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The expert's eye

At what point does a thermochromic material gain an advantage over electronics?

In many industrial fields, electronic equipment allows to obtain an unequalled precision. Today, their use is widespread. However, "all" electronics is not necessarily the ideal solution for industrial safety.

The use of thermochromic coatings is replacing thermocouples and/or thermometers: this is an industrial reality.

At what point does a thermochromic material gain an advantage over electronics?

When it is impossible to use electrical wiring

thermocouple-thermometreOne of the reasons for using a thermochromic coating in place of a thermometer and/or thermocouple may be the need to map the temperature in an environment where it is impossible to insert any electrical wiring.

This is the case, for example, in the aeronautics, space and defense industries, where thermochromic coatings are used to map the temperature gradient of an engine during operation.
The space in a combustion chamber is so small that the use of a thermocouple is absolutely unthinkable. A product such as a thermochromic paint, on the other hand, can be deposited in the combustion chamber. After drying, the engine is started, then stopped and dismantled. The irreversible nature of thermochromic paint makes it possible to analyze the gradient(s) of color change. This data gives access to the thermal map reached by the combustion chamber during operation. This information is essential for optimizing the design of future engines: limiting their fuel consumption, the release of certain gaseous pollutants and the fatigue of structures.

A thermochromic material is safe and can act in total autonomy

Technologies – OliKrom©Other fields call upon thermochromic materials for their capacity to act without electricity, in total autonomy. This type of demand occurs in particular for the storage of sensitive materials for years in the field of industrial maintenance (energy, petrochemical, nuclear...). In this case, electrical autonomy is a requirement.

Thermochromism is a thermodynamic process that acts as a passive solution. The color change occurs only when the temperature threshold is crossed.

Everything is in the initial programming of the material to present the good threshold of triggering of the switching to the temperature. Just like a living being, the color change information is written in the DNA of the thermochromic material. It is therefore a robust phenomenon that contrasts with the electronic fragility of a thermometer and/or thermocouple: failures, hacking, maintenance issues, etc.

To map an object as a whole...

In predictive maintenance and/or industrial safety, the need may be to access the thermal behavior of a large surface, an object or products in their entirety. It is the case, for example, of an industrial chimney (of an oven, a refrigerated truck...) for which we want to monitor its external temperature during operation. The use of a thermocouple and/or thermometer gives access to local information but not to the global temperature map.

On the other hand, the simple change of color of a thermochromic coating positioned outside this industrial chimney allows to identify the abnormal zones of heating. This is a simple way to monitor any shrinkage of the thermal insulation and to schedule a maintenance intervention. We are entering the world of the industry of the future, of predictive maintenance.

... or control a thermal evolution unitarily at lower cost

pigments-thermochromique-irreversibleThe thermochromic solutions approach is also selected in many sectors where unitary control is required. This is the case for example in the medical and/or food industry. Contrary to the use of a thermocouple and/or thermometer, a reversible thermochromic product with memory effect or irreversible thermochromic product allows to control the thermal evolution of an element on an individual scale, of each medicine, each packaging: to identify for example a break in the food cold chain, to attest the conformity of storage of a medicine, of a vaccine.

Another advantage of the thermochromic approach is that it combines the individual scale with ease of implementation and a low-cost solution. This is the case for all the indicators of well-being and comfort. For example, thermochromic tablets on a pizza box, a drink,... which indicate a good consumption temperature.

To meet the challenges of traceability or anti-counterfeiting

Finally, there are more subtle uses for traceability, to easily identify a break in the cold chain. A thermochromic indicator can for example be positioned at the level of a bar code. It becomes thermosensitive and can be modified by adding or removing a code in case of anomaly. This approach allows to remove an article from a supply chain, from sales without alerting (worrying) the consumer.

Finally, other uses call upon thermochromic materials to introduce security elements for the fight against counterfeiting. Depending on the needs, this can be visible. For example, a coating on a packaging that will change color if it is heated with a hot source to try to peel off a label and open a sealed document. In other cases, the thermo-reactive material is introduced and will be revealed during an authentication by an authority to demonstrate the origin of a product.

In conclusion

The applications are multiple! Many industrial fields select thermochromic materials. This approach of color modification (in case of anomaly/right temperature of consumption) has the advantage of being understandable by all, easy to use, and easy to interpret. For brands, it is often an element of differentiation. A simple way to modernize (rebrand) existing products. Bringing a note of design, innovation, interactivity with the environment, safety and consideration of the consumer's well-being.

It is however advisable to be particularly vigilant on the origin of these materials. Some families of leuco dyes, for example, available on the market may contain Bisphenol-A.

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