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Changes in phase composition and chain mobility in injection‐molded isotactic poly(propylene), crystallized from the melt with slow cooling rate and subsequently quenched, associated with aging at temperature well above Tg for 150 and 1 000 h, are studied using time‐domain 1H solid‐state NMR and XRD. All sample exhibit physical aging when exposed to elevated temperatures, and the physical aging kinetics was observed to depend on the morphology of the homopolymer iPP and aging temperatures. The significant increase in the tensile modulus in time was observed for injection‐molded iPP. The observed property changes induced by aging are attributed to microstructural changes within the semi‐rigid and amorphous fractions.

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Temperature rising elution fractionation (TREF) is a highly valuable and widely used tool for chemical composition separation of semicrystalline polyolefins. However, TREF operational conditions should be carefully selected due to their high impact on separation quality. This is especially true for polypropylene (PP)‐based polymers due to their slow crystallizing nature and defect distribution, which can further complicate the fractionation. In order to more fully understand this behavior, a systematic investigation was designed to determine the influence of support and cooling rate on preparative TREF of PP random copolymers. Possible measures to limit undercooling of PP and thus preventing so called co‐elution of different microstructures in TREF were demonstrated using glass beads as support during fractionation and cooling rate of 0.02°C/min. Support presence during fractionation acted as a nucleating agent to limit the elution of long isotactic chains in the low temperature fractions. Slow cooling rate along with support presence further improved the separation quality by giving the polymer chains enough time to overcome the undercooling.