Special Report – Wood-Plastic Composites: Wood is cellular, why not WPC?

Foaming agents from Bergen International are being used in ABS, polystyrene, PVC, PE and PP.

The use of chemical foaming agents in wood-plastic composites (WPC) is growing by “leaps and bounds” reports one additives supplier. Foaming contributes to reduced raw material usage and reduces the density of the profile.

“Our Hydrocerol chemical foaming agents (CFA) can help processors reduce the weight and density of the wood-plastic composite, allowing it to act more like natural wood,” explains Manfred Dicks, business director for Clariant Additive Masterbatches, Americas. “For the manufacturer, using this approach can reduce part weight, lower raw material costs and result in excellent aesthetics.”

Clariant’s CFAs consist of various combinations of exothermic and endothermic agents plus other processing aids.

Dennis Keane of Bergen International explains that the various types of foaming agents each have their strengths. “Endothermic agents are normally preferred for WPC because they produce a finer cell structure and help to improve extrusion rates. Exothermic agents produce a product with lower density, but should be used with caution in co-extrusion applications because of the possibility of bubbles breaking through the capstock layer. A blend of endo and exo seems to give the best of both worlds.”