Adhesive manufacturers continue to create lower-VOC products to meet and exceed stricter emissions regulations. Many are focusing on products that don't use solvents to cure.

"The next five years or so, we're going to see a decline in the use of solvent-based products," predicts Mark Stypczynski, manager of technical development for Liquid Nails. Instead, many manufacturers are turning to polyurethane and hybrid adhesives. "You are seeing more moisture-curing materials," he says. "The beauty is they don't really emit substantial amounts of anything."

Polyurethanes are a type of polymer for sealants and adhesives, says Doug Walker, vice president of sales and market development for Bondaflex. Hybrid polymers (based on isocyanate or polyethers and catalyzed with silanes) have traits of urethanes and silicones, he says.

Polyurethanes work well for below-grade applications because they allow less water migration, says Walker. Bondaflex makes adhesives under its own name and for private label customers, and recently released a soy-based hybrid adhesive.

Liquid Nails Polyurethane Construction Adhesive is made to provide maximum durability, the maker says. The low-VOC product will not crack, become brittle, or lose its flexibility with heat exposure; bonds to a range of substrates; has low shrinkage; and will not stain typical construction materials.

Many hybrids work better on bonding plastics, Walker adds, especially for outdoor applications such as around vinyl windowsydusvvzf and siding. The new products also deal with temperature fluctuations well, says James Downing, marketing manager of construction products for Bostik, allowing Bostik to recommend them for areas with "tremendous temperature cycling," such as the Northwest.

Additionally, Liquid Nails guarantees its polyurethane products will not stain materials. That's why it targets these products for marble and granite applications.

Hybrids and polyurethanes bond with many substrates, including plastic, metal, and wood, so customers can carry one tube instead of several others, says Jason Ringling, marketing director for Red Devil.

Along with its ability to be used on many surfaces, Henkel's polyurethanes have a final bonding strength three times greater than in its products with solvents, says Michael Terhardt, the manufacturer's marketing director for construction adhesives. Henkel includes polyurethanes in its OSI GreenSeries line.

But, certain factors hold these products back.

Frank Ghigliotty, who works in the hardware sales department at Lambertville, N.J.-based Niece Lumber, has heard customers complain about low-solvent products' workability. "When you get into the cool weather, it's hard to gun," he says. Customers also say the products don't have "as instant of a hold," and are more expensive, about $3 to $6 more per quart tube, he says.

Hybrids flow better than polyurethanes but cost about 15% to 20% more than conventional products, Walker says, making some hesitant to try them.

Still, Ghigliotty says people focused on green building, especially do-it-yourself homeowners, are attracted to low-VOC products. And, customers enjoy the lower odor.

Franklin Adhesives & Polymers' PROvantage brand of construction adhesive (Circle 165) is a proprietary solvent-based product that meets VOC restrictions in all 50 states. While its VOC content is higher than some hybrids and polyurethanes, PROvantage performs more like traditional products, the company says.

"PROvantage products can be extruded in cold temperatures and skin over quickly for a faster grab," says Scott Bowen, vice president of sales, distribution, and retail.

Niece Lumber's Ghigliotty says his company will continue to offer low-solvent products, even with the complaints. "They're definitely phasing [low-VOC products] in now," he says. "Eventually, you won't be able to get your hands on some of the [solvent-based] stuff being used."

As VOC restrictions continue to increase, manufacturers know they will have to keep pace.

"I think, realistically, we are all counting on the fact that we are going to see more states get regulations," Bowen says. "This is not just a U.S. market move but a global one as well."

However, until new technology can become as convenient and inexpensive as the solvent-based standard, many contractors will hesitate to make the change.

"I think what you'll see is that as they become easier to gun from the tube and the price comes down, you will see them used more and more," Ringling says.

–Victoria Markovitz