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What is a pesticide silicone surfactant or silicone adjuvant?

 

Agirculture additive has a strong potential market increase in recent years. By 2023, The growth of the global agricultural additives market will come from USD 3.13 billion in 2018 to USD 4.04 billion, and the compound annual growth rate is 5.24%. The market increase is due to the the popularity of global integrated pest management,the improvement of pesticide quality, the development of green additives solutions, and the limit requirements on crop residues. Surfactant accounts the biggest market share in agricultural additives and among the surfactant, silicone agriculture adjuvant is the top increasing group. As per some datas, the silicone agriculture adjuvant will have highest increasing till year 2023. The development of silicone agriculture adjuvant has changed the situation of agriculture additive field.  In the past few years, there are more than 50 different items got registration in USA and Canada. The demand and good feedback on silicone agriculture adjuvants also stimulated the global market demand on it. The crop protection company is also considering the use of silicone raw material in the developing of new products and biological acaricides, etc.

 

The North America market is the biggest market for agriculture additives, with the participation of top global brands like Dupont, Huntsman, Helena, and Momentive. In the Asia pacific market, with more investors in China, India and Thailand, the agriculture additive and silicone agriculture adjuvant will have high compound annual increase in Asia pacific market.

 

Why agriculture adjuvant is need in the crop protection?

In the crop growing process, pesticides and herbicides are necessary. But there is certain side effects in using them. One is environmental pollution, and the other is the cost. In the using of pesticides in large scale, it will lead to environmental pollution with pesticides residue. This wil affect the eco enviroment as well as health of people. If the dosage is too low, the insecticidal effect will not be good. If the dosage is too high, it will easily cause phytotoxicity and pollution to the environment.

 

So, in the use of pesticides, agriculture adjuvant is often used. They are inactive, but can increase the utilization rate of pesticides. And silicone adjuvant is widely applied in pesticides among all the agriculture additives for better effect. What would be the feature of pesticides mixed with silicone adjuvant?The excellent wetting ability of silicone adjuvant enable the liquid pesticide to spread fast on the surface of leave, strengthen the adhesion of the liquid pesticide, improve the utilization rate of the pesticide, lessen the loss of the liquid pesticide, and stop the pesticide from infiltrating the earth and leading to water pollution.

 

The application of Silicone Adjuvant in pesticides

 

In the 20th century, silicone surfactants are started to use as pesticide, and in the 1980s, the commercial promotion in agriculture industry began. In 1985, Monsanto New Zealand was the first in launching silicone surface agent L-77 ( Silwet M) . Extensive indoor chemical tests and field trials are made.

 

There are more than 5000 types and more than 10000 brands of silicone products in the market. The total global sales amount of silicone products is around 12 billion euro and the sales amount of Dow Corning has accounted for one third of the total amount. The second company is Momentive, which is also the top in the agriculture field. Silicone has many different properties such as good electrical property, good weather resistance, excellent air permeability, safety in touch with people, and low surface tension(which is related with agriculture industry).

 

Silicone surfactant has different types, and the most applied types are Polyether silicone oil, emulsified methyl silicone oil and amino silicone oil. The main functions are used as defoamer(for paint, ink and agriculture), wetting agent(for agriculture), leveling agent(for paint), hand feel agent(for textile and leather), and dispersing agent(for the dispersion of powder in water or oil). Besides, one of the biggest market is in cosmetics area. The global market share is around 3 billion Euro.

 

The structure and property of silicone surfactant

Silicone surfactants are grouped into four categories: cationic, anionic, nonionic and zwitterionic.  The hydrophilic part of silicone surfactant is various ionic groups or polyoxyalkylene ethers and the hydrophobic part of the silicone surfactant is polysiloxane. If classified according to their structure, organosilicon surfactants can have hydrophilic group on both ends or on side chain as well as block copolymer structure.The structure of non-ionic silicone surfactants is grouped into type A and type B, type A side chain is composed of polyoxyalkylene ether, and type B end group is polyoxyalkylene ether;

structure

 

The main function of silicone surfactant applied in agriculture area is for wetting and defoaming. The most popular function at present is wetting. The adding of silicone adjuvant in agriculture is very effective with low dosage. Generally speaking, 0.1% can have a good wetting ability. And 0.02% can achieve good effect. Organic fluorine has lower surface tension, but its wetting ability may not be as good as silicone product. There are various types of silicone surfactants, but those applied in agriculture area is limited. Its application in agriculture industry is not so long, but the effects are very obvious. Like around 10 years ago, Momentive has cooperated with agriculture department, which have promoted the development and application of silicone adjuvant in agriculture area.

Comparing with non-silicone surfactant, the obvious feature of silicone surfactants is low surface tension, high temperature resistance and good microbial resistance. The surface tension of non silicone surfactant is over 30mn/m, and the surface tension of silicone surfactant is 20mn/m. with the lower surface tension, the contact angle of water solution and solid surface will also be lower.

The surface tension of surfactant solution

Types of surfactant Mass fraction in water/% Surface tension(25℃)/mN.m-1
Alkyl polyoxyethylene ether(TX-10) 0.1 31.6
Alkyl polyoxyethylene ether(EO=4) 0.1 34.1
Sodium dodecyl sulfate 0.1 41.7
Non-ionic silicone surfactant 0.1 20.0
Ionic silicone surfactant 0.1 21.3

 

With the lower surface tension of silicone surfactant, the contact angle of hydrophobic surface is smaller. So, the wetting speed on the hydrophobic surface(like PU film) is faster and the wetting diameter is bigger.

