 490 249 271 480 520 Adapter C F 238 254 460 490 249 271 480 520 Die C F 238 260 460 500 249 271 480 520 Melt Temperature C F 238 260 460 500 243 271 470 520 Table 5 4 Typical Extrusion Temperature Ranges for Vandar Alloys Vandar Grades 2100 2122 2500 4602Z 8000 Parameters 8929 9116 6000 Barrel Settings C F Zone 1 232 249 450 480 243 260 470 500 Zone 2 232 249 450 480 243 260 470 500 Zone 3 232 249 450 480 249 271 480 520 Zone 4 238 254 460 490 254 277 490 530 Zone 5 238 254 460 490 254 277 490 530 Adapter C F 238 254 460 490 254 277 490 530 Die C F 238 260 460 500 260 282 500 540 Melt Temperature C F Table 5 5 Typical Extrusion Temperature Ranges for Impet Polyester 238 260 460 500 260 282 500 540 Table 5 6 Typical Extrusion Temp
43. or Impet Polyester 3 6 Table 3 5 Molding Conditions for Riteflex Polyester Elastomer i f 3 7 Table 4 1 Troubleshooting Guide Injection Molding f E 4 1 Table 5 1 Barrel Length to Diameter Ratios i i 5 1 Table 5 2 Typical Lengths of Feed Transition and Metering Zones f f 5 2 Table 5 3 Typical Extrusion Temperature Ranges for Celanex Polyester 5 3 Table 5 4 Typical Extrusion Temperature Ranges for Vandar Alloys 5 3 Table 5 5 Typical Extrusion Temperature Ranges for Impet Polyester f f 5 3 Table 5 6 Typical Extrusion Temperature Ranges for Riteflex Polyester Elastomer f 5 3 Table 6 1 Troubleshooting Guide Extrusion i 6 1 able of Contents List of Figures Figure 2 1 Balanced Runner and Cavity Layout 2 1 Figure 2 2A Various Gate Types Used in Injection Molds f f f 2 2 Figure 2 2B Various Gate Types Used in Injection Molds 2 3 Figure 2 3 Gate and Mold Design Affect Part Strength i 2 3 Figure 2 4 Flow vs Wall Thickness for Celanex 3300 f f 2 4 Figure 2 5 Molding Sequence Single Stage Reciprocating Screw Injection Molding Machine 2 8 Figure 2 6 Single Stage Reciprocating Screw Injection Molding Machine N 2 9 Figure 2 7 Recommended Metering Screw f f f 2 9 Figure 2 8 Check Ring Nonreturn Valve Used on Reciprocating Screw Injection Molding Machines 2 10 Figure 2 9 Internal Ball Check Nonreturn Val
44. oubleshooting guide in Chapter 4 contact your local Ticona representative or call Product Information Services at 1 800 833 4882 Table 3 1 Typical Injection Molding Parameters Safety and Health Information Before starting the injection molding process obtain and read the appropriate polyester Material Safety Data Sheet MSDS for detailed safety and health information They may be obtained by calling Customer Services at 1 800 526 4960 Use process controls work practices and protective measures described in the MSDS sheets to control workplace exposure to dust volatiles etc Molding Parameter Mold Temperature C F Melt Temperature C F Celanex 38 121 100 250 227 260 440 500 Vandar 38 121 100 250 238 282 460 540 Impet 110 121 230 250 271 299 520 570 Riteflex 24 93 75 200 171 266 340 510 Screw Speed rpm Back Pressure psi 60 125 0 50 60 125 0 100 60 125 0 25 60 125 0 100 Injection Speed fast medium to fast medium to fast fast Injection Pressure low to medium low to high as needed low to medium Cushion Inches 0 125 0 125 0 125 0 125 0 250 Barrel Settings C F Feed Zone 232 249 450 480 232 254 450 490 260 271 500 520 154 243 310 470 Center Zone 271 277 520 530 171 249 340 480 Front Zone 238 254 460 490 243 260 470 500
45. ovide an overflow well adjacent to weld area Change gate position to alter flow pattern Unmelted Pellets Increase melt temperature Increase back pressure Dry preheat the resin Use a press with proper screw design see Screw Design on page 2 9 for guidelines Check to be sure that the nonreturn check valve is working properly to prevent back flow Move the mold to a press with a larger shot capacity Sinks and Voids Increase injection pressure Increase injection forward time Increase injection hold time Use booster and maximum ram speed Increase injection speed Raise mold temperature for voids only Lower mold temperature for sinks only Decrease cushion 4 4 Table 4 1 Troubleshooting Guide Injection Molding Continued Problem and Corrective Action Sinks and Voids Continued Increase feed maintain proper cushion Celanex Vandar Impet Riteflex Increase size of sprue runners gates Relocate gates closer to heavy sections Warpage Part Distortion Equalize temperature in both halves of the mold eliminate hot spots Check mold for uniform part ejection Check for proper handling of parts after ejection Raise tool temperature Increase gate and runner size Increase fill speed Increase injection hold time Increase plunger forward time Increase cooling time Try increased pressur
