Their behavior opens new possibilities in the application of thermosets, such as a self-healing material or simple processibility in a wide temperature range.
[10] Thermoplastics are made of covalent bond molecule chains, which are held together by weak interactions (e.g., van der Waals forces).
The weak intermolecular interactions lead to easy processing by melting (or in some cases also from solution), but also make the polymer susceptible to solvent degradation and to creep under constant load.
Thermoplastics can be deformed reversibly above their glass-transition temperature or their crystalline melting point and be processed by extrusion, injection molding, and welding.
[11] Given this, if the chains can be held together with reversible, strong covalent bonds, the resultant polymer would have the advantages of both thermoplastics and thermosets, including high processability, repairability, and performance.
[14] In 2011, Leibler and co-workers developed silica-like networks using the well-established transesterification reaction of epoxy and fatty dicarboxylic or tricarboxylic acids.
[11] The synthesized networks have both hydroxyl and ester groups, which undergo exchange reactions (transesterifications) at high temperatures, resulting in the ability of stress relaxation and malleability of the material.
In the work done by Hillmyer, et al., about polyactide vitrimers, they demonstrated that the more ester groups present in the polymer, the faster the rates of relaxation will be, leading to better self-healing performance.
A surfboard made of vitrimers could be brought into a new shape, scratches on a car body could be cured and cross-linked plastic or synthetic rubber items could be welded.
Vitrimers, which are prepared from metathesis of dioxaborolanes with different commercially available polymers, can have both good processibility and outstanding performance, such as mechanical, thermal, and chemical resistance.
Recent NASA-funded work on reversible adhesives for in-space assembly has used a high-performance vitrimer system called aromatic thermosetting copolyester (ATSP) as the basis for coatings and composites reversibly bondable in the solid state – providing new possibilities for the assembly of large, complex structures for space exploration and development.
[17][18] Start-up Mallinda Inc. claims to have applications across the composites market from wind energy, sporting goods, automotive, aerospace, marine, and carbon fiber reinforced pressure vessels among others.