木質材料の改良に関する研究(第6報) : 竹材の吸湿・吸水特性に及ぼすポリマー量およびバルキング量の影響

In the present paper, the effects of polymer content and bulking action on the characteristics of water and water vapor absorption of bamboo-polystyrene combination (BPC) have been investigated.
The bamboo specimens(15(T)×2(R)×60(L)mm) used in this experiment were prepared from bamboo(Mosochiku ; Phyllostachys pubescens MAZEL) which were pre-treated with ethanol-benzene solution to extract soluble materials. The bambop impregnated styrenemethanol system under vacuum was polymerized by means of the heat-catalyst technique. The weight and dimensional changes(tangential direction) of both BPC and control were measured in water (25℃) or under 93% relative humidity at 25℃.
The results obtained are as follows :
(1) Though the amount of styrene-methanol solution that can be impregnated into bamboo increases along with the increasing ratio of methanol in the treating solution, when the methanol content is above 20% the amount of solution absorbed hardly increases at all.
(2) The polymer content decreases rapidly with the increasing methanol ratio of the treating solution. In the case of the treating solution which consists of 4 : 1 mixture of styrene and methanol, the bulking caused by polymerization shows maximum. The polymer content is in direct proportion to the bulking action.
(3) The initial swelling rate with absorption of water or water vapor is slower in the specimens which are polymerized with only styrene than with styrene-methanol system.
(4) The relation between the reduction of water or water vapor absorption and polymer content is linear. The relation between anti-swelling efficiency (ASE) and polymer content is also linear.
(5) The reduction of water or water vapor absorption and ASE increase with the increasing of bulking action.
(6) The sum of bulking action and swelling of BPC in water or water vapor is nearly equivalent to the maximum swelling of control. Also, the above-mentioned relation is found in the behavior of weight gain.