【作者】 朱耕宇；

【导师】 翁志学；

【作者基本信息】 浙江大学 ， 化学工艺， 2004， 硕士

【摘要】 聚四氟乙烯（PTFE）／无机粒子的复合是改进PTFE性能或实现功能化的重要方法。针对传统的机械共混过程中无机粒子在PTFE中分散性较差的缺点，本文开发了PTFE胶乳粒子与无机粒子共凝聚制备改性PTFE树脂的新方法，分别对凝聚剂作用下PTFE胶乳粒子与碳黑和无凝聚剂作用下PTFE胶乳粒子与不同粒径三氧化二铁粒子的共凝聚过程进行了研究，得到了无机粒子特性、凝聚剂品种和凝聚工艺条件等对凝聚率、共凝聚粒子粒径及其分布和形态的影响规律，并对共凝聚机理进行了初步探讨，为工业共凝聚法制备无机粒子改性PTFE树脂提供了理论基础。 采用KCl、CaCl₂和Al（NO₃）₃等无机盐为凝聚剂，进行PTFE胶乳粒子与碳黑的共凝聚。研究了胶乳种类、凝聚温度、搅拌转速等对共凝聚过程的影响规律。发现，当凝聚条件和凝聚剂相同时，Zeta电位数值较低的胶乳，更易凝聚，凝聚粒子较大。凝聚温度增高，共凝聚粒子逐渐增大，粒子形态趋向不规则，凝聚率有所降低；共凝聚粒子的粒径随转速增大而减小；电解质价数越高，凝聚反应速度越快，受转速的影响也就越大。SEM结果表明，共凝聚粒子为大量PTFE胶乳粒子包覆碳黑粒子，共凝聚粒子呈疏水性。初步探讨了共凝聚粒子的成粒机理。 在无凝聚剂作用下，进行PTFE胶乳粒子与不同粒径三氧化二铁的共凝聚。通过调整两种粒子的表面电性及Zeta电位值，利用静电作用使无机粒子吸附在PTFE胶乳粒子表面或PTFE胶乳粒子吸附在无机粒子表面，形成共凝聚粒子。以共凝聚过程体系Zeta电位的变化为主要表征量，着重研究了Fe₂O₃粒子表面电荷、pH值、Fe₂O₃／PTFE粒径比、粒子浓度等因素对共凝聚过程的影响。发现，PTFE和Fe₂O₃粒子电荷相反，Zeta电位绝对值相近，是最佳的共凝聚条件。通过添加适当的表面活性剂，可以使本来带负电荷的Fe₂O₃粒子改变电性后带正电荷，再与PTFE共凝聚。粒子的Zeta电位与体系的pH值相关，通过调节介质pH值，得到Zeta电位随pH值的变化曲线和发生共凝聚的合适pH值点。对于PTFE和2#Fe₂O₃，在pH=7时，PTFE的Zeta电位=-46mV，Fe₂O₃的Zeta电位=42.3mV，两者的粒子电荷相反，易共凝聚。对于纳米Fe₂O₃与PTFE的共凝聚过程，发现Zeta电位由负值逐渐增大，至凝聚结束时，Zeta电位与蒸馏水的Zeta电位相等，由此说明共凝聚过程浙江大学硕士学位论文是Fe20a粒子逐渐在PTFE表面沉积并吸附的过程。通过跟踪共凝聚过程粒度变化发现，共凝聚粒子是在两种粒子混合的短时间内生成的。 研究了无凝聚剂作用下PTFE/ FeZO。共凝聚粒子的形貌、组成、结构及稳定性，探讨了共凝聚机理。发现，两种粒子的粒径比不同时，所形成的共凝聚粒子的结构、形貌就不同。FeZO3/PTFE粒径比==7 .54时，形成的共凝聚粒子是PTFB小粒子包覆在FeZO。大粒子外的核壳型结构;Fe八/PTFE粒径比=1 .9时，共凝聚粒子不规则;而PTFE与纳米FeZO3共凝聚时，形成的是PTFE为核，Fezoa为壳的核壳结构粒子。超声洗脱结果表明，共凝聚粒子具有良好的结构稳定性。据此认为共凝聚过程分三步进行:第一步是靠静电力结合形成一次粒子，第二步是新形成的一次粒子在长程范德华力作用下发生聚沉形成二次粒子，第三步是体系中没有参与凝聚的PTFE和FeZO。粒子在共凝聚二次粒子上的吸附。纳米FeZO3与PTFE共凝聚时，主要是第一步，形成的一次粒子相对稳定。更多还原

