Study On The Effect Of Leaf Surface Microstructure And Chemical Liquid Properties On Droplet Spreading Behavior During Spraying

Improving the wetting and deposition of pesticide solution on crop leaves has always been popular in the study of plant protection.There is a great significance to the development of pesticides,the development of spray equipment and the innovation of spray technology,and to improve the usage efficiency of pesticides.The pesticide physical and chemical nature and the microstructure of the crop surface are important factors that affect the wetting performance of the pesticide solution droplets on the leaves of the crop,and are also important factors that affect the charging performance of the pesticide solution in the electrostatic spray.Surfactant is an important component that changes the physicochemical properties of the chemical liquid.Therefore,it is very important to study the effect of the surfactant and the microstructure of the crop surface on the wet spreading and deposition of the chemical liquid and the charging performance of the droplets in the electrostatic spray.The experiment selected non-ionic,anionic and cationic surfactants as the research object.The effects of the type and concentration of surfactants on the surface tension,contact angle,dynamic contact angle,and spreading diameter of the solution were studied through experiments,and compared with deionized water.The experimental results show that adding surfactants to the solution can significantly improve the wettability of the solution on the leaf surface.Analyze the surface tension of the surfactant to obtain its critical micelle concentration(CMC).In addition,non-ionic surfactants can rapidly reduce the surface tension of the solution in a very small concentration range of 0.005~0.1 g/L,anionic and cationic surfactants can achieve the same effect in the concentration range of 0.5~2 g/L,the effect shows that it has better surface activity than anionic and cationic surfactants;the measurement results of contact angle,dynamic contact angle and spreading diameter also show that nonionic surfactants have better wettability than anionic and cationic surfactants.The three-dimensional ultra-depth microscope was used to characterize the microstructures of different parts of cucumber leaves and the size of the hook hair on the surface of the leaves,and measured the spreading area of the solution in different parts of the leaves,and analyzed the effect of the microstructure of the leaves on the spreading area.The results showed that the wettability of the droplets on the front of the cucumber leaves was better than that on the back.At the same time,we found that the wetting relationship of the cucumber veins at all levels: tertiary veins> secondary veins> main veins.This is because the thick veins on the main veins and the back of the leaf,which increases the roughness of the leaf surface and hinders the wetting of the droplets on the leaf surface of the crop.This article measured the retention of droplets on the blades under different spray pressures,spray durations,and blade inclination angles.It was found that the adhesion of droplets on the blade is affected by the microstructure of the blade,the blade inclination and other factors.Combined with the structure size of the hook hair,the fall-off conditions of the droplets on the cucumber leaves were analyzed.The electrical conductivity,electrostatic spray charge-to-mass ratio and electrostatic spray droplet size of various surfactants at different concentrations were measured.The CMC,conductivity,the charge-to-mass ratio,droplet size and the interaction of these factors were analyzed.The results show that the charge-to-mass ratio of non-ionic surfactant decreases first and then tends to be constant with the increase of surface tension,charge-to-mass ratio of ionic surfactant increases first and then decreases with the increase of surface tension,the charge-to-mass ratio of nonionic surfactant increases all the time with the increase of conductivity,the charge-tomass ratio of ionomer surfactant increases first and then decreases with the increase of conductivity,the inflection point is related to critical micelle concentration.The experiment also found that we can choose to add different surfactants to get the desired relationship between the particle size and the charge-to-mass ratio.The non-ionic surfactant OP-10 can get a larger charge-to-mass ratio and a smaller particle size,while the ionic surfactants DTAB and Nekal BX can get a larger charge-to-mass ratio and a larger particle size.