高温快速热压处理对毛竹材物理力学性能的影响

选取4~6年生的毛竹Phyllostachys edulis材为原料，采用热压机对毛竹材进行高温快速热压处理，研究不同热处理温度（225，250，275，300，325，350和375℃）下竹材物理力学性能的变化。结果表明:随着热处理温度的升高，竹材平衡含水率和气干密度明显下降（P < 0.05），与未处理材相比分别降低了34.39%~53.95%和7.89%~13.04%。相同热处理温度下，弦向干缩率的变化率>体积干缩率的变化率>径向干缩率的变化率；当温度达到375℃时，弦向全干干缩率下降了86.81%，径向全干干缩率下降了83.60%，体积全干干缩率下降了83.95%，达各向的最大值。热处理温度升高，竹材顺纹抗压强度、抗弯强度和抗弯弹性模量均先增加后减少，其中，顺纹抗压强度在375℃时达最小值（63.78 MPa）；抗弯强度在250℃时达最大值（151.00 MPa），在375℃条件下达最小值（61.85 MPa）；抗弯弹性模量在300℃时达最大值（10 487.44 MPa），在375℃时达最小值（7 071.14 MPa）。认为竹材接触式快速热处理工艺提升了竹材尺寸稳定性和力学性能。

Physical and mechanical properties of Phyllostachys edulis with fast hot-pressing and high temperature

To improve dimensional stability and weather resistance of a material, heat treatment, with fast hot-pressing and high temperature, was used. Pieces of 4-6 year-old Phyllostachys edulis were selected. Samples were treated with different temperatures (225, 250, 275, 300, 325, 350, and 375℃). Physical and mechanical properties were tested before and after treatments. Results showed that with an increase of temperature, there was an obvious decrease in equilibrium moisture content (34.39%-53.95%) and bamboo density (7.89%-13.04%) both P < 0.05. With the same conditions, the following occurred:rate of change for tangential shrinkage rate > rate of change for volume shrinkage rate > rate of change for radial shrinkage rate. When the temperature reached 375℃, tangential oven-dry shrinkage rate decreased 86.81%; whereas, radial oven-dry shrinkage rate dropped 83.60%, and volume oven-dry shrinkage rate decreased 83.95%, reaching a maximum in all directions. Compression strength parallel to the grain, modulus of rupture (MOR), and modulus of elasticity (MOE) of the bamboo increased with temperature first and then decreased. Compression strength reached a minimum of 63.78 MPa at 375℃. MOR reached a peak at 250℃ with 151.00 MPa, and decreased to 61.85 MPa at 375℃. MOE performed best at 300℃ with 10 487.44 MPa, and worst at 375℃ with 7 071.14 MPa. Thus, this experiment proved that fast hot-pressing with high temperature can improve the dimensional stability of the bamboo, the mechanical properties also generally improved after treatments.