Preparation Of Transparent Bamboo And Its Functionalization Research

Silica-based glass is the most commonly used transparent building material,but it suffers from heavy mass,fragility,difficulty in degradation,and high manufacturing energy consumption.In recent years,the creation of transparent wood with high light transmittance has provided a new option to replace silica-based glass.However,the shortage of wood resources in China,high foreign dependence,and the defects of hydrophobicity,fire resistance,and poor scratch resistance of transparent wood have limited the development of transparent wood.China is the country with the most abundant bamboo resources and the earliest use of bamboo in the world.Compared with wood,bamboo has a shorter growth cycle and is cheaper;at the same time,bamboo has a microstructure similar to that of wood,which provides the possibility of creating transparent bamboo timber.For this reason,it is important to develop functionalized transparent bamboo materials with flame retardant,hydrophobic properties and scratch resistance.In this thesis,we first created transparent bamboo with high transparency and high haze by two-step method of delignification and vacuum impregnation,and investigated the ultrastructure and physicochemical properties of transparent bamboo;then,we overcame the key problem of poor fire resistance of transparent bamboo by coupling liquid sodium silicate with high transparency and strong fire resistance,and explored the chemical composition and microstructure changes of bamboo during the preparation of functionalized transparent bamboo.We also investigated the chemical composition and microstructural changes of bamboo during the preparation of functionalized transparent bamboo,and deciphered the relationship between the interfacial binding mechanism and the performance of functionalized transparent bamboo.In order to overcome the common problem that transparent bamboo does not possess super hydrophobicity and scratch resistance,two different functionalized transparent bamboo materials(PFTS-TMCS@LSS-TB and PR@EP-TB)were prepared through the modification of fluorochlorosilane and sliding ring topological network to achieve the flame retardant,hydrophobic properties and scratch resistance of transparent bamboo materials.The main research of this thesis is as follows:(1)The bamboo material was delignified using acidic sodium chlorite solution.Subsequently,liquid sodium silicate matching the refractive index of the bamboo cell wall was impregnated into the interior of the bamboo using a vacuum-anomalous pressure method to produce transparent bamboo with high transparency(71.9%)and ultra-high haze(97.5%).It was shown that the delignification treatment could completely remove the lignin macromolecules and increase the pore structure and cell wall active sites of bamboo;the delignification treatment did not significantly damage the internal cellulose skeleton structure of bamboo,but the mechanical properties of delignified bamboo were relatively reduced due to the removal of the adhesive material lignin,and the tensile strength was 24.33 MPa,which was 22%lower than that of natural bamboo(31.2 MPa)decreased by 22%.(2)In order to endow transparent bamboo with flame retardancy and self-cleaning properties,a functionalized transparent bamboo material(PFTS-TMCS@LSS-TB)with flame retardant and hydrophobic properties was able to be successfully prepared by vacuum impregnation of liquid sodium silicate and modification treatment with a fluorochlorosilane modifier(PFTS-TMCS),with a permeability of 70.8%and a haze of 96.7%.During the preparation of PFTS-TMCS@LSS-TB,the liquid sodium silicate not only successfully filled the internal pore structure in situ,but also chemically reacted with the free hydroxyl groups and other reactive groups of the bamboo cell wall to form new interfacial bonds,which eventually formed Si-O-Si structure and Si-O-C structure,increasing the internal bonding strength of PFTS-TMCS@LSS-TB.The reaction of PFTS-TMCS modifier with the free hydroxyl group on the surface of transparent bamboo(LSS-TB)then successfully grafted hydrophobic groups to the surface of LSS-TB,and its flame retardancy,thermal stability and hydrophobicity were superbly improved.the ignition time of PFTS-TMCS@LSS-TB was delayed from 20 s to 116 s,and the pyrolysis residual carbon was as high as 52.7%,which exceeded that of the pyrolysis residual carbon amount is 52.7%,which is 18.5 times higher than that of natural bamboo(2.7%),and its static water contact angle is increased to 154.7°.(3)The cross-linking and capping reactions of chain PEG-BA and cyclic α-CD macromolecules were able to successfully prepare poly(rolane)sliding ring macromolecules.The functionalized transparent bamboo with 78.2%transmittance and 83.5%haze was obtained by impregnating delignified bamboo by mixing it with epoxy resin for modification.The chemical component analysis revealed that the impregnation of poly(rolane)-modified epoxy resin(PR@EP)not only successfully filled the internal pore structure of bamboo during the preparation process,but also formed a three-dimensional cross-linked network of sliding ring topology with more chemical binding sites between PR and EP and the free hydroxyl groups of bamboo cell walls,while EP could also act as a new "knot" in the sliding ring topology network.The new "crust material" of the topological network provides hardness and strength support for the transparent bamboo material,increasing the internal bonding strength and stability as well as the scratch resistance of PR@EP-TB,with a scratch friction coefficient of 0.387 and a scratch depth of 37.2 μm,which is about 17.1%.Due to the presence of the sliding ring topological network structure,when PR@EP-TB is subjected to external forces,the forces can be uniformly distributed to the entire topological network,which generally ensures the mechanical properties and scratch resistance of the functionalized transparent bamboo material.In summary,based on the porous framework of bamboo,the common problems of hydrophobicity and poor fire resistance of transparent bamboo materials have been overcome by hydrothermal method,vacuum-atmosphere impregnation method and modification treatment of different polymers,and the bottleneck of scratch resistance of transparent bamboo materials has been broken through,and functionalized transparent bamboo materials with high permeability and high haze have been created,laying a scientific foundation for the industrial application of transparent bamboo materials.