Depleting conjugated C C bonds in tung oil/Eucommia rubber composite film: Fundamentally improve the flexibility and crack resistance for high-performance protective coating

Abstract

Extending the range of coating materials is a great challenge for sustainable societies. Tung oil generally forms compelling antibacterial and anti-insects coatings, which, however, are difficult to durable due to their intrinsic brittleness. This is because superfluous conjugated CC bonds and the excessive self-crosslinking of molecular chains encourage the rigidity of the polymer network. Herein, we report a design concept of consuming the conjugated trienes on tung oil molecules by the Diels-Alder reaction to enable tung oil/Eucommia rubber composite coating (ERTO) to achieve extraordinary flexibility. A key was to use Eucommia rubber, which can not only consume conjugated CC bonds to suppress self-cross-linking of the tung oil network but also act as a supple segment to form a flexible interpenetrating network with the tung oil molecular chain, rendering the fundamental improvement of the flexibility for ERTO. The results show that ERTO achieves excellent flexibility (easily withstands 180° repeatedly folding), higher stretchability (9.63%), and strong toughness (21.54 MPa). Moreover, the ERTO-based coating exhibits outstanding corrosion resistance (corrosion resistance period up to 7 days) and unprecedented antibacterial properties. These advantages enable the ERTO coating with tremendous potential and offer versatile applications such as architectural conservation, industrial corrosion protection, and the packaging industry.