辐射交联聚合物的结晶动力学(英文)

电离辐射在工业上应用的基础是聚合物的辐射交联,它们是绝缘电线和电缆的交联,热收缩性材料的生产,泡沫塑料等等。辐射引发交联已经被广泛地研究,特别是凝胶的形成和聚合物结构、辐照条件对交联度的影响。对于一般法和辐射法交联的聚合物却很少有人研究它的结晶过程。例如,已经证明除了在非常高的吸收剂量外,辐照的聚乙烯中总的结晶度不受影响,但对于聚丙烯和聚丁烯在凝胶点剂量时,它们的结晶度大大减少。辐照聚合物的重新熔融,进一步减少了总结晶度。 本工作表明不仅总的结晶度而且结晶动力学也受辐射引发交联的影响。结晶速率指出结晶划分成二种不同增长机理的过程。冷却速率是一个重要的因素,它决定结晶过程并影响与交联的半晶聚合物的结晶度和形态有关的其它性质。

CRYSTALLIZATION KINETICS OF RADIATION CROSSLINKED POLYMERS

Several industrial applications of ionizing radiation are based on radiation cross-linking of polymers: crosslinking of wire and cable insulation, production of heatshrinkable materials, plastic foam, etc. Radiation induced crosslinking has been thesubject of many studies, especialy the gel formation and effect of polymer structureand irradiation conditions on the yield of crosslinks. Much less has been done to stu-dy crystallization of crosslinked polymers in general and radiation crosslinked polymersin particular. It has been shown, for example, that the total crystallinity in irradia-ted polyethylene is not affected except at very high absorbed doses. On the otherhand it is significantly reduced in polypropylene and poly-1-butene already at doses about the gel point. In all cases remelting of irradiated polymers further reduced thetotal crystallinity. In this work it is shown that not only the total crystallinity, but also the crys-tallization kinetics are affected by radiation induced crosslinks. The rate of crystalliza-tion indicated that the crystallization can be separated in two processes with differentgrowth mechanisms. The rate of cooling is an important factor which determines thecrystallization procedure and affects other properties dependent on crystallinity andmorphology of crosslinked semicrystaline polymers.