Bewise Inc. www.tool-tool.com Reference source from the internet.
1. PP
1.1性能和用途
PP( Polypropylene聚丙烯)是与我们日常生活密切相关的通用树脂,是丙烯最重要的下游产品,世界丙烯的50%,我国丙烯的65%都是用来制聚丙烯。聚丙烯是世界上增长最快的通用热塑性树脂,总量仅仅次于聚乙烯和聚氯乙烯
PP 是结晶性塑料 ,一般为呈不规则圆形表面有蜡质光泽白色颗料。密度0.9-0.91g/cm³,是塑料中最轻的一种。有较明显的熔点, 根据结晶度和分子量的不同,熔点在170℃左右,而其分解温度在290℃以上,因而有着很宽的成型温度范围,成型收缩率1.0- 2.5%。PP的使用温度可达100℃,具有良好的电性能和高频绝缘性,且不受湿度影响。但低温下易脆,不耐磨,易老化。适于制作一般机械零件,耐腐蚀零 件和绝缘零件。此外,用PP料制做的铰链产品具有突出的耐疲劳性能。
1 .2 成型注意事项
PP的吸湿性很小,成型前可以不 要干燥,如果存偖不当,可在70℃左右干燥3小时。成型流动性好,但收缩范围及收缩值大,易发生缩孔,凹痕,变形。冷却速度快,浇注系统及冷却系统应缓慢 散热。PP在成型时要特别注意控制原料的熔化时间,PP长期与热金属接触易分解。易发生融体破裂,料温低方向方向性明显,低温高压时尤其明显。模具温度方 面,在低于50℃度时,塑件不光滑,易产生熔接不良,流痕,在90℃以上易发生翘曲变形。塑料壁厚须均匀,避免缺胶,尖角,以防应力集中。
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