Cell Structure\nVariation of Long-Chain Branched Polyether\nBlock Amide Regulated by Crystallization Behavior

A simple isothermal melt crystallization-foaming method\nwas proposed\nto explore the modulation of the foam cell structure in long-chain\npolyether block amide (PEBA) through annealing modulation crystallization\ncombined with the control of melt strength. The presence of long-chain\nbranched structure markedly enhances the melt strength of PEBA, while\nboth crystallinity and semicrystallization time decrease with an increasing\ndegree of branching. By adjusting the crystallization temperature\n(<i>T</i><sub>iso</sub>) and crystallization time (<i>t</i><sub>iso</sub>), foams with different cell structures were\nobtained. The cell size of unmodified PEBA initially increases and\nthen decreases with an increase in <i>t</i><sub>iso</sub>. In contrast, modified PEBA exhibits sufficient melt strength to\nsupport cell growth at <i>t</i><sub>iso</sub> = 0, leading\nto a decrease in cell size. When <i>T</i><sub>iso</sub> is\nless than 140 °C, the foaming process is influenced by both melt\nstrength and crystallization kinetics. As <i>T</i><sub>iso</sub> increases, the melt strength weakens and crystallinity decreases,\nresulting in an increase in cell size. This foaming method effectively\ncontrolled the cell structure of PEBA, expanding its potential applications.