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.