The Turbiscan® Stability Index from Formulaction offers fast, robust, and objective quantifying of sample evolution over time in one single click.

Since its introduction, the TSI is fast becoming the main criteria used to compare sample stability evolution, and is now extensively used in research and development, quality control and academic research.

In this blog post, we look at the following:

-    How significant is the TSI value?
-    Which value allows to consider the sample stable?
-    How much different are the samples in terms of global physical stability?

Using Formulaction’s vast experience (over 25 years) with stability and particle size characterization, and the knowledge of the static multiple light scattering (S-MLS) technology, it is possible to correlate the TSI value with a visual observation for better analysis of the TSI values and moving towards the stability prediction.
What is the TSI?

The Turbiscan® Stability Index is a dimensionless number gained by adding together all occurring destabilization phenomena in the sample that can be measured by noticeable change of the backscattering or transmission signal intensity along the sample height. These signal variations are directly linked to any destabilization in the sample, meaning that the higher the TSI value, the lower the stability.

How was the TSI scale developed?

Although the TSI provides a fast, efficient, and robust number for sample comparison, questions remain about the intensity of the destabilization and correlation with visual observation.

During Formulaction’s 25 years of experience in characterising liquid dispersions and colloidal systems, they have gathered a significant amount of stability measurement test results achieved with the Turbiscan that could be correlated with visual observation methods.

Their database contains thousands of samples of various types that their customers work with. These are both low and high concentrations, from nm to μm particle sizes, as well as emulsions and particle suspensions, and covers most of the application fields, including cosmetics, paint and coatings, food and beverages, dairy products, pharmaceutical injectable formulations, oil and lubricant emulsions.

From this large database, a TSI scale has been set to correlate a TSI number with destabilisation intensity and correlated to visual observation.

How does the TSI scale work?

While the TSI is a dimensionless number, it is a function of time. However, the time of calculation is not to be ignored when ranking samples. TSI values should be compared at the same aging time.

Once the TSI value, corresponding to a given state of destabilization, is calculated, the series of samples can be ranked and compared. The values are associated with a colour that allows for a direct analysis and sample validation, and can be seen below in the graph.

Where A+, A, B, C, and D correspond to the following key:

• A+ Visually Excellent - No significant destabilization is observed with the Turbiscan, and the sample remains visually stable. A+ ranking is the best stability mark.
• A Visually Good - Destabilization is detected but at the very early stage (migration or size variation). In the A ranking, no visual destabilizations are observed at this stage.
• B Visual Pass - The variations detected by the Turbiscan are higher than the early stage and correspond to the beginning of the destabilization. However, the destabilizations remain non-visual in most cases (>90%).
• C Visual Warning - Important stability destabilisation corresponding to large sedimentation and/or creaming, wide particle size variation, and small phase separation. The destabilisation may or may not be visible at this stage and the sample in this C ranking must be carefully monitored.
• D Visual Fail - Extreme and important variation. The destabilisation is most likely visible, corresponding to large sedimentation or creaming, phase separation, and a wide change in the particle size or colour.

How can you adjust the TSI scale?

The Turbiscan LAB, Turbiscan TOWER and Turbiscan AGS are all equipped with the latest software version, where the TSI scale can also be represented as a bar chart.

The TSI scale colour code is displayed on the LCD screen of the Turbiscan TOWER.

Since the sample validation may vary from one sample type to another, it is possible to adjust border values of the scale in order to optimise the visual validation.

For example, in oil fields an emulsion may fail the stability requirements at TSI >10, while for a vaccine, maximum acceptable TSI may not exceed 2.5.

Therefore, in these cases it is possible to adjust the values for more specific analysis. The TSI scale is based on the TSI Global.

Conclusion

The Turbiscan scale combines its benefits, such as the detection of early-stage destabilisation, non-disruptive measurement, real stability measurement, and Formulaction’s 25-year experience in measuring stability.

It correlates the TSI value with visual observation to allow even easier comparison with previous methods and helps with defining stability criteria for stability comparison and stability prediction.

Turbiscan is a unique tool providing full characterization of your formulation with an extremely wide range of applications, including electronics, polymers, raw materials, pharmaceuticals, food and beverages, agrochemicals and paint and inks.

For more information on how the TSI can assist with your own research, development and/or production, please call us on: 01442 876777 for a free, no obligation quote, or email us at: sales@fullbrook.com.

The methods, applications, and benefits of the Kemtrak DCP007 include the following:

•    ICUMSA Methods GS 1/3-7, GS 2/3-10 and GS 2/3-10
•    Determination of the solution colour of white, brown, and raw sugars as well as coloured syrups
•    Decolourisation of glucose syrups
•    A charcoal filter alarm
•    Manufacturing quality and control
•    Real time in-line continuous measurement
•    A zero maintenance LED light source that never needs replacing.

What is the ICUMSA Colour Scale and how is it used in sugar production?

The International Commission for Uniform Methods of Sugar Analysis (ICUMSA) describes a range of methods for the colorimetric determination of filtered sugar suspensions at known concentrations (Brix values).

The ICUMSA colour scale is used to measure the grade and quality of the sugar. The colour of sugar directly relates to the degree of refining – raw sugars being dark brown in colour whilst highly refined sugars are white in colour. The ICUMSA colour scale is a measurement of the yellowness of the sugar resulting from residual molasses not removed in the refining process and can be used to monitor and control the manufacturing process.

How can the Kemtrak DCP007 be applied to this process?

