Microstructure and Causal Mechanism of Inorganic-polymeric Composite Particles Prepared by Suspension Polymerization

Composite particles of iron red with styrene -butylacrylate with a diameter of the order ofμm 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 expressionγFe/water-γFe/oil=γwatercosθwater+γoilcosθoil. By introducing test data of surface tension and contact angle we obtained a result thatγFe/water<γFe/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 cosθoilhad risen along with polymerization. So it was theoretically probable after a period of polymerization thatγFe/water>γFe/oil, namely, the iron red particles should remove into the oil. However, even ifγFe/water>γFe/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 Fe3+, 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.