SINVOCHEM: SP-SC55, a dispersant that delivers more

Have you encountered the following problems and have been troubled by them for a long time?

A. Difficult to control the growth of particle size, crystallization or even caking of high challenging SC formulations (such as TC with low-melting-point raw materials, high solubility, salt-containing, formulation with high loading).
B. The difficulty of ensuring product stability during long-distance transportation under high-temperature conditions.
C. Quality fluctuation of TC from different sources or even different batches, resulting in poor availability to recipe.
D. The compatibility problem when tank mixing with other formulations or even fertilizers during field application.
E. The low retention rate of the formulation on the target results in poor efficacy.

The presentation of Dispersant SP-SC55 may take you out from the confusions. Let’s see how it works：

Structure and its function of SP-SC55

SP-SC55, a novel dispersant includes weak cationic groups, presenting good control of particle growth, electrolyte-resistance and enhanced deposition of pesticide droplet on foliar. Below is structure of SP-SC55, which will facilitate you understand its functions from perspective of functional groups:

Above groups imparts SP-SC55 outstanding performance on applications as below：

A. Superior in A.I. compatibility and make your recipe easy

Table 1.  Applied cases with SP-SC55 and its performance on trouble shooting

B. Performance on particle size control

Take 25% Pyraclostrobin SC as an example:
About 20 commercialized 25% Pyraclostrobin SC were detected against its stability after thermal storage, unfortunately found most SC appears varying levels of particle growth, crystal growth or even caking risk.

Given such phenomenon and in aim of finding out any relationship between A.I. quality and formulation stability, we collected A.I. of 30 batches from 8 Chinese manufacturers.

 
Below table tell the difference:

Table 2. A.I. difference among various batches or different producers

It can be concluded:  
a)Pyraclostrobin by its chemical is low melt point, polymorphic form and differs in purity. A.I. particles are susceptible to melt during formulation process and finally ruin the suspension.
b)To obtain a stable suspension, it is wise to check and chose A.I. of white color with low chromaticity, rod-shape, less aggregation among particles.

Although the negative and various qualities from different sources, we are excited to find SP-SC55 still has excellent compatibility with multi-grades of A.I.s when processing pyraclostrobin SC. Furthermore, SP-SC55 exert in synergy of crystal inhibition, when combined with other surfactant toward certain poor qualified A.Is.            

Controlled tests on monitoring particle size, wet sieve, suspensibility and rheological properties were conducted by comparison among 4 typical market sold dispersants as :
1.Dispersant SP-SC55
2.Dispersant A ---- Sulfonate, good control of particle growth   
3.Dispersant B ---- Phosphate, universal polymer features anionic
4.Dispersant C ---- Polycarboxylate, market leading
 

Test on particle size:  

Table 3. Change of Particle size detected by particle size analyzer (PSA)

Fig 1. Particle observation of treatment under microscope

Fig 2. Particle size distribution of treatment under RT and 54℃(14d)

After 14 days thermal storage, samples are taken to room temperature for 30 days more observation:  
Formulation with dispersant A, particle size (D90) grows from 3.89um to 5.46um, arising separation.   
Formulation with dispersant B, caking.
Formulation with dispersant C, particle size (D90) grows from 3.93um to 28.83um, A.I melting.  
Formulation with SP-SC55 present best control on particle size, A.I. particles can still be well protected by the dispersant.

Test on wet sieve:

Usually, the formed crystal or aggregated particles may excess range of particle size analyzer.

Wet sieve of sample under RT 90d, RT60d after 54℃(14d), RT90d after 54℃(14d) were further detected and can be demonstrated as:
* Either under RT 90d or RT90d after thermal storage, suspensions with dispersant SP-SC55 presents the best result of wet sieve rate over 98%.   
* Dispersant A/B/C all perform good(over 95% ) in case of aging under RT but arise problem like particle aggregation, serious crystal growth, heavy residue by wet sieve or even caking upon aging after thermal storage.
* As for SC contains pyraclostrobin, SP-SC55 is more applicable than other universal dispersant.

Fig 3. Sieve residue under microscope

Test on suspensibility:

Decrease of suspension rate correlated positively with particle growth.

Combined use of SP-SC55 with other Sinvochem’s dispersant (SP-SC55+CD ) was treated as optimized recipe and comparison test tell the difference on suspensibility:

*Aging 60 days after thermal storage, as for recipe with SP-SC55, suspension rate still reached over 90%. However for recipe with dispersant A/B/C, it shows reduced suspension rate below 85%, which seriously impact on pesticide application.
*As for optimized recipe (SP-SC55+CD), it can achieve a higher stability around 95%, indicating that a combined used of SP-SC55 with dispersant CD contribute to a more stable system for A.I with high impurity content.
  

