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Now and tomorrow: Self-healing paints and products enter plastics industry

SpecialChem / Jul 28, 2010

Exposures to harsh environments easily lead to degradations of polymers, paints and polymer composites. Development of micro-cracks followed by their coalescence can induce catastrophic failures of the plastics, rubbers and composites, and hence can significantly shorten structure lifetimes. Mimicking the nature, self-healing polymers target the partial or total repair of these injuries allowing a temporary or permanent functional usage. Among the industrialised breakthroughs we can quote, for example, self-healing paints penetrating automotive industry, self-healing silicone gels for electronics, the Reverlink™ range of products by Arkema based on the Supramolecular Chemistry.Bayer, Nissan, HMG Paints and others develop and commercialise self-healing 2-component polyurethane topcoats repairing scratches on painted car surfaces, including scratches from car-wash, off-road driving and fingernails. In supra-molecular chemistry, the bonds holding together small or large molecules are reversible physical bonds. Arkema’s R&D focuses on its application in the field of polymers, marketing the Reverlink™ range including semi-crystalline resins and elastomeric materials based on renewable sources. Multiple chemical or physical ways are investigated: In-situ healing systems, self-healing polymers, embedded healing agents, extrinsic systems. The chemical ways through embedded reactive healing ingredients are the most often studied using two-part healing systems micro-encapsulated or contained in hollow fibres or CNTs. The physical way using encapsulated solvent is demonstrated for thermoplastics but needs further studies for industrialisation. The physical way of intrinsic self-healing polymers is based on surface rearrangements, diffusion, wetting, reptation, randomization of macromolecules ensuring disappearance of cracks. Chemical ways for intrinsic self-healing polymers include reaction of unreacted species, broken molecule rebuilding, creation of labile bonds in lieu of chemical bonds. Advanced composites are a promising application field and promote a multitude of studies concerning, for the more sophisticated technologies, multiple times self-healing composites mimicking biological pervasive vascular network to supply the necessary healing components or high-performance composites for aerospace and defense combining the use of mendomer materials and magnetic microparticles and nanoparticles allowing to heat the composite up to its glass transition temperature by application of a magnetic field.

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