In this study, we developed a sustainable polyamide foam system. A new series of polyamide elastomers was synthesized using a bio-based dimer diamine monomer as a building block to copolymerize with aminocaproic acid and adipic acid through step-growth polymerization, followed by supercritical CO₂ foaming for the fabrication of microcellular foams. The introduction of the branched-structured dimer diamine monomer effectively restricted the molecular packing and hydrogen bonding density of the polyamide system, leading to numerous small crystals acting as nucleation sites for heterogeneous cell nucleation. Simultaneously, the branched long chains of the dimer diamine formed chain entanglement networks, which increased the material melt strength against the elongational stresses of cell growth. The synergistic effect provided by dimer diamine led to the successful manufacture of foamed samples with a high expansion ratio and robust dimensional stability, effectively overcoming the foaming difficulties of high crystallinity and insufficient melt strength in traditional polyamide 6 (PA6). In addition, this polyamide elastomer foam system could be recycled and reprocessed due to the advantages of non-crosslinking and additive-free. Therefore, the study’s findings constitute a promising direction for the usage of renewable sources in the development of foamable polyamide materials for sustainable applications in the plastics industry.

在这项研究中，我们开发了一种可持续的聚酰胺泡沫系统。使用生物基二聚二胺单体作为结构单元，通过逐步增长聚合与氨基己酸和己二酸共聚，然后通过超临界 CO ₂发泡制备微孔泡沫，合成了一系列新的聚酰胺弹性体。支链结构二聚二胺单体的引入有效地限制了聚酰胺体系的分子堆积和氢键密度，导致许多小晶体作为异质细胞成核的成核位点。同时，二聚二胺的支链长链形成 缠结网络，它增加了材料熔体强度以抵抗细胞生长的拉伸应力。二聚二胺提供的协同效应成功制造出具有高膨胀比和强大尺寸稳定性的发泡样品，有效克服了传统聚酰胺6（PA6）结晶度高和熔体强度不足的发泡困难。此外，这种聚酰胺弹性体泡沫系统由于具有非交联和无添加剂的优点，可以回收和再加工。因此，该研究的结果为使用可再生资源开发可发泡聚酰胺材料以在塑料行业中实现可持续应用提供了一个有希望的方向。