【作者】 陆绍荣；

【导师】 王霞瑜； 张海良；

【作者基本信息】 湘潭大学 ， 高分子化学与物理， 2005， 博士

【摘要】 环氧树脂有诸多方面的优点,然而,由于环氧树脂是交联度很高的热固性材料,它的裂纹扩展属于典型的脆性扩展,其固化物脆性大、耐热性差、抗冲击强度低、易开裂,难以满足日益发展的工程技术的要求,从而限制了环氧树脂的进一步应用。在环氧树脂中加入纳米粒子是提高其韧性的一种行之有效的方法。为此,本论文从纳米复合材料的结构特点出发,对国内外环氧树脂增韧的方法、增韧效果及增韧机理作了较为详细的综述。合成了三种不同类型的EP/SiO₂-TiO₂纳米杂化材料,通过实验及结果表征得到以下结论: 1、采用溶胶-凝胶法制备了接枝型、含有刚性-柔性链段及超支化聚合物的三种不同类型的EP/SiO₂-TiO₂纳米杂化材料。对合成材料的各种类型中间体和产物采用FTIR、XRD、1HNRM、AFM 、DSC、TG、UV-Vis、TEM 及SEM 等手段进行了表征。实验结果表明:EP/SiO₂-TiO₂纳米杂化材料薄膜的透光率高达80%以上。XRD 表明了SiO₂-TiO₂ 无机网络与环氧树脂基体是以化学键结合,而非简单的物理共混。AFM 及TEM 结果表明了在所研究的SiO₂-TiO₂ 含量范围内,SiO₂-TiO₂ 无机双组分复合粒子粒径在10¹00nm 之间。2、通过DSC 测试方法,采用Kissinger、Ozawa 及Crane 三种动力学模型,对不同含量的SiO₂-TiO₂接枝型EP/SiO₂-TiO₂预聚物/DDS固化体系进行了非等温固化动力学进行研究。结果表明:SiO₂-TiO₂ 的加入使固化反应的活化能提高,而固化反应级数基本不变,表明SiO₂-TiO₂的加入并没有改变固化过程机理。固化反应过程是一个较为复杂的反应。3、通过对改性材料的宏观力学性能和扫描电镜断面的结果分析表明,纳米SiO₂-TiO₂ 无机网络的存在,可以使环氧树脂固化物的韧性有较大的提高,同时材料的拉伸强度、弯曲强度也有不同程度的提高。在所研究的SiO₂-TiO₂用量范围内,改性材料的冲击强度提高了2³ 倍,即达到增强、增韧和增刚的作用。4、从材料冲击断面的扫描电镜（SEM）分析,SiO₂-TiO₂ 无机网络增韧改性环氧树脂的机理,主要是以纳米粒子诱导基体树脂产生屈服变形导致银纹化和孔洞化为主。5、固化物的蠕变和应力松弛实验结果表明:SiO₂-TiO₂ 无机网络的形成,使固化体系网络中的交联点增加,导致交联点间线形卷曲链段部分变形困难,增大了固化物更多还原

