摘要
采用悬浮聚合工艺制备微米级铁红和苯乙烯 -丙烯酸丁酯共聚物复合粒子 ,通过跟踪观察体系在预分散过程的变化 ,分析相关表面张力、润湿角的测定结果 ,解释了复合粒子微观结构成因。实验测试结果显示在高速预分散过程 ,铁红以大部分伸入溶液水相的形式存在于油水界面 ;在SEM下观察到复合粒子的微观结构是铁红存在于复合粒子表面形成嵌入式结构。
Composite particles of iron red with styrene -butylacrylate with a diameter of the order of μm were prepared by suspension technology. In the preparation process, initiator, iron red and other additives were put into blend of styrene with butyacrylate firstly, then the mixture is added into water which has dissolved dispersantes. After being ultrasonic agitated 5 min, that mixture of oil with water was pre-dispersed at high speed and then moved to reactor where polymerization occurred at 70℃ for 6h.The test data showed that energy at interface between oil and water was lower than both in oil and in water, so the iron red particles should move to interfacial zone automatically. It was lain on which state the whole energy would be the lowest that the iron red particles mostly projected into whether the oil or the water in the interfacial zone. To compare the interfacial energy between the oil and monomer with that between iron red and water, we transformed some known equation related interfacial energy to a expression γ Fe/water - γ Fe/oil =- γ water cosθ water + γ oil cosθ oil . By introducing test data of surface tension and contact angle we obtained a result that γ Fe/water < γ Fe/oil , which indicated that the iron red particles will mostly project into the water .The observational phenomena under microscope confirmed the theoretical discussion above. When the temperature was elevated from room temperature to polymerization temperature, surface tension and viscosity of the water solution increased. The surface tension and viscosity of the oil increased along with polymerization process, while the surface tension and viscosity of the water solution was almost unchangeable at the same time. The experimental results showed that the value of cosθ oil had risen along with polymerization. So it was theoretically probable after a period of polymerization that γ Fe/water > γ Fe/oil , namely, the iron red particles should remove into the oil. However, even if γ Fe/water > γ Fe/oil , it were difficult for iron red particles to return to oil again actually because the viscosity of oil was very high after a period of polymerization. As a result, the iron red particles were embedded in the polymer. The photograph of SEM of composite particles clearly showed that the iron red particles existed on the surface of composite particles. During the polymerization, the iron red particles, whose surface contained Fe 3+ , always contacted with oil where original free radical, monomer free radical and chain free radical coexisted. The FTIR of iron red extracted from composite proved that iron red had reacted with original free radical while no evidence for other free radical having reacted with iron red.
基金
国家自然科学基金资助项目 (A5 9874 0 0 3)&&