46. r alloys because they solidify very rapidly once they enter the mold cavity In some cases reduced fill speed can help cure warpage problems induced by orientation of the glass fibers in the material For specific recommendations see Table 3 3 Cycle Time Because Vandar alloys solidify rapidly cycle times can be extremely short Plunger forward time need only be long enough to deliver the molten charge to the mold and hold the material under pressure until the gate freezes The part should be sufficiently set up so that when it is ejected any impact does not cause dents or any other distortions Consequently overall cycle time is a function of part size and wall thickness Generally cycles for Vandar alloy moldings vary from as little as 5 seconds for small thin walled parts to 40 45 seconds for large thick walled parts Cycle times over 45 seconds are encountered only in rare instances where molds must be opened closed slowly due to special coring or where inserts must be loaded into the mold Back Pressure and Screw Speed Little back pressure and minimum screw speed should be used in molding glass fiber reinforced Vandar ina screw machine High back pressures and high screw speeds tend to reduce the length of the glass fibers in the material causing a reduction in physical properties Back pressure need only be high enough to compact the molten material in front of the screw as the screw rotates and retracts the screw spee
47. re for possible obstruction on parting line surface 4 1 Table 4 1 Troubleshooting Guide Injection Molding Continued Problem and Corrective Action Flashing Continued Improve mold venting Celanex Vandar Impet Riteflex Check machine platens for parallelism Move mold to larger clamp press Check parting line of mold for wear Splay Marks Dry the material before use Check for contamination such as water or oil leakage into the mold cavity Check for drooling Decrease injection speed Raise mold temperature Lower material temperature by Lowering cylinder temperature Decreasing screw rotational speed Lowering back pressure Lower nozzle temperature Decrease overall cycle time Open the gate s Move mold to smaller shot size machine Discoloration Purge heating cylinder Lower material temperature by Lowering cylinder temperature Decreasing screw rotational speed Lowering back pressure Lower nozzle temperature Decrease overall cycle time Check hopper and feed zone for contamination Check cylinder and plunger or screw fit for excessive clearance Provide additional vents in mold Move mold to machine with smaller shot size 50 75 of capacity for all polyesters Check ram and feed zone for proper cooling Nozzle Drool Lower nozzle temperature Lower material temperature by Lower
48. re information on design and material characteristics of polyesters consult the following Ticona publications which can be obtained by calling Product Information Services at 1 800 833 4882 E Designing With Plastic The Fundamentals Design Manual TDM 1 Bi Celanex Thermoplastic Polyester Short Term Properties CX 4 E Celanex 16 Series Polyesters B Vandar Thermoplastic Alloys Short Term Properties VN 4 B Impet Thermoplastic Polyester Short Term Properties IP 4 Oo Riteflex Thermoplastic Polyester Elastomer Short Term Properties RF 4 Material Safety Data Sheets MSDS for specific grades of Celanex Vandar Impet and Riteflex polyesters have been developed by Ticona MSDS sheets provide valuable safety health and environmental information Before processing these products read and thoroughly understand the appropriate MSDS They may be obtained by calling Customer Services at 1 800 526 4960 able of Contents Chapter 1 Overview General 1 1 Celanex Thermoplastic Polyester i i 1 1 Vandar Thermoplastic Alloys i i 1 3 Impet Thermoplastic Polyester 1 3 Riteflex Thermoplastic Polyester Elastomer 1 4 Chapter 2 Mold Design Equipment Selection and Preprocessing Mold Design 1 2 1 Conventional Runners f 2 1 Gates f i i 2 1 Venting i i i i 2 4 Mold Cooling i i i i 2 4 Melt Flo
