Ontario engineer bridges gap in WPC market
By Rebecca Reid, managing editor
Wood-plastics composites (WPCs) in North America have struggled to shed their 'decking-and-railing-only image', but now a design breakthrough by an Ontario bridge-builder could finally open the walkwa...
Wood-plastics composites (WPCs) in North America have struggled to shed their ‘decking-and-railing-only image’, but now a design breakthrough by an Ontario bridge-builder could finally open the walkway to a host of new developments.
Andrew D. Burgess, president of Burgess Engineering Inc., in Grimsby, Ont., used a unique WPC from PSAC Composites LLC to construct what is believed to be the world’s first bridge made entirely of a WPC.
Ideal for spanning gaps in hiking and snowmobile trails, rivers, gorges and water hazards on golf courses it was the strength and lightness of PSAC’s material, which PSAC says is twice as strong and twice as light as other WPCs, that made construction of the bridge possible.
PSAC didn’t set out to create an ultra-light and ultra-strong WPC; in December 2000, it discovered the process by chance while experimenting with ram extrusion and die-drawing to manufacture a high-density oriented polypropylene (OPP) for drumsticks, Frank Maine, chief technology officer at PSAC, said. When wood fibre was added to improve esthetics, a high-strength, low-density material emerged.
“When you pull the whole massive bullet though the orientation die, we stretch the material eight times its length and the PP does not stick to the wood fibre but instead creates a long void due to the stretching,” Maine explained. “Those voids make up 50 per cent or the composite, making it half the weight.” The lightweight material is also less expensive to transport, Maine added.
Dubbed EOW-PP — expanded, oriented wood-filled polypropylene — the material has a density of 0.55 grams per CC (g/cc) and costs of about 11 per cent of costs of goods sold (COGS) to transport, Maine said. By comparison, first-generation WPCs had densities of about 1.1 to 1.2 g/CC.
Unfortunately, PSAC couldn’t find funding for its EOW-PP and had to turn to a U.S. investor. As a result, the firm relocated to Kent, Wash., in February 2005; Maine continues to work out of Guelph, Ont.
While only a prototype model has been built to date, Burgess does plan to make these pedestrian bridges commercially available. Maine believes these bridges will be able to compete on cost with steel pedestrian bridges, which retail at about US$25,0000.
