Modeling of the lamellar structure of ethylene-1-octene copolymers

The parameters of the lamellar structure of melt crystallized ethylene-1-octene copolymers were determined with the usage of model calculations. Two models were employed: classical model of Hosemann and a variable local structure model. In the second model it was assumed that the crystallinity of stacks varies from stack to stack according to some distribution function P(j). Theoretical SAXS curves related to the assumed models were best fitted to the experimental curves and the parameters of stacks were determined. It was found that the second model gave much better fits then the model of Hosemann. Generally, the distribution function P(j) is asymmetric and positively skewed but its shape changes for the stacks crystallized at various temperatures. At higher temperatures, starting from the melting point, the crystallinity distribution can be well approximated by the Reinhold function. At lower temperatures, closer to the final solidification, the split Gauss function is a better approximation.