Interpreting compression resistance and resilience of spacer fabrics with morphological and mechanical changes of different polymeric spacer monofilaments

Customization of spacer fabrics to have the desired compression resistance and resilience is critical to promote their technical applications. The compression properties are mainly determined by the mechanical features of monofilaments used as spacer yarns. This study investigates the compression properties of spacer fabrics knitted with different polymeric monofilaments by analyzing their compression stress at 40% strain, residual strain, and energy absorption from cyclic compression tests. The monofilaments in the fabrics before and after cyclic compression were unraveled to test their tensile properties and morphologies for interpreting their different fabric compression properties. It was found that knitting monofilaments substantially alters their macroscopic and/or microscopic structures, thereby affecting the mechanical behavior of spacer monofilaments, and having different fabric structures and compression properties. Knitting polyethylene terephthalate monofilament damages the mesophase and induces a two-thirds decline in Young's modulus, while knitting polyamide 6 and polybutylene terephthalate monofilaments largely alters the macrostructures but maintains their good resilience. Spacer fabrics knitted with stiffer polyethylene terephthalate monofilaments have superior compression resistance but inferior compression resilience, while those knitted with softer and more resilient polyamide 6 and polybutylene terephthalate monofilaments have better compression resilience. Polyethylene monofilament is not suitable for spacer fabrics because of its low Young's modulus and poor tensile resilience. Polyethylene terephthalate spacer fabrics have the best compression resistance–resilience balance in terms of compression stress at 40% strain and residual strain in the fourth cycle required by the standard EN ISO 3386-1, while polyamide 6 and polybutylene terephthalate monofilaments are more suitable for long-term service due to their high compression resistance and resilience.