采用差示扫描量热法(DSC),广角 X 射线衍射(WAXD)等方法研究了取向聚丙烯(PP)片材的熔融重结晶行为.结果表明:熔融过程的残余晶体、重结晶产生的新晶体晶型和取向方向均未发生变化,均为α晶且沿着机器方向(MD)取向.熔融重结晶过程中熔融峰值温度和结晶度随着停留温度(Ts)升高先升高后逐渐降低.当Ts低于 155.0℃时处于退火区,取向PP片材晶体整体的框架结构依然存在.当Ts大于 169.0℃时取向PP片材完全熔化.当Ts在 155.0～168.0℃时处于自成核区,部分未熔化的晶体碎片构成了晶核,并在冷却过程中产生了结晶,且新晶体沿着残余晶体的方向取向.
Study on Melt Recrystallization Behavior of Oriented Polypropylene Sheet
The melt recrystallization behavior of oriented polypropylene(PP)sheet was studied by differential scanning calorimetry(DSC),wide-angle X-ray diffraction(WAXD)and other methods.The results show that the forms and orientation directions of residual crystals during the melting process and the new crystals generated by recrystallization have not changed,both of which are α crystal oriented along the machine direction(MD).During the process of melt recrystallization,the peak melting temperature and crystallinity first increase and then gradually decrease with the increase of the residence temperature(Ts).When Ts is below 155.0℃,the oriented PP sheets are in the annealing region,and the overall framework structure of the crystals still exists.When Ts is above 169.0℃,the oriented PP sheets are completely melted.When Ts is from 155.0 to 168.0℃,the oriented PP sheets are in the self-nucleation region,some unmelted crystal fragments form the crystal nuclei and re-crystallization occurs during the cooling process,with the new crystals oriented along the direction of the residual crystals.
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