POM LA543旭化成

POM LA543旭化成--聚甲醛（POM）均聚物，他的耐磨性好 低摩擦 润滑 中等粘度， 熔体流动速率:17 g/10min 密度:1.38 g/cm3 吸水率:0.3 % 成型收缩率:2 % 弯曲强度:89 MPa 弯曲模量:2650 MPa 硬度:81

POM in the extrusion process, the focus is to control the water temperature in the cooling tank, under the premise of maneuverability, as far as possible to increase the water temperature. The injection pressure of POM is high and the process length is longer. In order to ensure the filling of parts, relatively high injection pressure is needed. The larger the holding pressure, the higher the dimensional accuracy of POM parts. POM has large crystallinity and narrow melting range. When it is cooled and hardened, it often produces a large volume shrinkage of 2.8%. In order to make up for the size defect, it is necessary to have sufficient holding pressure. Therefore, in injection moulding of POM, increasing the holding pressure properly can reduce and eliminate the phenomenon of warping, shrinkage pits and internal holes in POM products. Injection pressure and time have different effects on the properties of homopolymer POM and copolymer POM. Injection pressure and holding time have obvious effects on the mechanical properties of homopolymer POM, but relatively small effects on the properties of copolymer POM. The elongation at break can be increased by properly prolonging the holding time of homopolymer POM.

POM按分子链中化学结构的不同可分为均聚甲醛和共聚甲醛两种，均聚甲醛一般是由无水聚甲醛聚合而得，共聚甲醛是由三聚甲醛与少量二氧戊环的共聚产物。正是由于结构上的不同，导致均聚和共聚甲醛在各项性能下存在差异。两者主要区别是：均聚甲醛密度、结晶度较高，熔点与HDT较共聚甲醛高10℃，强度、耐蠕变性能和耐摩擦性能更优越，但热稳定性差，加工温度范围窄约10℃，对酸硷的稳定性较低。共聚甲醛密度、结晶度、熔点、强度都较低，但热稳定性相对较好，不容易分解，加工温度范围宽30~50℃，对酸硷稳定性较好。

POM共聚甲醛是由美国Celanese公司1960年发明，并于1962年实现工业化生产，随后德国Hoechst和Celanese 的合资公司Hoechst-Celanese 、美国BASF、日本的宝理公司和旭化成公司、三菱瓦斯化学公司纷纷投入生产。随后巴斯夫公司、三菱瓦斯公司、宇部兴产公司、宝理和旭化成对合成过程进行了改进，各自具有独特的技术特点。宇部兴产公司在聚合过程中采用气相法。巴斯夫和三菱瓦斯公司所用溶剂为二氯乙烷，以环氧乙烷(或二氧戊环)为共聚单体。旭化成公司采用POM甲缩醛氧化直接合成70%高浓度甲醛的工艺。