Aging Effects on the Phase Composition and Chain Mobility of Isotactic Poly(propylene)

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.