Study on Latent Curing Agent of Epoxy Resin Based on Bio-Benzoxazine
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摘要: 以糠胺、香草醛、多聚甲醛为原料合成了一种生物基苯并噁嗪(V-fa)。选择双环戊二烯-苯酚型环氧树脂(DCPD-ER)为研究对象,将V-fa作为固化剂按不同比例加入到DCPD-ER中,同时以二氨基二苯甲烷(DDM)为固化剂进行对比研究。通过傅里叶红外光谱(FT-IR)、核磁共振氢谱(1H-NMR)对V-fa的化学结构进行了表征,确认了其结构。采用差示扫描量热(DSC)、FT-IR系统研究了树脂体系的固化反应。此外,使用动态热机械分析(DMA)、热失重分析(TGA)考察了固化物的热性能。研究表明,与DCPD-ER/DDM相比,DCPD-ER/V-fa的起始固化反应温度和固化反应活化能较高。DCPD-ER/V-fa固化物的玻璃化转变温度(Tg)、初始分解温度和800 ℃氮气下的残炭率均高于DCPD-ER/DDM的相应值,其Tg最高可达192 ℃。同时,V-fa的加入能够改善树脂体系的阻燃性能。Abstract: A bio-based benzoxazine (V-fa) was synthesized from furfuramine, vanillin and paraformaldehyde. Its chemical structure was characterized by Fourier-transformed Infrared (FT-IR) spectra and 1H-Nuclear Magnetic Resonance (1H-NMR) spectra. Result shows that this new benzoxazine monomer is synthesized successfully. Dicyclopentadiene-phenol epoxy resin (DCPD-ER) was selected as a research object. V-fa was added into DCPD-ER in different proportions as a latent curing agent. At the same time, a usual curing agent, diaminodiphenylmethane (DDM), was also used as a comparative study. The curing reaction of the resin system was studied by Differential scanning calorimetry (DSC) and FT-IR spectra. Results show that compared with DCPD-ER/DDM, DCPD-ER/V-fa has a higher initial curing reaction temperature and curing reaction activation energy. DCPD-ER/V-fa can cure at a high temperature, which is attributed to the reaction between phenolic hydroxyl groups produced by ring-opening reaction of the benzoxazine and epoxy groups. In addition, the thermal properties of the cured products were investigated by Dynamic Mechanical Analysis (DMA) and Thermogravimetric Analysis (TGA). Results show that the addition of V-fa can improve the heat resistance and thermal stability of the resin system. It is found that the glass transition temperature (Tg), initial decomposition temperature and char yield under nitrogen at 800 oC (Yc) of DCPD-ER/V-fa are higher than those of DCPD-ER/DDM, and the Tg and Yc can reach as high as 192 oC and 44%, respectively. Moreover, the flame retardancy of DCPD-ER/V-fa was evaluated on the basis of the results from TGA measurements. The limiting oxygen index (LOI) of DCPD-ER/V-fa can reach as high as 35.1, suggesting that the addition of V-fa improves the flame retardancy of the epoxy resin.
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Key words:
- epoxy resin /
- benzoxazine /
- bio-based /
- latent curing agent /
- thermal property
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表 1 V-fa、DCPD-ER/V-fa与DCPD-ER/DDM共混物的DSC数据
Table 1. DSC data of V-fa、DCPD-ER/V-fa and DCPD-ER/DDM blends
Sample T0/℃ Tp/℃ ΔH/(J·g−1) DCPD-ER/DDM 100 159 155 D/V-2 170 203 95 D/V-3 171 206 194 D/V-4 173 209 248 D/V-5 179 216 283 V-fa 163 203 266 表 2 DCPD-ER/V-fa与DCPD-ER/DDM固化物的DMA与TGA数据
Table 2. DMA and TGA data of cured DCPD-ER/V-fa and DCPD-ER/DDM
Sample E′/GPa Tg/℃ $T_{{ d}_5} $ /℃ Yc/% LOI DCPD-ER/DDM 1.6 168 311 6 19.9 D/V-2 2.4 172 339 23 26.7 D/V-3 2.2 181 329 28 28.7 D/V-4 1.9 187 325 33 30.7 D/V-5 1.7 192 316 44 35.1 -
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