Research And Characterization Of Liquefied Starch Modified MF Resin Based On Single Enzyme Method

Starch is a natural polymer compound in which glucose is a basic unit and is linked byα-1,4 glycosidic bonds.According to the difference of the connection keys,it is divided into amylopectin and amylose.In this paper,the product obtained by liquefying starch withα-amylase,melamine and formaldehyde were used as raw materials to synthesize ASMF resin adhesive under weak alkaline conditions.The effects of p H value,reaction temperature,molar ratio of formaldehyde to melamine,addition amount of starch liquefied product,and participation of starch liquefied product on the physical and chemical properties of ASMF resin were investigated.The structure of ASMF resin was characterized by ¹H-NMR、¹³C-NMR and FT-IR.The heat resistance of ASMF resin was tested by TG,and the hot pressing process of ASMF resin adhesive pressed into plywood was optimized by orthogonal experiment.The enzymatic method was compared with the product obtained by acid liquefying starch.The morphology of the particles was observed by SEM and analyzed by FT-IR.Finally,the performance of AMF resin and ASMF resin adhesive synthesized by tapioca starch in two liquefaction modes was carried out.And cost analysis.The main research results of the thesis are as follows:（1）Using starch liquefaction product A-1,melamine and formaldehyde as main raw materials,ASMF-a and ASMF-b resin adhesives were synthesized under weak alkaline conditions.When the p H value of the reaction system was9.0 and the reaction temperature was 88±1℃.When the molar ratio of formaldehyde to melamine is M_F/M_M is 2.0 and the amount of starch liquefaction product A-1 is 40%,the synthesized ASMF-a resin has superior performance.At this time,the solid content of ASMF-a resin is 68.45%,the viscosity is77.5m Pa·s,the bonding strength is 1.523MPa,which is higher than the national class I plywood standard,the formaldehyde emission is 1.292 mg·L^-1,and the storage period is 27 days;ASMF-b resin has a bonding strength of 1.043 MPa and a storage period of only 5 days.（2）It can be obtained by ¹H-NMR、¹³C-NMR and FT-IR analysis that the main dehydration condensation reaction between methylol melamine occurs in the MF resin;in the ASMF-a resin,not only maltose,but also maltose,There is also a Mannich reaction in the dehydration condensation reaction between methylol in glucose and methylol melamine.（3）The TG results showed that the curing agent,the amount of starch liquefied product added,and the resin state（solid and liquid）all have an effect on the heat resistance of ASMF resin.The addition of curing agent moves the maximum thermal decomposition temperature of the solid sample of ASMF resin to the high temperature zone;as the amount of amylolytic product increases,the maximum thermal decomposition temperature of the ASMF resin moves to the high temperature zone,and the final residual carbon rate ASMF resin Slightly lower than the MF resin;the structural difference between the resin pre-cured in air and the resin cured in nitrogen results in a difference in the thermal decomposition process of the ASMF resin in different sample states,but does not affect the maximum thermal decomposition temperature.The final carbon residue rate was:solid resin（11.26%）>liquid resin（7.07%）.（4）SEM observation of starch liquefaction products A-1 and A-2 showed that the degradation rate of starch by concentrated sulfuric acid was higher than that ofα-amylase,and the starch structure after gelatinization was loose and susceptible toα-amylase.Attack,as time goes on,the hydrogen bond of the double helix structure of the crystallization zone is destroyed,the order is reduced,the particles are broken into pieces of different sizes,and concentrated sulfuric acid can reach this level in a short time.In the final A-1（c）figure,less intact particle morphology of the starch can be observed,and in the A-2（c）figure,the small molecule particles are completely destroyed into fragments.The results of FT-IR analysis showed that both liquefaction methods reduced the crystallinity of starch;comparing the N-OKI values,it was found that A-2decreased more than A-1 and the crystallinity was lower.（5）FT-IR analysis of ASMF-a(m _AS/m _M=0.4)and AMF-a（m _A/m _M=0.4）resins showed that the two resin groups were consistent with the corresponding characteristic absorption peaks.The displacement and intensity of the absorption peak are slightly different.Take the N-H stretching vibration and the O-H bond stretching vibration absorption peak at 3320 cm^-1.Here,the absorption peak intensity AMF-a resin is relative.Stronger,indicating that the resin has more N-H bond and O-H bond content.