AKRON, OHIO — Picture this: engineers specifying joists and beams made of recycled plastic in construction applications. They even have the option to specify structural-grade plastic lumber.
Now, at least, the ground is broken on that utopian view: As of April 10, the American Society for Testing and Materials formally approved a standard for recycled plastic lumber decking.
"This document is a big leap forward," said Rich Lampo, a materials engineer with the U.S. Army Corps of Engineers who was the document's secondary author. "What we're striving for is to be able to provide all the tools to design all-plastic structures."
The standard, titled "Standard Specification for Polyolefin-Based Plastic Lumber Decking Board," covers plastic lumber that is greater than 50 percent resin by weight, said Prabhat Krishnaswamy, the primary author, and vice president of Engineering Mechanics Corp. of Columbus, Ohio.
"It is a major accomplishment for the marketing of plastic lumber into residential decking applications," he said. "What this standard implies is that manufacturers can now put an ASTM stamp on their plastic lumber, as they do with plastic piping, which would make it more readily acceptable to building-code bodies, architects, etc."
This is a substantial change since the early days of recycled plastic in construction applications, when product failures and lack of understanding about lumber properties made the material a hard sell.
"The whole manufacturing knowledge base that wasn't there before is there now," said Donna Stusek, administrator with the Ohio Department of Natural Resources' Division of Recycling and Litter Prevention. "We're hoping now that recycled lumber won't get a bad rap. A lot of it failed early on."
Of the $70 million to $90 million decking market, plastic lumber now accounts for a 30-40 percent market share, said Alan Robbins, Akron-based president of the Plastic Lumber Trade Association.
Important issues needed to be addressed for plastic lumber to reach that point, Lampo said. The material could not be measured by traditional methods used for plastic or wood.
"Taking coupon-level pieces would be almost impossible because you have so many variations of plastic lumber," he said in a May 2 telephone interview. "Each manufacturer, almost, has its own species. There was no sense in trying to regulate that. We have set some minimums relative to performance, to mechanical and physical properties. You can make it out of whatever you want, as long as you meet the standards."
Test methods are now specified for compressive qualities, density, flexural and sheer properties, thermal expansion, creep testament and fastener withdrawal, Krishnaswamy said.
The standard is a starting point, not a finishing point, Robbins said. The legwork accomplished while completing the decking-board standard has set the pace for others in progress.
ASTM standards that currently are in draft form include a specification for structural-grade plastic lumber, flexural properties of marine piles, guides for the testing of plastic lumber and plastic decking construction.
"Now the products have some good science behind them," Robbins said. "People purchasing these materials can hold onto them. This really allows these products to move in the marketplace and allows people to understand the material."
Some of the science is especially significant, said Rob Krebs, communications director for the American Plastics Council of Arlington, Va.
"They've found that the plastic lumber actually gets stiffer over time ... unlike wood that not only may need to be treated with harsh chemicals [but also] is subject to eventual disintegration," he said.
Research during the past six years revealed that ultraviolet rays cause polymers to cross-link, Krebs said.
At ReNew Plastics in Luxembourg, Wis., sales manager Lonnie Vincent feels that the recycled plastic lumber his company produces for decking applications finally has been validated.
"Now you can go up against the lumber guys and have a valid product," Vincent said. "The engineers will be able to specify this in. Before, there wasn't a standard. They didn't have anything to compare it to."
The six-year effort gained support from the APC, the Ohio Department of Natural Resources, the New York State Department of Economic Development and the Plastic Lumber Trade Association.