The Kemtrak DCP007 process photometer has a high-performance long-life LED light source, precision optical filters and robust fibre optics that results in an ICUMSA colour analyser with outstanding performance and reliability.

The Kemtrak DCP007 process photometer is recommended to accurately measure ICUMSA colour. The Kemtrak DCP007 employs proprietary dichromatic measurement technology that compensates for particulates, allowing accurate colour measurement without the need for filtration.

Due to the proprietary dichromatic four channel measurement technology, particulates in the process media can be compensated for in real time providing an accurate measure of colour without the need for filtration. A primary “absorbing” wavelength then accurately measures colour changes in the process medium, while a second reference wavelength, which is not absorbed by the process medium, compensates for particulates and/or fouling of the optical windows.

Since optic fibres are used to transfer light to the measurement point and back, the measurement cell contains no electronics, moving parts or sources of heat that result in condensation on the optical surfaces. Standard measurement cells are machined in sanitary grade stainless steel with sapphire windows.

How should I set up and configure the Kemtrak DCP007 for my own work?

ICUMSA recommend the absorption of light at 420nm for white and light-coloured sugars and 560nm for darker sugars. 720nm is recommended for the reference wavelength to measure and compensate for the turbidity of the solution.

The Kemtrak DCP007 process photometer will accurately measure ICUMSA colour for a known concentration sample using the Brix value (degrees Brix or °Bx). ICUMSA colour is calculated as follows: ICUMSA Colour = 1000 × As/b c
Where:
As = absorbency of the solution (DCP007 primary measurement)
b = the optical path-length (cm)
c = concentration (g/mL) (using the Brix value).

Colour score is expressed in RBU (reference base units) per ICUMSA standard method(s). Where an end user specific base reference is used, the DCP007 can be adjusted accordingly.

The process Brix value, measured using a separate density or refractive index analyser, is input into the Kemtrak analyser through a 4-20mA analogue input to correct for differences in sugar concentration.

As an alternative where a live density measurement is not available, process Brix values can be manually entered into the analyser.

The Kemtrak DCP007 should be configured for the desired measurement range for maximum resolution and accuracy.

An optical path-length of at least 10 cm or more is recommended for low colour white sugars, whilst shorter path-lengths are necessary for darker sugars. Please contact us directly for specific configuration details regarding measurement wavelength and selection of optical path-length for the desired measurement range.

Where can I find out more about the Kemtrak DCP007?

Head over to our dedicated webpage on the Kemtrak DCP007 for more information on this popular instrument.

To discuss your requirements or for a free, no-obligation quote, please call us on: 01442 876777 or email: sales@fullbrook.com.

What is crude oil?
 
Crude oil is a yellow-to-black liquid consisting of hydrocarbons of various molecular weights and other liquid organic compounds.

Crude oil will not mix with water, however under certain conditions crude oil will form an oil-in-water emulsion with a turbidity proportional to the oil concentration.

The Kemtrak TC007 can be used to measure:

•     0 – 10% light crude oil in water
•     Real time continuous measurement
•     Oil in produced water
•     Condensate and cooling water.

How can the Kemtrak TC007 be used to measure crude oil in water?

Crude oil in water can be accurately measured using a Kemtrak TC007 process turbidimeter.

One of the main benefits of the Kemtrak TC007 process turbidimeter is that all of the electronics, including the long-life, high performance LED light source and photodetectors, are encased within the TC007 analyser enclosure, allowing safe operation in even the most hazardous of environments.

Industrial grade optic fibres are used to transfer low power cold light from within the TC007 analyser enclosure to the sampling point and back.

As crude oil will not mix with water, it is vital that the sample under analysis has a turbulent flow to ensure sample homogeneity.

The image below shows 5% light crude oil in water directly after being shaken (left) and then after five minutes (right):

What were the results of the analysis?

The calibration below was made using light crude oil (ρ=830 kg.m -3 @15°C, ν=3.51 mm.s -1 @20 °C) between 0 – 5 % oil in distilled water.

The sample was hand shaken (5s) then immediately analysed.

How do you install the equipment to undertake this analysis of crude oil in water?

The most critical factor necessary for this analysis is a turbulent flow. It is recommended to use a narrow bore measurement cell and install this on a bypass line where water is available to zero the instrument and flush the cell when not in use. A narrow bore 1⁄4” or 1⁄2” NPT thread type measurement cell is typical for this application.

Under operation the high-speed turbulent flow will keep the sapphire windows free from deposits. When not in use the measurement cell should be flushed with water to prevent sticky deposits from accumulating on the optical surfaces.

The image below shows the Kemtrak 1⁄4” NPT industrial fibre optic measurement cell available in 316L, Monel 400, titanium or Hastelloy.

The cell has the added benefits of being maintenance free and containing scratch-resistant sapphire windows. In addition, as there are no electronics or moving parts, this makes it the perfect choice for use in hazardous areas.

Where can I find out more about the Kemtrak TC007 and its applications?

To discover more about how this popular instrument can help with colour monitoring, chemical concentration, water measurement in organics, and more, please contact us on 01442 876777 or email us at: sales@fullbrook.com.

The use of paints, inks, and coatings across a wide range of industries has continued to grow over recent years, driven by high demand from the automotive, electronics, construction and aeronautics industries.

Both water and solvent borne formulations continue to be challenged to provide more competitive and environmentally friendly materials. Those working in the industry are often searching for new, original formulas that use more sustainable materials.

