Surface activation of wood for graft polymerisation

An investigation of graft polymerisation of wood surfaces chemically modified with propionic, crotonic, or methacrylic anhydride has been undertaken. All samples exhibited weight gains when reacted with styrene in the presence of a free-radical initiator. However, solid-state NMR and FTIR evidence showed that there was only grafting of monomer in the case of methacrylic anhydride modified wood. With the other two modifications, it is clear that the styrene is in intimate contact with the wood, but that there is no chemical bond. Wood flour modified with crotonic anhydride followed by styrene grafting was heated with aqueous NaOH. Following such treatment, it was observed that the ester bond was readily hydrolysed. However, with methacrylic modified and styrene grafted samples, the ester bond was resistant to hydrolysis. Lap joints were formed by hot pressing veneers of modified wood with monomer (styrene or methyl methacrylate) plus initiator at the interface. Extremely strong bonds were found in the case of methacrylic anhydride modified samples.