Supertough\nPolylactide Blend Foams with Controlled\nCell Size

The mechanical properties of polymeric foams are strongly\nassociated\nwith their cellular structure. However, the relationship between the\ncellular structure and the mechanical behavior of polymeric foams\nis complicated by the interdependence of cell size and expansion ratio.\nHerein, we explored the relationship between cell size and impact\nstrength in poly(lactic acid) (PLA)/rubber blend foams by controlling\nthe cell size while maintaining a constant expansion ratio. Surprisingly,\na cell size-induced brittle-to-tough transition was observed at a\ncritical cell size. Foams exhibited brittleness when the cell size\nexceeded this critical threshold, whereas smaller cell sizes led to\nimproved toughness. The increased toughness was attributed to the\nrobust interaction of stress fields generated by adjacent cells and\nrubber particles, which could hinder the progression of cell-induced\ncrazes into cracks, resulting in greater energy absorption. This study\nprovides a universal strategy for enhancing the resilience of polymer/rubber\nblend foams.