Study On Impregnation Modification Of Poplar With Melamine Urea-formaldehyde Resin And The Effect Of Electron Beam Irradiation

Fast-growing forest inferior wood has been able to replace or partially replace hardwood resources by impregnation modification.However,for the impregnation of thick fast-growing forest planks,it may encounter problems such as excessive molecular weight of the impregnation which is difficult to infiltrate into deep part of the boards,and deformation of the boards caused by unsuitable heat curing process.In this paper,the thermocuring preparation process of poplar which were impregnated with small-molecular-weight melamine modified resin was studied,and the application of electron beam radiation technology in this field was explored.The main contents of the impregnated wood process are: impregnation of small molecular weight melamine modified urea-formaldehyde resin into poplar wood by the process of vacuuming and then pressing,setting appropriate heat curing conditions,and testing various properties.The preparation of the impregnation liquid mainly explores the ratio of formaldehyde/urea(F/U),the amount of melamine added,the amount of ammonia added,the drying process and other factors to optimize the impregnation liquid.The electron beam(EB)irradiation part explored the effect of EB irradiation on the mechanical properties of impregnated wood products and the reduction of formaldehyde emission,and the EB radiolysis process of melamine modified urea-formaldehyde resin.Experimental results show:(1)When the F/U ratio is about 1.1,the amount of melamine added is 6% to 10%,and the amount of ammonia added is 8% to 15%,the cured product not only has excellent bending resistance,but also can reach National standard E1 formaldehyde emission standard.(2)By comparing the flexural strength,indentation hardness,compressive strength,24 hr water absorption,and the weight loss rate of the finished product under ultrasonic leaching conditions,it was found that EB irradiation can promote impregnation before thermal curing.All aspects of the performance of the finished wood.(3)Irradiation of finished impregnated wood containing formaldehyde by electron beam irradiation.The experimental results show that electron beam irradiation can effectively reduce the finished impregnated wood containing formaldehyde emission.The higher the initial formaldehyde emission,the more obvious the effect,but the electron beam is used.Irradiation does not completely remove formaldehyde.(4)Characterization of the change of resin structure before and after irradiation of melamine-modified urea-formaldehyde resin by nuclear magnetic resonance spectrometer(carbon spectroscopy)and Fourier infrared.The results show that the melamine-modified urea-formaldehyde resin after electron beam irradiation has a triazine ring and nitrogen.Hydrogen bonds,ether bonds,etc.are partially decomposed.Analysis by synchronous thermal analyzer showed that the melaminemodified urea-formaldehyde resin after irradiation was more stable than the non-irradiated melamine-modified urea-formaldehyde resin,but the melamine modification was carried out after heating to the final temperature due to the consistency of the reaction additives.The residual quality of urea-formaldehyde resin is basically the same.