Introduction
Is your viscometer approaching the end of its life?
Are you starting to feel that your trial and error, ‘rheology-light’ approach to formulation is becoming dated?
Or are there longstanding product performance issues that you’re failing to gain traction with, where you suspect rheology may hold the answer?
If the answer to any of these questions is yes, then it may be time to assess just what a modern rheometer can do, most especially relative to a cheaper viscometer. Rheometer design and functionality has advanced considerably over the course of the last decade and today’s instruments offer an extremely broad range of test capabilities, wrapped in software that makes them accessible to less expert users. Such systems support the industrial adoption of rheology and deliver cost benefits far beyond those returned by viscometers, from R&D, through formulation and into manufacture. Here, we look at the top five measurements offered by rheometers that enhance their value relative to viscometers and provide some example studies to illustrate the potential benefits.
Reasons
- A broader measurement range – extend your viscosity flow curve
- Relevant yield stress measurement – generate accurate data for every sample type
- Oscillatory testing – characterize microstructure and control solid-liquid transitions
- Axial testing – quantify tackiness and extend viscosity measurement capabilities
- Sophisticated test sequences - delve deeper into process and product performance
Examples
- Non-drip ketchup
- Shower gels with shelf appeal
The functionality and/or shelf appeal of shower gels is routinely enhanced through the inclusion of suspended components. For these products, stability often relies on the combined action of surfactants and an associative polymer such as a HASE (hydrophobically-modified alkali soluble emulsion) polymer. By associating with surfactant micelles, these polymers can form an interconnected network with an apparent yield stress which immobilizes the suspended component in a desirable distribution. Where this is the formulation strategy, then determining an optimal level of associative thickener is clearly crucial.
- Better butter?
Spreadable butters are formulated specifically for ease-of-use when the product is removed from the fridge. Here then it is the temperature dependence of behavior that is crucial. Download the full application note to see results from a single frequency oscillatory temperature ramp performed on two butter samples: one spreadable; the other normal. The samples were evaluated over the temperature range 4°C to 35°C via small amplitude oscillatory testing using a Kinexus rotational rheometer (Malvern Instruments) with a roughened parallel plate geometry to minimise slippage. Standard loading and pre-configured test sequences were applied. The applied temperature ramp rate was 2 °C/min.
- Squeezing toothpaste
The squeeze flow behavior of toothpaste was measured to extend shear viscosity data into a commercially relevant regime inaccessible via conventional rotational testing. Tests were carried out at 25 °C using a Kinexus rotational rheometer with a 60 mm parallel plate and a pre-configured squeeze flow sequence. Measurements were made at two different gapping speeds: 2 mm/s and 10 mm/s. Sample size was 1 g (toothpaste density 1.3 g/cm3).
- A faster manicure
Many commercially available nail varnishes are effectively ‘daylight’ curing, but UV curing products – ‘hybrid’ and ‘soak-off’ gels – are increasingly popular in a market that has evolved dramatically over the last decade or so. The curing process for soak-off gels tends to involve a relatively high degree of polymer cross-linking which results in a finish with substantial resistance to acetone. A fast cure has obvious benefits, especially since these soak off products are primarily applied by beauticians, but finish is clearly critical.
Download the full Application Note as PDF
Malvern provides the materials and biophysical characterization technology and expertise that enables scientists and engineers to investigate, understand and control the properties of dispersed systems. These systems range from proteins and polymers in solution, particle and nanoparticle suspensions and emulsions, through to sprays and aerosols, industrial bulk powders and high concentration slurries. Used at all stages of research, development and manufacturing, Malvern’s instruments provide critical information that helps accelerate research and product development, enhance and maintain product quality and optimize process efficiency. Our products reflect Malvern’s drive to exploit the latest technological innovations. They are used by both industry and academia, in sectors ranging from pharmaceuticals and biopharmaceuticals to bulk chemicals, cement, plastics and polymers, energy and the environment. Malvern systems are used to measure particle size, particle shape, zeta potential, protein charge, molecular weight, mass, size and conformation, rheological properties and for chemical identification, advancing the understanding of dispersed systems across many different industries and applications. www.malvern.com Material relationships http://www.malvern.com/en/ [email protected]
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