Materials that change color with pressure
OliKrom is the industrial leader in custom materials that change colors under pressure.
Every day, we design and produce smart pigments and dyes, and formulate inks and paints. We adjust the hue to detect impact or deformation.
A piezochromic coating (from the Greek piezô "to press, to squeeze" and chromos "the color") is by definition made of a pigment/dye whose optical properties change according to macroscopic mechanical stimuli (pressure, shock, impact). By experience, we know that there is still a significant gap between the market expectations and the technological maturity acquired by piezochromic materials.
As soon as you give us a request, our teams study your specifications, your industrial environment, your regulatory and economic constraints, etc.
This analysis allow us to select the generation of piezo-sensitive materials best suited to your request and your deposition technique.
We then produce your customized piezochromic pigment and/or dye, then we formulate the piezo-sensitive ink and/or paint.
The piezochromic properties are controlled at each step, and rectified if necessary, to deliver at the end of the development a compound that meets your expectations.
With 15 years of experience, our expert chemists and engineers have developed many chemical examples based on organic compounds, organometallic complexes, inorganics, polymers and polymer composites. Each of these families has its advantages and disadvantages.
Everything happens at the molecular level. The physical phenomenon responsible for piezo-induced effects is a modification of structures. The mechanisms involved are mainly molecular reorganization within a solid (iron, cobalt, copper, molybdenum derivatives...); modification of chemical structures containing an open/closed form, a cyclization, a process of isomerization of E/Z double bonds.
According to the specificity of your request, our teams program the piezosensitive compound. By chemical modification, we adjust the sensitivity threshold at the pigment scale and modulate the optical properties in the ultraviolet, visible and/or infrared regions.
We distinguish two main classes of piezoreactive compounds, depending on whether the transition is reversible or irreversible.
Modification of the colors following the application of a pressure, and return to the initial coloring when the stress returns to its initial level. Possibility to adjust the optical properties, the threshold value with the percentage of deformation, elongation.
Definitive transition above a defined pressure threshold (of shock effects). Possibility to adapt the threshold (energy) of triggering, the coloring between the initial state and final state.
Thanks to molecular engineering, our team will program the material as closely as possible to your project. To obtain the reversible or irreversible character, we will finely modulate the proportion of organic or inorganic entities within the piezochromic material:
- The organic material provides the degree of flexibility required to ensure the speed of the phenomenon and the absence of fatigability.
- The inorganic component provides the "light resistance".
We will then adjust the colourchanging threshold, its speed, the colors involved..... Every day, our teams create new pigments and custom colorants based on piezochromism.
It is a subtle balance to create, to control and adapt the piezochromic property according to your need, your targeted product.
In the field of piezosensitive pigments and dyes, the formulation stage (preparation of inks and paints) is critical. It is too often neglected due to a lack of knowledge of the physical processes involved: materials science, thermodynamics...
We know that the application of shear forces associated with the passage of the tricylinder and / or ball mill can modify the crystallinity of the particles. That a simple additive, that a simple variation of the polarity of the medium and/or the pH can affect the thermodynamic equilibrium at the origin of the phenomenon of colorchanging, or the optical transitions by modifying the respective positioning of the electronic states.
This ultra-reactivity of piezosensitive pigments and/or dyes to their environment, obliges us to check at each step of the formulation, the maintenance of the smart property.
This also explains why :
- we create our own piezochromic pigments (dyes)
- but only supply our products in the form of inks, varnishes and paints,
- to guarantee the performance of the coating, the application of the piezosensitive product (spray gun, airbrush...).
All our products are manufactured on our ISO 9001 certified industrial site in Pessac, France, according to rigorous manufacturing processes and under the permanent supervision of our quality manager.
Each batch is traced and accompanied by a performance certificate. Any deviation is recorded, analyzed and corrected as part of our continuous improvement policy.
By experience, we know the main pitfalls encountered with pressure-induced derivatives: the evaluation of the right threshold, the loss of properties during the formulation and/or the industrial process, the low coloring power, the fatigability of the process, the toxicity of some constituents, the presence of thermochromic effect, etc.
In the world of smart materials, our team accompanies you from A to Z, from the idea to the final pressure-induced compound. This allows us to intervene effectively at each stage of the project: research and development, pre-industrialization and industrialization.
Aeronautic, space, Defense
In the aeronautical, space and Defense fields, the use of piezochromics coatings is studied to control the health of composite structures.
Over the last decades, the adoption of composite materials has been increasing (airplanes, helicopters, engines, missiles). This craze can be explained by the advantages of these materials over metallic compounds: their high stiffness and specificity, which allow for lighter and more efficient structures, great flexibility in design, and fatigue resistance.
One of the fundamental issues is the health control of structures and the early detection of damage. This is generally done either by visual inspection or by various non-destructive testing (NDT) methods such as ultrasonic, eddy current, etc.
The use of piezochromics coatings on the surface of a composite allows to associate a color modification to the damage (threshold value). According to the request, the impact can affect the absorption and/or emission of a luminescence signal.
Piezosensitive coatings in aeronautics represent a first level of surveillance allowing a controller to quickly detect an anomaly.
In the field of industrial maintenance (energy, petrochemical, nuclear...), the use of piezosensitive derivatives is also of great interest for the visual detection of potential shocks or deformations of some industrial parts : high/low sensors at the surface.
Among the potential sectors of such smart sensors, we can mention the oil industry (pipelines, tubes, bars, welds, tanks), the naval industry (control of hulls), the automotive industry (control of engine blocks), the steel industry, the boiler making and the piping in manufacturing.
The development of piezoreactive sensors also interest the energy sector: nuclear reactors, boilers, piping, turbines, etc. (maintenance of installations), the railway industry in manufacturing and maintenance, particularly for safety components (axles, wheels, bogies), civil engineering and construction...