Preparation And Application Study Of Bio-based Waterborne Polyurethane Sustained Release Film

As an indispensable agricultural production mean,pesticides are an important guarantee for ensuring food security and agricultural harvest.Due to high pesticide residues and increasingly serious environmental pollution,traditional chemical pesticides have received widespread attention.Botanical pesticides are more and more widely used in the field of pest and disease control because of the safety to non-target organisms and the environment.However,most botanical natural compounds have poor water resistance and strong volatility,resulting in low effective utilization and short persistence in practical applications.These shortcomings are effectively made up with the introduction of polymers.In this paper,two different bio-based waterborne polyurethanes carriers were prepared using different chain extenders.Botanical pesticides tea saponin and citral were respectively embedded in the polyurethane films with blending ultrasonic to prepare cationic aqueous polyurethane / tea saponin emulsions(TWR)and anionic aqueous polyurethane / citral emulsions(PC).The slow-release properties,chemical resistance,rainfastness,and biological activity of composites were explored.The main results were as follows:(1)FTIR,DMA,DSC and tensile testing were used to characterize TWR composite emulsions and composite films.The interaction mechanism between cationic aqueous polyurethane and tea saponin(TS)was clarified,and the slow-release properties of TWR composites were explored.The results showed that the release rate of TS from the composite films could be tailored by controlling TS content.The tensile strength,storage modulus,thermal stability of the composites and the rainfastness of TS on leaves were greatly enhanced by embedding TS in the polyurethane films.The activity experiment showed that TWR composites had a synergistic inhibitory effect on the mycelia growth of rice blast.(2)PC composites were evaluated by DLS,TEM,SEM and Gel rate testing.The result showed that the composite emulsions were uniform and stable without using any additives;citral increased the degree of cross-linking of PC composites.The adhesion properties assay of PC composites showed that composite emulsions could form films on the surface of bitter gourd and the films had the ability of rainfastness.The chemical resistance of composite films could be tailored by controlling citral content.The PC-0.5composites only swelled in water,but were broken in 40% ethanol aqueous solution.Field experiments showed that PC-0.5 composites could extend the volatilization time of citral from 7 hours to 84 hours,and the control effect against Bactrocera cucurbitae was 70.74%higher than that of the citral treatment at 5th day.In conclusion,bio-based waterborne polyurethanes as carriers,can effectively improve the hydrophobicity of TS and slow the volatilization rate of citral.At the same time,it provides the desirable field properties of botanical pesticides and provides technical basis for the efficient application of botanical pesticides in agricultural production.