Study On Surface Properties Of Sodium Silicate Modified Poplar Wood

Populus tomentosa has the advantages of high yield,light weight,high strength,good elasticity,and easy mechanical processing.It is often used in furniture,flooring,building materials,interior decoration materials and other fields.In this paper,the fast-growing poplar was the research object,and inorganic salt(sodium silicate)was used as the modification reagent.Sodium silicate impregnated modified poplar wood was prepared by vacuum pressure method.Sodium silicate enters the wood cells and chemically reacts with the lignin and extracts contained in the wood,which will have a certain impact on the surface properties.Therefore,it is very important to study the effect of sodium silicate on the surface properties of poplar wood.The research results provide certain technical and theoretical guidance for the application of poplar wood in furniture building materials and interior decoration materials.The main conclusions are as follows:(1)Sodium silicate impregnation significantly improves the physical and mechanical properties of poplar wood.Compared with the unmodified wood,the weight gain rate of the modified wood after 3 hours of impregnation treatment increased to 42.15%,the density increased from 0.455 g/cm3 of the unmodified wood to 0.672 g/cm3,and the compressive strength increased by 76.19%,the end surface hardness,tangential surface hardness,and radial surface hardness increased by 82.22%,55.05%,and 55.96%respectively.The wear of the radial section and the tangential section were reduced by 46.99%and 41.81%,respectively.Through scanning electron microscope,X-ray diffraction and X-ray photoelectron spectroscopy,the changes in the microscopic morphology,crystal structure and chemical structure of the modified wood were analyzed.Studies have shown that the end surface and diameter surface of the modified wood can clearly see the filled sodium silicate solid content,as the impregnation time was extended,the sodium silicate solid content impregnation in the wood will increase,and the pores in the poplar wood played a physical filling role.Sodium silicate modification treatment did not change the unit cell structure of poplar wood,which reduced the crystallinity to a certain extent,as the impregnation time prolonged,the crystallinity decreased,obviously.However,the impregnation of sodium silicate into the wood fills the internal pores of the wood and can withstand greater stress,so it can still strengthen the wood even when the crystallinity was reduced.There were not only C and O elements in the modified wood,but also Na and Si elements,indicating that sodium silicate can be effectively impregnation into the wood,resulting in a Si-O-C chemical structure and forming a hydrogen bond,thus indicating sodium silicate was not only filled in physical form,but also forms a chemical bond.(2)Sodium silicate modification has an effect on the color of poplar wood surface.the modified treatment reduces the brightness of the wood surface,and makes the surface brightness gray and dark,but it was still in the middle brightness area.Its color tends to yellow-green as the impregnation time was prolonged,and its purity gradually improves.After finishing the wood with water-based and oil-based varnish,the surface color becomes more obvious.The sodium silicate modification makes the contrast of the wood surface texture clearer,and the texture of the poplar tangential section was more scattered and loose than the radial section,and the grain spacing was also larger.The modification treatment also reduces the gloss of the poplar wood surface,and the parallel texture gloss(GZL)is higher than the vertical texture gloss(GZT),and the two were linearly related.Compared with the uncoated wood,the glossiness of the poplar wood surface was obviously improved many times after the two varnish coatings.(3)The modification treatment improves the surface wettability and surface free energy of the poplar wood.Sodium silicate modification can effectively improved the surface wettability of poplar wood.As the impregnation time increases,the surface wettability gradually becomes better,and water dilution can simultaneously improved the surface wettability of poplar wood.From the analysis of the wettability changes of the three water-based paints,the wettability of the acrylic-polyurethane copolymer modified paint was better than that of the acrylic paint,followed by the acrylic paint,the wettability of polyurethane paint was worse than the other two paints.Modification makes the surface free energy of poplar wood gradually increase with the impregnation time,and its surface polarity component,dispersion component,acid-base component all increase to varying degrees.The surface free energy of poplar radial section was better than that of tangential section.Sodium silicate modification makes the adhesion of the paint film on the surface of poplar wood worse,but from the grade ratio of the wood paint film adhesion after modification,it can be seen that the modification treatment will not be excessively affected,causing the paint film adhesion to become Worse and unqualified products appear.