This means we need to look closely at controlling the characterisation of these innovative formulations. The main benefits of applying Formulaction's Rheolaser Coating to these processes are:

•  Formulating and reformulating biocompatible and solvent free solutions
•  Gaining precise knowledge and understanding of formulations, including drying kinetics, drying steps, etc.
• Evaluating the impact of the formulation ingredients, and film formulation parameters, i.e. Temperature, Humidity, Substrate, Film Thickness, etc.
•  Determining the optimal drying protocol time, such as time and temperature.

How was the study carried out?

The experiments were performed by Rheolaser Coating High Temperature on a bi-component epoxy adhesive at different temperatures.

The Rheolaser Coating high temperature measurement is based on an optical technology - Diffusing Wave Spectroscopy (DWS). This is where a laser illuminates the coating, and the photons travel through the coating thickness and interact with the coating's scatterers (Particles, Droplets, Polymers, etc).

The different optical paths of the photons create interfered backscattered waves forming an image on the camera composed of bright and dark spots = Speckle Image.

When the coating undergoes important microscopic dynamic activity (liquid-like), the speckle image will be fluctuating, some bright spots become dark and some dark spots become bright. The fluctuation speed is directly correlated to the scatterers motion and thus to the visco-elastic properties of the material.

Thanks to our dedicated image analysis, it is possible to determine a characteristic frequency, the microscopic dynamics (μD or mD), which directly correlates to the speckle image fluctuation.

For example, figure 2.a below shows a liquid sample drying / curing at a fixed temperature over time. A high value of μD indicates fast speckle image fluctuation, corresponding to a liquid sample (fast scatterers motion). On the other hand, a low μD value is a sign of a slower evolution of the speckle image and solid-like behaviour. Therefore, it is possible to precisely monitor curing kinetics of the coating.

For powder coatings, during curing at an elevated temperature, the coating changes from solid to liquid to solid form, thus the scatterers mobility change. A μD value decrease means that the  mobility decreases and vice-versa. Examples of these can be found further down in this post. It also possible to follow the microscopic mobility versus temperature during a temperature increase.

A low value of μD indicates low speckle image fluctuation, corresponding to a steady state of the sample. On the other hand, a peak of mobility (μD) is a sign of a faster evolution of the speckle image, generally corresponding to phase transition (figure 2.b).

What were the results of the study?

1.    Determination of the different drying steps and characteristic times
Figure 3 below shows the microscopic dynamics (mD) versus time for a 100 μm thick technical paint sample at 90 °C.

The graph shows a clear identification of the different drying steps (i.e. Evaporation, Packing, Drying) and allows us to determine the characteristic times (Open Time, Tack-Free, Dry-Hard, Dry-Through).

For this sample, at 90°C and for 100μm thickness, the evaporation stage takes 1 minute (the open time), the packing finishes after 6 minutes and the sample is completely dry after 9 minutes (dry through).

In conclusion, the instrument allows us to determine the different drying steps and characteristic times from Room Temperature up to 250°C.

2.    Determination of the influence of humidity and temperature

The instrument also allows the exploration of the differences in the drying kinetics between different formulations or at different drying conditions (e.g. Temperature, Humidity, Thickness, Substrate Porosity, etc).

Figure 4 (below) shows the drying kinetics of the same technical ink under different drying conditions. This includes the same temperature but at varying humidity (as shown by the red and blue curves) and the same humidity but at different temperatures (as shown by the blue and pink curves).

For all the experimental conditions, the instrument allows the identification of the different drying steps (i.e. Evaporation, Packing, Drying, etc.) and to determine the characteristic times, as displayed in the table inset (tc1 = Open time, tc2 = tack-free, tc3 = dry-through).

At the same temperature (30 °C), the increase of the humidity (from 30% to 60%) slows down the drying kinetics (blue and red curves) and at the same humidity (30%), the increase of the temperature (from 25°C to 40°C) accelerates the drying kinetics (blue and pink curves).

The instrument is sensitive to the temperature and humidity influence on the drying kinetics. In conclusion, this solution allows formulators to optimize the drying protocol and processes.

Due to its specific functionalities, the software also allows us to easily rank the drying kinetics of different formulations, temperatures, humidity, thicknesses, and substrates.

Therefore, the faster the microscopic dynamics evolution (mDE) increases, the faster the drying.

Figure 5 above shows the microscopic dynamics evolution (mDE) versus time for a technical ink at different humidity and different temperature. The pink curve, at 40°C and 30% humidity, shows the fastest mDE increase, so the drying is the fastest. The red curve, at 25°C and 60% humidity, shows the slowest mDE increase, so the drying is the slowest under these conditions.

Here, the variable parameters were temperature and humidity, but it is possible to vary the formulation ingredients, the thickness, and the substrate. The software also provides a quantitative information, the time ‘t90’ (seen in the red boxes, inset fig. 5).

The ‘t90’ corresponds to the time when the sample’s microscopic mobility is reduced by 90%, “90% dried”. The ‘t90’ is extremely useful for a wide range of applications where there is a need to optimize the process and determine when microscopic mobility reduces by 90%, so it is then possible to start the next processing step.

For some formulations, the ‘t90’ is associated with the ‘open time’. In conclusion, this solution allows the formulators to compare, rank and screen different formulations and drying conditions.

Conclusion

Formulaction’s Rheolaser Coating offers a new in-situ, non-invasive and efficient method to better understand different materials, allowing formulator’s to:

•    Monitor and know precisely the curing and drying kinetics
•    Determine the characteristic times of the film forming process
•    Analyse from room temperature up to 250 oC with humidity control
•    Evaluate the impact of the formulation, including the temperature, the thickness, the humidity, the substrate
•    Optimize the manufacturing protocol.

