Effect of high-temperature heat treatment on the physical and mechanical properties of Taxodium hybrid'Zhongshanshan'wood
Taxodium hybrid'Zhongshanshan'is an excellent asexual variety of the genus Taxodium that was selected by crossbreeding.However,this wood species has many drawbacks such as poor dimensional stability and low me-chanical strength,which limits the scope of its application.The superheated steam treatment method was used for the treatment of the Taxodium hybrid'Zhongshanshan',and the specific studies were conducted on the effects of treat-ment temperature(175,195,or 215 ℃)and treatment time(1,2,or 4 h)on the physical properties,chemical composition and mechanical properties of Taxodium hybrid'Zhongshanshan'.The experimental results indicated that,in terms of physical properties,the increase of treatment temperature and the prolongation of treatment time gradually changed the surface color of wood from light yellow to dark brown,in which the treatment temperature had a more significant effect on the color compared to the time.The mass loss rate of heat-treated wood increased with the in-crease of treatment temperature and the extension of treatment time,and the effect of treatment temperature on mass loss rate was more obvious than that of the time.In addition,the saturated swelling rate and over-dry shrinkage rate of the heat-treated wood decreased with the increase of temperature,and the ASE(anti swelling efficiency)gradually in-creased with the increase of treatment temperature,and the dimensional stability was obviously improved.In terms of chemical properties,the mass ratio of hemicellulose of the heat-treated wood decreased significantly with the increase of temperature,when the temperature reached 215 ℃,the mass ratio of hemicellulose decreased by approximately 65％compared with the untreated wood,and the cellulose mass fraction decreased by 11.47％compared with the un-treated wood.In terms of mechanical properties,high-temperature treatment had a negative effect on the modulus and rupture(MOR)and modulus of elasticity(MOE)of wood,especially the treatment temperature had a significant effect.When the treatment temperature reached 215 ℃ and the treatment time was 4 h,the MOR of the heat-treated wood decreased by 27.74％and the MOE decreased by 31.45％.The mechanical properties of Taxodium hybrid'Zhongshanshan'itself are poor,and the heat treatment would further reduced the mechanical strength of Taxodium hybrid'Zhongshanshan'wood.However,after the heat treatment,the wood achieved beautiful color and good di-mensional stability,which suggested that using the heat-treated wood for decorative wall panels and other cir-cumstances that do not require high mechanical properties.
high-temperature heat treatmentTaxodium hybrid'Zhongshanshan'dimensional stabilityphysical and mechanical property
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