A Future of Bigger Structures, Better Standards

One key trend in the pultrusion industry is the development of better polyurethane chemistry, says Harry M. George, a polyurethanes expert at Bayer MaterialScience LLC, which recently formed a partnership with Martin Pultrusion Group. “Polyurethane is the pultrusion resin of the future,” George says. “Polyurethane chemistry offers many benefits over the chemistries traditionally used in the pultrusion process. Not only can polyurethane chemistries be customized on a project-by-project basis to provide greater strength, as well as better working and performance characteristics than polyesters, vinyl esters and epoxies, but polyurethane resins are also free of the hazardous styrene emissions common to polyesters and vinyl esters.”

Another key development, says Witcher, is that cross-sections in pultruding have become larger during the past few years — a possible advantage for engineers and end users in markets such as construction and infrastructure. Applications embracing this trend include scaffolding and sheet piling.

The electrical utility market is also ripe for pultrusion, Witcher says, because designers and engineers from electrical utility companies are becoming more comfortable with specifying FRP composites for use as poles, towers and cross arms. Those designers and engineers appreciate structural performance and durability, and to some degree, the industry is still constrained by lack of standards and communication in structural applications, experts say.

Standards play an important role in acceptance of new materials. A design standard is an engineer’s tool to guide the process of selecting the right material when performing structural design for civil engineering structures. A standard provides credibility of a material used in structural applications; identifies performance criteria for design, specification and installation of products; reduces liability exposure for both the designer and manufacturer; and educates engineers on the proper use of materials.

To that end, the American Composites Manufacturers Association (ACMA) Pultrusion Industry Council is developing a Load Resistance Factor Design (LRFD) standard for FRP pultruded structures. This standard would provide critical information for designers and engineers to specify pultruded FRP composites as a replacement for traditional construction materials.

“The benefits of pultrusion are clear, and with ongoing innovation and better communication to engineers and end users, the future looks bright for this area of the industry,” Witcher says.

Benefits of Pultruded Products

HIGH STRENGTH
Stronger than structural steel on a pound-for-pound basis. Has been used to form the superstructures of multistory buildings, walkways, sub-floors and platforms.

LIGHTWEIGHT
Pultrusions are 20-25 percent the weight of steel and 70 percent the weight of aluminum. Pultruded products are easily transported, handled and lifted into place. Total structures can often be preassembled and shipped to the job site ready for installation.