Temperature rising elution fractionation of PP/PE alloy and thermal behavior of the fractions

In this paper, a PP/PE alloy prepared by sequential polymerization of ethylene and propylene was fractionated with temperature rising elution fractionation and a variety of fractions were obtained. Thermal analysis was conducted to probe the microstructures of fractions. Four types of fraction with different melting behaviors were identified: random copolymer with no melting peak, multiple-block ethylene–propylene copolymer exhibiting plural melting peaks, ethylene-predominant copolymer with single melting peak and ethylene–propylene block copolymer with double melting peaks. The production of these components was also discussed in terms of polymerization process and the nature of active sites in the catalyst.