Fractionation of ethylene–propylene copolymers

Abstract

AbstractEthylene–propylene (EP) copolymers were fractionated according to chemical composition, molecular weight, or monomer sequence length, which are fundamental distribution factors. Cloud points of polyethylene (PE), polypropylene (PP), and EP copolymer were determined prior to the fractionation. From the results, it was estimated that xylene–butyl cellosolve and tetralin–ethyl carbitol systems were suitable for the fractionations according to chemical composition and molecular weight, respectively. EP random‐type copolymers were fractionated using a xylene–butyl cellosolve system. Separations according to chemical composition were obtained as expected. Then, the above polymer fractions were further fractionated in a tetralin–ethyl carbitol system. and the dependence on molecular weight was observed fairly well. Furthermore, fractionation according to monomer sequence length was satisfactorily achieved by solvent extraction using ethyl ether, n‐hexane, cyclohexane, and n‐heptane. Therefore, it is concluded that the more detailed characterizations of EP copolymers are made possible by a combination of these techniques.