Preparation And Application Of Hyperbranched Active Ester

Due to the good mechanical and electrical properties,chemical resistance,and processability,epoxy resins are the most widely used thermosetting resins.They have found applications in many fields,especially in the electronics and electrical industies.With the continuting development of 5G telecommunication technology,the frequence and power of signals are becoming bigger and bigger,which demands a smaller transmission loss and lower water absorption in the electronic packaging epoxies.In order to address those demands,considering the characteristics of the hyperbranched polymer and active ester,we combine the advantages of both and design,for the first time,a hyperbranched molecule which has active ester terminal groups and stiff backbones.When part of the curing agent of bisphenol A epoxy resin(DGEBA)is replaced by the hyperbranched active ester,the dielectric and mechanical properties can be improved.The main contents of the thesis are as follows.(1)A hyperbranched polymer with phenolic terminal groups,HBPE,were synthesized via one-pot method using triphenol methane and 1,4-dibromobutane as monomers.When acetic anhydride was used as the acylation reagent to react with HBPE,residual hydroxyl groups were left on the terminal groups of the obtained hyperbranched active ester,which is coded as HPAE-OH.HPAE-OH was then added to DGEBA and cured with methylnadic anhydride(MNA).Samples were cured using the optimized cure scheme which was determined using DSC,and properties were measured.Results show that the glass transition temperature(Tg)and dielectric properties of cured samples first increase then decrease with increasing HPAE-OH loading.The tensile and impact strengths are also improved and show similar trends.The optimized performance is achieved at 5%HPAE-OH loading.(2)Active ester terminated hyperbranched active easter,HPAE,was synthesized when acetyl chloride was empolyed as the esterification reagent.Effects of reactant ratio,temperature,and solvent were studied,and optimized reaction condition was obtained.A model compound of HPAE,PEAE,was synthesized.Effects of different initiators on initiation effectiveness of active ester/DGEBA systems were evaluated by DSC,and optimized candidate was determined.The optimum loading amount of HPAE was determined based on the conversions of HPAE/MNA/DGEBA systems,which were estimiated by infrared spectroscopy and DSC.(3)HPAE was used to modify DGEBA/MNA,and properties of cured samples were measured.Tg of cured HPAE/DGEBA/MNA decreases with HPAE loading.At 10%loading,the dielectric constant and dielectric loss tangent in the range of 1 to 30 MHz were in the range of 3.36-3.54 and 0.001-0.016,respectively.Addition of HPAE also improves overall mechanical properties.At 5%HPAE loading,the impact strength reaches 27.41 kJ/m2,which is much higher than that of the unmodified system.At 10%HAPE loading,the saturated water absorption decreases from 0.65%which corresponds to the unmodified system to 0.55%.