Influence of modified lignosulfonate GCL4-1 with different molecular weight on the stability of dimethomorph water based suspension

Abstract Modified lignosulfonate GCL4-1, an excellent pesticide dispersant, was ultrafiltrated into three fractions (with the molecular weight of less than 10,000, 10,000–30,000 and more than 30,000, respectively) and the effects of these fractions on the dispersive stability of dimethomorph (DMM) water-based suspensions were investigated. DMM suspension without dispersants was unstable owing to the strong aggregation of particles, while the stability was increased after the addition of GCL4-1 fractions, which can be adsorbed on the particle surface and weaken the aggregation of particles. Moreover, the higher the molecular weight of the fraction, the larger the adsorption capacity was. However the zeta potential of DMM particles is not only determined by the adsorption amount of GCL4-1 fractions, but also by the sulfonated degree of GCL4-1 fractions. GCL4-1 fraction with a molecular weight of 10,000–30,000 exhibits strongest dispersive property to DMM particles because of its high sulfonated degree and strong adsorption capacity. When the molecular weight of GCL4-1 is more than 30,000, the dispersive ability becomes weak.