The Research And Application Of Sodium Alginate As A New Accessory Ingredient In Pesticide Formulations

Sodium alginate(ALG)is a kind of non-toxic,biodegradable,natural macromolecules and it has a wide range of applications in food,biological,pharmaceutical,and other fields.In this thesis,low molecular weight of sodium alginate is prepared through degradation.The low molecular weight of sodium alginate was used as a growth promoting agent in seed coating and its influence on the germination of corn and rice seeds was investigated.Sodium alginate was blended with polyvinyl alcohol(PVA),which is a traditional film agent of seed coating formulation and the performance of sodium alginate and its blend membranes for coating was studied.Multilayer polyelectrolyte composite membranes were formed though the electrostatic force between sodium and chitosan and its slow-release properties for pesticide were studied.The main findings are as follows:Low molecular sodium alginate was prepared by traditional thermal degradation,hydrogen peroxide assisted by microwave degradation,and Fenton agent degradation.The factors that affect the degradation process were investigated and the differences between these three kinds of degradation methods were assessed.And the structure of sodium alginate was studied by FT-IR.The influence of the alginate on the germination and seeding growth of seeds after coating processing was investigated.The longer the reaction time,the higher the temperature,the greater the H2O2 dosage,the molecular weight of sodium alginate is lower and the power of microwave has little influence on the degradation.Fenton degradation is more efficient than traditional thermal degradation,which doesn't need to be heated.During the process of degradation of alginate,1,4 glycosidic bond was rupture first,however,the ring bond of sodium alginate begun to rupture when the degradation condition become harder.When coated by low molecular weight sodium alginate(14.1k,Mw),the germination rate of maize seeds increased from 85%to 96%and rice seeds increased from 91.3%to 96.7%.The low molecular weight sodium alginate also has promotion effect on seedling growth:the fresh weight of corn roots increased by 50.4%,the fresh weight of corn shoots increased by 38.1%,the fresh weight of rice roots increased by 61.2%,and the fresh weight of rice shoots increased by 37.7%.Low molecular weight sodium alginate not only can promote the germination of seeds but also can promote the growth of seedlings.A series of sodium alginate and polyvinyl alcohol blend membranes with different mixing ratio were prepared by the method of solution casting.The blend membranes were characterized by SEM,ATR-FTIR,mechanical property test,water vapor transmittance test and contact angle test.The ALG and its blend membrane have good film-forming performance and comprehensive mechanical properties.Coated by sodium alginate,the germination of corn and rice have increased from 85%,91%to 92%,93%respectively.The root fresh weight of corn and rice seedlings increased by 18%,25%,and the shoots fresh weight of corn and rice seedlings increased by 12%,20%.The hydrogel beads with the multilayer structure alternately wrapped by sodium alginate and chitosan were prepared by the method of layer-by-layer assembly.The structure and properties of the hydrogel beads were characterized by means of Fourier transform infrared spectroscopy(FTIR),scanning electron micrograph(SEM),thermogravimetry(TG),water-up tests and release studies.The results of the experiments showed that polyelectrolyte complexes of alginate and chitosan with the multilayer structure formed on the surface of the hydrogel beads.The decrease of thermodynamic stability with increasing membrane layer and the behavior that membranes dropped off from the surface of the hydrogel beads during the swelling process indicated that the number of membranes coated on the hydrogel beads was not the more,the better.The cumulative release dosage were 61.2,20.4,7.3,4.9,1.3,and 1.2 mg respectively when the release time was 33 h,which indicated that the wrapping method of hydrogel beads can effectively control the release of drugs and improve sustained-release performance of the hydrogel beads.This method is expected to be a new method for seed coating,for it is simple and has a good performance in controlling drug release.