Biological, Mechanical, and Thermal Properties of Compressed-Wood Polymer Composite (CWPC) Pretreated with Boric Acid
Keywords:Wood-polymer composite, boric acid, biological resistance, mechanical properties, surface hardness, compressed wood, thermal resistance, vinyl monomers
Compressed-wood polymer composite (CWPC) was prepared by in situ polymerization of vinyl monomers, styrene (ST), methylmethacrylate (MMA), and their combination (50:50, v/v) under hot-compression of treated sapwood of Japanese cedar (Cryptomeria japonica D. Don.) to a dry set of 50 and 70% of original radial dimension. Boric acid (BA) was impregnated into wood at 1.00% aqueous solution concentration prior to monomer treatment. CWPC with and without BA-pretreatment was tested in terms of biological resistance and mechanical and thermal properties.
Boric acid pretreatment imparted CWPC total resistance against decay test fungi Tyromycespalustris and Coriolus versicolor, representing brown- and white-rot fungi, respectively. CWPC showed remarkable resistance against Formosan subterranean termite Coptotermes formosanus, and BA-pretreatment contributed to a total inactivation of termite activity. Surface hardness of CWPC was superior to wood polymer composite (WPC) obtained at the same polymerization temperature and time by a conventional heat process in an oven without compression. Modulus of elasticity and rupture were also considerably improved with this newly introduced in situ polymerization process, suggesting the great potential of CWPC for exterior use. Thermal analysis revealed a reducing effect of boron on heat release of CWPC during combustion.
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