To product a composite board tougher than a gypsum plaster board (GB) being brittle and fireproof, wood meal-gypsum composites were made from beta-type calcined gypsum and wood meal of Hinoki (Chamaecyparis obtusa Endl.) or of Nara(Quercus spp.). The boards were tested in bending and fire resistance.
The composites have higher elasticity than GB in the ratio of wood meal content(WMC)up to 16%. Strain of composites waslower than that of GB in the ratio of up to 8% WMC for Hinoki and up to 14% WMC for Nara. Modulus of rupture (MOR) of the composites was higher than that of GB in the range from 10 to 16% WMC for Hinoki, but little change in MOR for Nara. Energy of rupture in bending (EOR) indicating the toughness increased in the ratio of over 10% WMC for Hinoki compared that of GB, whereas it decreased for Nara. By flame test, the composites ignited in the ratio of over 20% WMC. Temperature of the composites rose in proportion to WMC up to 20%. Since flammable organic materials of low molecular weight were removed from the wood meal by extraction with cold water, fire resistance of the composites increased.
Evaluating from all the factors of density, elasticity, MOR, strain, EOR and inflammability, the composites made with 10% wood meal content of Hinoki may be the best. Nara wood meal is useful only for an extender of the composites.