Rheological property:

The rheological properties and stability of SC are somewhat related. In order to quickly judge the stability of the formulation, the MCR302 advanced rheometer was used to perform temperature scanning analysis of the η-T curve and frequency scanning analysis of the |η*|/tan(δ)-ω curve, to determine whether the samples by different recipe underwent caking or crystallization during thermal storage.

Fig 4. η-T curve of25% pyraclostrobin SC

Fig 5. |η*|/tan(δ)-ω curve of 25% pyraclostrobin SC

During the heating and cooling process of the 25% Pyraclostrobin SC, there was no significant change in viscosity for both formulations with SP-SC55 and dispersant A. However, the viscosity of formulation with dispersant B increased significantly during the cooling process, indicating that the small-molecule phosphate ester from dispersant B had already peeled off from the particle surface under high temperature conditions and could not adsorb well on the particle surface to prevent aggregation.

By comparing the loss factor tanδ, stability of samples after thermal storage at room temperature, as well as the ease of filling and pouring can be quickly determined when the angular frequency ω is 100 rad/s. The SP-SC55 recipe has a G′<G″ and tan δ＞1, indicating that the solid-liquid phase transition is relatively fast, making it easier for packaging, and with better performance during thermal storage and transportation under high-temperature environments. Its rheological performance is superior to that of dispersant A and B.

C. The effect of inhibiting crystal growth is prominent under high-temperature storage conditions

Most exported formulated products are need to be shipped for a long time under high-temperature and high-humidity shipping conditions. At the same time, in tropical areas with high temperature all year round, higher requirements are put forward for the heat-resistant stability of the formulation. Compared with general dispersants, SP-SC55 has better adsorption performance on A.I. particles under high temperature, which can effectively inhibit crystal growth and prevent caking during storage and transportation under high-temperature environments. Below tests give the demonstration:

1. Test on 430g/l Tebuconazole SC

Table 4. Test on stability of 430g/l Tebuconazole SC

Fig 6. Particle morphology of 430g/l Tebuconazole SC after 70℃ /14d

2. Test on 20%Tebuconazole+20%Propionazole SC

Fig 7. Test on stability of 20%Tebuconazole+20%Propionazole SC and particle morphology after 70℃ /14d

Compared with dispersant A(commercially product promoted for A.I. of LMP). The recipe with SP-SC55 at a high temperature of 70℃, particles are in the form of oil droplets. At this time, the A.I. has already melted, but the particles are evenly dispersed without aggregation, forming a solution similar to an emulsion in water(EW). This indicates that SP-SC55 still has strong adsorption and dispersion effects on the particle surface under high temperature conditions.

D. Anti-electrolyte ability in against with unstable dilution in case of pesticide of multiple A.Is, blended types of pesticide formulation as well as combined use of pesticide with fertilizer.  

Active component of fertilizer generally include acidic group like carboxylic acid or phosphonic acid, existing in form of water soluble salt upon dilution, thus generates a high electrolyte environment for agrochemical components and results in poor stability of dilution. The reason behind is :
a)Competitive adsorption of multiple components at the particle interface leads to system broken.
b)Crystal grow due to increased solubility of A.I.

Moreover, in case of air spray with low water volume or even high hardness water, dispersion and stability of drug may be seriously suffered. Under high electrolyte condition, thickness of double electric layer are typically several nanometers for ordinary dispersant. Electrostatic repulsion force further reduce along with increased salt. The tertiary amine incorporated into SP-SC55 release more cationic ion, creating effective adsorption on solid-liquid interface, realizing the high loading of components in complicated dispersion.

Here are some applied cases of SP-SC55:

a)A.I exists as salt in formulation
Eg. Propamocarb hydrochloride is hard to co-exist with xanthan gum, while in assistance of SP-SC55 and another Sinvo’s surfactant, the problem can be solved.

 
b)High hardness water, tank mix of fertilizer and pesticide

Table 5. Iron concentration of mixture of 17.5% Bifenthrin SC and fertilizers

When 17.5% Bifenthrin SC is mixed with water-soluble fertilizers containing trace, medium and high levels of elements, the ion concentration of the mixed solution becomes relatively high, especially when mixed with fertilizers containing high level of elements. Besides, the mixture features acidic pH and poor dilution stability. A certain tank-mix agent for better compatibility is needed.

