Q. What is the difference between Type I and Type II adhesives?

A: The titles of “Type 1” or “Type 2” are applied to adhesivesused to glue wood. Type 1 is basically fully waterproof. Type 2 is waterresistant. Both can also withstand a bit of heating without failure.

 

In either case, unless theglued wood product will be used outdoors or is subject to frequent wetting,either type will work well for furniture, cabinets, and similar. (Do notconfuse these titles with the same nomenclature used for hardwood plywood. Theplywood titles include further specifications about the interior veneer (innerply) quality, as well as adhesive type.)

So, how does a gluemanufacturer rate their glue as Type 1 or Type 2? They make some birch plywoodwith three plies using their adhesive for gluing the veneers together. Aftercuring the adhesive fully, for Type 1 testing, the sample of 1 x 3 inches isboiled in water for four hours, then dried at 145F for 20 hours, then boiledfor four more hours and then cooled immediately and tested wet for bondstrength using a shear test (trying to slide the veneers past each other).

Obviously, this boiling andheating test is much more severe than any glued wood product that we make willsee in its life. But this test procedure is a valid way to compare one adhesiveto another. Certainly a Type 1 adhesive can be used with confidence in almostany exposure. (Note that this is a test for the adhesive. All the proceduresfor making a suitable wood joint must also be followed to achieve highperformance.) The shear strength required and the amount of wood failure versusglue failure is specified in the standard.

For Type 2, the sample used is2 x 5 inches. The sample is soaked in water (not boiled) for four hours. Thenthe sample is dried at 120 F for 19 hours. Then the sample is soaked and driedagain two more times, for a total of three cycles. To pass the test, the samplemust not have delaminated. As before, this test is much more severe than almostany wood products will experience in use. However, it does allow for some “gut feeling” about the durability of theadhesive when exposed to water, such as with a water-based finish and a dryingoven, or in use.

 

Technical Note: The correctnames are ANSI/HPVA Type 1 or

ANSI/HPVA Type 2. Often we shorten them to “Type 1” and “Type 2.” The abbreviations in theselong titles are referring to the sponsoring and development associations. Thisis a voluntary standard; a great option for avoiding a government standard,rule or regulation. Let’s hopethat it is not abused. ANSI = American National Standards Institute and HPVA =Hardwood Plywood and Veneer Association.

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