Synthesis And Properties Of Melamine Formaldehyde Resin Under Ethylene Glycol System

Melamine formaldehyde resin(MF)is one of the earlier industrialized chemical products.Because of its excellent performance,it has been widely used in coatings,a fixing agent for a water repellent and foam.However,production of resin are all the melamine resin produced in the water system with the methanol as a stabilizer,lack of the study on the synthesis and application of melamine resin in non-aqueous media.Polyurethane foam,a new synthetic polymer materials,has been widely used in decoration,packaging transportation and automotive for its anti-shock and heat insulation.However,the polyurethane foam has a low oxygen index of about 18,easy to burn and smoke emissions,and most of the current polyurethane foam used in the polyether-based system,the lack of its own flame retardant system.In this paper,based on the research of preparation process,reaction mechanism and application areas,the melamine formaldehyde resin was prepared by paraformaldehyde and ethylene glycol or polyethylene glycol instead of formaldehyde and water respectively,mainly for the synthesis and application of melamine resin in non-aqueous media and the raw materials of polyurethane foam lack for their own flame retardant system.Moreover,melamine-based polyurethane composites and melamine polyurethane foam was prepared by cross-linking curing of the modified Melamine formaldehyde resin and MDI.The main research contents and results are as follows:1.Synthesis and characterization of MF resin in non-aqueous mediaThe modified melamine formaldehyde resin was synthesized by using melamine and paraformaldehyde as raw materials,ethylene glycol or polyethylene glycol as solvent,KOH and triethanolamine as the catalyst.The effects of the addition of EG or PEG,molar ratio of F/M,pH,reaction temperature and the amout of urea(U)on the properties of the resin were studied.The results showed that the best ratio of m(EG):m(M):m(F),n(F):n(M)and m(U):m(M):m(F)were 0.9:1:0.6,2.5:1 and 0.09:1:0.6 respectively,the best reaction temperature was 95 ℃ and the best pH was 9 under the EG system.While under the PEG system,the best ratio of n(F):n(M),m(U):m(M):m(F)and m(PEG200):m(M):m(F)or m(PEG400):m(M):m(F)were 2.5:1,0.09:1:0.6,1.8:1:0.6 and 2.1:1:0.6 respectively,the best reaction temperature was 95 ℃,the best pH was 9.The synthesized MF resin had low water content(2.8 %),low free formaldehyde(0.4 %)and good storage stability(>240 d).Both FTIR and 13C-NMR confirmed that EG and PEG200 were involved in the reaction of etherified MF resin,while PEG400 was not involved.The results of 13C-NMR analysis of EG-modified MF resin showed that 38.7 % of EG was involved in the etherification polycondensation of MF resin.2.Preparation and properties of melamin-based polyurethane compositesThe different series of melamine formaldehyde resin film were prepared with melamine formaldehyde resin of modified and MDI by solvent-forming method.The contact angle of the liquid on different samples was measured by contact angle measuring instrument.The surface free energy and components of each sample were calculated by LW/AB method.The thermostability of different MDI samples was analyzed by thermogravimetric analysis.The mechanical properties of different MDI sample films were tested by using a universal mechanical testing equipment.The results showed that the surface free energy and components of the MPU1,MPU2 and MPU3 film were decreased gradually,which indicated that the wettability of the film surface was also decreased gradually.When the dosage of MDI reached 28 %,the water absorption rate of MPU3 film was the lowest,the water absorption in water and alkali was 7.3 % and 4.4 % respectively,and the elongation at break and tensile strength reached 198.83 % and 6.08 MPa respectively.The reason is that the matrix MF resin and isocyanate cross-linking reaction,resulting in a certain segment and branched structure of the polymer.With the increase of the amount of MDI,the initial thermal degradation temperature of MF resin film,the thermal stability,and the final residual mass were decreased.3.Preparation and flame retardancy of melamine-based polyurethane foamThe melamine-based polyurethane foam was synthesized by the modified melamine formaldehyde resin,and then the APP and PER complex system was applied in the flame-retardant polyurethane foam to prepare the halogen-free flame-retardant foam with good performance.The flame retardancy and thermal decomposition were studied in this paper.Those were found: when the mass ration of APP and PER was 4:1 and the amount was 30 %,the oxygen index of flame retardant polyurethane foam(MAP-3)was 31.3 %,which was 36.1 % and 7.9 % higher than that of APP-0 and APP-3 respectively.The heat release rate(HRR)and total heat release(THR)of the flame-retardant polyurethane foam were decreased by 83.3 % and 70.5 % compared with APP-0 and APP-3,respectively.Moreover,the decrease of toxic gases and smoke indicated that APP / PER synergistic system has a good anti-smoke effect.The FTIR and scanning electron microscopy(SEM)showed that the residual carbon after burning of the flame-retardant polyurethane foam is mainly composed of aromatic compounds,phosphorus-containing compounds and methyl structure,and a dense continuous carbon layer was formed on the foam surface,which prevented the matrix foam continued burning.The results by TGA and thermal decomposition kinetics showed that APP/PER synergistic flame-retardant system can improve the thermal stability of flame retardant polyurethane foam.