Thermoplastic polymers as modifiers for urea-formaldehyde wood adhesives. III. In situ thermoplastic-modified wood composites

Acrylic monomers and free-radical initiators were dispersed in an aqueous urea-formaldehyde (UF) suspension and polymerized in situ to afford a suspension containing 5 wt % thermoplastic (5 g of thermoplastic/100 mL of suspension). The viscosity of the thermoplastic-modified UF suspension (65 wt % s...

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Bibliographic Details
Published in:Journal of applied polymer science 2008-03, Vol.107 (5), p.3200-3211
Main Authors: Das, S, Matuana, L.M, Heiden, P
Format: Article
Language:English
Subjects:
Applied sciences
Composites
crosslinking
Exact sciences and technology
Forms of application and semi-finished materials
impact resistance
Polymer industry, paints, wood
Technology of polymers
thermosets
toughness
Wood-based materials
Wood. Paper. Non wovens
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Summary:Acrylic monomers and free-radical initiators were dispersed in an aqueous urea-formaldehyde (UF) suspension and polymerized in situ to afford a suspension containing 5 wt % thermoplastic (5 g of thermoplastic/100 mL of suspension). The viscosity of the thermoplastic-modified UF suspension (65 wt % solids at 25°C) ranged from 240 to 437 cP versus 121 cP for the unmodified UF control. Wood-flour composites (sugar maple and 50 wt % adhesive) were prepared with thermoplastic-modified UF suspensions and cured with the same cycle used for the composites prepared with the unmodified UF adhesive (control). The effect of the thermoplastic-modified UF adhesive was evaluated on the notched Izod impact strength and equilibrium moisture uptake of the wood-flour composites. The notched Izod impact strength of the composites prepared with modified UF adhesives increased by as much as 94% above that of the control. The increase depended on the initiator and the monomer composition. The modification affected the equilibrium moisture uptake and rate of moisture uptake in the wood-flour composites. Preliminary results for particleboard prepared with 10 wt % modified UF adhesive (5% thermoplastic in the UF resin) and unoptimized cure conditions confirmed a significant effect of the thermoplastic modification on both the internal-bond strength and thickness swelling of the particleboard. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
ISSN:0021-8995
1097-4628
DOI:10.1002/app.25526