剪切分散工艺制备环氧树脂/粘土纳米复合材料的结构与力学性能研究

Study on Structure and Mechanical Properties of Epoxy/clay Nanocomposites Prepared by Shear Dispersing Method

采用十二胺盐处理的蒙脱土(MMTDDA)和环氧(E-51)/4,4′二胺基二苯砜(DDS)体系为研究对象,分别通过普通搅拌(磁力搅拌)和高速剪切分散(高速乳化均质机)两种分散MMTDDA的工艺制备了环氧树脂MMTDDA纳米复合材料。透射电镜(TEM)观察表明,普通搅拌分散法制备的纳米复合材料中存在较多粘土团聚体,而通过高速剪切分散施加一定外部剪切力细化分散粘土团聚体,则有利于粘土片层在固化过程中充分解离,力学性能明显提高。在一定剪切速率下,力学性能随剪切分散时间的增加而增加;当粘土含量为3wt%时,冲击强度可由32.1kJ/m2提高到43.9kJ/m2,提高近36.8%,弯曲强度也有一定提高。动态热机械性能(DMA)分析表明,环氧树脂/MMTDDA纳米复合材料的储能模量在玻璃态没有明显改善,但在玻璃化转变区具有一定的提高;玻璃化转变温度(Tg)和损耗模量都得到不同程度的提高,Tg由纯环氧树脂的209.6℃提高到环氧树脂/MMTDDA(3wt%)纳米复合材料的214.9℃,提高近5.3℃,且粘土片层的分散解离效果越好,提高的幅度越大。

Two comparative processing methods, general stirring with magnetic bar and high shear dispersing with high-speed emulsifying and homogenizing mixer (HEHM), were used to disperse and pulverize clay particles modified with dodecyl amine (DDA) in order to prepare finely exfoliated epoxy/clay nanocomposites. It can be observed from Transmission Electron Microscopy (TEM) graph that large clay aggregates still exist in the cured epoxy/MMTDDA nanocomposites prepared by general dispersing method, only the small clay particles or the external layers of large clay aggregates can be partially exfoliated. While the fine exfoliation can be achieved by exerting external shearing force on clay aggregates and the mechanical properties are dramatically improved. At a constant shearing speed, the mechanical properties are increased with the dispersing time. Impact strength is enhanced to 43.9 kJ/m2 from 32.1 kJ/m2, which is about 36.8% higher than that of pristine epoxy. The flexural strength also can be increased. Dynamic Mechanical Analysis (DMA) indicates that store modulus of epoxy/MMTDDA nanocomposites is not improved in glassy region, but have an increase in glass transition region. The glass transition temperature (Tg) of epoxy/MMTDDA (3 wt%) nanocomposites is increased up to 214.9°C from 209.6°C, which is about 5.3°C higher than that of pristine epoxy, and the increase of Tg will depends on the dispersion and exfoliation of clay particles.