ANSWER: Both water-based and solvent-based contact cements are available. The water-based versions certainly have environmental advantages over the solvent systems in terms of toxicity, environmental impact and flammability. However, solvent-based systems offer several performance advantages over their water-based cousins.

First, water-based systems take longer to dry, depending upon temperature and humidity conditions. Further, the water-based formulations are based on polychloroprene resins that are different than the polychloroprene resins used to formulate solvent systems. Most of these do not develop as high a strength as the solvent-based versions.

Water-based contact cements have been used successfully by other professional installers and have been proven to perform well in countertop lamination as long as the installer realizes the requirement for longer drying time. The very large surface area of countertop laminates generally makes the issue of adhesion performance pretty much a moot point, as both systems have more than adequate adhesion for the application at hand.

-BOB SMITH and ROGER LOHMAN

QUESTION: I am a chemical engineering student in Guatemala, and am currently doing some research on adhesives, but I’m having trouble finding information about very "mild" adhesives. By mild adhesive, I mean something that would permit the removal of a paper bonded to metal, but without leaving any residual paper on the metal’s surface – like the Post-it® note adhesive but a little stronger. Does this type of adhesive exist?

ANSWER: There are numerous "mild" or "temporary" pressure sensitive adhesives. These can be purchased in bulk-liquid or hot melt form and then coated using commercially available pressure sensitive coating equipment. Or they can be purchased from any number of coater/converters who coat these adhesives on release liners (with our without a facestock attached). Temporary bonding grades are available across a wide variety of peel properties.

As you might suspect, these adhesives are quite soft and have a relatively low glass transition temperature, making them tacky at room temperature. These temporary pressure sensitive adhesives are formulated to provide high-speed coating application as well as clean release from various substrates.

Such bulk adhesives are available from most of the pressure sensitive adhesive suppliers in the United States. I am not sure who supplies these materials in Guatemala, but some of the major U.S. suppliers include National Starch & Chemical, Ashland Specialty Chemicals, Rohm and Haas, Solutia, H.B. Fuller, ATO-Findley, Franklin International, and many other smaller suppliers. U.S. suppliers of precoated "transfer film" or finished constructions using such adhesives would include 3M, Avery Dennison, MACtac, FLEXcon, Adhesives Research, SCAPA Tapes, Tyco International, and others. I suspect there are local suppliers or distributors of such pressure sensitive materials in your region.

-BOB SMITH