49. resin may hang up and degrade over a period of time of elevated temperatures should be avoided For more information on runnerless molding contact your local Ticona representative or call Product Information Services at 1 800 833 4882 2 6 Annealing The main purpose of annealing is to stabilize part dimensions by accelerating the effects of stress relaxation Few applications require annealing Polyester resin parts properly designed and molded in a hot 93 121 C 200 250 F mold have sufficient dimensional stability for all but the most exacting requirements However if resin parts are to be used at higher temperature over 93 C or 200 F and dimensional stability is required then annealing is recommended Annealing relieves residual stresses in moldings causing most stress relaxation shrinkage to occur in the annealing operation rather than in service Caution In some cases stress relief through annealing can lead to part warpage especially if shrinkage is nonuniform Multiple test parts should be produced initially to determine if this problem arises Polyester resin parts may be annealed in an air circulating oven capable of maintaining uniform temperature throughout its interior Recommended annealing temperature is 204 2 8 400 5 F Annealing time depends primarily on part thickness part geometry and processing conditions It is good practice to determine minimum annealing time and t
50. rototype parts having the same geometry as the final part Shrinkage measurements on a spectrum of molding conditions should be included to define the range of variations Note that changes in gating weld lines mold cooling etc may change shrinkage of the final part versus the prototype part Contact your local Ticona representative or call Product Information Services at 1 800 833 4882 for further information on part shrinkage before molds are sized to final dimensions Note In designing molds extreme care must be exercised when using shrinkage data from ISO or ASTM test specimens These data should be used only as a guide for plastic material property comparisons See Tables 2 3 2 6 Table 2 3 Celanex Grade Shrinkage Celanex Polyester In In Flow Grades Direction 96 Unreinforced 0 018 0 020 1 8 2 0 Unreinforced Flame Retardant 2016 0 025 0 030 2 5 3 0 Glass Reinforced General Purpose 3200 3201 0 005 0 007 0 5 0 7 3202 0 004 0 006 0 4 0 6 1462Z 3300 3400 0 003 0 005 0 3 0 5 Glass Reinforced Flame Retardant 3112 0 005 0 007 0 5 0 7 3116 0 010 0 014 1 0 1 4 3210 3216 0 004 0 006 0 4 0 6 3310 0 003 0 005 0 3 0 5 3316 0 003 0 005 0 3 0 5 High Impact 1632Z 4202 0 003 0 007 0 3 0 7 4300 4302 0 003 0 005 0 3 0 5 Good Surface Finish 5200 0 004 0 006 0 4 0 6 5300 7862Z 0 003 0 005 0 3 0 5 Low Warp General Purpose 6407
51. s Parameters Celanex Vandar Impet Riteflex Barrel Settings C F Zone 1 232 271 450 520 232 271 450 520 254 271 490 520 182 199 360 390 Zone 2 232 271 450 520 232 271 450 520 254 271 490 520 188 204 370 400 Zone 3 232 271 450 520 232 282 450 540 260 282 500 540 188 204 370 400 Zone 4 238 271 460 520 238 288 460 550 266 288 510 550 193 210 380 410 Zone 5 238 271 460 520 238 288 460 550 266 288 510 550 193 210 380 410 Adapter C F 238 271 460 520 238 288 460 550 266 288 510 550 193 210 380 410 Die C F 238 271 460 520 238 293 460 560 271 293 520 560 199 221 390 430 Melt Temperature C F 238 271 460 520 238 293 460 560 271 293 520 560 199 221 390 430 Foreword This processing and troubleshooting guide PE 6 contains updated information on injection molding and extrusion parameters for the Ticona Polyester products and was written to help processors tool builders and part designers take full advantage of their excellent material properties and processing characteristics They comprise the following B Celanex Thermoplastic Polyesters B Vandar Thermoplastic Alloys B Impet Thermoplastic Polyesters E Riteflex Thermoplastic Polyester Elastomers For mo
52. s of the molding process Clamping Systems The clamp keeps the mold closed by either a toggle mechanism or by a hydraulic cylinder Polyester resins can be processed on either type The clamp force should be 3 to 4 tons per square inch of projected surface area including runners Mold Construction The recommended mold steel hardness for all polyester products is H 13 pem q Check Ring ng Oper Plastication Check Ring Closed Injection Figure 2 8 Check Ring Nonreturn Valve Used on Reciprocating Screw Injection Molding Machines Plastication Injection Figure 2 9 Internal Ball Check Nonreturn Valve Used on Reciprocating Screw Injection Molding Machines 2 10 Resin Storage During storage avoid climatic temperature and humidity extremes which can lead to excessive moisture adsorption on the surface of virgin and regrind material Avoiding these extremes are particularity important when storing regrind because of its very large surface area In any case virgin and regrind materials must be dried to recommended moisture levels before molding begins Use of Regrind Properly dried polyester compounds have excellent thermal stability during molding This permits the successful use of regrind in the molding process Regrind should be E Free of contamination M Combined with virgin resin in the ratio of no more than 2596 regrind to 75 virgin resin see note below for exceptions
