Troubleshooting Guide. PS Sheet extrusion. Chatter marks. Voids (PITS) Lack of gloss. the temperature at which sticking is occurring.

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1 Troubleshooting Guide PS Sheet extrusion Chatter marks Sheet sticking to cooling (polish) rolls Balance roll temperature to approximately 10oF below the temperature at which sticking is occurring. Unstable drive Check electrical loading, lubrication points, wear on chain or gear assembly. Too much tension on rubber pull roll Adjust roll synchronization. Effect of vibration of an adjacent equipment Check current variation, polish roll drive chain. Erratic pull from winder and trim grinders Set pull slightly below take-off speed. Voids (PITS) Vapor trapped in polymer Maintain consistent hopper level. Remove build-up from screw. Adjust temperature profile. Increase back pressure. Clean polymer from vent. Lack of gloss

2 Low die temperature Raise die temperature to approximate melt temperature. Lack of melt homogeneity or poor plasticization Raise barrel temperatures. Increase back pressure. Brittleness High article and/or sheet orientation See "Excessive orientation". Article excessive cooling (polish rolls too cold) Increase temperature of cooling rolls. Poor plasticization Raise back pressure. Excessive regrind used Decrease regrind percentage. Too much GPPS (crystal) blended with HIPS Decrease GPPS percentage. Lines in sheet Contamination inside die or damage of die lips Clean and repair die. Check for screen pack rupture. Polymer temperature too low

3 Discoloration in sheet Burnt polymer in extruder or die Check extruder feed. Calibration of heaters. Complete clean-up may be necessary. Contaminants in sheet Ruptured screen pack Replace screen pack. Contaminants in feed Check feed and regrind supply. Gauge variations Improper adjustment of die lips and restrictor bar Adjust restrictor bar. Pressure surging Adjust to correct heat profile. Insure consistent feed. Adjust back pressure. Variable speed of take-of equipment Synchronize take-off equipment including winder. Excessive orientation

4 Excessive cooling (polish) roll pressure Reduce cooling roll contact pressure. Increase pressure to a safe maximum Insufficient back pressure. Polymer temperature too low Large temperature differential between stock and die Equalize temperatures. Too thick rolling bank at nip of polish rolls Maintain smallest most uniform bank possible at nip. Strong tension between polish rolls and rubber rolls Maintain slack in sheet between polish and rubber rolls. Pressure surge Inconsistent feed Maintain consistent hopper level and material blend. Moisture Use a devolatizing vent, dehumidifying dryer and increase drying time of feed. Build-up on screw Improper back pressure Adjust to a safe pressure maximum. Excessive stock temperature

5 Polymer build-up on screw Excessive water cooling of screw Shut off water source. Temperature control malfunctioning Check and calibrate heaters. Polymer coming out from vent Excessive back pressure Lower back pressure. Plugged screen pack Replace screen pack. Polymer build-up on screw Reduced output rate Inconsistent feed Check feed hopper for fused chunks. Polymer plasticizing too soon in feed zone Adjust to proper heat profile. Too much water cooling on screw Shut off water source, clean screw.

6 Bridged screw RPM too low Increase RPM to a maximum. Bulk density of feed not compatible with screw design Reduce % of regrind. Consult with suppliers on screw design.