Study On The Properties Of Rubber Wood Modified By Combining Impregnation And Heat Treatment

As a fast-growing wood,rubber wood is limited in its range of applications due to its poor material quality and perishability.Heat treatment can improve the dimensional stability and corrosion resistance of wood.Based on the conditions of heat-treated rubber wood,this work discussed the research of impregnated/heat-treated modified rubber wood.The work firstly used predecessor heat treatment technology to discuss the influence of heat treatment temperature and time on the physical and mechanical properties of rubber wood.Mechanical properties,dimensional stability,color,etc.were used to determine the better heat-treated rubber wood process.Due to the loss of mechanical properties of heat-treated wood,the process of obtaining heat-treated rubber wood was used to investigate the compensation effect of impregnated rubber wood and impregnated/heat-treated rubber wood on mechanical properties,and the optimum process of impregnated rubber wood and impregnation/heat treatment was determined.The main research of the study is as follows:(1)The process parameters of heat-treated rubber wood was explored by using heat treatment temperature and time as process factors.The results show that the flexural strength and impacted toughness of the rubber wood after heat treatment were obviously decreased,and the decline was more obvious with increasing temperature and time.The flexural strength was decreased by 49.34%and the impacted toughness was decreased by 62.44%at the heat treatment temperature of 200? for 4 hours.The temperature played a major role in the reduction of flexural strength and impact toughness.After the heat treatment,the modulus of elasticity and the axial compressive strength of the straight grain showed a general trend of decreasing first and then increasing,and reached the maximum value at 170?.After the heat treatment,the dimensional stability of the rubber wood was greatly improved,with a maximum reduction of 89.51%.After heat treatment,the increase in instantaneous contact angle of the rubber wood,the color was deepened,and the ratio of carbon to oxygen increased.In the micro analysis,the 3300 cm-1 of the heat-treated rubber wood was weakened,indicating that the number of hydroxyl groups decreased.The XRD results showed that the relative crystallinity of the heat-treated rubber wood was increased.In regression analysis,with brightness and relative crystallinity as independent variables,flexural strength,impacted toughness,and resistance to shrinkage-swelling as performance dependent variables,there was a strong linear correlation.Therefore,experimental data of destructiveness could be predicted by the non-destructive testing.(2)Calcium chloride and sodium carbonate(CC&NC)and calcium acetate and urea(CA&CN)were impregnated with the different precursors concentrations in the rubber wood,under different pressures and atmospheric conditions,and the results were evaluated by mechanical properties.Under the condition of pressure,the maximum mechanical properties appear when CC&CC and CA&CN impregnated the concentration is 1.0-1.5 mol/L,indicating that the concentration was moderate.At atmospheric pressure,the concentrations of 1.0 mol/L were chosen for both CC&NC and CA&CN.In the FTIR and XRD,impregnated CC&NC had better mechanical properties because calcium chloride and sodium carbonate formed calcium carbonate adhered to the surface and interior of the wood.(3)Impregnated/heat-treated wood adopted the first impregnation and then heat treatment process.Four kinds of drying methods before heat treatment,the impregnated CA&CN mechanics compensation was better than CC&NC.According to different drying sequence and times,at most one drying process was suitable for impregnated/heat-treated rubber wood process.At the same time,the dimensional stability of the impregnated CA&CN/heat-treated and heat-treated wood is comparable.In micro and TG analysis,there was no chemical reaction between calcium acetate and urea impregnated at high temperatures,but impregnation retarded the decomposition of rubber wood.(4)By the weight loss rate characterization,the resistance to brown rot of rubber wood is better than white rot resistance.The changes in the weight loss rate of heat treated wood,impregnated CA&CN,impregnated CA&CN-heat treated and impregnated zinc oxide/heat treated wood resistant to white rot were below 30%,and resistant to brown rot were about 10%,respectively,indicating that the above four methods were resistant to rot,in addition,the processing wood added with preservatives was more resistant to rot,and the weight loss rate is as low as 3.36%.The superposition test of impregnation with different treatment methods was used to obtain the order of influence of various factors on the corrosion resistance of rubber wood.For white rot resistance,preservatives>impregnation of CA&CN>heat treatment>impregnation of zinc oxide.For brown rot resistance,preservatives>heat treatment>impregnation of CA&CN>impregnation of zinc oxide.