Building new opportunities for plastics: plastics provide solutions for resilient, low-cost buildings and infrastructure; NORTH AMERICA

Tolinski, Michael

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If the importance of plastics in the building and construction industry sometimes seems overlooked, it might simply be because of theiroverwhelming diversity of applications. Wood-plastic composites (WPC) are just one very visible part of the story; other plastics are literally out of sight--hidden behind walls, pushed to the edges as trim, buried underground, or disguised as wood or stone.

Plastics from various polymer families offer cost-effective, energy-conserving, long-term performance when used for siding, roofing, fencing, floor and wall coverings, insulation, windows and doors, pipesand drains, and adhesives. Around 18% of all plastics are targeted for the building and construction (B&C) market, according to figures cited by SPE's Plastics in Building & Construction Special Interest Group (SIG).

The decision to form the SIG last year was based on responses to asurvey of SPE members, says Mark Barger, SIG chair and scientist at The Dow Chemical Co. (Midland, Michigan USA). B&C represents a significant market for roughly 21% of processors, and is relatively high ona list that includes the automotive, consumer product, medical, and electronics markets. The SIG fills a need that SPE members identified, says Barger.

Hidden among the benefits of plastics in B&C are opportunities forreducing construction labor costs, a major concern for builders. From the standpoint of the contractor, plastics present a "value proposition" when they allow greater use of prefabricated, pre-finished structural elements that can be quickly assembled. Barger sees builders as gradually moving away from standard "stick-construction" methods that have been used in North America for centuries. "The building industry is probably where the auto industry was at the turn of the 20th century, when it was still very labor intensive." Helping minimize on-site labor, prefabricated elements incorporate plastic and composite trim and foam insulation, along with other integrated structural features.

Durability & Low Maintenance

Another opportunity for plastics is based on the consumer demand for building products that require little or no maintenance, adds Barger. Pre-finished, plastic-based construction materials can make low maintenance a selling point that justifies their higher price (which can be double that of conventional lumber, per lineal foot).

Traditional materials don't meet all the low-maintenance needs of the market, says Joseph Fay, who gave a keynote address on B&C at ANTEC[TM] 2008 and is a technical fellow at Ciba Corp. (Tarrytown, New York USA). To be competitive, plastic products often must resemble wood or stone--and maintain the resemblance for a long time.

"One of the benefits of most plastics used in construction is thatthey're generally rot-resistant," unlike wood, says Fay. This gives plastics an advantage over wood in common exterior applications such as siding and injection-molded shutters. Maintaining wood components is expensive and time-consuming, since they often require repairs andscraping before repainting. But with polypropylene or other inherently rot-resistant plastics, surface preparation or remediation, if necessary, is minimal. Moreover, "it's very difficult to tell the difference between painted wood and painted plastic."

Of course, "plastics are not inherently weatherable." Exterior grades need to be formulated to resist light and the elements, and roof-tile grades may require extra flame retardants, Fay adds. And some plastic formulations invite their own problems (such as additives in PVC that attract microbes and algae). But eventually, even tougher applications will become possible, as users better understand how to modify plastics for property retention and reinforcement.

Flexible WPC Processing

Meanwhile, efficient lower-cost processing has helped increase themarket share for one major family of plastic-based materials in B&C:wood-plastic composites. This has driven WPC's dramatic growth over the past decade, and variations in processing offer additional opportunities for these composites.

One key cost-effective process technology for WPC is direct extrusion with in-line compounding, explains Paul Andersen, senior manager of process technology and new development for Coperion Corp. (Ramsey,New Jersey USA). This single-stage continuous process eliminates excess operations by directly linking the compounding step with the profile-extrusion step, mixing wood-fiber and resin and extruding the material into decking or other profiles in one continuous line.

"One of the things that you certainly eliminate is the energy that's required to reheat pelletized material and bring it up to temperature," says Andersen. He estimates the energy savings of direct extrusion to be 0.1 to 0.15 kilo watt-hour per kilogram. Direct/inline processing also minimizes material-conveying costs, drying costs of the hygroscopic wood-fiber, and labor costs in WPC operations, compared with pellet-based extrusion with independent compounding lines.

Additionally; alternative kinds of extruded-WPC applications can benefit from variations in the direct-extrusion scheme, Andersen explains. For example, "you could have multiple customized profile lines that are being fed from one compounding line." One very large compounding extruder could supply six or more separate profile-extrusion lines. For customized, lower-volume WPC trim or fascia products, a two-step compounding/extrusion process using pelletized WPC may make more sense than a direct/inline process used for decking board.

Out With the Old ...

In this slow economy and construction market, another bright spot for plastics lies underground, says Nicole Butler of Gros Executive Recruiters, Inc. (Brentwood, Tennessee USA), one of the members of theformation committee of the B&C SIG. She has observed that several companies are looking for plastics specialists for pipe and infrastructure applications. "It is probably one of the only areas in building and construction that's in a growth mode right now." Particularly in the USA, old pipes are deteriorating, and the typical choice for replacing them is plastic pipe, she adds.

Regarding plastics companies that supply the broader B&C market, Butler notes that not all are waiting passively for the economic downturn to end. Although some companies are waiting for the market to improve ("burying their heads in the sand," she says), others are "usingthis downtime to set the stage so that when the market does turn good, they come out on top." These companies are making a lot of improvements such as personnel changes at the senior executive level, even though this can be costly to do while sales are down. But such creativity with people and processes will be vital during the recovery of a stalled construction industry.

Editor's note: SPE's Plastics in Building & Construction SIG was formed in fall 2007 to promote the dissemination of technical and market knowledge about plastics materials for residential and commercial buildings and infrastructure. Five hundred people (both SPE members and nonmembers)joined the SIG within its first ten months of existence, and the group is planning several technical sessions for ANTEC[TM] 2009 in Chicago. Activities and contacts for the SIG are shown at www.4spe.org/communities.