Smoke suppression of graphene platelets fabricated by Friedel–Crafts reaction in brominated flame-retarded PS

Abstract

Graphene nanoplatelets (GNPs) were introduced into polystyrene (PS)/brominated polystyrene (BPS) blends to suppress the large amounts of smoke generated from brominated flame retardants during combustion. A Lewis acid catalyst (AlCl₃) was added to initiate Friedel–Crafts reaction to produce macrocarbocations interacted with graphene sheets by electrostatic attraction, leading to an improved dispersive state of GNPs in polymer matrix. And the scanning electron microscopy (SEM) showed that more compact and integrated char barriers were formed in PS/BPS/GNPs/AlCl₃ composite. Cone calorimeter tests revealed that the continuous and uniform char barriers of GNPs fabricated by Friedel–Crafts reaction prevented the spread of combustion, reduced the heat release in the initial stage of combustion, and especially suppressed the smoke release effectively. The mutual influences among the char barrier effect of GNPs, the electrostatic attraction between macrocarbocations and graphene sheets, the catalytic degradation of Lewis acid catalyst, the solid lubricant effect and the heat gathering effect of GNPs caused the complex microstructure changes, which lead to the complex rheological behaviors of PS/BPS/GNPs/AlCl₃ composite. The pyrolysis products showed that the light carbon decreased and the heavy carbon increased in PS/BPS/GNPs/AlCl₃ composite, revealing that the char barrier of GNPs fabricated by Friedel–Crafts reaction played an effective protective layer to prevent polymer form erosion of high temperature.