Studies On The Effects Of Compression Treatment On The Structure And Impregnation Of Phenol Formaldehyde Resin Of Populus Cathayana Wood

Compression impregnation treatment has been paid more and more attention because of its high efficiency,high impregnation ability and easy to use.However,the change process of wood cells during compression treatment is not very clear,and the effect of pore change on impregnation,especially for resin with high molecular weight and viscosity is not systematic enough.Therefore,this paper takes Populus cathayana as the research object,uses the universal mechanical testing machine to compress and recovery in the range of 10%?60%.With the help of micro density instrument and scanning electron microscope(SEM),the changes of cell morphology in the compression process and the corresponding recovery process are studied;the internal porosity in the compression process is measured by differential calorimetry scanner(DSC)and mercury intrusion porosimetry(MIP)The relationship between compression ratio and weight percent gain of Populus cathayana was explored by using water-soluble low-molecular-weight phenol-formaldehyde resin(PF)as the impregnation solution under different compression ratios,and the resin impregnation amount and corresponding impregnation contribution rate were studied according to the weight change of Populus cathayana test,and the relationship between compression ratio and weight percent gain of Populus cathayana was explored through Ultra-depth-of-field microscope and Fourier transform infrared spectroscopy(FTIR)And ATR infrared imaging(ATR)was used to analyze the distribution and functional group changes of resin in Populus cathayana after compression impregnation,which provided scientific guidance for the subsequent compression treatment of impregnation of low molecular weight PF.The main conclusions of this paper are as follows:1.Compression deformation first appears in the region with the lowest micro density.It then extends to the area with a higher micro density.Compression is the accumulation of this process.The vessel was compressed more than wood fibre during the compression and wood ray bending deformation occurs,when the compression ratio is less than 40%,the micro density of wood increases as a whole,completing the first stage of compression.The wood fibre was compressed more than the vessels,and the wood ray was twisted and deformed,and some wood rays are entirely broken,when the compression ratio is higher than 40%,completing the second stage of compression.The recovery deformation firstly shows that the whole compression area recovery at the same time.It showed locoregional improvement until the end of the recovery process when the recovery ratio was higher than C-40%.After the compression force is released ultimately,the micro density of wood almost returns to the state before compression.The recovery deformation firstly shows that the whole compression area recovery at the same time.it shows locoregional recovery until the end of recovery process when the recovery ratio was higher than C-40%.After the compression force is released ultimately,the micro density of wood almost returns to the state before compression.2.The results of SEM showed that the surface porosity decreased with the increase of the compression ratio.The thermal porometer test results showed that compression treatment could effectively increase the cumulative pore volume of Populus cathayana,especially in the range of 1 nm?20 nm and 200 nm?400 nm.The mercury intrusion porosimetry results showed that the volume of mesopores and micropores with pore diameter above 500 nm decreased with the increase of compression ratio,and new pores would be produced during compression.3.In the range of 10%?60%compression ratio of Populus cathayana,with the increase of compression ratio,the amount of phenol-formaldehyde resin impregnation increased from 0.016g/cm~3 to 0.487 g/cm~3.The contribution rate during the release of the compression process increased from 32.43%to 66.65%.At the same time,under all compression ratios,the impregnation amount of phenol-formaldehyde resin reached 60%of the total amount within 30min.To improve the volume and efficiency of industrial impregnation,a higher compression ratio was recommended.The effect of during the release of the compression process should be paid attention to.There was a positive proportional linear relationship between the weight percent gain and the compression ratio.When the compression ratio is less than 60%,the weight gain rate increases by 0.38%when the compression ratio increases by 1%,when the phenol-formaldehyde resin solution was impregnated into Populus cathayana,its molecules could not only be immersed into the cell cavity,but also into the cell wall,and chemical cross-linking was formed with the components of the cell wall.