The Performance Of SSOS On Chloropicrin Microencapsulation

Microcapsules were prepared by spray drying with self-made SSOS(Starch Sodium Octenyl Succinate)as wall material and volatile pesticide chloropicrin as core material.The process conditions were optimized by single factor experiment and response surface experiment.The results showed that the pH value of the system was 9,the temperature was 35 ℃,the time was 4.6 h,the amount of OSA(octenyl succinic anhydride)was 5%,and the degree of substitution could reach 0.0255.The significance of each factor can be determined by response surface experiment,it can be concluded that the reaction time and the amount of OSA are the most sensitive factors affecting the degree of substitution,Among the two factors,reaction temperature and reaction time,reaction system pH and reaction temperature had the most significant influence on the degree of substitution.The emulsification properties of wall materials were studied.Through single factor experiment,the optimum technological conditions for influencing the emulsifying properties of wall materials were obtained: the mass fraction of SSOS was 4,emulsifying time was 25 min,and the degree of substitution was 0.0245,no other emulsifier was needed.With the increasing of the degree of substitution,the coprecipitation property,HLB value and viscosity of SSOS were improved accordingly.The SSOS was characterized by IR and XRD,which showed that the synthesized SSOS did not destroy the crystal structure of starch and the ester group was added,so SSOS could be used as a good wall material for microcapsules.The embedding rate of microcapsules was used as the evaluation index.The single factor experiment and response surface test were used to optimize the process conditions.The results showed that the mass fraction of solid was 4,the ratio of wall to core was 2.5: 1,and the inlet temperature was 190 ℃,the amount of crosslinking agent was 0.9,the embedding rate could reach 76%.The significance of each factor can be determined by response surface experiment,it can be concluded that the mass fraction of solid and the ratio of wall to core were the most sensitive factors affecting the embedding rate,in the two factors,the mass fraction of solid and the ratio of wall to core,the ratio of wall to core and the amount of crosslinking agent,the interaction of these two groups had the most significant influence on the embedding rate.The SEM characterization of the microcapsules showed that there was no obvious damage on the surface of the microcapsules,and the size of the microcapsules was uniform.The capsules formed by spray drying were hollow in shape.The particle size of microcapsules was found to be in the range of 5.8~11.8um.The properties of the prepared microcapsuleswere studied.The results show that the microcapsules have good storage stability.Under the condition of room temperature,the core and wall materials were kept good for one month,and there were no obvious damage.The simulated release study showed that it can be released completely in the simulated environment for 3 days.The thermal stability of the microcapsules was analyzed.The core material was released before 200 ℃,and the wall material was degraded well afterwards.