Fig 8. Observation on dilution stability by introducing tank-mix agents of compatibility

(From left to right, the order is: tank mix agent A, tank mix agent B and SP-SC55 Dilution are based on mixture of 17.5%SC with 4 grades of fertilizer)

Among the four water-soluble fertilizer tank-mix systems ,serious instability was observed with the use of tank mix agent B and C within 0.5 hours. However, SP-SC55 maintained good tank-mix stability for 24 hours and effectively controlled the growth of particle size in system.

In conclusion:

As in-can dispersant or tank-mix compatibility agent, SP-SC55 has better electrolyte resistance, which improves tank-mix stability when used with pesticides and fertilizers. It is worth noting that there is type of liquid fertilizer on the market which is dissolved in strong acid with a pH value around 2. SP-SC55 is generally not suitable for this. In fact, the strong acidity may also affect stability of agrochemical active ingredients, the combined use with such fertilizer should also be avoided.

c)Improve the dilution stability upon aerial spray package

Table 6. Aerial spray packages contains multiple composition

Table 7. Application effect of Aerial spray packages

(TSI was calculated using Turbiscan to analyze stability of diluted solution.)

In aerial spray package II, the system contains only dispersion phase. Both tank mix agent C and SP-SC55 showed good dispersibility. However in package I, which is mixed system of dispersion phase and emulsion phase, SP-SC55 present better compatibility with the package compared to commercial tank mix agent C.

E. Boost drug adsorption on foliar so as to enhance utility of pesticide

Several suspension concentrate were prepared by using SP-SC55, dispersant A. B and C respectively. The amount of pesticide deposited on crop leaves was measured to evaluate utility of pesticide droplet.

Table 8. Comparison of deposition promotion between SP-SC55 and other types of dispersants

It is demonstrated that SP-SC55 exhibited excellent performance in promoting deposition in above SC formulations ,compared with dispersant A.B and C. Table 8 record the promotion rate on droplet deposition compared by SP-SC55 with dispersant A.B.C respectively.   

Further tests were conducted to evaluate the effectiveness of the SP-SC55 formulation system in bioassay. 250 g/L Pyraclostrobin EC was used as a standard control to compare the efficacy of 25%Pyraclostrobin SC with different dispersion systems.

Condition of green house bioassay
Target: cucumber powdery mildew and wheat powdery mildew
Pesticide dosage and usage : 40 ml/acre by spraying, following NY/T 1156.11.11-2008

Fig 9. Result of green house bioassay
（Left：cucumber powdery mildew、Right：wheat powdery mildew）

Table 9. Comparison of efficacy promotion among SP-SC55 and other type of dispersants

Fig 10. The effect of different formulation system on cucumber powdery mildew

Fig 10 shows any dispersion system of 25% pyraclostrobin SC can not reach the same efficacy like 250 g/L Pyraclostrobin EC. But efficacy differed greatly and consistent results were obtained for both crop targets. Compared with the control dispersant system, the efficacy of SP-SC55 system increased by 62.5%, 77.27%, and 56.00% for cucumber powdery mildew at 3 d after application, and by 61.29%, 58.66%, and 76.56% for wheat powdery mildew.(Table 9)

Condition of field trial
Target: Holly powdery mildew and watermelon anthracnose                  
Use : By spraying, following GB/T 17980.26-2000

Fig 11. Result of field trial
（Left：holly powdery mildew、Right：watermelon anthracnose）

Table 10. Comparison of efficacy promotion among SP-SC55 and other type of dispersants

Fig 12. The effect of different formulation system on holly powdery mildew

In field efficacy tests, the efficacy of the 25% pyraclostrobin SC varied for different dispersion systems, and consistent results were obtained for both crops. Compared with the control dispersant system, SP-SC55 increased the efficacy by 14.09%, 17.02%, and 11.16% for holly powdery mildew at 3 d after application and by 27.74%, 11.36%, and 12.12% for watermelon anthracnose at 14 d after application.(Table 10)

Through numerous green house and field efficacy comparisons, the SP-SC55 formulation system exhibited a synergistic property, with fast and also long-lasting effect than other types of control dispersant systems.

If you are interested in cooperation with SINVOCHEM, please contact:

Alex. Lee |SINVOCHEM
Email: alex@sinvochem.com
Tel: 0086-15094373731