Other key benefits of this new technology include:

•    Objectivity and accuracy in monitoring the curing/drying
•    The option of performing analysis on any type of substrate
•    Enables both temperature and humidity control
•    Provides in-situ and contactless measurement
•    Sensitivity to mobility at the nanometer scale.

For more information about the Rheolaser Coating, please call us on 01442 876777 or email us at: sales@fullbrook.com.

Maintaining sustainable growth while preserving natural resources is one of the biggest challenges the world currently faces.

It is predicted that by 2040, we will be using 30% more energy than we are today, which will require constant technological advances in battery production.

The battery market is expected to see substantial growth over the next few years due to:

•    A booming global automotive industry
•    Growing demand for energy storage systems and UPS systems
•    Growth of the electric vehicle market
•    Increased applications in the industrial motive sector
•    Growing consumption of rechargeable batteries in consumer electronics.

This means there is an increasing need for those working in this field to be innovative and create new solutions that can keep up with the pace of change across all these sectors.

What are the stages involved in battery production?

The battery production process can generally be broken down into the following steps:

1.    Precursor formation
2.    Chemical conversion of precursor
3.    Electrode slurry preparation
4.    Electrode manufacturing
5.    Cell assembly
6.    Cell formation and testing.

Each step is vital for the final performance and should be well characterized, optimized, and verified. Over the last few decades, innovation in this field is constantly increasing. The development and the improvement of battery efficiency we see today is due to innovative new materials and fabrication process. Therefore, the characterization of these materials is a key step to:

•    optimize performance
•    understanding the differences between materials
•    acquiring the application knowledge for the process

Overall, there are three main aspects that should be controlled:

1. The stability: the best powder-liquid dosing accuracy accounts for superior process stability and constant slurry properties and avoid batch-to-batch variations.

2. Rheological proprieties of battery slurries: tweaking the rheological behaviour of battery slurries by adjusting the operating parameters without making any changes to the slurry formulation.

3. The film formation process: after slurry application on the electrode foil, determining the best drying protocol (time, temperature) to optimize the battery’s features and production.

How was this study carried out?

The experiments were performed by Rheolaser Coating high temperature on NANOMYTE BE-45 (NCA) slurry, Lithium Nickel Cobalt Aluminium Oxide powder from NEI Corporation.

The Rheolaser Coating high temperature measurement is based on an optical technology called Diffusing Wave Spectroscopy (DWS). A laser illuminates the coating, the laser photons travel through the coating thickness and interact with the coating's scatterers (particles, droplets, and polymers).

The different optical paths of the photons induce interfered backscattered waves forming an image on the camera composed of bright and dark spots = Speckle Image.

When the coating presents significant microscopic activity (liquid-like), the speckle image will be fluctuating, some bright spots become dark, and some dark spots become bright. The fluctuation speed is directly correlated to the motion of the “scatterers” and thus to the visco-elastic properties of the material.

With dedicated image analysis, it is possible to determine a characteristic frequency, the microscopic dynamics (mD), which directly correlated to the speckle image fluctuation.

A high value of mD indicates fast speckle image fluctuation, which corresponds to a liquid sample (fast particle motion). However, a low mD value is a sign of a slower evolution of the speckle image and indicates solid-like behaviour.

With this technology, we can also precisely monitor film formation and drying kinetics of the coating. During drying or curing steps, the coating changes from liquid to solid form, meaning the viscosity and elasticity increase significantly.

As a result, both particle mobility and speckle image fluctuations decrease. The values for this vary from high mD value (liquid) to a lower plateau value (solid and no evolution of the structure), as presented in figure 1 above.

What were the results?

Figure 3 below shows the microscopic dynamics (mD) versus time for different sample thicknesses (100 and 250μm) and different temperatures (50 ℃ and 100°C).

From the sudden decrease of the mobility (mD), the characteristic ‘open time’ can be determined. The ‘open time’ is influenced by the wet film thickness and temperature. At the same temperature (50 °C for example), the open time Tc of the thinner sample (100μm, green) is shorter than the Tc of the sample 250μm thick (blue). The same influence is valid at 100 °C.

This result shows that the instrument allows to monitor the battery’s slurries microscopic dynamics (mD) at different drying conditions providing a characteristic time, Tc, which could be tuned by the formulation or other process parameters (Sample Thickness, Temperature, Humidity, etc.) to fit the best with the fabrication process needs.

Another interesting information is the exact determination of the drying time, the time when the mobility (mD) of the sample reaches a steady state (a plateau). To do so, we will focus on the time when the mD reached a plateau at 10-3 (Hz) (as shown in Figure 4).

When the mD level reaches a plateau at 10-3 (Hz) the sample dynamics contribution is almost negligible, indicating that the sample is completely dry. So, it allows the measurement of the drying time Td.

Figure 4 shows that the drying time is influenced by the thickness and temperature. At the same temperature (100°C for example), the drying time (Td) of the thicker sample (250 μm, yellow) is longer than the Td of the sample 100 μm thick (red).

The same influence is valid at 50 °C. To facilitate the ranking of different formulations or other process parameters influence on the drying (Thickness, Temperature, Humidity...), the software allows the measurement of the microscopic dynamics evolution, mDE (Figure 5).

The curves (Figure 5) correspond to the areas under each mD curve (Figure 4) at a selected time window. The mDE is directly correlated to the drying speed. The faster the mDE reaches 100%, the faster the drying.

