Research On Properties And Mechanism Of Fast-growing Poplar And Ailanthus Treated By Multi-functional Modifier

In this research, three kinds of wood modifier (MU. MFU and DMDHEU) were used to modify the fast growing poplar 107, fast growing poplar Zhong lin-46 and Ailanthus altissima. The physical-chemical properties and modified mechanism of wood were investigated. The main conclusions are summarized as follows:(1) After modification with eight kinds of MU wood modifier, the density, mechanical strength and dimensional stability were improved. The stress relaxation decreased to 74% which improved the plasticity of wood samples. To investigate the mechanism, the XRD, XPS, SEM-EDXAet al were used to analyze the untreated and treated wood samples. The results showed that MU contained lots of amino(-NH2) and hydroxyl(-OH) which can react with the hydroxyl of wood structure. The MU can condensate by dehydration during the wood drying process that the wood modifier can exist in the wood inner structure.(2) The MFU can improve the dimensional stability and themal stability of fast-growing poplar Zhong lin-46 remarkablly. The chemical content result of untreated and treated wood samples showed that the content acid accumulator insoluble lignin and holocellulose decreased. Moreover, the dynamic mechanic properties ofwood improved. The instrumental analysis demonstrated that the melamine can decrease the hydroxyl of MU and Methylene-ether which could improve the heat-resistance and themal-stability of wood modifier. After modification by MFU, the properties of wood sampls were improved.(3) Compared with the traditional wood preservative, the MU was belong to low-poisonous wood modifier.The wood decay experiment results showed that the mass loss of modified wood samples decreased to 6.16-29.23% and the decay class was increased. The oxygen index of modified wood samples increased to 44%. The color difference data showed that the L index decreased to 64.52-78.05, a index and b index increased. After modification, the wood became dark but the texture clear.(4) Ailanthus altissima was easy to crack during the drying process and the dimensional stability was poor. The molecular weight of DMDHEU was small. The modified wood samples were treated by hot press. The major mechanical properties of wood samples were improved remarkable. The 72h water absorption was decrease to 70.57%, while the hot press modified modified wood samples decreased to 66.24%. TG results showed that the mass loss of untreated wood samples, modified wood samples and hot press wood samples was 8.25%、21.49% and 19.03%. The themal stability of wood samples was improved..(5) Modified NCC was added to the MU modifier and the results showed that the NCC can improve the thermal stability and properties of modifier. While the content of NCC was 2.0%, the dispersion of NCC was poor. Moreover, the water absorption and physical properties were better than MU modified wood samples. XRD, SEM and XPS showed modified NCC had large surface area which can react with the wood modifier and wood groups.(6) In conclusion, the MFU wood modifier was better than the MU wood modifier for the wood modification result. The DMDHEU can improve the dimensional stability and thermal stability of wood samples. NCC can increase the thermal stability and strength of the MU modifier. Take the price of three prepolymer into consider, DMDHEU was the most expensive in three pre-polymer, so the products should depend on the request of market.