Study On Copolymerization Modification And Performances Of The Melamine Impregnated Resin Adhesive

Melamine formaldehyde resin(MF),as a kind of thermosetting resin,is used widely.However,the structure of melamine resin is crispy due to the three-dimensional network with high density of crosslinking density after the curing,which limits its widespread and long-term usage.As a result,the modification of MF resin is very necessary.The mechanisms of melamine resin polymerization were studied when the amino Benzenegeneration(BG)and urea(U)were used as modifying agents respectively.The effects of different dosage of modifier on the performance characterization and cured copolymerization resin were respectively investigated.Meanwhile,the aziridine(AZ)was used as crosslinking agent to modify the melamine resin.The effect of different dosage of AZ on curing mechanism and the bond strength of MF resin were investigated in details.The results were as follows:(1)The MF resin modified with BG.Infrared spectroscopy(FT-IR),in combination with the hydrogen nuclear magnetic resonance spectra(1H-NMR)technologies,confirmed that BG was successfully grafted onto the MF resin.The adding of BG strengthened the energy storage modulus and increased the composite's glass transition temperature according to the results of DMA technology.Thermogravimetric(TGA)analysis implied that the thermal stability of MF resin was increased because of the adding of BG.The tensile strength and toughness of the dipping laminated plate were increased.The elongation at break was increased by 22% at the addition of 15% BG,namely the best addition.(2)In order to obtain better toughness and economic benefit,U was used as the modifier to modify BG-grafted MF resin.1H-NMR and FT-IR spectra showed U participated in the polycondensation reaction.The analysis of DMA indicated the energy storage modulus and glass transition temperature were both decreased;The thermal degradation temperature was decreased according to the analysis of TGA;The toughness was increased.The tensile strength was decreased,but could still meet the demand of tensile strength of the dipping laminated plates.The elongation at break was increased by 11.9% at the addition of 20% U,namely the best addition.(3)The effects of different dosages of AZ on MF resin.FT-IR spectrum showed the addition of AZ can do copolymerization reaction with MF resin and facilitate the curing.DMA showed that the changes of the energy storage modulus was different and the glass transition temperature was decreased,indicating that AZ improved the curing;The tensile strength of the dipping laminated plates' mechanical property was increased.The best comprehensive properties occurred when the dosage of AZ was 1%.And the moderate of aziridine agent could decrease the curing temperature,improve the toughness,and increase the elongation at break by 5.5%.(4)Based on the best toughening methods in the first two chapters,2% AZ was added to study the effects of AZ on the performances of the modified copolymer resin.The FT-IR showed the curing speed of modified resin was improved.Tensile test showed that tensile strength and toughness of the dipping laminated plate were both increased,and the resistance to combustion and boiling water resistance were improved.