This result provides more statistics that allow us to rank the mobility of different formulations or other process parameters and their influence on drying time. Figure 5 shows a ranking in agreement with the drying times determined for the different samples (Figure 4).

The software also allows us to determine another characteristic time, ‘t90’, where the slurry’s microscopic mobility decreases by 90% (inset figure5). For this slurry, the ‘t90’ is very close to the ‘open time’ identified in Figure 3 (‘t90’ ≈ ‘Tc’) due to the significant decrease of the mobility (Figure 3).

Conclusion

The Rheolaser Coating high temperature presents an in-situ, non-invasive and useful method to better understand your different materials, which allows:

•    The monitoring and precise knowledge of the curing and drying kinetics
•    The determination of the characteristic times of the film forming process
•    The evaluation of the formulation parameters impact on the film formation
•    The optimization of the manufacturing protocol according to different substrate materials.

 Stabilizing beverage emulsions is a challenging task due to:

• emulsions can be highly concentrated
• variation in raw material quality
• resistance to dilution
• low viscosity

Emulsion destabilization can also include size variation which will affect the taste and the long-term stability (or ‘ring’ formation), as well as particle migration (i.e sugar, pulp, proteins, etc). These phenomena may lead the consumer to consider the product as poor quality.

Therefore, it is important to understand and enhance the stability of such products, to ensure the best customer perception and the conservation of flavour.

Turbiscan Technology Applications

Formulaction’s popular Turbiscan Technology can be used for a variety of applications, including the following:

• Dairy products – quantifying and detecting characteristic destabilisation of milk-based products, determining droplet size variation, creaming of fat droplets, sedimentation of calcium or chocolate particles.
•  Flavour emulsion – the kinetics of coalescing without the necessity to dilute the sample.
•  Soft drinks – detection of ring formation, colour change, pulp/sugar/protein sedimentation.
•  Desserts – detect destabilisation phenomena of cream, dessert foam, ice cream, etc.
• Raw materials – Rapid monitoring of the efficiency of stabilisers, thickeners, etc.

In addition to these applications, this Turbiscan technology also has the following strengths:

• The shortening of analysis times, which can be up to 200 times faster than a visual test.
• Detect and quantify any type of destabilisation, e.g sedimentation, flocculation, creaming, agglomeration, size variation, etc.).
• Use of the Turbiscan Stability Index (TSI) to enable quick comparisons of different samples, ranking of the samples according to stability. The higher the TSI, the lower the stability.
• No dilution and non-intrusive analysis allows determination of real shelf life.
• A temperature range from 4 °C to 80 °C.
• An objective method with graphical and numerical data.
• Quick screening of formulations.

Summary

Formulaction’s Turbiscan Technology has been used in over 1200 publications to date, and over 200 patents across more than 50 countries. Some of these include:

•  The Effect of Fat Content on the Creaming of Milk
•  Formulation of Chocolate Milk
•  Use of the Turbiscan for Measuring Foam Stability Properties of Food Ingredients.
•  Particle size and stability of UHT bovine, cereal and grain milks.
•  Impact of Weighting Agent and Sucrose on gravitational Separation of beverage Emulsions
•  Factors Affecting Initial Retention of Microencapsulated Sunflower Seed Oil/Milk Fat Fraction Blend.

To find out more about the Turbiscan Technology and how it can help your research and development, please call us on: 01442 87677 or email: sales@fullbrook.com.

We will also be happy to discuss your requirements further and provide a free no-obligation quote.

Recently, the powder coatings market has seen significant growth, and is used across a wide range of industries. Normally, the powder coating process involves putting a coating on an item electrostatically, which is then cured by heat. However, this process is developing further due to:

•    The finish being harder and tougher than standard paint and guarantees an excellent chemical resistance.
•    These industries are searching for more eco-friendly and sustainable systems

However, the nature of powder coatings means that you need to bear in mind special properties to avoid defects such as the orange-peel effect.

How can the High Temperature Rheolaser Coating help?

This new technology from Turbiscan can assist by:

•    Development of  low energy curing formulations
•    Using greener ingredients that comply with environmental regulations and their impact on the curing process
•    Optimising the gel time by following the curing kinetics.

How were the experiments in this study carried out?

The experiments were all performed with the high temperature Rheolaser Coating on different powder coatings, using different temperatures and different experimental protocols.

Based on an optical technology called Diffusing Wave Spectroscopy (DWS), the instrument uses a laser to illuminate the coating, whereby the photons travel through the coating thickness and interact with any scatterers.
The different optical paths of the photons create interfered backscattered waves. This forms an image on the camera composed of light and dark spots and is referred to as a “speckle image”.

When the coating presents important microscopic dynamics activity (liquid-like), the speckle image will be fluctuating, meaning some bright spots become dark and some dark spots become bright. The fluctuation speed is directly correlated to the scatterers motion and thus to the viscoelastic properties of the material.

Using dedicated image analysis, it is possible to determine a characteristic frequency, the microscopic dynamics (μD or mD), which directly correlates to the speckle image fluctuation.

For example, figure 2.a below shows a liquid sample going to dry/cure at an imposed temperature over time.

A high value of μD indicates fast speckle image fluctuation, corresponding to a liquid sample (fast scatterers motion). On the other hand, a low μD value is a sign of a slower evolution of the speckle image and solid-like behaviour. Therefore, it is possible to precisely monitor the curing kinetics of the coating.

For powder coatings, during curing at an imposed temperature, the coating changes from solid to liquid to solid form, thus the scatterers mobility change. A μD value decrease means mobility decrease and vice-versa.

