The cell growth-induced orientation of mica in lightweight flexible poly (vinyl chloride) foams and its enhancement on sound insulation

The lightweight flexible poly(vinyl chloride) (PVC)/mica composite foams with low density (0.51 g/cm3) which is 40-60% reduction and high sound insulation performance (an average STL of 28.3 dB) were prepared in this work. And the influences of mica content and foaming time on the cell morphology, mica distribution, and sound transmission loss (STL) were investigated. It was observed that the PVC/mica foams not only showed good sound insulation properties, but also maintained ultra-light in weight when the mica content was below 10 wt%. In addition, as the foaming time became longer, the cell density increased and the cell-wall thickness decreased. As a result, the bi-axial stretching induced by the cell growth would drive the mica platelets to orient along the thin cell walls, which significantly increased the sound insulation properties. Simultaneously, the flexibility and reusability of the foams were tested by cyclic compression. When the mica content was below 10 wt%, the PVC/mica composite foams showed low compressive stress and low permanent strain.