Properties evaluation of semi-crystalline and amorphous polymers injected in AISI P20 molds repaired by welding

ABSTRACT >Injection molds can fail after a certain period of use, which may compromise the final part’s integrity and quality, but that can be solved using welding repair processes. This work aimed to investigate the influence of AISI P20 molds repaired by Gas Tungsten Arc Welding (GTAW) and Nd-YAG laser-welding processes on the properties of injection-molded parts with semi-crystalline (polypropylene) and amorphous (polycarbonate and acrylonitrile butadiene and styrene terpolymer) thermoplastics. Welds were prepared by machining 0.8 mm-deep 40 mm x 5 mm grooves to be filled by GTAW and Nd-YAG laser-welding deposits, in order to simulate the repair of AISI P20 molds. All polymers were injected into weld-repaired and unrepaired molds, and then evaluated in terms of microstructure, crystallinity degree, mechanical properties and gloss. The results suggest that the repaired region for both studied welding processes, despite the difference in hardness of the weld region, does not significantly affect the properties of semi-crystalline and amorphous injected polymers.

摘要：注塑模具在使用一定周期后可能发生失效，进而影响最终制品的完整性与质量，不过可通过焊接修复工艺解决该问题。本研究旨在探究经钨极气体保护焊（Gas Tungsten Arc Welding，GTAW）与Nd-YAG激光焊修复的AISI P20模具，对采用半结晶型（聚丙烯（polypropylene））及无定形型（聚碳酸酯（polycarbonate）、丙烯腈-丁二烯-苯乙烯三元共聚物（acrylonitrile butadiene styrene terpolymer））热塑性塑料制备的注塑件性能的影响。为模拟AISI P20模具的修复过程，研究人员通过加工深度0.8 mm、尺寸40 mm×5 mm的凹槽，再采用GTAW与Nd-YAG激光焊进行堆焊以制备修复焊缝。将所有热塑性塑料分别注入经焊接修复与未经修复的模具中，随后从微观结构、结晶度、力学性能以及光泽度四个方面对注塑件进行表征评估。结果表明，尽管两种焊接工艺对应的修复区域硬度存在差异，但二者的修复区域均未对半结晶型与无定形型注塑聚合物的性能产生显著影响。