It also possible to follow the microscopic mobility versus temperature during a temperature increase. A low value of μD indicates low speckle image fluctuation, corresponding to a steady state of the sample. On the other hand, a peak of mobility (μD) is a sign of a faster evolution of the speckle image, generally corresponding to phase transition (figure 2.b below).

There is an example of powder coating microscopic mobility evolution versus temperature during a temperature increase in section one of the results below.

What were the results of the experiments?

1. Detection of characteristic temperatures: Determination of the optimal curing temperature

Figure 3 below shows the microscopic dynamics (mD) versus temperature. The sample is a 400μm thick white powder coating heated from RT to 250°C. The graph shows a clear identification of the different curing steps.

Around 50°C a first peak appears due to the mobility increase during the particle’s deformations. At around 80°C, the peak corresponds to the coalescence of the film. Starting from 125°C, the thermal energy allows the curing and the creation of the three dimensional thermoset network. After the curing and the film formation, an expected peak appears around 250°C. The final dynamics increase is due to the polymer decomposition.

To verify the physical correspondence of the different pics (fig. 3), a visual inspection was done after different curing temperature (fig. 4).

If the curing temperature is less than the decomposition temperature (200°C for example), the coating will form a smooth white film. But if the curing temperature is 250°C, the coating formed will be uneven and brown.
Thus, from the microscopic dynamics (mD) versus temperature (fig. 3), it’s possible to determine the optimal curing temperature.

2. Detection of characteristic curing time and influence of the temperature on the curing process

To go further and fine tune the results presented previously, the instrument allows the study of the microscopic mobility versus time at a fixed temperature. Figure 5 below shows the microscopic dynamics (mD) versus time for the same white powder coating discussed in section 1 at 125°C and 400μm thick. The inset image is a zoom on the first 5 minutes.

When the sample is heated to 125°C, the microscopic mobility increases (during ≈10s, inset fig. 5) because of the polymer melting.

Then, when the polymer has melted, the curing starts, the three dimensional thermoset network forms and the microscopic mobility decreases. For this sample at 125°C, the microscopic mobility (mD) decreases, and achieves a plateau after around 4h.

Looking more closely at this, figure 6 below shows the microscopic dynamics (mD) versus time for curing of the same sample, and same sample thickness, but at 3 different temperatures. The inset is a zoom on the first 5 minutes.

The inset of figure 6 allows a focus on the early stages (i.e. the first 5 minutes) of the curing. For the different curing temperatures, the mechanisms observed are qualitatively the same. Firstly, the microscopic mobility increases because of the polymer melting (for the first ≈10s). Then, when the polymer is melted, the curing starts, the three dimensional thermoset network forms and the microscopic mobility decreases.
 
An interesting discrimination is detected later in the experiments at longer times (fig. 6). At 125°C the curing takes around 4h for this sample (blue curve). If the curing temperature is increased to 200°C (  green curve) takes around 1h to reach the same plateau level. So, by increasing the temperature from 125°C to 200°C, we can reduce the curing time from 4h to 1h, thus increasing the speed of manufacture.

However, if the curing temperature increase continues (to 250°C, red curve fig. 6), the sample presents an expected increase of the mobility after 30 minutes. This is due to the polymer decomposition at this temperature, which confirms the result observed in section 1. Most importantly, this instrument allows the formulators to optimize the curing protocol.

3. Detection of characteristic curing time and the influence of the formulation on the curing process

Figure 7 below shows the microscopic dynamics (mD) versus time for 4 different powder coating formulations: Epoxy resin, Polyurethane resin, Polyester resin and Hybrid. All the samples are applied at the same thickness (400μm) and analysed at the same temperature of 200°C.

When the samples cure at 200°C, the microscopic mobility increases during the early stages because of the polymer melting. Then, when the polymer is completely melted, the curing starts, the three dimensional thermoset network forms and the microscopic mobility decreases.

The graph above shows a clear difference between the different samples and the sensitivity of the technique. The instrument is also able to distinguish the curing kinetics an d the differences between the different formulations (i.e. different polymers or different additives).

The software provides a smart way to rank the curing kinetics of different samples (or different curing temperatures, different polymers, different substates, different formulations, etc).

Figure 8 below shows the microscopic dynamics evolution (mDE) versus time for the 4 different powder coating formulations.

This means we can easily rank the curing kinetics of the different formulations. The faster the microscopic dynamics evolution (mDE) increases the faster the curing. The software also gives a quantitative information corresponding to the time ‘t90’ (in the inset red boxes in Figure 8) where the sample microscopic mobility is reduced by 90%.

For these materials, the ‘t90’ is very close to the end of the melting time, and the start of the curing, due to the important change of the mobility at the end of the coalescence.

The solution then allows you to compare, rank and screen different formulations.

Conclusion

In summary, the high temperature Rheolaser Coating offers a new in-situ, non-invasive and efficient method to better understand the different materials you work with. Allowing you to:

• Monitor and know precisely the curing and drying kinetics
• Determine the characteristic times of the film forming process
• Analyse from room temperature up to 250 degrees with humidity control
• Evaluate the impact of the formulation, time and temperature parameters on the formation of materials
• Optimize the manufacturing protocol.
  

To find out more about the high temperature Rheolaser coating, please contact us on 01442 87677 or email us at: sales@fullbrook.com.

In this post, we discuss how the Turbiscan Stability Index (TSI) from Formulaction can help you establish surfactant efficiency and emulsion stability.