【Abstract】 It is an important method to modify polytetrafluoroethylene (PTFE) by compositing PTFE with inorganic particles. In order to overcome the disadvantage of poor dispersion of inorganic particles in PTFE in the usual mechanical blending, a new method, in which PTFE latex particle were hetero-coagulated with inorganic particles, was developed to prepare modified PTFE. The hetero-coagulation of PTFE latex particles and carbon black particles under the function of coagulation agent, and hetero-coagulation of PTFE latex particles and Fe2O3 particles without coagulation agent, were investigated. The influences of inorganic particles characteristic, coagulation agent kinds, coagulation condition on hetero-coagulated particles size distribution and morphology was obtained. The mechanism of particle formation in the hetero-coagulation was discussed. The results would provide base for preparing modified PTFE by hetero-coagulation in industrial scale.Hetero-coagulation of PTFE latex particles and carbon black particles have been studied with different coagulation agent, such as A1(N03)3, CaCk and KC1. The influence of latex kinds, temperature, agitation speed on hetero-coagulation process were investigated. When the coagulation conditions and coagulation agent were same, PTFE latex with lower Zeta-potential could be easily coagulated. The diameter of hetero-coagulated particles increased and morphology was more irregular when temperature was increased. As agitation speed increased, the diameter of hetero-coagulated particle diameter decreased. SEM experiment showed that a hetero-coagulated particle was a carbon black covered by many PTFE latex particles. The composite particles prepared by this method were hydrophobic. The particle formation mechanism of composite particles was discussed.Hetero-coagulation of PTFE latex particles and Fe2O3 particles was carried out without coagulation agent. Effect of Fe2O3 particles charge, pH, Fe203/PTFE particle size ratio and Fe2O3 particle concentration on hetero-coagulation were investigated. The results showed that when charges of the two kinds of particles were opposite and the absolute value of Zeta-potential were approximate, PTFE latex particles and Fe2O3 particles were easily to hetero-coagulate. Through adding some cationic surfactant to adjust Zeta-potential of Fe2O3 particles, Fe2O3 particles with negative charge couldbecome positive and hetero-coagulate with PTFE to form hetero-coagulated particles. Zeta-potentials of the particles were related to pH. The relationship between pH of the dispersion medium and Zeta-potentials, and suitable pH for hetero-coagulation were obtained. Since Zeta-potentials of PTFE and 2# Fe2O3 were -46mV and 42.3mV, respectively, they would be hetero-coagulated easily. It is found that Zeta-potentials increased gradually from negative in process of hetero-coagulation of PTFE and nanometer Fe2O3 and Zeta-potentials was equal to that of distilled water when hetero-coagulation was finished, which indicated that Fe2O3 particles gradually deposited and adsorbed on PTFE particles in the hetero-coagulation process. Through observing the variation of particles size in the hetero-coagulation process, it found that hetero-coagulated particles were formed shortly after the mixing of two kinds particles.The morphology, composition and structure of PTFE/ Fe203 hetero-coagulated particles were studied. It found that morphology and structure of PTFE/ Fe2O3 particles varied with Fe2O3/PTFE particle size ratio. When Fe2O3/PTFE particle size ratio=7.54, the hetero-coagulated particle had core-shell structure with Fe2O3 particle in the core. When Fe2O3/PTFE particle size ratio=1.9, the hetero-coagulated particles were composed of irregular aggregates. The hetero-coagulated particles generated from hetero-coagulation of PTFE and nanometer Fe2O3 also had core-shell structure, but PTFE particle became the core. The hetero-coagulated particle was stable under ultrasonic function. The formation of hetero-coagulated particle undergoes three stages: the first更多还原