Ionomer as inherently crosslinked foam

Many foam applications require a crosslinking step to enhance durability, strength, and stability of the foam by creating a three-dimensional network of polymer chains. Crosslinking improves material properties like durability, thermal stability, and chemical resistance by chemically bonding polymer chains together. This process enhances the foam's ability to resist tearing, recover from high deformation, and heat stability, making it suitable for high-performance uses where non-crosslinked foams would fail. Crosslinking also results in a more uniform, closed-cell structure, which improves water resistance and dimensional stability. The primary techniques for crosslinking low-density polyethylene (LDPE) and ethylene-vinyl acetate (EVA) foams are chemical crosslinking (e.g via peroxides) and radiation crosslinking. This can be done in a semi/continuous process as shown in Figure 1 and 2 or in a discontinuous manner as typical in the bun foaming process. In this invention, we show that Ion-Pair-Comonomer based LDPE ionomers display intrinsically a crosslinking network that foams at the chemical blowing agent decomposition temperature without the need of chemical or radiation crosslinking. This feature enables such PE-ionomer to replace permanently crosslinked materials with ionic crosslinks that are thermally reversible. This not only makes the process to make this foam simpler by removing a crosslink step, but it also enables recyclability of such foams. Additionally, we expect good foam recovery from large applied deformation (compression).