Polycarbonate-based hybrid ternary blend with regulated silica dispersion and distribution towards high environmental stress crack resistance, high strength and high toughness

Abstract

Polycarbonate (PC) has a very low environmental stress crack resistance (ESCR). This work aims at increasing its ESCR as well as its tensile strength and toughness via a hybrid ternary blend (HTB) which is composed of PC, hydroxyl-rich polyvinyl butyral (PVB) and hydroxyl-rich silica (SiO2). Selective distribution and fine dispersion of SiO2 in the dispersed phase (PVB) through hydrogen bonding between the PVB and SiO2 endows the HTB with high ESCR, tensile strength and toughness. Two processes are compared to develop the HTB. One is composed of two steps: the SiO2 is dispersed in the PVB dissolved in anhydrous ethanol; after the removal of the ethanol, the resulting (PVB/SiO2) is then blended with the PC in the molten state. The other process is composed of a single step: PVB, SiO2 and PC are directly blended in the molten state. The two-step process yields better properties: The PC/(PVB-10/SiO2-2) containing 10 wt% of PVB and 2 wt% of SiO2 shows higher melt flow index, tensile strength and toughness. More importantly, its ESCR in carbon tetrachloride is 5 times that of the PC. We envision that this work provides a new perspective to the theory of HTB, and opens a promising route to prepare high-performance PC with excellent practicality.