Study On The Adhesive Properties Of Low Temperature Curing Epoxy-cyanate Resin

The epoxy-cyanate(EP-CE)resins which have good heat resistance,excellent dielectric property and mechanical property are used in the fields of aviation,aerospace and electronics,etc.as an important structure-function material.To achieve a fully-cured state with good mechanical properties,the EP-CE resins are cured at 180?,and even have to undergo a post-cure processing above 200?.However this high curing temperature may be impractical in some cases,for example,repair composites usually have to be cured at low temperature(80?150?).But curing the resin at a lower temperature by adding catalyst may result in an incomplete cross-link density,and lead to a lower glass transition temperature(T_g)and potentially a decrease in mechanical performance,dielectric property and heat resistance.So far,there is a lack of the systematic study pertaining to the effect of low temperature curing process on the properties of EP-CE resins in the literature.In this paper,the influences of four kinds of catalysts including copper acetylacetonate(Cu(acac)₂),dibutyltin dilaurate(DBTDL),copper naphthenate,2-ethyl-4-methylimidazole(EMI)and three kinds of curing process conditions(80?/96h,120?/48h and 100?/12h+150?/12h)on the properties of cured EP-CE(60/40 Wt)resins are investigated.The influences of different amounts of the four kinds of catalysts on the curing reactivities,T_g and the curing degree of the EP-CE resins are researched through the DSC analysis.The optimum content of Cu(acac)₂,DBTDL,copper naphthenate and EMI is 160ppm,160ppm,50ppm and 1%respectively.The catalytic curing kinetic parameters of EP-CE resins are analyzed with the Kissinger and Ozawa equation.The results show that the four kinds of catalysts can significantly reduce the activation energy of the resin.Based on the DSC study mentioned above,the effects of three kinds of curing process on the curing degree,T_g,chemical structures and thermal properties of a EP-CE resin system catalyzed by Cu(acac)₂and a EP-CE resin system catalyzed by EMI are researched respectively through the DSC tests.The thermal property of the catalyzed resins is evaluated by the TG test.The changes in structure of resins are studied through the FTIR.And the variations in performances of resins cured by the three kinds of low temperature curing process are also researched by mean of analyzing the shear strength and dielectric property.(1)Copper acetylacetonate catalyzed resin systemThe three kinds of curing process have significant effects on the curing degree,T_g,150?shear strength and the dielectric loss of resins.The curing degrees of the cured resin cured with three curing processes are 75.35%,95.2%and 96.38%respectively.The glass transition temperatures are found to be 84.78?,131.94?and 143.65?respectively.The 150?shear strengths are 3.16MPa,13.77MPa and 17.59MPa respectively.The room temperature shear strengths are 20.91MPa,21.14MPa and22.28MPa respectively.The dielectric constants at 10GHz are 2.39,2.96 and 2.94respectively.And the dielectric loss at 10GHz are 0.02235,0.02047 and 0.01979respectively.The three curing processes do not have obvious effects on the TG of resins.The IR analysis results of the resins catalyzed by the Cu(acac)₂during the curing process show that the trimerization of CE is the major reaction at the beginning of the reaction.And as the cuing reaction continues,the isocyanurate and oxazolidinone are produced.(2)EMI catalyzed resin systemThe rule of influencing of low temperature cuing process on the EMI catalyzed resin system is similar to that on the Cu(acac)₂catalyzed system.However,the EMI catalyzed resin system has a higher curing degree,T_g,dielectric constant and shear strength,and the dielectric loss decreases when the curing process is operated at 80?or 120?.During the curing process,the rule of change in the characteristic functional group of catalyzed resins is similar to that of the Cu(acac)₂ catalyzed system.