The wetting speed and wetting diameter of surface surfactant on PU film

Surfactant types Wetting Speed Wetting Diameter/mm
Without surfactant 1 1.0
OP-10 2.6 3.0
Silicone surfactant 1 6.4 23
Silicone surfactant 2 7.8 32
Silicone surfactant3 12.6 40

 

The function of silicone adjuvant in agriculture pesticides

Pesticides are the necessary chemicals used in the growing process of crops, vegetables and fruits. They are applied to kill various germs, pests, and weeds. The reason is that most pesticides (including herbicides) are soluble in oil but not soluble in water; therefore before using them, pesticides need to be emulsified into an oil-in-water emulsion. Later water also need to be added to dilute them into very low concentration. The diluted emulsion will be sprayed onto the leaves, stalks and stems of crops, fruits, vegetables as well as weeds to inhibit or kill the growth of various germs, pests, and weeds. Generally, the surface tension of the aqueous solution with other surfactant is above 30 mN/m; but the surface tension of the aqueous solution of silicone surfactant is mostly around 20 mN/m. The surface tension of aqueous solution is related with its wetting ability and wetting speed on the solid surface. The lower the surface tension, the faster the wetting on the solid surface and the larger of the wetting area. On the surface of leaves and stems, there is a thin hydrophobic wax film. When the leaves and stems are sprayed with pesticide emulsion with normal surfactants, the spreading area is small and the wetting speed is slow. Because of the capillary effect, the pesticides cannot penetrate into many small pores. And those pests can still survive where it is not wetted by pesticides. The situation is similar on herbcides as the weeds cannot be removed if herbicides cannot penetrate into the pores of the weeds. If the herbicide formulation can be added with a small amount of organic silicone adjuvant, the using amount of of herbicide can be lessened to one third. As with the very low surface tension of silicone surfactants, the pesticide emulsion can have rapid wetting and penetrating into every small part of the leaves, stalks and stems of plants. And the effectiveness  of the pesticides can be strengthened and the effect of time can be prolonged.

The effect of herbicides added with silicone adjuvant on weeds control rate(%)

Without use of herbcides 0
Herbcides+normal surfactant 40
Herbcides +silicone adjuvant 1 80
Herbcides +silicone adjuvant 2 76
Herbcides +silicone adjuvant 3 81

From the data, it can be seen that the control rate on weeds has been improved by 100% comparing with silicone adjuvant and non silicone adjuvant.

 

Adding silicone surfactants into Avermectin pesticides, the initial lethality of red spider mites can be 100% and some can still reach 65% after 21 days

The effect of silicone surfactant on lethality on red spider mites

Types Start 7days 14 days 21days
+Water 10 5 0 0
Pesticides(0.12g/L))+non silicone surfactant 100 85 55 45
Pesticides+ silicone surfactant 100 80 95 65

 

The use of silicone adjuvant in pesticides and herbcides is very significant with its low surface tension. With the lower surface tension, the contact angle with the hydrophobic solid surface is smaller, and the wetting speed is faster, and the wetting diameter is large. Thus, the amount of herbicides can be decreased by more than one-third but with the same control rate of weeds. Also the amount of pesticides can be reduced, as well as get better killing effect on pests and longer function time.

 

Silicone adjuvant can greatly improve the spreading force and adhesion of the liquid pesticide on the surface of plants or pests, increase the utilization rate of pesticides, speed up the pests’ absorption of pesticides, and get a better insecticidal effect, thereby reducing the amount of pesticide spray.Silicone adjuvants can promote the penetration of systemic pesticide liquid through stomata, and strengthen the resistance to rain erosion. Further spray is not needed after rain.Silicone adjuvant can also reduce the using amount of pesticide and water, lower down pesticide pollution, and decrease pesticide residues. It can be used together with fungicides, insecticides, and plant growth regulators.

 

Top Global company in Silicone Agriculture Adjuvant

Momentive is the top 2nd company in silicone field, and its shanghai based agriculture department has set up agrochemical laboratories for indoor biological activity determination and formulation development. Its agriculture silicon adjuvant products are applied in agricultural fields in large scale such as pesticides,plant growth regulators, foliar fertilizers, etc., and the effects are very outstanding. Momentive’s Silwet series of agricultural synergists have good market reputation around the world. The Silwet series can be used in field sprays, as well as be added into pesticide formulations. Its performance in improving pesticide effect, lessening water consumption, reducing labor intensity, and saving average costs is very significant. Silwet 408, Silwet L77 and Silwet 618 are the popular types in the agriculture markets.

 

What should be the using amount of silicone adjuvant in agriculture products?

Silicone adjuvants are very efficient and eco friendly non-ionic surfactants. Its application in agriculture industry has changed the pesticide formulations and application techniques greatly. Because of its good wettability, permeability, expandability , good compatibility, foaming, foam suppression and foam stabilization, it can improve the utilization and application effect on a significant scale, as well as decrease the using amount of pesticides by 30%-50 %.

 

Although silicone adjuvant has significant effect in the use with pesticides, attention should be paid in its use to ensure a better function. While use silicone adjuvants together with pesticides, the concentration and the dosage should be strictly controlled. The recommended concentration of silicone adjuvants mixed with different kinds of pesticides is: herbicide 0.025%-0.15%, fungicide 0.015%-0.05%, insecticide 0.025%-0.1%, and plant growth regulator 0.025%-0.05%. The using amount together with powerful insecticides or herbicides should be decreased to prevent phytotoxicity.

 

With the development of silicone adjuvant products from different companies, farmers will have more choices to choose the top quality silicone adjuvant to improve the out yield of their crop products with less cost.

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