Interpenetrating polymer network with variable crosslink density for self-healing

Activiteit: Talk or presentation at a conference


Thermally reversible chemical reactions, especially the Diels-Alder reaction, have been extensively studied for self-healing applications. To seal defects, heat is needed to shift the reversible bond equilibrium to a less-bonded state and gain mobility. However, this may lead to a non-desirable loss of structural integrity. To address this issue, interpenetrating polymer networks (IPN), combining a network of reversible covalent bonds with an irreversible network, are being studied in this work.

The IPN’s are made of an irreversible epoxy-amine elastomeric network swollen with a reversible Diels-Alder thermoset with the aim to obtain an overall thermoset like material. The idea of these IPN’s is not only to be able to self-heal without loss of structural integrity, but also to prevent macroscopic damage, at strains where a normal thermoset would fail. When a deformation is applied, the weaker reversible links break such that mainly the irreversible elastomeric network remains, which stretches to absorb the energy of the deformation, preventing crack formation. Once the deformation is removed the broken reversible bonds are brought back together, due to entropy elasticity of the elastomeric network, allowing the material to recover its crosslink density and mechanical stiffness.

Dynamic mechanical analysis has been extensively used to characterize these IPN’s, to study their mechanical response to an increasing strain and to monitor the recovery of properties on damaged samples. Repeated healing tests, on samples in which reversible bonds were broken resulting in losses of stiffness of up to 20%, have shown full recovery after healing at 90°C for 12h and 100°C for 10 min. At 80°C, 10°C below the glass transition temperature of the reversible network, decreases in stiffness of up to 10 % could be fully recovered after 36h of healing. Visual confirmation was obtained through optical microscopy. The microstructure of these IPN’s was studied using atomic force microscopy.
Periode4 jun 2019
Evenementstitel7th International Conference on Self-Healing Materials (ICSHM2019)
LocatieYokohama, Japan
Mate van erkenningInternational