Study On Synthesis And Structural Characterization Of Melamine-Sugar-Formaldehyde Resin (MSF) Copolycondensation Resin

The objective of this study is to manufacture wood adhesive of melamine-sucrose-formaldehyde copolycondensation resin with low release of residual formaldehyde to reduce the pollution problems. In this paper, sucrose was used to preparer new and environmentally friendly adhesives. Meanwhile, the synthetic process, curing condition and preparation mechanism of MSF had also been investigated.(1) With the bonding strength as evaluation criterion, the dosage of sucrose (mass percent of melamine), dosage of borax (mass percent of melamine), pH and F/M molar ratio, were discussed as the main factors to the preparation technology of adhesive based on one factor test. The orthogonal experiment were used to optimize parameters, the dosage of sucrose, dosage of borax, F/M molar ratio were chosen as three affective factors, which have three levels respectively. Through orthogonal test, we found that the order of significant was:the dosage of sucrose> dosage of borax>F/M molar ratio and the optimum parameters were:the sucrose dosage80%, the sucrose dosage3.0%, F/M molar ratio2.2.(2) The Chemical quantitative analysis method were used to discuss the influence of dosage of sugar and F/M molar ratio on formaldehyde emission. We found out that:the hydroxymethyl content was decreased from 19.79%to10.05%, the formaldehyde content was decreased from1.44%to0.74%and the free formaldehyde release was decreased from6.0mg/L to2.1mg/L, when the sucrose dosage was increased from0%to170%; the hydroxymethyl content was decreased from10.99%to8.77%, the free formaldehyde release was decreased from0.80%to0.44%and the free formaldehyde release was decreased from2.1mg/L to0.84mg/L, when F/M mole ratio was reduced from3.0to2.4.(3) We used the ammonium chloride to explored curing behavior. Experimental results showed that:the pH value, Curing time and curing temperature of MSF resin reduced when ammonium chloride was added.(4) With the bonding strength as evaluation criterion, the combined effects of flour dosages (mass percent of adhesive), curing agent dosage (mass percent of adhesive) and curing time were investigated and optimized by using response surface methodology (RSM). The result showed that:factor X1、X2、X3and interaction factor X1X2、X12、X22、X32are all significant to the model, interaction factor X1X3、X2X3are not significant to the model. The optimized regression was as follow:y=0.84-0.03X1+0.041X2+0.041X3+0.05X1X2-0.041X12-0.074X22-0.044X32. The optimum conditions were as follows:curing agent dosage0.6%, flour dosage13.78%and curing time5.94min. The response value could reach0.86MPa.(5) The changes of formaldehyde content and hydroxylmethyl content in the preparation of MSF were discussed, the FTIR spectra was used to analyse the structure of SMF. The results showed that:under alkaline conditions, sucrose could aggregate with hydroxyl methyl MF resin, condensation polymer was mainly combined by-CH2-bonds, the second was ether bond.