Research On The Grain Growth Phenomenon On The Stability Of Imidacloprid 480 G/L SC

The increasing of particle size of active compound in suspension concentrate (sc) during storage period is called the granular grown phenomena. This phenomenon is commonly collected with the effects of Ostwald ripening and particle concentrations. It is seriously occurred in SC of high concentration, resulted in delamination and agglomeration in a short period, and even caused the useless of preparation, which significantly limits the development of this preparation. To solve this problem, this research choose the SC of imidacloprid (480g/L) as experiment subject, taking the change of the granular size during storage as main index, to study the effect of different ricinate, viscosity, processing technic on the physical stability of suspension concentrate. The main findings are as follow:1.The flowing point test was used in primary selection of ricinate. The best concentration of each assistant was determined according to the viscosity curve. Based on the orthogonal test, selecting the best formula of Imidacloprid 480g/L SC. The final prescription was as follow:imidaclopment 42.5%(mass fraction, the follows were as the same)ricinate dispersant S 3%; NP-101.0%; T36 1.0%xanthan gum 0.15%,glycol 3.5%,defoamer 0.25%,water up to 100%。2. In the above formula, we compared the dispersant T36, viscosity, initial particle size, temperature and pH value for the granular grown phenomena of 480g/L imidacloprid suspension growth during storage.the dispersant T36 and the initial size were the main Influencing factors of the granular grown phenomena. Controling the initial size of 1.8um microns, the amount of 1.0% T36 or extending the grinding time could Effectively restrain of this phenomenon. When the temperature is higher than 35℃during storage period, the effect of the granular grown phenomena will aggravate. But the effects of viscosity and pH on particle size of active compound are not significant. Meanwhile, based on the detection of the effect of particle size on the rate of delamination, the relationship is positive, but there is no linear relation.3. The result of the study on the change of particle size during storage period suggests that no linear relation exists between the cube of particle size and storage time. Thus, the LSW formula is not suitable for the detection of Ostwald ripening in SC. According to the results of microscopic images, the Ostwald ripening and Particles gathered were existed simultaneously, both of them led to the growth of granular size. The right amount of T36 could do help to contain the Particles gathered and the small size distribution could restrain Ostwald ripening.