Study On Properties Of Modified Low Molar Ratio Melamine Modified Urea-formaldehyde Resin Of Three Agricultural And Forestry Residues

In order to effectively utilize biomass resources and improve the utilization of biomass resources,this paper selects(WS)walnut dregs(WD)and tea(Tea)as research objects,and explores WS,WD,Tea as melamine modified urea-formaldehyde resin(MUF)The possibility of modifiers.WS,WD,and Tea were pulverized to more than 300 mesh(48um)using ultra-fine grinding technology.The reactivity of WS,WD,and Tea and formaldehyde solution was measured,and WS,WD and Tea were added to the third stage of MUF resin synthesis.Copolycondensation is performed.The basic properties of resin pre-curing were tracked and analyzed,and the effects of WS,WD,and Tea on viscosity,p H,and gel time during resin pre-curing were characterized.The effects of WS,WD,and Tea on resin bonding strength and formaldehyde release were evaluated.With the help of thermogravimetric analyzer,the influence mechanism of WS,WD and Tea on the thermal degradation performance of modified MUF resin was discussed,and the theoretical basis was provided for WS,WD and Tea modified MUF resin.The main conclusions are as follows:(1)The reaction activity of WS,WD,Tea and formaldehyde is affected by the reaction temperature and reaction time.When the p H of the reaction solution is 8,the optimal temperature for the reaction of WS,WD,Tea and formaldehyde is 90~oC,and the reaction time is 0.5h-1.5h.Tea has the best reactivity with formaldehyde,followed by WD,and worst by WS.(2)When the mass ratio of WS,WD,Tea and the weight ratio of WS+Urea,WD+Urea,Tea+Urea is 0.15,0.10,0.15,the basic properties of the prepared walnut shell-based melamine-modified urea-formaldehyde resin(WS+MUF),walnut-meal-based melamine-modified urea-formaldehyde resin(WD+MUF),and Tea-based melamine-modified urea-formaldehyde resin(T+MUF)reached Optimal,the formaldehyde emission of the prepared plywood decreased by 69.43%,71.05%and 75.43%,respectively,and the wet bonding strength of plywood made of WD+MUF and T+MUF resins increased by 38.60%and24.00%,respectively.WS,WD,Tea have a certain inhibitory effect on the gel time and curing of MUF resin,which may lead to an increase in the hot pressing time of the resin when preparing plywood,but it is beneficial to extend the pot life and storage life of the resin.(3)The thermal degradation of WS,WD,Tea,MUF0,WS+MUF,WD+MUF,T+MUF can be divided into three thermal degradation stages:dehydration stage,rapid pyrolysis stage and carbonization stage.As the heating rate increases,the maximum thermal degradation conversion rate and the thermal degradation peak temperature increase accordingly.After the introduction of WS and WD respectively in the resin synthesis process,the residual amount of the resin thermal degradation carbon decreases and the high temperature resistant component decreases;after the introduction of Tea in the resin synthesis process,the resin thermal degradation carbon residual amount increases and the high temperature resistant component increases.(4)The thermal degradation activation energy of WS,WD,Tea,MUF0,WS+MUF,WD+MUF,T+MUF was calculated using Kissinger equation and Flynn-Wall-Ozawa equation.After the introduction of WS and WD in the resin synthesis process,respectively,the thermal degradation activation energy of the resin decreases.After the introduction of Tea in the resin synthesis process,respectively,the thermal degradation activation energy of the resin increases and the thermal stability of the resin increases.Tea modified MUF resin can strengthen the resin network structure and obtain better modification effect.