The objective of this study was to analyse the influence of various parameters on the stability of emulsions including surfactant choice, temperature and concentration, using the Turbiscan AGS and Tower as well as the TSI.

What are emulsions?

Emulsions are defined as unstable colloidal systems that may experience many destabilisation phenomena, such as flocculation, creaming, and coalescence, that can be caused by a variety of reasons, including lack of surfactant to stabilise the interfaces, and attractive forces, etc.

This means that if you are formulating an emulsion, it is important to know the origins of these processes and how to overcome them, to achieve a stable final product.

Due to the presence of small and big droplets, as well as chemical interactions - droplets tend to flocculate, although the addition of surfactants may minimise this problem.

This study investigated how different surfactants influenced the flocculation of the droplets, as well as the effect of surfactant concentration and the storage temperature.

What was the measurement protocol?

An O/W emulsion was formulated using oil (triglyceride) , 1% xanthan, and one of two additional non-ionic surfactants with different lipophilic chains. These were Tween 80 (HLB 150 and Tween 65 (HLB 10.5).

A reference emulsion was also studied, with no additional surfactant present.

How were the destabilisation phenomena detected?

Using the Turbiscan technology, destabilisation phenomena were detected in these formulations, showing evidence of pure coalescence in the samples without any droplet migration.
How were the phenomena quantified?

The TSI can monitor the coalescence kinetics in the samples versus ageing time. It does this by adding up all the variations detected in the sample (size and/or concentration). At any given ageing time, it was found that the higher the TSI, the more inferior the stability of the sample.

The effect of both surfactants can be compared to the reference, which showed that Tween 65 has no influence on the stabilisation of the coalescence in this sample, as its HLB is not high enough to play a stabilising role. This is compared to Tween 80, which significantly decreases the kinetics of coalescence.

This means that to increase the stability of the emulsion, surfactant Tween 80 must be added to this formulation. However, it’s important to remember that the surfactant is an expensive part of the final product, and the global stability is not proportional to the amount of surfactant.

As a next step, we then need to identify the optimal amount of surfactant to achieve the best stability for the lowest price.

How was this determined?

An analysis was made with a 0%, 0.5%, 1% and 2% of surfactant, and the TSI was computed for each formulation after 1 day of ageing.

The results showed that the optimum amount of surfactant for this particular formulation is 1%. The TSI was similar for the 2% of surfactant, which shows that increasing the upper limit beyond 1% is unhelpful for stability and increases the cost for no reason.

Summary

The Turbiscan allows the qualification of the best surfactant for a given emulsion to minimize the coalescence rate. This is possible in all types of concentrated dispersions without dilution, by comparing different formulations and optimising the best one.

The Turbiscan also provides a unique tool for monitoring the kinetics of system destabilisation, and quantifying it accurately after identifying the phenomena.

Inline process refractometers and sensors can perform industrial measurements continuously, and in real time. This technology is also known as PAT (Process Analytical Technology), and here at Fullbrook Systems, we provide Schmidt & Haensch’s leading range of inline refractometers that allow you to monitor and control your processes without product loss or process divergence.

With Schmidt & Haensch’s process refractometers, quality control and the determination of liquid concentration and mixing ratios becomes simple. Measurements are always reliable and independent of turbidity, colour, absorption, and viscosity. This ensures the highest precision and improved process control.
How does Process Analytical Technology work?

Process Analytical Technology (PAT) is a manufacturing methodology for high value chemicals and pharmaceuticals. Critical Process Parameters (CPPs) and Key Performance Indicators (KPIs) of the process are comprehended, well-defined and continually monitored to ensure that the pre-defined Critical Quality Attributes (CQA) of the final product are consistently achieved.

PAT measures key quality and performance indicators in both raw and in-process materials in real-time. A well-designed PAT-based process is stable, ensuring that the critical parameters and indicators remain within pre-described limits to safeguard product quality and process safety.

What instruments does the range include and what are their benefits?

The current range of Schmidt & Haensch inline refractometers include:

• iPR-EX – this provides permanent inline real-time measurement of the concentration of dissolved solids and is suitable for all applications in explosion-proof areas.
• SENSO REF Compact Refractometer – this high precision, compact instrument opens a new field of miniaturization for process refractometers. With a new optical design, the actual sensor is the size of a golf ball.
• iPR Compact² Refractometer – a precise, fast, and reliable refractometer offering permanent, real-time concentration measurement of dissolved solids in solutions or liquids in process.
• iPR-B³ – this automatically operating process refractometer measures the refractive index continuously and thus, the concentration of a binary or quasi-binary liquid mixture. The measurement is independent of light intensity from the light emitting diode (LED) and is free from signal drift, providing high precision, and thus better process control. The newly developed process refractometer iPR B³ replaces the well-established iPR Basic².
• iPR-FR² - this flagship refractometer is outwardly indistinguishable from the iPR-H2, although the integrated optics and electronics are designed to provide a very wide measuring range from 1.3200 – 1.5300 RI (0-100 Brix). With a resolution of 0.01 Brix, and an accuracy  of +/- 0.05 Brix. Due to its integrated water-cooling system, measurements at process temperatures of up to 150 °C are easily achievable.
• iPR-HR² - offering the highest resolution and precision, this refractometer can be applied to very low solid concentrations.

Look at our inline refractometer comparison chart to quickly compare the differences between each instrument, and see which one will suit you best:

Which industries can these refractometers be applied to?

