Research on Dynamic Surface Tension Testing Technology of Surfactants: Based on Asha ® Improvement of the Wilhelmy Plate Method in Technology

The importance of surface tension meter in dynamic surface tension testing

1.1 The Physical Essence of Surface Tension

Surface tension is a key parameter that characterizes the interfacial properties of liquids and has a wide range of impacts in industrial applications. usesurface tensiometerThe ability to accurately measure the interaction forces between liquid molecules, especially in dynamic environments, is crucial for industries such as coatings, pharmaceuticals, and food. For example, the surface tension of pure water at 20 ℃ is about 72 mN/m, but after adding surfactants, this value can be reduced to 30-40 mN/m, which affects the droplet spreading performance.

1.2 Time dependence of dynamic surface tension

Dynamic Surface Tension (DST) describes the process of surface tension changing over time. modernsurface tensiometerBy using high-speed sampling technology, the adsorption kinetics of surfactants can be tracked on a millisecond time scale. For example, when using the Wilhelmy Plate method to measure SDS solutions, if the instrument's time resolution is insufficient, it may miss key data in the early stages of adsorption, affecting the reliability of experimental conclusions.

2. Dynamic testing technology of surface tension meter and its advantages and disadvantages

2.1 Traditional surface tension testing methods

Different testing methods vary in measurement accuracy, time resolution, and applicability. As shown in the table below:

2.2 Technical bottleneck of dynamic surface tension meter

traditionsurface tensiometerThe main challenges in dynamic testing include:

• Mechanical response delayThe Wilhelmy Plate method typically uses stepper motors, resulting in a minimum time step of>50ms, which cannot meet the requirements of high dynamic process testing.

• Sensor bandwidth is limitedThe sampling frequency of conventional pressure sensors is less than 100Hz, making it difficult to analyze the millisecond level adsorption behavior of surfactants.

• Interface disturbance issueThe micro convection effect during the infiltration process may affect data accuracy and lead to test deviation.

3. Asha ® Technical improvement of Wilhelmy Plate surface tension meter

3.1 Intelligent correction of infiltration speed

Asha ® Technology approvedReal time feedback adjustment of platinum plate movement speedEnsure synchronization between adsorption kinetics and interface formation. Adopt the following algorithm:

vn+1=vn+k⋅∂t∂γv_{n+1} = v_n + k \\cdot \\frac{\\partial t}{\\partial \\gamma}vn+1=vn+k⋅∂γ∂t

Among them, vnv_nvn is the current infiltration rate, and γ \ \ gamma γ is the surface tension. This method enablessurface tensiometerThe time resolution has been increased from the traditional>100ms to 1ms, which helps to accurately analyze the adsorption process.

3.2 High precision measurement of piezoelectric ceramic sensors

Compared to traditional sensors, piezoelectric ceramic sensors provide faster response and higher accuracy:

In the 0.1 CMC Triton X-100 solution test,surface tensiometerEquipping piezoelectric sensors can capture the sudden drop in tension (Δ γ=15 mN/m) at t=2ms, which traditional methods cannot distinguish.

3.3 Performance improvement of dynamic surface tension testing

Adopting Asha ® technicalsurface tensiometerHas the following advantages:

• temporal resolution1ms data sampling interval, capable of analyzing rapid adsorption processes.

• Motion control accuracyThe displacement deviation of the piezoelectric actuator is less than 0.1 μ m to avoid interface disturbance.

• Dynamic correction of contact angleCalculate the contact angle by fitting the wetting curve, reducing the deviation to ± 0.5 °.

4. Limitations analysis of static testing methods

traditionsurface tensiometerThere are the following issues in static testing:

• Time matching imbalanceThe immersion pullback time (10-30 seconds) of the Wilhelmy Plate method far exceeds the adsorption time of the surfactant (<1 second), resulting in missing measurement data.

• Interface disturbance deviationExcessive infiltration speed may lead to microcirculation, resulting in higher measured surface tension values.

5. Experimental data analysis of surface tension meter

5.1 Experimental conditions

• test sampleSample1 (branched nonionic surfactant), Sample2 (straight chain anionic surfactant)

• equipment: Asha ® Technology Wilhelmy Platesurface tensiometer(Sampling frequency 1 kHz)

• environmentTemperature 25 ± 0.1 ℃, humidity 50% RH

5.2 Adsorption kinetics analysis

The time tension curves of two surfactants were experimentally measured, indicating that:

• Initial stage (t<10ms): The tension of Sample 1 decreases rapidly (72 → 58 mN/m), while Sample 2 decreases relatively slowly (72 → 55 mN/m).

• Stable stage (t>500ms): Sample 1 has an equilibrium surface tension of 40.3 mN/m, while Sample 2 has an equilibrium surface tension of 38.7 mN/m.

The adsorption kinetics parameters calculated by fitting the data are as follows:

The results indicate that the branched structure of Sample 1 reduces the molecular arrangement energy barrier and increases the adsorption rate, while the electrostatic repulsion of the sulfonic acid groups in Sample 2 affects the adsorption equilibrium.

6. Conclusion

1. Dynamic surface tension meterShould have high temporal resolution to match the adsorption kinetics characteristics of surfactants;

2. Asha ® Technological improvementssurface tensiometerBy using piezoelectric ceramic sensors and intelligent infiltration algorithms, the time resolution is improved to 1ms with a deviation rate of less than 1%;

3. This technology is suitable for the research of surfactants in industries such as coatings, inks, and cosmetics, and can provide accurate dynamic surface tension data support.