53. s to the lowest practical limits in view of possible adverse effects To the extent that any hazards may have been mentioned in this publication we neither suggest nor guarantee that such hazards are the only ones that exist Celanex Vandar Impet and Riteflex thermoplastic polyesters are not intended for use in medical or dental implants Products Offered by Ticona Celcon and Hostaform acetal copolymer POM Celanese Nylon 6 6 Celanex thermoplastic polyester Impet thermoplastic polyester Vandar thermoplastic polyester alloys Riteflex thermoplastic polyester elastomer Celstran Fiberod and Compel long fiber reinforced thermoplastics Encore recycled thermoplastic molding resins Fortron polyphenylene sulfide PPS GUR specialty polyethylene UHMWPE GHR very high molecular weight high density polyethylene HDPE Topas cyclic olefin copolymer COC Vectra liquid crystal polymer LCP Duracon acetal copolymer POM and Duranex thermoplastic polyester are offered by Polyplastics Co Ltd Fortron is a registered trademark of Fortron Industries Technical Information 1 800 833 4882 Customer Services 1 800 526 4960 Ticona 90 Morris Avenue Summit New Jersey 07901 3914 908 598 4000 1999 Ticona Printed in U S A 99 324 2M 1199 Ticona
54. shing Only suitable for thin sections degating Only suitable for thin sections i TAB Used to stop jetting when other means are DIAPHRAGM Used for single cavity concentric not available and when a restricted gate is moldings of ring shape with medium or small desired Also enables area of greatest strain to be internal diameter removed from the molding p INTERNAL RING Similar to diaphragm gate EXTERNAL RING Used for multicavity concentric Used for molds with large internal diameters moldings of ring shape or where diaphragm gate or to reduce sprue runner to molding ratio cannot be used Figure 2 2A Various Gate Types Used in Injection Molds 2 2 SECTION B B r gt C FLASH Provides simultaneous filling over the whole length of the mold to give even shrinkage along the length SECTION C C VERTICAL RING Symmetrical gating at one end of components with long holes e g knife handles Narrow angle submarine gate will break off on mold opening TUNNEL OR SUBMARINE Te SUBMARINE GATE DESIGN POOR DESIGN RECOMMENDED DESIGN I S Wide angle 60 submarine gate will provide clean break in small size gate area Figure 2 2B Various Gate Types Used in Injection Molds POOR DESIGN GOOD DESIGN Fibers broken Gate enters thin section opposite wall Radiused gate located So fibers can turn without breaking Figur
55. t Gate Melt Flow From Secondary Sprue in 3 Plate Mold for Celanex Impet and Vandar Higher modulus grades Polyesters Part Gate Land Thickness Diameter Length Inches Inches Inches Less than 0 125 0 030 0 050 0 040 0 125 0 250 0 040 0 120 0 040 Venting Because of the rapid mold filling qualities of polyester resins adequate mold venting is necessary to preclude the burning of material from compressed air Vents should be located at the edge of the cavity furthest from the gate Suggested vent size is 0 001 inch deep x 0 125 inch wide These vents should be cut in the mold parting line from the edge of the cavity to the outside of the mold Vents should be deepened beginning 0 125 inch from the cavity Venting is particularly critical at knit lines and the last segment of the cavity to fill Mold Cooling Productivity and part quality are directly influenced by proper mold cooling Polyester resins when cooled below the melting point solidify rapidly with the potential for achieving fast molding cycles This requires a well designed mold cooling system that provides a uniform mold temperature with cooling channels near thicker part sections and when possible directly in mold inserts and cores For proper mold temperature control a separate temperature controller for core and cavity is recommended Temperature controls capable of reaching 121 C 250 F will provide sufficient flexibility for most molding
