Problem 1: Discolor, embrittlement, black spot appeared.
Analysis: The main reasons are plastic, UV-absorbe, antistatic agent decomposed in barrel because of high temperature or stay in barrel for a long time, then injected into mould with melted plastic. Detail reasons as below,
1).Reason of injection part,
A.Heating system out of control, the temperature of barrel is too high lead to plastic decomposed and turn black.
B. Defect in screw or barrel, cause plastic stay in barrel for a long time, and long time heating lead to decompose. Should inspect screw tips are worn or not or if there are metal foreign material.
C. Plastic reason, some kinds of plastic such as ABS decomposed in barrel because high temperature
2). Reason of mould
A, Mould can not exaust smoothly, plastic is easy to scorching, or sprue bush is too small, shear force too large led to scorching.
B.There are unsuitable lubricating oil or mold releases in mould
3).Reason of Plastic
The processed plastic if not clean, too many volatiles, high humidity, too many impurities or recycle material polluted.
4) Reason of processing
A, injection pressure too high, injection speed too fast, back pressure too high, rotation speed of screw too high will led material too high temperature and decompose.
B, Should clean barrel regularly, remove unstable additives.