Highly expanded, highly insulating polypropylene/polybutylene-terephthalate composite foams manufactured by nano-fibrillation technology

Abstract This paper presents a new nano-fibrillation method to produce highly expanded microcellular polypropylene (PP) foams with high thermal insulation properties. Polybutylene terephthalate (PBT) nano-fibrils were formed in the PP matrix through a melt spinning process to increase the foamability of PP resins which have inherently low melt strength. In this process, the two immiscible polymer phases are extruded and drawn into fibers. In the fiber composite, the PBT nano-fibrillar reinforcement phase typically has an average diameter of less than 200 nm. The results show that the presence of the long aspect-ratio nano-fibrils enhances the foamability of the PP matrix, and the foamed samples achieved high thermal insulation properties (~32 mW∙m−1∙K−1). As the capital investment and development time costs of the existing technologies for improving foamability are high, the new manufacturing method can provide significant economic and technical advantages for producing highly expanded and insulating PP-based foams.