56. ty of the users to investigate whether any existing patents are infringed by the use of the materials mentioned in this publication Any determination of the suitability of a particular material for any use contemplated by the user is the sole responsibility of the user The user must verify that the material as subsequently processed meets the requirements of the particular product or use The user is encouraged to test prototypes or samples of the product under the harshest conditions likely to be encountered to determine the suitability of the materials Material data and values included in this publication are either based on testing of laboratory test specimens and represent data that fall within the normal range of properties for natural material or were extracted from various published sources All are believed to be representative Colorants or other additives may cause significant variations in data values These values are not intended for use in establishing maximum minimum or ranges of values for specification purposes We strongly recommend that users seek and adhere to the manufacturer s or supplier s current instructions for handling each material they use Please call 1 800 833 4882 for additional technical information Call Customer Services at the number listed below for the appropriate Material Safety Data Sheets MSDS before attempting to process these products Moreover there is a need to reduce human exposure to many material
57. unnerless Molds Continuing increases in the costs of labor materials etc have been a driving force for cost reductions in processing and the production of moldings of better quality at lower prices This in turn has sparked a new interest in automation including the use of runnerless molds The increased demand for such molds has resulted in a rapid expansion of runnerless molding technology and a proliferation of commercially available runnerless molds Runnerless molds as the name implies are molds in which no sprues and runners are produced with the parts The material being molded is kept in a plasticized state all the way from the heating cylinder of the injection molding machine to the gate in the mold cavity and only molded parts are removed from the mold each time the press opens No sprues or runners are produced and therefore none need to be reprocessed as in conventional molding Runnerless molding provides excellent opportunities for material and cost savings with many additional benefits Product quality and productivity can be improved and there is little or no scrap to regrind Polyester compounds have been successfully molded in virtually all types of commercially available runnerless molds As with other thermoplastic resins runnerless molds should have adequate temperature control and be designed with generously rounded bends in the runner system Sharp bends in the runner system as well as other areas where
58. ure absorption B Exceptional dimensional stability Resistance to a wide range of chemicals oils greases and solvents B Excellent electrical properties Celanex PBT also offers outstanding processing characteristics including B Fast cycles M Absence of volatiles during processing E The significant advantage of accepting high levels of reprocessed product up to 50 for certain grades Rigidity heat resistance creep resistance and electrical properties are among the superior performance characteristics that differentiate Celanex thermoplastic polyester from other engineering thermoplastics Celanex resins are supplied in unreinforced grades and in grades formulated with glass fiber and minerals Some products are categorized as flame retardant UL94 V 0 others are general purpose Table 1 1 lists grades of Celanex Thermoplastic Polyesters and recommended processing methods Table 1 1 Celanex Grades and Processing Methods Processing Methods Type of Material and Grade Unreinforced 1300 Injection Molding Extrusion 1400A 1600A 1602Z 1700A 2000 2000 2 2000 3 2000 2K 2001 2002 2002 2 2002 3 2003 2003 2 2003 3 2004 2 2008 2012 2 2016 Glass Reinforced General Purpose 1462Z 3200 3200 2 3201 3201 2 3202 2 3300 3300 2 3400 2 G
