Effects of different thickeners on the stability of pesticide oil dispersion

In order to clarify the effect of different thickeners on the stability of oil suspension system with mineral oil as dispersion medium, 12.5% oxadiargyl + pyrazosulfuron-ethyl oil dispersion was used as the research object. The effects of three types of thickeners (including organic bentonite, organic polymer and gaseous silica) and organic bentonite used with other two types of thickeners on the physical stabilities of oil dispersions were studied by rheology and multiple light scattering methods. The results showed that the flow characteristic index (n) of all samples were less than 1, which was a pseudoplastic fluid with thixotropic properties. Except the combination of organic bentonite and organic polymer Atlox Rheostrux 100, the system was more in line with the Casson equation. While other samples were more in line with the Herschel-Bulkley equation. Organic bentonite has a relatively good performance to increase the stability of the system when used alone. Two kinds of organic polymer thickeners, including Atlox Rheostrux 100 and Atlox Rheostrux 200, had different performance. Atlox Rheostrux 100 had more significsant effect than that of Atlox Rheostrux 200, which might result from their different molecular structures. Two gaseous silica thickeners exhibited little effect, because they can’t form hydrogen bonds effectively. When organic bentonite used with other two types of thickeners, organic bentonite and organic polymer combination can improve the performance. Particularly, organic bentonite 869 and Atlox Rheostrux 100 combination was better than others, wich suspension system had high viscosity and good thixotropy, and excellent physical stability. However, organic bentonite 869 and hydrophobic silica R974 combination had no improvement. The results showed that both rheological and multiple light scattering can characterize the physical stability of the oil dispersion, and the novel orgainc polymer thickener and organic bentonite have synergistic effect, combination reasonable can greatly improve the stability of the oil dispersion.