This paper analyses the thermal behaviour of six EVA copolymers supplied by REPSOL Company. In relation to crystallization and melting temperatures, both of them decrease when the vinyl acetate percentage increases, in agreement with the fact that polyethylene is a semi-crystalline material, whereas polyvinylacetate is an amorphous polymer. Actually, when the vinyl acetate percentage reaches 30%, the copolymer is practically amorphous. The non-isothermal crystallization was modelled with the modified Avrami model that showed, with the exception of EVA-460 (the material with higher vinyl acetate percentage), the presence of a secondary crystallization due to spherulite impingement in the later stage of the non-isothermal crystallization. The TG analysis indicated two weight loss stages, the first one due to acetic acid loss and the second one due to fragments of polymer backbone, which appear as two separate peaks in the DTG plots. Finally, due to the linear dependence of melting and crystallization temperatures and of the minimum value of DTG peaks on vinyl acetate percentage, it can be concluded that both TG and DSC techniques can be employed to determine the vinyl acetate percentage of a certain copolymer.

本文分析了REPSOL公司提供的六种EVA共聚物的热行为。关于结晶和熔融温度，当乙酸乙烯酯百分比增加时，两者均降低，这与聚乙烯是半结晶材料而聚乙酸乙烯酯是无定形聚合物这一事实相一致。实际上，当乙酸乙烯酯百分比达到30％时，该共聚物实际上是无定形的。使用改良的Avrami模型对非等温结晶进行建模，除EVA-460（具有较高醋酸乙烯酯百分比的材料）外，该模型还显示由于非球状晶体在后期的球晶撞击而导致二次结晶的存在。等温结晶。TG分析显示了两个减肥阶段，第一个是由于乙酸的损失，第二个是由于聚合物主链的片段，在DTG图中显示为两个单独的峰。最后，由于熔融和结晶温度以及DTG峰的最小值与乙酸乙烯酯百分比的线性关系，可以得出结论，TG和DSC技术均可用于确定某种共聚物的乙酸乙烯酯百分比。