COMMOM PROBLEMS IN PROCESSING CLEAR PLASTICS
PLASCO WISHES TO THANK THE FOLLOWING SUPPLIERS - ARCO, MOBAY,
CYRO, EASTMAN, DOW, CONTINENTAL, GE & POLYSAR. THE FOLLOWING GUIDE
IS A COMPOSITE OF THEIR EXPERTISE AND RECOMMENDATION.
PROBLEM | TYPICAL CAUSES | SOLUTIONS |
silver streading, splay , bubbles | moisture | check dryer operation; drying conditions; use a desiccant dryer. |
entrapped air | raise back psi; reduce screw decompress; add or enlarge vents. | |
overheated resin | reduce barrel temps, back psi, screw rpm; lower inj psi, rate; open gates. | |
contamination | check dryer, hopper; purge barrel. | |
voids | material volume | increase packing, hold time, mold temp, or shot; enlarge gates. |
dark specks | charred resin flakes | purge machine, clean tip, non-return valve; check for excessive temp. |
haze, cloudiness | impurities, or low process temps | check contamination; increase drying, mold or melt temps. |
gate blush | melt fracture & stresses at gate | raise melt; reduce inj speed; check sharp edges at gate; enlarge gate. |
brittleness poor impact | poor part design, stresses, wet resin | check dryness; review design; lower regrind %, inj psi, sharp corners. |