PUR-T对POM球晶成核与生长过程的影响

以聚酯型热塑性聚氨酯(PUR-T)作为聚甲醛(POM)球晶生长抑制剂,采用热台偏光显微镜,即时在线跟踪POM球晶的成核与生长过程,研究了PUR-T在其不同用量以及不同结晶温度下对POM球晶成核及生长过程的影响。结果表明,PUR-T存在下,POM的成核密度明显增大,并随结晶温度的提高基本呈下降趋势;在结晶温度为155℃及以下时,PUR-T对POM成核时间基本无影响,156℃以上时,使成核时间明显增加,158℃的增加尤为显著。PUR-T使POM球晶生长速率明显下降,且结晶温度越高,生长速率下降幅度越大;PUR-T质量分数为5%～15%时,用量变化对生长速率的影响甚微。同时,PUR-T使POM结晶过程的成核参数和折叠链表面自由能增加,表明PUR-T的加入使POM成核难度增大,球晶生长所需克服的能量增加。

Effects of PUR-T on Nucleation and Growth of POM Spherulite

Polyester type thermoplastic polyurethane(PUR-T)was used as the growth inhibitor of polyoxymethylene(POM)spherulites,and the nucleation and growth process of POM spherulites were on-line tracked by means of polarized light microscopy with hot stage.The effects of PUR-T with different content at different crystallization temperature on the spherulites nucleation and growth of POM were studied.The results show that in the presence of PUR-T,the nucleation density of POM increases obviously,and the density of POM nucleus decreases basically with the increase of crystallization temperature.However,the nucleation time is not affected basically at 155℃or below,and the nucleation time increases obviously at 156℃or high than,especially at 158℃.The growth rate of POM spherulites is obviously decreased by PUR-T,and the decrease of growth rate is more greater with the increase of crystallization temperature.When the mass fraction of PUR-T is 5%–15%,the change of content has little effect on the growth rate.At the same time,the nucleation parameters and the surface free energy of the folding chain are increased with adding PUR-T,which indicates that the nucleation difficulty increases and the energy needs to overcome in spherulite growth increases.