Sustainable biobased composites from norbornylized linseed oil and biomass sorghum fillers

Abstract

Thermosets and composites sourced from environmentally benign natural sources are in huge demand. In that context, norbornylized linseed oil was used as the key sustainable polymer precursor for thermosets and glass fiber reinforced hybrid biocomposites via three different curing techniques. At first, norbornylized linseed oil was copolymerized by dicyclopentadiene whereas its epoxides were cured via latent cationic initiator, and copolymerization with disulfide containing acid moieties. Further, biomass sorghum fillers were incorporated into the epoxides to fabricate stronger, cheaper, light weight and more sustainable products. The activation energies and crosslink efficiency of the thermosets were calculated first. To evaluate the commercial significance of the products fabricated, synthetic bisphenol-A based epoxides and commercial standards of epoxidized linseed oil-based thermosets and composites were analyzed side by side. Finally, natural flax fiber reinforced composites were also fabricated to make green composites. The thermo-mechanical properties of the composites were investigated using universal testing machine and thermogravimetric analysis. Steric hindrance and ring strain energies seem to have tangible role in the curing process whereas the presence of ring structures increased the crosslink density and mechanical strength. Fine tunability of composite properties by the selection of a specific curing technique was demonstrated by virtue of different curing mechanisms. While outperforming commercial linseed oil epoxides, the norbornylized linseed epoxides-natural fiber composites exhibited comparable performance properties to synthetic bisphenol-A epoxy-glass fiber composites. Therefore, such biocomposites can be viable replacements of harmful bisphenol-A epoxides in the composite industry, especially in the non-structural automotive composite parts.