Design And Synthesis Of Low Dielectric Eugenol Epoxy Resin Modified With Hydrosiloxane

Epoxy resin is widely used in the fields of building coatings,adhesives,aerospace and electronic packaging due to its excellent processability,high adhesion,high strength,excellent electrical insulation,low shrinkage,and low cost.At present,the fast emerging sectors of 5G and high-frequency electronic packaging devices have put forward higher requirements for the low dielectric properties of epoxy resins.However,the polar groups in the epoxy resin systems cause the epoxy resins to have higher dielectric constant(D_k)and dielectric loss(D_f).Therefore,it is necessary to develop low D_kepoxy resins without sacrificing its inherent advantages to broaden its potential application fields.In this paper,eugenol epoxy(EUEP)was selected as matrix resin,novel degradable,low-viscosity and heat-resistant low dielectric epoxy resins were designed and synthesized to meet the current applications needs in 5G and electronic packaging by introducing low polarity atom and large steric hindrance groups such as liner/cyclic/cage hydrosiloxane were used as modifiers to increase free volume.Based on the low polarity of Si-O,three linear hydrosiloxane modified epoxy hybrid resins(PMEP-0.8,PMEP-1.0 and PMEP-1.6)were synthesized using hydrogen-containing silicone oil(PMHS-x)as the modifier,and cured with methylhexahydrophthalic anhydride(MHHPA)and diaminodiphenyl methane(DDM),respectively.Dielectric test results indicated that the D_kof the MHHPA curing system was lower than that of the DDM curing system,and the D_kof PMEP-0.8-MHHPA was the lowest,at 2.96(10.0 MHz),due to the low polarity,high dissociation energy and large molecular volume of PMHS-x.Non-isothermal curing kinetics revealed that the E_aof the PMEP-1.6 system was lower than that of the PMEP-0.8 and PMEP-1.0 systems because more EUEP were grafted onto the PMEP-1.6,resulting in an increase in reactive groups and thus increased reaction activity.DMA and mechanical performance test results indicated that the glass transition temperature(T_g)and mechanical strength of PMEP-1.6 system were higher than those of PMEP-0.8 and PMEP-1.0 systems because PMEP-1.6 contains more rigid benzene ring structure,wherein the T_gof PMEP-0.8-MHHPA was 72.9℃.Furthermore,PMEP-x-MHHPA and PMEP-x-DDM could be degraded after 3 days in alkaline conditions at 80°C,providing new insights for the development of novel bio-based degradable and low dielectric epoxy systems.To further reduce the D_kand increase the T_g,tetramethylcyclotetrasiloxane(D4H)was selected as the modifier to prepare cyclic hydrosiloxane modified epoxy hybrid resin(DEP),and allyl glycidyl ether(AGE)was chosen to prepare model compound(AGDEP)with similar structure to DEP.Viscosity test results showed that adding D4H significantly lowered the viscosity of the resin,with DEP having a viscosity as low as 0.315 Pa·s.Dielectric test results indicated that DEP-MHHPA had the lowest D_kat 2.87(10.0 MHz),because of the low polarity,high dissociation energy and large molecular volume of D4H as well as the large volume steric hindrance of EUEP.DMA and mechanical performance test results demonstrated that DEP-MHHPA and AGDEP-MHHPA have lower T_gand modulus,as well as increased elongation at break,as a result of the inclusion of D4H;among them,DEP-MHHPA has a T_gof 100.3℃.In addition,free volume fraction(FFV)was obtained by modeling and analyzing the cured products,and the maximum FFV of DEP-MHHPA was 7.63%;The larger the FFV,the smaller the density and the lower the D_kof the resin.This novel DEP will broaden the cutting-edge applications of low dielectric epoxy resins with low viscosity.Cage type POSS(POSS-H)was synthesized from orthosilicate ethyl ester and used as a modifier to prepare POSS-H modified epoxy hybrid resin(SHEP)based on the method of reducing D_kand improving heat resistance by utilizing the large free volume and large steric hindrance effect of cage type POSS.Non-isothermal curing kinetics revealed that the SHEP-MHHPA system has comparatively high reaction activity,addressing the issue of low POSS/epoxy reaction activity.Compared with the MHHPA curing system in the previous two chapters,the resin system with the best dielectric properties was selected(the D_kof SHEP-MHHPA system at 10.0MHz was 2.73,T_gwas 103.2℃).To improve its practicability,hollow glass microsphere(S4630)was chosen as an modifier,a silane coupling agent(KBM603)was used to modify its surface to improve its compatibility with the resin matrix,and the effects of introducing different amounts of S4630-KBM603 on various properties of x%-S4630-KBM603@SHEP-MHHPA were investigated.XRD test results indicated that x%-S4630-KBM603@SHEP-MHHPA had a certain degree of crystalline due to the introduction of the crystalline polymer of POSS-H.Mechanical,thermo-mechanical and dielectric test results demonstrated that the introduction of S4630-KBM603 could improve the tensile strength and T_gas well as reduce the D_kof x%-S4630-KBM603@SHEP-MHHPA,wherein the T_gof40%-S4630-KBM603@SHEP-MHHPA was as high as 114.2℃,and the D_kwas as low as 2.18(10.0 MHz),which will provide effective guidance for better design and preparation of cutting-edge engineering materials.