| Organic pesticide has broad-spectrum, it can reduce pest and insect pests, improve crop yields, but because of its excessive use, has caused many problems, such as environmental pollution, how to reasonable, moderate use of organic pesticides is a problem to be solved urgently. And the sustained release preparations of pesticides can reduce the use of pesticides and prolong the validity period of pesticides, thereby reducing the pollution of the environment.In this paper, a lambda-cyhalothrin polyurea microcapsules suspension was prepared by interfacial polymerization. The influence of polymer on dispersion property and stability and the stabilization mechanism be studied by using Turbiscan LAB analyzer,rheometer, laser particle size analyzer, and the stabilization mechanism of polymer on micro-capsule suspension is clarified. The results showed that the stability index of the blank sample 6h was 15.75, whereas the kinetic indices of 2.5% polyvinyl alcohol and 0.3%sodium alginate quality fraction were 4.00 and 3.08 respectively. The apparent viscosity of the blank was 8.55 × 10-3 Pa·s at low shear rate (0.01 ～100 S-1),The apparent viscosities of samples with 2.5% mass fraction of polyvinyl alcohol and 0.3% mass fraction of sodium alginate were 71.89 Pa s and 28.19 Pa s, respectively. the storage modulus of the blank was 0.03 Pa; at low scanning frequency (0.01 Hz-1 Hz), The storage modulus of the sample containing 2.5% by mass of the polyvinyl alcohol sample and the sample containing 0.3% by mass of sodium alginate was 12.75 Pa and 3.96 Pa, respectively. It is shown that the addition of high molecular weight polymer can improve the rheological properties of the microcapsule suspension and enhance the physical stability, and the higher the apparent viscosity and viscoelasticity, the more stable the sample. At the same time, after adding high polymer, freeze-thaw stability will not change. Therefore, polymer can improve the stability of microcapsules suspension. The possible mechanism is that the polymer has a larger space structure, which improves the viscosity of the sample by the formation of the bit resistance effect, thus effectively reduces the aggregation between the microcapsules and enhances the dispersion of the samples.The Pickering emulsion was prepared by hydrophobic modified sodium alginate(NaAlg-Ugi) in conjunction with hydrophilic nano-SiO2 particles, and the effects of nano-SiO2, NaAlg-Ugi addition, ionic strength and pH factors on the stability of emulsion were investigated. The effect of the SiO2 particulate concentration and glutaraldehyde dosage on the performance of the micro-gel was investigated by using the stable Pickering emulsion system as a template. The results show that when the SiO2 particles are added to 1.0-2.0g/L, the NaAlg-Ugi concentration is the 0.5-2.0g/L, pH value for weakly acidic(4.18-5.07), the salt concentration is the 0.01m/L, the stability of the Pickering emulsion is better. The micro-gel obtained from the stable Pickering emulsion crosslinking, and the range of drug loading rate is 72.4% to 92.1%. When cross-linked glutaraldehyde is added to 8.0mL, the micro-gel performance is the best; the insufficient addition of glutaraldehyde can cause the cross-linking not complete, excessive adding can cause partial cross-linking degree too high, micro-gel carrier range is 80.1% to 92.1%. The results of thermal stability showed that the decomposition temperature of lambda-cyhalothrin could be increased from 153.00 to 210.4 ℃ by the micro-gel loading. The rapid release experiment showed that the concentration of SiO2 particles was 0.1g/L,the content of glutaraldehyde was 8.0mL,and the release rate of 6 hours was 78.71% in methanol solution, which indicates that the micro gel has good sustained release performance under this condition, and the micro gel loading can improve the thermal stability of lambda-cyhalothrin.Using modified sodium alginate (NaAlg-Ugi) as a macromolecule surfactant to stabilize the lambda-cyhalothrin emulsion, the calcium ion crosslinking of lambda-cyhalothrin microcapsules were prepared by electrostatic spinning (electrostatic spray) technology. The results showed that the aqueous solution of lambda-cyhalothrin was stable with 1.0% NaAlg-Ugi solution, which could crosslink with the calcium chloride solution by electrostatic spraying to form microcapsules. The results show that the high voltage value of the electrostatic spray equipment is increased from 12KV to 20KV, and the particle diameter of the microcapsules is smaller and relatively homogeneous, and the size range is around 5μm-2μm. The results of thermal stability showed that the microcapsule encapsulation increased the decomposition temperature of lambda-cyhalothrin from 153.00 to 223.13 ℃. The rapid release experiment showed that the microcapsules produced by 20KV Voltage showed better release, and the release rate of 6 hours in pure water was 4.29%, 13.28% in phosphate buffer and 72.2% in methanol solution. It is shown that the higher the spinning voltage, the particle diameter of the microcapsules will be smaller and homogeneous, the sustained release performance is better, and the microcapsule encapsulation can improve the thermal stability of the lambda-cyhalothrin. |
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