Sequence showing how a complex-shaped object is made by successively deforming and heating it.
PARIS, FRANCE: Resins are used for their lightness, strength and resistance in sailboards, aircraft and electronic circuits. However, these resins can no longer be reshaped. Only certain inorganic compounds, including glass, offered this possibility until now. Combining such properties in a single material was done by a team led by Ludwik Leibler, CNRS Researcher at the Laboratoire “Matiere Molle et Chimie” (ParisTech) who developed a new class of compounds capable of this remarkable feat.
These materials are repairable, recyclable and reshaped in a reversible manner at high temperature. And, quite surprisingly, it also retains certain properties specific to organic resins and rubbers. It is light, insoluble and difficult to break. Inexpensive and easy to produce, this material could be used in numerous industrial applications, particularly in the automobile, aeronautics, building, electronics and leisure sectors.
Replacing metals by lighter but just as efficient materials is a necessity for numerous industries, such as aeronautics, car manufacturing, building, electronics and sports industry. Due to their exceptional mechanical strength and thermal and chemical resistance, composite materials based on thermosetting resins are currently the most suitable. However the definitive shape of the part to be produced. In fact, once these resins have hardened, welding and repair become impossible. In addition, even when hot, it is impossible to reshape.
This is because glass is a unique material, once heated, it changes from a solid to a liquid state in a very progressive manner (glass transition), which means it can be shaped as required without using moulds. Conceiving highly resistant materials that can be repaired and are infinitely malleable, such as glass, is a real challenge both in economic and ecological terms. It requires a material that is capable of flowing when hot, while being insoluble and neither as brittle nor as “heavy” as glass.
Researchers from the Laboratoire “Matiere Molle et Chimie” developed a novel organic material made of a molecular network with original properties: under the action of heat, this network is capable of reorganizing itself without altering the number of cross-links between its atoms. Like silica and some inorganic compounds, this novel material also goes from the liquid to the solid state or vice versa. The material thus acts like purely organic silica. It is insoluble even when heated above its glass transition temperature.
Remarkably, at room temperature, it resembles either hard or soft elastic solids, depending on the chosen composition. In both cases, it has the same characteristics as thermosetting resins and rubbers currently used in industry, namely lightness, resistance and insolubility. Most importantly, it has a significant advantage over the latter as it is reshapeable and can be repaired and recycled under the action of heat. This property means it can undergo transformations using methods that cannot be envisaged either for thermosetting resins or for conventional plastic materials.
This work was supported in particular by CNRS, ESPCI ParisTech and the Arkema group.
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