There have previously been reported on chemical treatments to improve the faults such as hygroscopicity, dimensional change and anisotropy. In recent years, two techniques of the radiation-induced and heat-catalyst polymerization have been devised for the polymerization of various monomers in wood and other cellulosic materials.
In the present paper, changes of some properties on the heat-catalyst polymerized bamboo-plastic combination are reported. Bamboo used in this experiment is MOSOCHIKU (Phyllostachys pubescens MAZEL). Methyl methacrylate (MMA) and styrene (St) are used as monomer, and benzoyl peroxide (BPO) as initiator is used.
The monomer containing BPO was impregnated into bamboo pieces in the vacuum system. After the impregnation, the treated pieces were wrapped up by aluminium foil, and then they were polymerized at 68±0.5℃ for 8 hours.
The results obtained are as follows :
1 ) In both treatments with MMA and St, Fig. 3 shows the linear relation between the conversion and the concentration of BPO. However, in the treatment with St, above 1.5% (wt.) concentration of BPO, the relation deviates from line depicting a slow curve.
3 ) Figs. 4-7 show the reduction in water absorption and in water vapor absorption, and anti-swelling efficiency (ASE) in relation to absorption of liquid water and water vapor by the treatments with MMA and St. The reduction in water absorption and in water vapor absorption increases along with increased polymer content. The ASE in relation to absorption of liquid water and water vapor increases approximately with increase of the polymer content, although the bulking effect of the polymerization of monomer may also be influential.
In both treatments with MMA and St, the reduction in water absorption is greater than the reduction in water vapor absorption. And also, this relation could be applied to ASE.
3 ) It is found in Fig. 8 that the deflection in bending as determined by the untreated bamboo is much greater than that determined by the bamboo-plastic combination. The relation between the bending properties and polymer content is shown in Figs.9 and 10. The stress at proportional limit and modulus of elasticity in bending for the treated bamboo increase in the linear relation along with increase of the polymer content. Though the modulus of rupture in bending increases linearly to about 15 % polymer content, it is improved little by little with increase of the polymer content beyond this value.
4 ) The linear relation between the hardness and polymer content is shown in Figs. 11 and 12. In the inner and outer bark sides, the hardness of the treated bamboo is two times or more as large as that of the untreated bamboo.