|Mao, Lijun - PLANET POLYMER TECHNOL|
|Chen, Liang - OWENS CORNING SCI & TECH|
Submitted to: American Chemical Society Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: August 1, 1999
Publication Date: N/A
Technical Abstract: A wood adhesive was developed by crosslinking cornstarch and polyvinyl alcohol (PVOH) with hexamethoxymethylmelamine (Cymel 323) in the presence of citric acid as a catalyst. Plywood manufactured from this adhesive exhibited excellent mechanical properties, comparable to many of the commercially available urea-formaldehyde plywood adhesives used for interior applications. The optimal viscosity of the starch-based adhesive with 30% solid content was 7000 cps, allowing easy application to wood surfaces by brush. The ideal concentration of crosslinking agent was between 15-20% (solid-weight basis) with optimum curing temperature and curing time of 175 deg C and 15 minutes, respectively. Expectedly, due to the high starch loads, the adhesive had poor water- resistance properties and physical properties of plywood samples soaked in water deteriorated rapidly. However, addition of 7% latex in adhesive formulations greatly improved water resistance and reduced the adhesive viscosity. When latex containing samples were completely immersed in water for 2 hours or exposed to 93% relative humidity for 30 days, >90% failure was found to be in the veneer and less than 10% failure was due to the deterioration of adhesive joints. Interestingly, soaking for 24 hours in water greatly disrupted the bonding in plywood. However, upon drying, most of the physical properties were recovered.