Inter and intra-molecular branching distribution of tailored LLDPEs inferred by melting and crystallization behavior of narrow fractions

Here we report the melting and isothermal crystallization behavior of two sets of fractions obtained from a film-grade metallocene catalyzed ethylene-1-hexene resin with enhanced mechanical properties. One set of fractions was obtained by molecular weight fractionation, the second set was obtained fractionating by content of 1-hexene. The melting behavior, crystallization kinetics and supermolecular morphology of the fractions are analyzed in reference to the behavior of model systems with uniform inter-chain branching content and a random intra-chain distribution. While melting and crystallization kinetics of molecular weight fractions conforms to the bivariate (molecular weight-comonomer content) distribution of the original copolymer, the behavior of 1-hexene compositional fractions indicate a blockier branching distribution in the highly branched high molar mass fractions. Major differences with model random copolymers are also observed in the supermolecular morphology of the latter fractions.