Improving processability for in‐mold coating formulations

Abstract

AbstractIn‐mold coating (IMC) being 100% solids upon polymerization is an environmentally friendly alternative to traditional painting/coating. The standard commercial IMC formulation contains 2.8 wt% carbon black (CB) to achieve the electrical conductivity needed for maximum transfer efficiency during electrostatic painting. This formulation, however, makes the primed surface deep black and significantly increases the viscosity. To address this issue, our previous research evaluated the use of single‐wall carbon nanotubes as an alternative to CB. It was found that IMC with 0.15 wt% SWCNT provides the same level of conductivity as the standard IMC, but a much clear coating. However, the processability of this new formulation was adversely affected. In this research, other carbon‐based materials, that is, carbon nanofiber (CNF), multi‐wall carbon nanotube (MWCNT), and industrial graphene (grapheneblack [G]), were evaluated. Results indicate that the same level of conductivity can be reached by adding 1.6 wt% CNF, 1.8 wt% MWCNT, or 11.3 wt% G. Results also suggest that IMC with 1.8 wt% MWCNT has the best curing process, IMC with 11.3 wt% G has the highest flowability, and all three new formulations have a slightly better greyscale reading than the standard IMC.