Influence of Chain Extender on The Thermal, Rheological, and Supercritical Foaming Behavior of Polyamide-12

Abstract

In this study, the influence of chain extender (CE) concentration on the batch foaming behavior of Polyamide 12 (PA 12) under supercritical CO₂ batch foaming is investigated. Foam density and expansion behavior were analyzed as a function of processing temperature and pressure. Significant improvements in foam structure and density were observed with increasing CE content. This led to fine and uniform morphologies, accompanied by a substantial increase in cell density. Optimal performance was achieved at 0.5 wt.% CE, where the smallest cell size and the highest nucleation density were obtained, along with low foam densities in the range of approximately 0.06 to 0.09 g/cm³. Rheological analysis revealed that CE incorporation significantly increased melt viscosity, elasticity, and strain-hardening behavior, enhancing melt stability during cell growth. DSC analysis indicated a reduction in crystallinity and the formation of heterogeneous crystalline structures, with crystallization temperatures shifting to higher values, and a broader melting behavior was observed. These findings provide critical insight into the role of modification and processing conditions play in the effect of foam structure and performance, offering a naive strategy for of PA 12 batch foaming.