Thesis (M.Sc.)--Chulalongkorn University, 1998

The use of rubber wood (Hevea braziliensis) flakes for particleboard with polymeric diisocyanate (pMDI) as binder was investigated. The effects of releasing agents, isocyanate index (polyol content), binder content in surface/core layers, cure temperature, cure time, and moisture content of the flakes on the properties of rubber wooden particleboards which contained pMDI as binder were studied. The properties of the particleboard also were compared with those of phenol-formaldehyde (PF) binder. The particleboard prepared from rubber wood flakes with pMDI binder gave the high quality particleboards which was durable under severe condition, low water absorption and thickness swelling, high modulus of rupture, modulus of elasticity, and internal bonding strength. Moreover, pMDI binder could be cured at low temperatures, within a short time, and the binder consumption was small. The scanning electron micrographs of the rubber wooden particleboard prepared from the high moisture content flakes showed the better packing characteristic than the flakes at low moisture content. The staining method (using Lofton-Merritt as staining agent) showed that the pMDI binder could penetrate into the wood matrix and diffuse to uncoated areas, while PF resin could not. This phenomena confirmed that pMDI binder has a better performance than the PF binder. The rubber wooden particleboards with pMDI binder demonstrated that it could be used for structural applications.