天然重晶石填料的改性作用与机理研究

【作者】 赖博杰；

【导师】 倪秀元；

【作者基本信息】 复旦大学 ， 高分子化学与物理， 2007， 硕士

【摘要】 重晶石（硫酸钡）是一种天然形成的斜方晶系无机盐,为中性体质填料。由于其具有电绝缘性和磁场屏蔽性,受到人们的关注,正成为重要的功能性填料;我们前期工作发现,作为填料使用时,天然重晶石还具有一个重要的特点,即可以达到很大的填充比例,甚至达到50%,并具有促进熔体流平的作用。本文选择工程塑料聚碳酸酯（PC）和聚苯硫醚（PPS）为载体,分别系统地研究了天然重晶石对聚合物流变行为和结晶行为的作用,并对作用机理进行了探讨,主要内容和结果如下:1.研究了PC/BaSO₄复合体系的流变行为,发现在天然重晶石的用量为1%-5%的条件下,能有效降低PC的熔体粘度,从而具有改善PC加工流动性的功能。此外,天然重晶石填料使得PC熔体剪切变稀行为更明显,在低ω区域表现出似固体行为。建立了流变数学模型,较好地描述了PC/BaSO₄复合体系的流变行为;并通过模型计算得到,天然重晶石的加入使得熔体的流动活化能减小,当天然重晶石体积百分比为1.38%时,流动活化能从101.7kJ·（mol·K）^-1减低到45.3 kJ·（mol·K）^-1。还利用logG’～logG”关系曲线的温度依赖性,探讨了熔体的相结构。2.XPS和FTIR分析表明,天然重晶石钡离子与PC基体之间存在较强的相互作用,并根据分析结果得到相互作用方式,即天然重晶石的Ba²⁺与PC的C=O基团发生了键合作用,导致C=O的红外吸收峰发生分裂,并且使得Ba 3d5轨道电子向低能方向移动3eV。认为这种相互作用降低了聚合物分子链的柔顺性,使基体分子链间的缠结点密度降低,从而降低熔体粘度。3.采用莫志深方程,研究了PPS/BaSO₄复合体系的非等温结晶动力学。研究结果表明,在天然重晶石用量为10%-40%的条件下,莫志深方程能够较好地描述其非等温结晶行为。相同的降温速率条件下,复合体系的相对结晶度下降。与纯PPS相比,复合体系显示出低诱导期、高结晶速率和较小的半结晶时间值t_1/2等特点,天然重晶石粒子具有明显的成核效应。并利用偏光显微镜,研究了PPS的晶体形态。4.通过制备一种含天然重晶石和PPS的悬浮液,获得了表面质量和耐腐蚀性能优良的涂层,涂层抗冲击性能大于50 kg·cm。更多还原

【Abstract】 Barite （Barium sulfate） is a crude rhombic salt; it is a neutral filler. Now, it is becoming an important functional filler because of its electric insulation and magnetic shield. Our previous research found that when the barite was used as filler, it had an important advantage that the high filling percentage can be achieved, and some may even exceed 50%. In this paper, we chose engineering plastics polycarbonate （PC） and polyphenylene sulfide （PPS） as the carriers, systematically studied the rheological behavior of barium sulfate modified polycarbonate composite material and crystallization behavior of the barium sulfate modified PPS composite material, discussed their reaction mechanism. The main content and the results were as follows:1. Studied the rheological behavior of PC/BaSO₄ composites. Found that only 1%-5% of BaSO₄ which were added in PC can greatly reduce the melt viscosity of the PC, thereby improving the high-temperature processing mobility of PC. In addition, the adding barium sulfate makes the shear-thinning behavior more obvious, and the composites indicated the solid-like behavior at the low frequency region. We established a rheological model. The result of curve fitting between experimental data and the prediction of rheological mode indicated that the rheological behavior of PC/BaSO₄ composites could be well described by this rheological mode. We calculated the activation energy of the composites and concluded that the addition of BaSO₄ reduced the activation energy of the composites. The activation energy reduced from 101.7 kJ·（mol·K）^-1 to 45.3 kJ·（mol·K）^-1 when the volumn fraction of BaSO₄ was 1.38%. Using logG’～logG" curve and the temperature dependence, we explored the phase structure of melt blend.2. The XPS and FTIR analysis indicated that there is strong interaction between Ba²⁺ of barium sulfate particles and the carbonyl of polycarbonate matrix, which resulted in the split of the infrared absorption peak of the carbonyl and made Ba 3d5 orbit shift 3eV to lower energy. We thought the reaction reduced the flexibility of the polymer molecular chain and the density of entanglement points. It resulted in the reduction of the composite’s viscosity and the rheology enhancement of PC/BaSO₄ composites.3. Non-isothermal crystallization behaviors of PPS/BaSO₄ composites were studied by the Mo equation. The results showed that when the contents of barite were 10%-40%, Mo equation could characterize the non-isothermal crystallization behavior of PPS and its composites. At the same cooling rate, the crystallinity of the composites decreased. Barium sulfate particles have obvious nucleation effects. The composites show low induction period, high crystallization rate and short half crystallization time. In addition, we had studied the crystal conformation of PPS by the polarized light microscopy.4. We had prepared one new type of suspension containing natural barite and PPS. The coating had good impact strength and anticorrosion properties. The impact strength of the coating was higher than 50 kg·cm.更多还原