Cell Structure Variation of Long-Chain Branched Polyether Block Amide Regulated by Crystallization Behavior

A simple isothermal melt crystallization-foaming method was proposed to explore the modulation of the foam cell structure in long-chain polyether block amide (PEBA) through annealing modulation crystallization combined with the control of melt strength. The presence of long-chain branched structure markedly enhances the melt strength of PEBA, while both crystallinity and semicrystallization time decrease with an increasing degree of branching. By adjusting the crystallization temperature (Tiso) and crystallization time (tiso), foams with different cell structures were obtained. The cell size of unmodified PEBA initially increases and then decreases with an increase in tiso. In contrast, modified PEBA exhibits sufficient melt strength to support cell growth at tiso = 0, leading to a decrease in cell size. When Tiso is less than 140 °C, the foaming process is influenced by both melt strength and crystallization kinetics. As Tiso increases, the melt strength weakens and crystallinity decreases, resulting in an increase in cell size. This foaming method effectively controlled the cell structure of PEBA, expanding its potential applications.