Synthesis and hard water resistance mechanism of polycarboxylate dispersant for pesticide water dispersible granules

A new type of dispersant for pesticide water dispersible granules (WDGs), sodium salt of methacrylic acid/styrene/sodium p-styrene sulfonate copolymer (SMSS) was designed and synthesized by by free-radical polymerization in solution. Atrazine WDG was prepared to evaluate the dispersion performances of SMSS. It is found that the as-synthesized dispersant has strong resistance to hard water and high performance, and the suspensibility of 90 wt% atrazine WDG could reach 93.21% and 90.81% in standard hard water and three-fold standard hard water respectively. The hard water resistance mechanism of the as-synthesized SMSS dispersant is proposed as follows: SMSS could inhibit the formation of insoluble calcium polycarboxylate and magnesium salts, and prevent desorption of dispersant molecules from the surface of atrazine particle, thus maintain the suspension stability of WDG in water with high hardness.