Studies on the influence of polymerization time,ratio of core material to wall material and percentage of SDS on the preparation of abamectin capsule suspensions

Abamectin capsule suspensions(CS) with methyl methacrylate as wall material were prepared by emulsion polymerization. The influence of polymerization time, ratio of core material to wall material(core to wall) and percentage of SDS on the entrapment rate, drug-loading rate and mean size of CS was studied, stability at high and low temperature and the controlled release effect were also studied.The results showed that the entrapment rate, drug-loading rate and mean size of CS were positive correlation with the polymerization time. The entrapment rate and drug-loading rate were relatively steady when the polymerization time was more than 3 hours, and the change of mean particle size was obviously reduced when the polymerization time was more than 1 hours. The drug-loading rate and mean size were significantly affected by core to wall. As the core to wall increased from 1∶ 5 to 1∶ 2, the drug-loading rate increased from 15.59% to 30.33% and the D50 varied from 5.47 μ m to 2.18 μ m. The influence of percentage of SDS on entrapment rate and drug-loading rate was not evident, but it was evident on mean particle size. When the percentage of SDS was 8% , the D50 of CS was smallest and the particles were more uniform. It indicated that each of the three factors had certain effects on the microencapsulation of abamectin. The acceptable abamectin capsule suspensions which had uniform mean size, regular shape, high entrapment rate and drug-loading rate, good stability at high and low temperature and good sustained release effect could be made when the polymerization time was more than 3 h, the core to wall was between 1∶ 3 and 1∶ 2 and the percentage of SDS was between 6% and 8%.