Film Forming Agent with Outstanding Water Resistance POWERBLOX™ Filmer-17 Film Forming Agent

By: Ji Jing, Technical Service & Development, Industrial Solutions Asia Pacific, Dow Inc.

Flowable concentrate for seed treatment (FS) is a pesticide formulation with film-forming property for seed treatment. FS is made from pesticide active ingredient, film forming agent, wetting agent, dispersant and other additives. It can be directly used or diluted, and cover on the seed surface to form a “coat” with a certain strength and permeability. The “coat” can bind the pesticide active ingredients and prevent falling off, absorb water in the soil to expand without being dissolved, allow water and air to pass through for seeds germination, and ensure the contained pesticides and fertilizer to release slowly. Therefore, FS has the effect of killing underground pests, improving seed germination rate and promoting healthy growth of seedlings.

Film forming agent is an important component in FS. At present, commonly used film forming agent in the market include polyvinyl alcohol (PVA), methyl cellulose, poly acrylates and other polymers with bonding and film forming properties. However, the polymers with higher bonding properties usually have lower film strength, poorer seed flow ability, less uniform appearance. Conversely, the polymers with higher film strength usually have lower adhesion strength, and easier to fall off from the seed surface; the hydrophilic polymers are easy to be dissolved in water, and the hydrophobic polymers often have negative influence on seed germination. This causes some of the current FS products in the market still have some performance defects, such as high attrition rate, poor water resistance and so on. In response, Dow developed a safe polymer dispersion for FS, POWERBLOX^TM Filmer-17 Film Forming Agent.

Water resistance is required for seed coating, especially for the seeds in paddy field, such as rice seeds. Good water resistance of coat avoids the loss of active ingredients during seed immersion and crop growth process. The most highlighted advantage of POWERBLOX^TM Filmer-17 Film Forming Agent is its outstanding water resistance. POWERBLOX^TM Filmer-17 Film Forming Agent was added into a 30% thiamethoxam FS formulation with 10wt% concentration, and then coated corn seeds. The result of water resistance is shown in Figure 1. After immersing in water, the darker the color of the water, the worse the water resistance of the coat. The results showed that POWERBLOX^TM Filmer-17 Film Forming Agent provided excellent water resistance. This is because of its balanced hydrophilic-hydrophobic property. However, cellulose and polyvinyl alcohol (PVA) were strong hydrophilic, resulting in the film dissolved in water and the loss of active ingredient.

The appearance of the seeds after coating is shown in Figure 2. It can be seen that POWERBLOX^TM Filmer -17 Film Forming Agent provided a film on the seeds with uniform appearance and extensive coating coverage.


Attrition rate is one of the important performance of FS. Two different methods were used to destroy the seeds’ coat. One was shaking method, and the other was dropping method. Then measured attrition rate respectively.  A new measurement method was established to improve the repeatability and stability of the attrition rate results. As shown in Figure 3, after the coat being destroyed, the seeds in the container were moved to another glass vial. Solvents were added into the vial to fully dissolve the active ingredient (AI) on the seed surface. In addition, solvents were added into the container to clean it completely, so that the active ingredients which remained in the container can be fully dissolved. Finally, high performance liquid chromatograph (HPLC) was used to determine the weight of active ingredient in two solutions, and attrition rate was calculated.  The attrition rate of the coated seeds which destroyed by the shaking and dropping methods was 2.7wt% and 5.5wt% respectively, which can meet the relevant standard requirements.

Safety is the most important requirement for FS. The basic requirement for safety is comparing with the seeds without coating, no negative influence on germination rate and seedling height. The result of germination experiment is shown in Table 1. It can be seen that seed germination rate (4 days) and seeding height (10 days) of the seeds with FS contained POWERBLOX^TM Filmer-17 Film Forming Agent was equivalent with the uncoated seeds, indicating that POWERBLOX^TM Filmer-17 had no negative influence on seed germination, and was safe for seeds. POWERBLOX^TM Filmer-17 is a dispersion with balanced hydrophobic-hydrophilic polymer, which not only provide good water resistance, but also ensure that in the seed germination process, water can be absorbed through the coat, and doesn’t influence seeds germination and the growth of seedlings.
Conclusion

POWERBLOX^TM Filmer-17 Film Forming Agent was used to make 30% thiamethoxam FS formulation, and then coated the corn seeds, the results showed that its water resistance was outstanding. It can provide a film on the seeds with uniform appearance and extensive coating coverage. The attrition rate was low. The germination result showed that POWERBLOX^TM Filmer-17 had no negative influence on seed germination. POWERBLOX^TM Filmer-17 Film Forming Agent is a safe, high-performance film forming agent that can be used in high-quality FS formulation.


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