The refractometers from Schmidt & Haensch can be used in the following industries:

• Food and beverages – for the quality control of chocolate, coffee, yoghurt, honey, and other food additives, as well as the dilution or evaporation process control in the juice and jam industries.
• Chemical, petrochemical, and chemical fibres – this includes the concentration measurement of solvents in chemical fibre production, such as sulphuric acid and caustic soda.
• Sugar, starch, and sweeteners – carry out the Brix measurement of cane sugar, beet sugar, starch and molasses, monitor crystallisation processes or impurity detection in condensate.
• Biofuels – monitor your bio-extraction and fermentation processes, and measure the concentration of gelatine, glue, citric acid, and lysine.
• Pharmaceuticals – monitor chemical reactions and use for the quality control of final products in accordance with Pharmacopoeia requirements.
• Pulp and paper – measure the concentration of modified starch for sizing paper production and monitor the recovery process of black liquor.
• Tobacco – monitor your washing baths, flavours, and fragrances control, and measure the concentration of active ingredients during extraction.
• Semiconductors and electronics – monitor the purity of solvents and other chemicals used for etching or cleaning in LCD displays and chip manufacturing.
• Mechanical processing and the mining industry – measure the concentration of coolants and the dosing of cutting oils and lubricants.

To find out more about how our inline refractometers can help you, please call us on: 01442 876777 or email us at: sales@fullbrook.com where we will also be happy to provide you with a free, no obligation quote.

Adjuvants such as Aluminium Salt (Alum) are often added to vaccines to enhance their immune responses. These adjuvants can aggregate and settle over time due to their electrical charges.

This can result in a compact sediment that can be difficult to redisperse depending on the strength of the bonds between the particles. If this occurs within the shelf life, the following problems present themselves:

• Knowing whether the injected dose remains the same, i.e., do all active ingredients pass through the needle of the syringe despite the large, compacted aggregates?
• Or is it the case that the therapeutic efficacy and the immunogenicity are reduced (i.e., the masked antigen in the aggregate does not get injected).

How does the Turbiscan technology in this study work?

Based on Static Multiple Light Scattering, the Turbiscan technology works by sending a light source into a sample and acquiring the backscattered and transmitted signal all over its height. By repeating this measurement over time at adapted frequency, the instrument enables us to monitor physical stability. The signal is then linked directly to the particle concentration and size according to the Mie theory, knowing the refractive index of continuous and dispersed phase.

What methods were used in this study?

To prevent the loss of immunogenicity, the solution is subjected to a controlled flocculation (by variation of the pH or ionic strength). This results in weakly-bonded particles that form a loose flocculation and produce a low-density sediment (containing a large amount of water) that is then easy to redisperse.

Conventional method: Sedimentation Volume Ratio (SVR)

The conventional method to determine the flocculation tendency of vaccines is to measure the height of the sediment (SVR) on completion of suspension settling after 24 hours. The SVR is the ratio of the settled sediment height to that of the initial suspension. A higher SVR value should translate to better suspendibility as the sediment is less compact. This ratio can be measured with the Turbiscan from via the evolution of the backscattering signal.

New method: Settling Onset Time

Although the conventional SVR method is reliable, it is unfortunately still too long for quality control or routine testing. The new Settling Onset Time method is more convenient due to its quick response time (less than 30 minutes).

The Settling Onset Time corresponds to the time to reach 50% of the clarification of the suspension (50% of maximum light transmitted through the sample). Settling Onset Time is then determined from the transmission signal by determining the time for which clarification area at 50% of transmission gets higher than a few millimetres.

To validate the new Settling Onset Time as a new screening method, the relationship between SVR at 24 hours and the Settling Onset Time was determined with suspensions of AIPO4, at a different pH (3 to 9), ionic strength (0 to 1000 mM NaCl) and either with or without the model antigen (BSA or lysozyme).

How were measurements carried out?

Turbiscan measurements were made using 20mL of suspension in a flat-bottom cylindrical glass vial, and each data set was collected over a period of 24 hours.

The Settling Onset Time after 30 minutes and the sedimentation volume ratio (SVR) after 24 hours for each sample were obtained from the transmission and the backscattering data, respectively.

What were the results of the study?

The results showed a 2-slope curve depending on whether the system is flocculated or deflocculated.

1. When the suspension is deflocculated, (e.g., low pH and without NaCl) the AIPO4 particles remain as discrete units resulting in a slow sedimentation rate. This then prevents the entrapment of solvent within the sediment. Here, it tends to compact to a hard cake and is difficult to redisperse. This is reflected by a low SVR value.

2. In a flocculated suspension (e.g., medium to high pH and/or high ionic strength), the loose structure of the floccs is difficult to preserve in the sediment that contains a large amount of entrapped water. The volume of final sediment is relatively large, reflected by a larger SVR. The sediment rate is high and is strongly dependent on the flocculation level.

Controlling these properties guarantees a good redispersion of the sediment and by extension its immunogenicity. The lower the Settling Onset Time, the more powerful the therapeutic efficiency.

Conclusion

The Turbiscan can help researchers design a correctly flocculated Alum-containing formulation. By varying the pH, ionic strength, and the quantity of antigens, it is possible to identify the ideal conditions that favour a flocculated system. The use of the settling characterisation methodology outlined above supports this decision.

The Settling Onset Time and SVR data from the Turbiscan analysis identified the transition zone between the flocculated and deflocculated states of AIPO4 formulations.

Finally, since the analytical time is much shorter, the Settling Onset Time values can replace the SVR data, as it is more adapted to formulation screening activities.