Adhesives Magazine

Ask Dr. Dave

May 1, 2008
In his May 2008 column, Dr. Dave discusses the best adhesive for laminating bamboo panels and low-odor RTV silicone options.

Question: In your opinion, what is the best adhesive for laminating bamboo panels?

Answer: The traditional way of making these laminates is to use hot-pressed urea formaldehyde and, to a lesser extent, phenol-formaldehyde adhesives. However, in recent years customers and legislators have become conscious of formaldehyde emissions from these adhesives; melamine-formaldehyde adhesives have become more common because of lower formaldehyde emissions. If your application does not require water resistance, then a polyvinyl acetate (PVA) emulsion adhesive will be suitable. In fact, blends of PVA emulsions with melamine formaldehyde resins have been shown to reduce formaldehyde levels considerably.

Question: We would prefer to avoid the vinegary smell of the RTV silicones we currently use in our bathroom cabinet and tub assemblies. Do the lower-odor versions of these products work as well?

Answer: RTV silicones are convenient one-component sealants that cure by reaction with moisture from the atmosphere. Your current product is known as an acetoxy silicone. During the curing reaction with water, short-chain molecules in the liquid silicone called siloxanes link together to form a tough, rubbery sealant, and give off acetic acid (vinegar) as a byproduct. The common low-odor silicones have similar cure chemistry but give off different byproducts, which are typically called oximes or alcohols. The odors vary from musty to virtually no odor. Although my experience has been that the acetoxy products have slightly better adhesion, for your application the adhesion should be more than adequate. In fact, all silicones will eventually turn yellowish over several years in a bathroom setting, and the slightly lower adhesion will actually help you in removing them before re-caulking.

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