Biobased epoxy film derived from UV-treated epoxidised natural rubber and tannic acid: Impact on film properties and biodegradability

Abstract Deriving resins or prepolymers from natural resources is becoming more relevant in the current times due to depleting fossil resources. The manuscript describes preparation of epoxy resin from epoxidised natural rubber (ENR) via ultraviolet (UV) treatment, followed by investigation on the properties of the films produced by blending the natural rubber-based epoxy resin with another naturally resourced compound, tannic acid as the hardener. It is noteworthy that the purpose of the UV treatment is to produce shorter rubber chains by cleaving the C C of the rubber, and this is important to improve its compatibility with common solvents. Such approach can break the rubber without significant change to the amount of epoxide group. Upon blending with tannic acid, the epoxide group in the rubber was found to react with phenolic -OH of the acid and formed crosslinked networks. Consequently, significant improvement in gel content, glass transition temperature as well as other physicochemical properties were observed. Biodegradability test was also conducted on the films by burying the samples in soil-compost mixture, and the high percentage of natural content in coatings allow most of them to exhibit significantly higher post-burial weight loss compared to petroleum-derived epoxy film that served as a control.