Recyclable high latent heat flexible PEG/EVA phase change composites were constructed via dynamic ion crosslinking networks and applied to enhance the dimensional stability of EVA foam materials

The latent heat of phase change in iPCMs reaches up to 110.14 J/g. • iPCMs are flexible materials with a maximum elongation at break of up to 527.25%. • iPCMs exhibit excellent dimensional stability and recyclability. • The transverse thermal shrinkage rate of FEVA-iPCMs decreased by 56.05%. • The longitudinal thermal shrinkage rate of FEVA-iPCMs has been reduced by 57.66%. Developing organic phase change materials that simultaneously exhibit high latent heat, shape stability, and recyclability remains a significant challenge, particularly in achieving an effective balance between suppressing phase change component leakage and maintaining high latent heat. In this study, we constructed a crosslinked framework via esterification between polyethylene glycol (PEG) and pyromellitic dianhydride (PMDA) and introduced zinc acetate to form a dynamic ionic crosslinking network; meanwhile, ethylene-vinyl acetate (EVA) provided flexibility and encapsulation support, enabling the successful fabrication of a recyclable, high-latent-heat, flexible solid-solid phase change material (iPCMs). We systematically investigated the effects of the equivalent ratio of PEG to PMDA on the structural characteristics, thermal behavior, rheological properties, mechanical performance, and recyclability of the iPCMs. The results demonstrate that the as-prepared iPCMs achieve a phase change latent heat of up to 110.14 J/g and a maximum elongation at break of 527.25%, while exhibiting excellent recyclability, stable shape retention, and well-preserved performance after 100 thermal cycles. Furthermore, we incorporated the iPCMs into an EVA foaming system, where the iPCMs not only restricted EVA molecular chain mobility through the ionic crosslinking network but also slowed gas diffusion within the cells and thermal relaxation of the EVA matrix via a phase change-induced temperature-regulating effect, thereby significantly improving the dimensional stability of EVA foams at 70 °C. Specifically, the transverse and longitudinal shrinkage rates of FEVA-iPCMs-4.5 are 1.89% and 1.77%, respectively, representing reductions of 56.05% and 57.66% compared with those of FEVA. This study provides a viable new pathway for developing high-performance, recyclable composite phase change materials and for realizing their functional applications in polymer foaming systems.