Electrical Conductive Surface Functionalization of Polycarbonate Parts with CNT Composite Films during Injection Molding

Abstract

This study describes a reactive process to transfer an electrical conductive polycarbonate (PC) film onto the surface of bulk polycarbonate by an injection molding process using hyper branched poly (ethylenimine) (PEI). Due to a nucleophilic substitution reaction between the amino groups of the poly (ethylenimine) and the carbonate groups of the PC, a stable covalent crosslinking is established. The resulting conductive layer has an average thickness of about 3 -7 µ m and a surface roughness that depends on the roughness of the cavity. The lowest resulting electrical surface resistivity of the final injection molded part of 5.58 ∙ 104 Ω per square is measured for a composites film loaded with 5 wt.% CNT . The crosslinking PEI layer has a thickness of about 50 nm, which equates with the hydrodynamic radius of a random PEI molecule with molecular weight of about 750.000 g∙mol-1. As a consequence, all PEI intermediate surface films remain completely on the PC parts.