59. ures Final extrudate quality can be greatly affected by even small changes in the temperature of the melt Generally speaking the slower the extrusion rate longer residence the greater effect these changes will have Therefore a variable voltage or proportioning controller is best for keeping the melt thermally homogeneous Pressure changes during production indicate changes in viscosity and output rate of the melt Diaphragm type transducers which measure fluctuations in pressure are recommended Startup In starting up an empty machine set temperature controllers for the die adapter and barrel using the appropriate temperatures provided in Tables 5 3 through 5 6 When they reach their operating temperatures bring the remaining barrel temperatures up to the proper settings After they have held the proper temperature for 20 30 minutes turn the screw on at low RPM and start feeding polyester into the hopper Carefully check both the ammeter and pressure gauges As melt appears at the die it may be hazy At that time temperature and head pressure should start to stabilize Purging and Shutdown A machine should never be shut down while polyester remains in it A medium to high density polyethylene should be used to purge the extruder Temperature controllers should remain set at running conditions Purge all of the polyester from the extruder Continue running until all of the purge is out of the machine Then shut dow
60. ve Used on Reciprocating Screw Injection Molding Machines 2 10 Figure 2 10 Hopper Dryer Unit i i f 2 12 Figure 5 1 Typical Screw Design 5 1 Figure 5 2 Polyester in Wire Coating i i 5 4 Figure 5 3 Polyester in Tube Extrusion f f f 5 5 Figure 5 4 Polyester in Sheet Extrusion y 5 6 vi vii Overview Chapter 1 General Chapter 1 contains an overview of the four polyester product groups available from the Ticona Corporation Celanex Thermoplastic Polyesters Vandar Thermo plastic Alloys Impet Thermoplastic Polyesters and Riteflex Thermoplastic Polyester Elastomers Brief descriptions of each product group are followed by a table which identifies the various grades within the product group and processing methods best suited for each grade Celanex Thermoplastic Polyesters Polybutylene terephthalate PBT the polymer from which Celanex products are compounded is semi crystalline and is formed by the polycondensation of 1 4 butanediol and dimethyl terephthalate The base polymer can be compounded with various additives fillers and reinforcing agents Because of their composition and degree of crystallinity these products exhibit a unique combination of properties that includes B High strength rigidity and toughness Low creep even at elevated temperatures Outstanding resistance to high temperatures B Minimal moist
61. w 7 i i 2 4 Mold Shrinkage y i T 2 4 Runnerless Molds i i i 2 6 Annealing f f i f 2 7 Molding Process 2 8 Plastication i 2 8 Injection i 2 2 8 Molding Equipment i 2 9 Screw Design 2 9 Nozzle i i 2 10 Nonreturn Valves i i i 2 10 Clamping Systems i 2 10 Mold Construction i 2 2 10 Resin Storage 7 2 11 Use of Regrind T 2 11 Drying Resin f 2 11 Drying Equipment i f 2 11 Drying Process 2 13 General Drying Guidelines 2 13 Chapter 3 Processing Injection Molding General i i i 3 1 Safety and Health Information 3 1 Celanex Polyester Molding Conditions i 3 2 Drying Requirements i i i i 3 2 Melt Temperature f f f f f 3 2 Mold Temperature 4 1 B f 3 2 Injection and Holding Pressure 3 2 Injection Speed f f 3 2 Cycle Time f f f f 3 2 Back Pressure and Screw Speed B B a i 3 3 Startup i i 3 3 Shutdown 3 3 ible of Contents Chapter 3 Processing Injection Molding Continued Vandar Alloy Molding Conditions i 3 4 Drying Requirements i i 3
62. xtrusion i i i 5 5 Vacuum Tank i i 5 5 Sheet Extrusion f f f f f 1 f 5 6 Polishing Roll Stand i 5 6 Chapter 6 Troubleshooting Extrusion Introduction i 6 1 Troubleshooting Guide 6 1 ible of Contents List of Tables Table 1 1 Celanex Grades and Processing Methods i 1 2 Table 1 2 Vandar Grades and Processing Methods f f 1 3 Table 1 3 Impet Grades and Processing Methods i 1 3 Table 1 4 Riteflex Grades and Processing Methods f f 1 4 Table 2 1 Runner Size Recommendations f f 2 1 Table 2 2A Size Recommendations Rectangular Edge Gate for Celanex Impet and Vandar Higher Modulus Grades Polyesters f 2 4 Table 2 2B Size Recommendations Direct Gate From Secondary Sprue in 3 Plate Mold for Celanex Impet and Vandar Higher Modulus Grades Polyesters 2 4 Table 2 3 Shrinkage Celanex Polyesters i f 2 5 Table 2 4 Shrinkage Vandar Alloys f f 2 6 Table 2 5 Shrinkage Impet Polyesters 2 6 Table 2 6 Shrinkage Riteflex Polyester Elastomers f f f f 2 6 Table 2 7 Drying Guidelines 2 13 Table 3 1 Typical Injection Molding Parameters i i 3 1 Table 3 2 Molding Conditions for Celanex Polyester f f 3 2 Table 3 3 Molding Conditions for Vandar Alloys f f f f 3 4 Table 3 4 Molding Conditions f

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