真空热处理对家具用奥克榄木材物理力学性能的影响

热处理是提高木材尺寸稳定性的有效方法之一,目前热处理主要针对室外等较恶劣的用材环境,采用高温(>200℃)处理。针对家具材装饰性要求高、使用环境变化较温和等特点,以家具常用材奥克榄木材为实验材料,研究真空(≤0.06 MPa)条件处理后奥克榄木材物理力学性能的变化,以确定适用于家具用材的真空低温热处理工艺。将奥克榄木材以0.06 MPa、不同温度(120,140,160,180,200℃)处理5 h,测定不同处理温度下木材的全干密度、湿胀率、干缩率、色差、抗弯弹性模量、抗弯强度、冲击韧性及硬度变化,并比较低温(120,140,160℃)和常规温度(180,200℃)处理及未处理奥克榄木材的物理力学性能。结果表明:物理性质方面,随温度升高,奥克榄材色加深,处理后奥克榄与未处理材相比,色差值ΔE为6.1~25.9;全干密度随处理温度呈波动状态变化,在200℃处理时达最低值,较未处理材下降30.9%;干缩率、湿胀率均明显下降,但在120℃升高至140℃、160℃升高至180℃时变化幅度较小。力学性能方面,随炭化温度升高,抗弯强度、抗弯弹性模量先增大后减小;冲击韧性降低,140℃之后变化幅度趋缓,200℃时降幅最大为52.42%;不同温度热处理后的端面硬度较未处理材均有所上升,径、弦变化不明显。与常规热处理和未处理处理材相比,真空低温热处理可改善木材的尺寸稳定性,降低炭化对于木材材色变化的影响,且不明显降低木材的力学性能。

Physical and mechanical properties of Aucoumea klaineana wood after vacuum heat treatment for furniture components

Heat treatment is one of the most effective methods to improve dimensional stability of wood.The current heat treatment of wood is mainly for outdoor materials being used in harsh environments,usually adopting a high temperature(>200℃)treatment.In view of the high decorative requirements of furniture materials and the mild indoor environment,it is desired to find a thermal treatment process which is suitable for furniture wood materials.Therefore,a vacuum low-temperature heat treatment(≤0.06 MPa,≤200℃)was tested to treat one commonly used furniture material,Aucoumea klaineana wood,and the physical and mechanical properties of the treated wood were examined.The A.klaineana wood was firstly treated at 0.06 MPa with different temperatures(120,140,160,180 and 200℃)for 5 h,and then the oven-dry density,bulking ratio and shrinkage,chroma,bending strength,bending modulus of elasticity,impact toughness and hardness were tested.The results showed that,as for physical properties,with the treatment temperature increased,the color of A.klaineana wood was darkened,and the chroma differenceΔE was between 6.1 and 25.9 compared with the untreated wood.Compared with untreated materials,the oven-dry density fluctuated with temperature increased,and reduced by 30.9%at 200℃,which was the most reduction.The shrinkage rate and swelling ratio were significantly decreased,while the rate changed slightly when temperature increased from 120 to 140℃and increased from 160 to 180℃.As for mechanical properties,with the increase of the treatment temperature,the impact toughness decreased and the change rate was slowed down after 140℃,and the largest decline was 52.42%at 200℃.The bending strength and the bending modulus of elasticity increased firstly and then decreased as the temperature increased.The hardness on the cross-section increased at all temperatures compared with the untreated wood,and changed slightly on the radial and tangential sections.In general,compared with the conventional heat treatment,the vacuum low-temperature heat treatment was an effective method to improve the dimensional stability and reduce the impact of carbonization on wood color without compromising the loss of mechanical properties of wood.