THE COCRYSTALLIZATION OF POLYMERS - POLYETHYLENE AND ITS COPOLYMERS

This paper covers study of the molecular constitution requirements for the cocrystallization of chemically similar polymeric species. The authors have directed attention of both homopolymer-copolymer mixtures and copolymer mixtures of polyethylene. Molecular weight and composition fractions were used exclusively. Molecular weights of the components were matched in order to study the influence of chain structure. Differential scanning calorimetry and selective extraction techniques were used to assess whether cocrystallization occurred. Linear polyethylene, and random copolymers which contained up to 2 mol percent of either ethyl or acetate branches, cocrystallized upon rapid crystallization from the melt. When the branching content was greater than about 3 mol percent, cocrystallization did not occur. Copolymers containing about 1-2 mol percent were found to cocrystallize with one another. However, copolymers containing higher counit contents did not cocrystallize with one another or with samples containing a smaller amount of counit.