Preparation Of Quaternized Waterborne Epoxy Resin System And Its Influence On Wood Properties

As a renewable resource,wood is widely used in construction,furniture,decoration and other fields.However,due to its tipical problems of poor dimensional stability,easy deformation and decay,the use of wood is severely limited.In this paper,the waterborne epoxy resin system with high stability,small particle size and antibacterial function was prepared by chemical modification method and then was introduced into the wood via vacuum-pressure impregnation method.The dimensional stability and decay resistance of wood were enhanced after the in-situ cross-linking of waterborne epoxy resin inside wood.The main results are as follows:(1)Two kinds of epoxy oligomers with different functional degrees(i.e.difunctional degree and tetrfunctional degree)were selected to prepare the quaternized waterborne epoxy resin(QWEP)systems with different particle sizes.The stability of QWEP system and the bacteriostatic performance of cured samples were studied.The results show that the particle size of the QWEP system reaches the nanometer level and has good stability.The results of antibacterial properties show that the cured QWEP can inhibit the growth of Staphylococcus aureus and Escherichia coli.(2)The QWEP with better comprehensive properties was chose and injected into the wood by vacuum-pressure impregnation method.The morphological structure,dimensional stability,mechanical strength,and decay resistance of treated wood were mainly studied.The results showed that the weight percentage gain and bulking efficiency of the treated wood reached 42.5% and 4.5%,respectively.Investigation by Scanning electron microscope(SEM)indicated that the QWEP can enter into the wood structures and cured inside them.Nano-indentation test results showed that the hardness and modulus of cell wall treated wood were increased from 0.43 GPa and 15.8 GPa to 0.76 GPa and 20.0 GPa,respectively.The mechanical test results showed that the tensile strength and compressive strength of the treated wood were increased by 26.3% and 32.7%,respectively.Combined with the bulking efficiency,morphological structure and nanoindentation test results of wood treated with QWEP,it can be seen that the QWEP can enter the wood cell cavity and penetrate the cell wall,thereby improving the wood properties.The dimensional stability test showed that the anti-swelling rate and anti-shrinking rate of the treated wood under the three cycles of soaking-drying reached 39.8% and 34.0%,respectively.The results of the decay resistance test show that the decay resistance grades of the treated wood to both white-rot fungus and brown-rot fungus had reached strong anti-corrosion I.(3)Different contents of chitosan(CS)were added to the QWEP system,and the stability of the waterborne epoxy resin system synergistically cross-linked by CS,the water resistance,mechanical and antibacterial properties of the cured samples were studied.Then,the quaternized waterborne epoxy resin/chitosan(QWEP-CS)system with excellent performance was selected to treat the wood,and the dimensional stability and decay resistance of the treated wood were analyzed.The results show that the addition of CS can improve the crosslinking degree of the QWEP-CS system.When the CS content was 50%(QWEP-50CS),the stability,water resistance and mechanical properties of the system are the best.The antibacterial test results showed that the addition of CS could synergistically improve the antibacterial properties of QWEP,and the antibacterial rates of QWEP-50 CS against Staphylococcus aureus and Escherichia coli were 99.4% and 100%,respectively.After being treated by QWEP-CS system,the dimensional stability was improved,and the anti-swelling rate and anti-shrinking rate of treated wood reached 19.3% and 27.3%,respectively.After being infected by white-rot fungus and brown-rot fungus,the Mass loss rate of the treated wood were lower than that of the untreated wood,indicating that the decay resistance was improved.