Construction of a three-dimensional network in branched PETG to prepare PETG composite microcellular foam with outstanding mechanical properties at low temperatures

In response to the escalating demands in cold chain logistics, in this study, we developed a high-compression strength foam resistant to low temperatures using a proficient and accessible approach. The microcellular foam was prepared through chain modification and in situ-fibrillated technology of polytetrafluoroethylene (PTFE). An epoxy chain extender, ADR4468, was incorporated to enhance the foamability of poly(ethylene glycol-co-cyclohexane-1,4-dimethanol terephthalate) (PETG). In addition, chain-extended PETG (CEPETG)–PTFE nanocomposites were formulated by integrating a PTFE three-dimensional (3D) nanofiber network. The PTFE nanofiber serves as an effective nucleation agent owing to its large specific surface area and undergoes a crystal-shaped transformation to further augment its strength. By leveraging the synergistic influence of these two principles, we employed the scCO2 foaming technology to obtain CEPETG–PTFE nanocomposite microcellular foam, which exhibited high-compression strength at low temperatures. The introduction of the chain extender improved the foaming characteristics of PETG. Consequently, the expansion ratio of the PETG foam increased from 5.18 to 36.01. Moreover, the formation of the PTFE 3D nanofiber network decreased the cell size from 16.16 to 2.38 μm. Furthermore, the low-temperature compression of the foam increased by 266 %, with an improvement in its toughness.