Modification of diisocyanate-based particleboard and plywood glues with natural polymers: polyphenols, carbohydrates, and proteins
1989
Dix, B. | Marutzky, R.
Investigations aimed at finding some fast-setting glues for exterior plywood and particleboard based on diisocyanates in combination with compounds from renewable resources like tannins, proteins, and starches revealed the following: The mechanical properties of particleboard bonded with unmodified tannin extracts from spruce (Picea abies) and pine (Pinus sylvestris) were inferior. The fortification of the tannin extracts with diisocyanate increased the bonding strength and reduced the thickness swelling. With one exception, particleboards bonded with nonemulsifiable diisocyanate modified with glutin or maize starch (extender content up to 20%) had exterior-grade quality (German standard V100 for flat-pressed boards). Veneer plywood, which is conditionally weatherproof (German standard AW), can be produced by applying diisocyanate together with tannins or starches. The veneer wood species, the glue mixtures, the pressing conditions, and the fillers have to be adjusted to the diisocyanate type and to the extender. Modified, emulsifiable diisocyanate gave plywood with better strength and wood failure than glue formulations with nonemulsifiable diisocyanate.
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