Self-Healing via UV Light
At the University of Southern Mississippi in Hattiesburg, researchers have developed a new polyurethane (PU) system with self-healing properties. Additives contained in the material allow mechanical surface blemishes such as scratches to "heal" as the result of chemical reactions induced by UV radiation. The reactions are triggered by two additives in the PU, oxetan and chitosan. Oxetan is a cyclic ether with an oxygen atom in the ring. Chitosan is a naturally occurring polyaminosaccharide derived from chitin.
If the material is objected to excessive mechanical stress, the oxetan rings break at the damaged location, creating reactive groups. Upon exposure to UV radiation, the chitosan forms new ether compounds in the polyurethane network. The UV radiation used in the experiments corresponds roughly to that contained in sunlight. The healing process for scratches in the surface takes between 30 and 60 minutes.
Compared to other self-healing polymer systems, the benefit of the newly developed material is that no change in temperature is needed to activate the cross-linking reactions. In addition, only relatively small amounts of the oxetan and chitosan additives need to be added to the PU system. An additional benefit is that both additives are available at relatively low costs. The researchers see potential future applications as coatings primarily in the automotive, packaging, electronics and medical technology sectors.
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