【作者】 刘黎明；

【导师】 王少阶；

【作者基本信息】 武汉大学 ， 材料物理与化学， 2005， 博士

【摘要】 高分子纳米复合材料是由分散相的大小为纳米级的微粒分散体系与聚合物复合所得的材料,它能明显提高体系的物性,所以聚合物基纳米复合材料迅速发展为最先进的复合材料之一。在聚合物基纳米复合材料中,其中聚合物/层状硅酸盐纳米复合材料在制备方法、结构、性能及应用方面优点突出,已成为当前基础研究和应用开发的热点。 本文成功制备了一系列环氧树脂/累托土、环氧树脂/蒙脱土纳米复合材料,测量了复合材料的力学、热学性能,并用X射线衍射仪、红外分光光度计和正电子谱学技术研究了复合材料的微观结构,并对环氧树脂/累托土复合材料与环氧树脂/蒙脱土复合材料的微结构和宏观性能进行了比较。主要内容如下: 1.制备了累托土重量百分比含量分别为0.2%、0.5%、0.8%、1.0%、1.2%、2.0%的环氧树脂/累托土纳米复合材料。XRD研究表明,累托土在环氧基体中较易被剥离成纳米片状。利用冲击、拉伸实验仪及DSC分析仪研究了复合材料的宏观性能,结果表明,只需添加0.5%的有机累托土,纳米复合材料的冲击性能、断裂伸长率、耐热性能就得到很大提高。利用正电子寿命谱技术研究了材料的自由体积及界面特性,结果表明,发现累托土的加入没有改变环氧树脂中的平均自由体积孔洞的大小,但减少了树脂的自由体积浓度。且累托土片层与环氧基体之间形成了界面层。 2.制备了环氧当量分别为188、222、263、550、1110g/mol的环氧树脂/累托土纳米复合材料以研究环氧当量对复合材料微结构与宏观性能的影响。XRD研究表明,环氧当量越高,越易生成剥离型纳米复合材料。环氧当量较低时,生成以插层型为主的复合材料。利用冲击、拉伸实验仪及DSC分析仪研究了复合材料的宏观性能,结果表明,随着环氧当量的提高,无论是纯环氧树脂或纳米复合材料的冲击强度和玻璃化转变温度都下降,但纳米复合材料的力学和热学性能都优于纯环氧树脂,并且在环氧当量较大时,材料的力学性能得到更多的提高。利用正电子寿命谱研究材料微结构表明,随着环氧当量的增加,材料的自由体积浓度降低。但其平均自由体积孔洞大小基本不变。当复合材料从插层型过渡到剥离型时,复合材料的自由体积浓度急剧变化。符合多普勒展宽谱研究结果表明,S参数对累托土的加入很敏感。S参数的变化说明在复合材料中的累托土已经发生了结构变化。在多普勒展宽商更多还原

【Abstract】 In this dissertation, the epoxy/rectorite and epoxy/montmorillonite nanocomposites were prepared successfully. The effects of clay content, epoxide equivalent and curing temperature on microstructure of the nanocomposites were studied by X-ray diffraction (XRD), infrared spectrometry and positron annihilation lifetime spectroscope (PALS), and the properties of the nanocomposite also were investigated. The main results are as follows.1. Nanocomposites with different rectorite content were prepared. At low contents, mechanical and thermal properties of the nanocomposites have significant improvements in terms of the impact strength, the breaking elongation and the glass transition temperature compared to the neat epoxy, and it is found that the rectorite with low content is easier to form exfoliation structure compared to that with high contents. FT-IR spectra showed that the reaction between the rectorite and epoxy matrix occurred, and at the same time, the PALS measurements indicate that the free-volume concentration in nanocomposites is decreased with the increase of the clay content and the size of free volume holes isn’t affected by the clay content.2. The epoxy/rectorite nanocomposites with different epoxide equivalent ranged from 188g/mol to 1110g/mol were prepared. In nanocomposites, the formation of exfoliated structure was observed from XRD pattern at epoxide equivalent > 263. The PALS measurements indicate that the fraction of free volume holes in nanocomposites was strongly affected by epoxide equivalent, in paticular, the free-volume concentration was dramatically decreased with the increasing epoxide equivalent from 188 to 263. And the interface layer between epoxy and rectorite layers was formed and rapidly increased also from epoxide equivalent 188 to 263. The increased percentage of impact strength in nanocomposite compared with neat epoxy is bigger with the increase of epoxide equivalent , and this result can be explained as the proportion of exfoliated structure in epoxy matrix become higher with the increase of epoxide equivalent, and because exfoliated nanocomposites have higher phase homogeneity than the intercalated counterpart, the exfoliated structure is more desirable in enhancing the properties of the nanocomposites. The S parameter indicates the rectorite structure change and the high sensitivity of positron annihilation to the entry of rectorite into epoxy. The low momentum part of CDB ratios of the nanocomposite of epoxy 1110 can be ascribed to the contribution of the momentum of electrons in polymer, and the high momentum part can be ascribed to the contribution of the momentum of electrons in rectorite.3. The epoxy/rectorite nanocomposites at different curing tempeature ranged from 70°C to 200°C were prepared. We find that the formation of exfoliated structure is difficult when the curing temperature is low(<90°C). At the range from 90°C to 200°C, the clay in matrix can all be exfoliated . The nanocomposite cured at medium temperature possess highest storage modulus and high glass transition temperature . The PALS measurements show that the size of free volume holes isn’t affected by curing temperature and the free-volume concentration was decreased with the increasing cure temperature. The positron lifetime distribution in nanocomposite has been obtained by the new computer program-MELT, and the results suggest that the distribution of free-volume-hole size is narrower when the composite is cured with medium temperature.4. The epoxy/rectorite nanocomposites and epoxy/ montmorillonite with different clay content were prepared. The rectorite is more easily exfoliated compared with montmorillonite. Only small amount of rectorite(<0.8%) can improve the mechanical and thermal properties of the nanocomposites, but in order to improve the properties of composite , higher montmorillonite content is needed(>2%). The size of free volume hole isn’t affected by the two kinds of clay. Rectorite with higher surface area has more chances to interact with epoxy matrix, so it has stronger restriction on the motion of the molecule chain, which lead to smaller free volume concentration. Only small amount of rectorite(<l%) can prevent the phase seperation in matrix, but higher montmorillonite loading(>3.0%) can prevent the phase seperation.更多还原