【Abstract】 Epoxy resin possesses many excellent properties of materials, however, as the kind of thermosetting material is with a high cross-link density, the behavior of its crack growth shows that it is of typical brittleness, which leads to some weak points, such as the great brittleness in the curing state, low heat-resistance, low impact strength, easy crackness. So it difficult to satisfy the requirements of the developing engineering technology, .In this paper, on the basis of the structure characteristic of nanocomposites , toughening method, toughening effect, toughening mechanism of epoxy resin have been studied in detail. Three kinds of EP/SiO₂-TiO₂ hybrid materials have been synthesized. The experimental results are given as follows: 1.Three kinds of EP/SiO₂-TiO₂ hybrid materials containing grafted compound, rigid-flexible spacers and hyperbranched polymer have been synthesized via sol-gel process. Those materials were characterized by FTIR, XRD, 1HNRM, AFM, DSC ,UV-Vis, TEM and SEM, etc. The experimental results indicated that the transparency of EP/SiO₂-TiO₂ hybrid films is over 80%. SiO₂-TiO₂ inorganic networks and epoxy matrix combined with chemical bonding, and was not the simple blend. The results of AFM and TEM indicated that SiO₂-TiO₂ particle sizes is about 10¹00nm. 2. The non-isothemal curing kinetics of EP/SiO₂-TiO₂ prepolymer and DDS systems was studied by dynamic differential scanning calorimetry （DSC） through three kinds of kinetic methods（Kissinger, Ozawa and Crane kinetic model）. The results showed that SiO₂-TiO₂ can enhance curing reaction activation energy （Ea）, and do not change the reaction order. This shows that the curing mechanism is not changed by addition of SiO₂-TiO₂ , and the curing reaction is a complex process. 3. The mechanical properties and the fracture surface of SEM indicated that the toughness of epoxy resins was enhanced greatly by adding SiO₂-TiO₂ , the tensile strength and bending strength were also improved to some extent. The impact strength of the modified systems was enhanced to 2-3 times in the range of SiO₂-TiO₂ contents. 4. From SEM analyzing of impact fracture surface, the roughness mechanism of SiO2-TiO2 inorganic networks was mainly craze and hole. It is that SiO2-TiO2 nano-particles could induce epoxy matrix yielding deformation and resistance to crack propagation.. 5. The experimental results of the creep behavior and the stress relaxation of the curing systems indicated that the crosslinking points of the curing networks increased the formation of SiO2-TiO2 inorganic networks. Which led to the difficult deformation for the linear curled segments between crosslinking points, the increased the balance force values ,so it made the crosslink density and resistance deformation of epoxy resin improved greatly. 6. The investigation on dynamic mechanical properties of cured materials showed that the storage modulus of materials was improved and damping decreased by adding SiO2-TiO2 nanoparticles. It might be due to the fact that the crosslink intensity of curing systems enhanced, and the motion of epoxy resin molecular chain was hindered. The glass transition temperature （Tg） was about 30⁴0℃higher than that of pure epoxy resin. 7. The investigation on the activation energy of the glass transition temperature for α-relaxation peaks at different frequency showed that, when SiO2-TiO2 contents was 3.25%, the activation energy of α-relaxation peaks is 455KJ/mol, it is 62KJ/mol higher than that of the pure epoxy resin （392KJ/mol）. The results mean that the internal tribological performance, strength and the glass transition temperature of composites materials improved. It was due to the fact that SiO2-TiO2 networks can restrict effectively the epoxy resin molecular chains movement. 8. The results of DSC and TG showed that the glass temperature and the decomposition temperature of EP/ SiO2-TiO2 hybrid materials improved greatly with contents of SiO2-TiO2 increasing. This indicated that SiO2-TiO2 inorganic networks can improve not only the mechanical properties of materials, but also improve thermal properties. 9. When SiO2-TiO2 contents is 0.67¹.97wt.%, EP/ SiO2-TiO2 hybrid materialshave a good antibacterical behavior under the light of fluorescent. This is because TiO2 can absorb electron-hole pairs, and has photocatalytic effect. It is the mainly reason that SiO2-TiO2 has a good antibacterial and bactericide function. 10. According to the experimental results of the wear and the SEM images of the wear surface. The friction coefficient and wear loss of the modified systems could be effectively decreased at a relatively low level （1.32².60 wt.% SiO2-TiO2）. It was found that the incorporation of SiO2-TiO2 networks into epoxy caused a considerable improvement of tribological characteristics. The micro-hardness was also improved. The wear mechanisms are mainly abrasive and fatigue wear. 11. Based on the electrical property, nano-SiO2-TiO2 can be dispersed in epoxy matrix homogeneously, which made the crosslink intensty of materials improve. So due to the motion of molecular chains of materials was hindered which made the surface resistivity, the bulk resistivity, the dielectric constant and the dielectric loss decrease, While the electrical breakdown strength and arc resistance improved.更多还原