The Shear‐Accelerated II–I Phase Transition of Isotactic Poly(1‐Butene)

Abstract

The II‐I phase transition of isotactic poly(1‐butene) (iPBu) leads to improved mechanical performance. However, this will take several weeks and increase storage and processing costs. In this work, shear forces were introduced into the supercooled iPBu melt, and the effects of isothermal crystallization temperature (Tc) and shear temperature (Tshear) on crystallization and phase transition were explored. Shear‐induced transcrystalline morphology of Form II with a significantly shortened crystallization induction period can be observed at relatively high Tc (105 °C). Besides, the shear‐induced Form II can transit to Form I faster than the unsheared one. In addition, the phase transition rate increases as the Tshear decreases, with the fastest rate occurring at Tshear of 120 °C. The half transition time (t1/2) is measured as 6.3 hours, much shorter than the 20.7 hours required for unsheared samples. The accelerated phase transition of iPBu can be attributed to the stretching of molecular chains resulting from shear treatment. This study provides a quantitative analysis of the influence of the shear treatment and the Tshear on the II‐I phase transition rate. And it also presents a cost‐effective and straightforward approach for expediting the phase transition process.This article is protected by copyright. All rights reserved