塑膠射出成型拉伸試片退火處理後拉伸強度之探討

Abstract

本研究以聚碳酸酯（PC）、聚甲醛樹脂（POM）、聚苯乙烯（PS）、丙烯樹脂（PP）為材料，探討射出成型塑膠拉伸試片於退火後之拉伸強度的改變，並比較不同退火時間對結晶性塑膠與非結晶性塑膠之拉伸強度的影響。 高分子塑膠在射出成型製品上，常會有殘留應力與內應力的產生，成型時的噴流現象、剪切作用與冷卻後收縮不均等原因亦會造成塑膠分子鏈結構與結晶性的差異。根據以往文獻指出，退火處理可改善塑膠殘留應力與改變結晶度，本實驗將塑膠於射出成型後，利用退火處理之方式，使得殘留應力變小，分子結晶度變好，而強化機械性質。 由於不同的退火時間所改善殘留應力與結晶度之程度不同，因此其機械性質亦不同。 本實驗將不同退火時間之試片，以拉伸試驗法求得退火處理前後試片之拉伸強度。實驗結果發現材料的拉伸強度會隨著退火處理時間增加而增加，而拉伸強度增加的比率卻會隨著時間增加而減少。另外比較非結晶與結晶性塑膠，可以發現結晶性塑膠退火處理後拉伸強度增加的效果比非結晶性塑膠效果好。並且在射出成型塑膠製品上，其退火處理一小時的拉伸強度增加的效果最為顯著。

This purpose research is to find out tensile strength of the plastic injection test pieces after annealing. The test pieces are made of PC, POM, PS, and PP materials. The relation of the crystalline micro-structure of the plastics with tensile strength was also studied. Plastics often present internal and residual stress in injection molding. Besides, fountain flow effect and shearing of the molten plastics in the mold change the micro-structure. This experiment is emphasized on the effect of annealing of the injected plastic test pieces. This study also makes comparison of the tensile strength among semi-crystalline, amorphous, engineering, and general plastic after annealing. In the analysis of four different plastics, it was found that the tensile strength grows with the annealing time. The test was further concluded that semi-crystalline plastics are generally have higher strength than the amorphous. After 1-houred annealing, the plastic injection test piece reached the highest strength.