Design And Synthesis Of Novel Epoxy Resins And Relationship Of Their Structures And Properties

Because epoxy resin has excellent heat-resistance property,good flow property and low cost,it is widely used in coating,chemical anticorrosion,electronic appliances,vehicle,and so on.The diglycidyl ether of bisphenol A(DGEBA)which has been industrially produced,used as resin matrix in aerospace and other fields.However,with the increase of the amount of resin matrix in aerospace,the defects are more and more prominent,resulting in poor heat resistance and mechanical property.Therefore,the design and synthesis of epoxy resin which has good processing performance,excellent heat-resistance property and well mechanical properties have great significance.In this paper,two monomers are selected:4-(4-hydroxyphenyl)-2,3-phthalazin-1(2H)-one(DHPZ)and fluorene-9-bisphenol(BHPF),an epoxy resin with DHPZ structure and an epoxy resin with BHPZ structure are synthesized and confirmed by ~1H NMR and FT-IR.The epoxy value is determined by non-water titration with HBr-AcOH.The epoxy value of the synthesized epoxy resins are 0.28-0.32/100g and 0.40-0.42/100g,name ER30 and ER41.The solubility and rheology of ER30 and ER41 are tested,the results show that both of them have good solubility and rheology,and both of them have wider processing windows.The thermal properties of ER30 and ER41 are characterized,the TGA shows that the different weight loss temperature of ER41 is higher than ER30,but the residual carbon ratio of ER30 at 800°C is larger,and the DSC shows that the glass transition temperature of ER30 is higher than ER41.Modified DGEBA/DDM(4,4'-diaminodiphenylmethane)curing system with ER30containing DHPZ structure and ER41 containing BHPF structure.The blends of ER30/DGEBA system,ER41/DGEBA system and ER30/ER41/DGEBA system are prepared by melt blending,and the curing kinetics are studies,determines the suitable curing processes.The products after blending and curing are tested for rheological property,thermal property,mechanical property and scanning electron microscopy(SEM).The mechanical properties of ER30/DGEBA/DDM system are generally improved.When the addition amount of ER30 is 30 wt.%,the impact strength and flexural strength reach the maximum,they are 61.24 KJ/m~2 and 156.43 MPa,which are increased by 67%and46%.When the addition amount of ER30 is 10 wt.%,the flexural modulus reaches the maximum,it is 3.74 GPa,which is increased by 57.8%.Observing the impact section of different blend systems by SEM,the result shows that the main reason for the increase of impact strength is the deflection and disproportionation of cracks.In the ER41/DGEBA/DDM system,the increase of ER41 content causes the viscosity of the blends to decrease with the increase of temperature.At 100°C,the time of sharp rise of viscosity of different blends show a trend of decreasing first and then increasing.When the content of ER41 is 30wt.%,the gel time is longer than that of pure DGEBA.The different weight loss temperature is basically the same at different contents of ER41.The glass transition temperature of the blend system with ER41 is greatly improved,comparing with the pure DGEBA curing system,when the addition amount of ER41 is 20 wt.%,the Tg reaches the maximum,it is 194°C.In the ER30/ER41/DGEBA/DDM system,the glass transition temperature and impact strength are slightly improved when the mass ratio is 0.5:0.5:9.With the increase of ER30 and ER41content,the flexural strength and flexural modulus are greatly improved.When the mass ratio of ER30/ER41/DGEBA is 1.5:1.5:7,the flexural strength and flexural modulus are increased by 40%and 38%.