Effects of swelling and annealing on the viscoelastic behavior of solution‐crystallized and melt‐crystallized samples of fractionated polypropylene

Dynamic viscoelastic measurements, E′ and E″, were carried out on solution‐crystallized and melt‐crystallized samples of fractionated isotactic polypropylene over the temperature range of −100°C to 150°C. The molecular weight ranged from 1.26 × 104 to 1.77 × 105. The effects of swelling and annealing on the α and β peaks were more pronounced for the lower molecular weight fraction than for the higher one. It was found that both the untreated solution‐crystallized and quenched melt‐crystallized samples contain a fair amounts of a constrained amorphous phase in which the molecular motions were so depressed that the corresponding peak could be observed as the low‐temperature component of the α peak. These constraints on the molecular motions are considered to originate from the spatial restrictions imposed by the presence of the surrounding crystallities.