Weatherable Polyolefin Capstocks for WPC Decking

Highly weatherable polyolefin-based compounds for the outer or “cap” layers of dark-color wood/plastic composite (WPC) decking newly launched by Teknor Apex Co., Pawtucket, R.I., reportedly provide greater durability and scratch-resistance than widely used competing compounds, while helping manufacturers to contain costs.

After 5,000 hours in QUV accelerated weathering tests, Weatherguard WG-9000 Series capstock compounds exhibited a color change of less than 0.5 Delta E for dark brown. They are said to offer five- to tenfold improvements in elongation and impact strength in comparison with a standard competing compound, while sacrificing only 15% in tensile strength.

The Weatherguard WG-9015 LG grade contributes to cost containment because it is designed to be used as a 50% concentrate in a blend with a fractional-melt index polyethylene. For manufacturers looking for a cost-effective grade that requires no blending with polyethylene, Weatherguard WG-9003 LG is used as a 100% capstock. Both grades are sold pre-colored to meet the customized color palette of the end customer.

While ionomer resin is often used as an ingredient in capstocks to increase scratch resistance, the WG-9015 LG grade, when used as a 50% concentrate with polyethylene, provides greater scratch resistance in comparison with a similar compound containing 20% ionomer, while avoiding the need for this expensive polymer.

Made from a blend of wood flour and polyolefin plastics, WPC decking is increasingly popular as an alternative to traditional treated wood because of its superior appearance, lower maintenance, and longer lifespan, noted John Macaluso, industry manager for building & construction for Teknor Apex’s Vinyl Div.

Said Macaluso, “The cost-containment possibilities of our new Weatherguard capstocks offer a valuable advantage in the competition between WPC and wood. And, while great strides are being made to incorporate recycled content in the inner core of deck boards, the quality and durability of the capstock becomes even more important for obtaining the performance and aesthetic benefits over traditional wood.”

The new WG-9000 Series compounds add to an already extensive series of capstock compounds in the Weatherguard product line, including formulations for use with PVC substrates in decking, railings, fencing, siding, windows, and doors, plus other capstock products for polyolefin substrates used in the WPC deck market. Teknor Apex supplies these products on a custom basis, with formulations tailored to customer requirements for color, gloss level, and many other properties.