The role of the matrix in a composite profile is partly to bind the reinforcement together, and partly to keep the reinforcement correctly positioned in relation to the cross section with a view to optimal utilization of the mechanical properties. The type of matrix also determines properties such as corrosion resistance, electrical insulation properties, and fire and temperature resistance.
The following three types of matrix are fundamentally well suited to the pultrusion process: polyester, epoxy and phenol.
Polyester is the most frequently used matrix as it produces a composite with good all-round properties.
Unsaturated polyester can be divided into three main groups: orthopolyester, isopolyester and vinylester. Compared with orthopolyester, isopolyester increases impact resistance, provides greater flexibility, and increases resistance to temperatures. It also increases corrosion resistance.
Vinylester has even better corrosion resistance and thermal properties. Since vinyl ester has greater elongation properties than ortho- and isopolyester, it also provides a composite with better impact resistance and improved fatigue properties.
Epoxy is used primarily for carbon-reinforced profiles, giving composites better fatigue and mechanical properties. Epoxy is more resistant to thermal influences and has better electrical properties.
Phenol is used when there are requirements to high fire resistance, temperature resistance, low smoke generation, and flame retardation when subjected to fire.