【作者】 史建设；

【导师】 杨绪杰；

【作者基本信息】 南京理工大学 ， 材料科学与工程， 2010， 博士

【摘要】 凹凸棒石具有的较大长径比和一维纳米纤维状结构以及较弱的棒晶间相互作用,使得其在聚合物的增强改性上具有独特的优势和吸引力,是制备高性能聚合物复合材料的理想增强体。本论文在对天然一维纳米材料凹凸棒石进行提纯并接枝改性后应用于工程塑料尼龙6,制备了具有新型结构和优良性能的凹凸棒石／尼龙6复合材料,深入系统地研究了复合材料的制备、结构与性能。具体内容如下：通过传统的挤出注射工艺制备了未改性凹凸棒石／尼龙6复合材料。结果表明,凹凸棒石在尼龙6基体中有着较好的分散,所制得复合材料具有较高的力学性能。凹凸棒石的加入不会改变尼龙6的结晶形态,在尼龙6的结晶过程中起到了异相成核的作用,提高了尼龙6的结晶温度,加快了尼龙6的结晶过程,但会降低尼龙6的结晶完善程度,并增加尼龙6的结晶活化能。采用缩合聚合法对凹凸棒石进行表面接枝聚氨酯预聚体改性。结果表明,接枝改性后接枝物分子链与凹凸棒石表面上的羟基发生了化学键合,聚氨酯接枝物主要分布在凹凸棒石的表面,而在体相中独立存在的几率较小。接枝后凹凸棒石的粒径明显增大,粒子中间颜色较深,周围颜色较浅,呈现较为明显的核壳状结构。通过加入明矾水溶液来沉降水性聚氨酯乳液,实现对凹凸棒石的包覆,形成具有核壳结构的聚氨酯包覆凹凸棒石。当所制备水性聚氨酯乳液与凹凸棒石的质量比为3：1时,可取得比较理想的包覆效果,凹凸棒石棒晶被单个包覆,包覆层厚度约为10nm。此时凹凸棒石表面聚氨酯的包覆量约为9%。聚氨酯改性凹凸棒石／尼龙6纳米复合材料研究表明,通过对凹凸棒石进行有机改性可以促进凹凸棒石在尼龙6基体中的分散,改性凹凸棒石与尼龙6的界面模糊,说明两者相容性较好,存在较强的界面相互作用。由于表面修饰层与基体树脂高分子链发生交联、缠结,形成纳米复合材料的柔性界面层。因此纳米复合材料的力学性能得到了有效改善,对材料韧性的提高尤为明显。当聚氨酯包覆凹凸棒石的用量为10%时,复合材料的拉伸强度提高了34.7%,冲击强度提高了85.7%。拉伸破坏时,复合材料具有明显的屈服后断裂特征；冲击破坏时,随着聚氨酯包覆凹凸棒石用量的增加,复合材料的断面变得越粗糙。聚氨酯包覆凹凸棒石的加入,也可显著提高复合材料的储能模量和玻璃化转变温度。聚氨酯包覆凹凸棒石／尼龙6纳米复合材料的熔体为假塑性流体,随改性凹凸棒石含量的增加,材料的非牛顿性减弱。两步法制备了POE弹性体接枝的凹凸棒石。接枝产物的FTIR、XPS以及XRD分析结果表明,POE弹性体通过化学键结合到了凹凸棒石的表面。TG结果表明,接枝到凹凸棒石表面的POE弹性体大约为9.5%。凹凸棒石的POE接枝改性能大幅提高复合材料的冲击强度,并在一定程度上改善凹凸棒石在尼龙6基体中的分散性。更多还原

【Abstract】 Attapulgites are especially attractive candidate for the reinforcement modifier of polymers owing to their characteristics such as a high aspect ratio, nanofibrillar structure and the poor interaction between rod shape crystals. In the dissertation, naturally attapulgite nanofibers were purified and then modified by grafting polymer. The modified particles were used as a new type reinforcement for nylon 6 and the resulted attapulgite/nylon 6 nanocomposites possessed promising mechanical performance. The preparation, structure and properties of attapulgite/nylon 6 nanocomposites were investigated fully. The main contents are as follows:The attapulgite/nylon 6 nanocomposites were prepared by traditional extrusion and injection processes. The results showed that the composites possess better dispersion of the filler and better mechanical properties. The addition of attapulgite into nylon 6 did not change its crystalline form, but increased the crystallization temperature and promoted the heterogeneous nucleation of nylon 6. On the other hand, The crystallization sizes of attapulgite/nylon 6 nanocomposites were reduced, and the crystallization activation energies of composites were increased.Modification was performed by grafting polyurethane prepolymer via condensation polymerization on the surfaces of attapulgite. The results demonstrated that the grafting molecule chains were combined with the hydroxyl groups on attapulgite surfaces via chemical bonds. The grafting polymers were mainly distributed on the surfaces instead of bulk. The diameters of attapulgite were enlarged obviously. The color was dark in the center while it was light around. The grafted particles presented a definite core-shell structure. Attapulgite was coated with polyurethane latex with aluminium potassium sulfate dodecahydrate as demulsifying agent in the form of a core-shell structure. Attapulgite could be coated singly while the weight ratio of polyurethane latex to attapulgite was 3:1. The coating was about 10 nm thick, and the mass content of polyurethane was 9%.Investigation on polyurethane modified attapulgite/nylong 6 composites indicated the surface modification had significant effect on the improvement of the dispersion of filler in the polymer matrices. The interfaces between modified attapulgite and nylon 6 were blurred, which demonstrsted the modified particles had good compatibility with the matrices and there were strong interface effects between the two phases. The mechanical performance and especially impact strength of composites were improved since the modification chains cross-linked and twisted with the nylon 6 chains, and flexible interface layers thus formed. For instance, incorporating 10% polyurethane coated attapulgite into nylony 6 leaded to 34.7% increase in tensile strength and 85.7% increase in impact strength. The tensile fracture surfaces of composites had a distinct character of yielding fracture, and the impact surfaces of composites were much rougher with the increasing of modified attapulgite. The storage modulus and Tg of composites were improved as the addition of polyurethane coated attapulgite. The polyurethane coated attapulgite/nylon 6 composites could be seen as the non-Newtonian fluids, and the non-Newtonianism of composites were reduced with the increasing of polyurethane coated attapulgite.Maleic anhydride-grafted polypropylene(POE-g-MAH) were grafted on the surfaces of attapulgite by two steps method. Modified attapulgite nanoparticles were characterized using Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), transmission electron X-ray diffraction (XRD), and thermogravimetric analysis (TG). The results showed that POE chains were combined with the hydroxyl groups on attapulgite surfaces via chemical bonds, and the mass content of POE was 9.5%. The surface modification of attapulgite was attempted to increase the dispersion of attapulgite and the impact strength of the composites.更多还原