SELF-HEALING ELASTOMERS
BY ANKE NELLESEN, MAX VON TAPAVICZA, JÜRGEN BERTLING
Elastomeric polymers are used nowadays in a broad variety of highly demanding applications. Due to alternating loads, microsized cracks leading to failure of components may occur in the material, even before its loading- and lifetime-limit. Equipping of technically relevant elastomers with a self-healing agent would be a promising strategy to avoid this problem. Such a ma- terial should be able to prevent further growth of the crack and to seal parts of, or even the complete microcrack, to restore the mechanical properties.
The idea to equip an elastomeric matrix with a self-healing agent is bio-inspired: In case of damages, a variety of plants segregate latex particles and proteins that crosslink in an addition reaction and close the fissure.
The elastomers investigated in this research are EPDM (ethylene propylene diene-terpolymer type M), NBR (nitrile butadiene rubber) and SEBS (styrene ethylene butadiene styrene), a thermoplastic elastomer. It was found that blending the elas- tomeric matrix with middle- or high molecular polymers leads to distinctive self-healing results for EPDM and SEBS. Another presented, but not successful, strategy is the partial microencapsulation of two-component adhesives. The most promising results were found for ionic elastomers, so-called ionomers, some of which were able to restore its elongation at break completely compared to the undamaged material.