| Résumé : |
Rheology is defined as the study of the deformation and flow of matter.1 The rheology of a fluid system governs both in-process efficiency and final product quality. It is therefore critical to the manufacturing of liquid personal care products, such as shampoo and liquid soap.
For example, if a product is too thick, problems may arise with pumping and packaging; too thin, and it may run straight through the consumer’s hands. Getting the rheology just right can be challenging from a manufacturing perspective, but is central to the product’s success
In the manufacture of these products, conventional rheometry testing typically takes place off-line, with sampling required from the process stream. This can take approximately ten minutes (depending on the number of measurement points required), not including the time needed to obtain the sample, send it to a QC lab and conduct internal checks.
Once analysed, if the product does not meet specifications, it often has to be scrapped or re-worked, resulting in large volumes of waste being generated, or excess energy being consumed. It has been estimated, that the annual product loss in liquid personal care products globally is the equivalent to two million bath tubs (around 320 million litres). A large part of this could be reduced through the use of in-line rheology measurements.
The rheological properties from off-line measurements are often also considered, with assumptions, as directly applicable to real process flows. However, this approach only provides a retrospective characterisation of a fluid sample and the measurement does not account for any changes to the sample when extracted from a process, such as cooling down and gelling or settling. It is often therefore considered unsatisfactory.
As in situ measurements are conducted within the flow environment, they deliver a direct, real-time rheology measurement, which provides essential, accurate information to plant managers and QC professionals about the product as it is being processed. Due to the critical nature of rheology in processing liquid personal care products, the ability to monitor rheology in-line, in real time could elevate rheometry from a QC tool at the process end-point to one which is able to control and optimise processes and material structures.
To realise this goal, Machin et al. developed a novel, in-pipe, tomographic measurement capable of obtaining real-time rheological information of process fluids within pipe flows.2 This is termed electrical resistance rheometry (ERR). Its ability to predict rheological parameters was validated at the industrial pilot plant of a multinational manufacturer.
The trial focussed upon the characterisation of a wide range of industrial personal and homecare products, including shampoos, fabric washes, conditioner and body washes. The aims were to compare rheological parameters obtained from ERR directly with off-line rotational rheometry and to determine its suitability to operate as an in-line quality control technique. |
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Novel in-line rheology measurement technology in GLOBAL PERSONAL CARE, Vol. 22, N° 10 (11/2021)
