原儿茶酸环氧树脂的制备与应用性能测试

Preparation and application of epoxy resin derived from protocatechuic acid

环氧树脂质脆需要增韧才能满足应用要求,以天然原儿茶酸(Protocatechuic acid,PA)和环氧氯丙烷为原料,通过两步法反应合成原儿茶酸环氧树脂(PA-EP),并将其作为特种环氧树脂用于双酚A环氧树脂(E-51)的改性研究。采用傅里叶红外光谱仪(FTIR)、核磁共振(1HNMR)、电位滴定仪和黏度仪对产物进行结构表征和性能测试。FTIR和1HNMR分析表明成功合成目标产物,环氧值为0.73 eq/100 g,25℃下黏度为43.2 Pa·s。力学性能分析表明,当PA-EP与E-51质量比为10%时,PA-EP/E-51固化物的力学性能最佳,拉伸强度、弯曲强度和冲击强度比纯E-51分别提升了37.4%、17.2%和82.9%。冲击断面的扫描电子显微镜(SEM)结果表明,10%PA-EP/E-51固化物呈现良好的韧性断裂特征。动态机械分析(DMA)和热重分析(TG)结果表明,随着PA-EP含量的增加,固化物的玻璃化转变温度(T_(g))由纯E-51的116.0℃提高到12.5%PAEP/E-51的137.3℃,失重10%的温度和最大分解速率的温度都略微下降,但800℃残渣量由纯E-51的5.9%提高到12.5%PA-EP/E-51的9.8%。

The brittleness of epoxy resin needs toughening to meet the application requirements. Protocatechuic acid epoxy resin(PA-EP) was synthesized from protocatechuic acid(PA) and epichlorohydrin via two-step reaction,and used as special epoxy resin for the modification of bisphenol A epoxy resin. The structure and properties of the PA-EP were characterized by fourier transform infrared spectrometer(FTIR), nuclear magnetic resonance spectroscopy(1HNMR), potentiometric titration and viscosity tester. FTIR, 1HNMR and viscosity analyses indicate that the target product are synthesized with epoxy value of 0.73 eq/100 g and viscosity of 43.2 Pa·s at 25℃. The mechanical properties of PA-EP/E-51 thermosets are better than others when the mass ratio of PA-EP to E-51 is 10%. The tensile strength, flexural strength and impact strength are increased by 37.4%, 17.2% and 82.9%, respectively. The scanning electron microscope(SEM) images of impact section show that PA-EP/E-51 thermosets exhibit ductile fracture characteristics. Dynamic mechanical analysis(DMA) and thermogravimetry(TG) results indicate that the glass transition temperature(T_(g)) increases from 116.0℃(neat E-51) to 137.3℃ with 12.5% of PA-EP/E-51. The weight loss10% and the maximum decomposition rate temperature are decreased slightly while the residue content of 800℃increases from 5.9%(neat E-51) to 9.8%(12.5% PA-EP/E-51).