Development of completely bio‐based epoxy networks derived from epoxidized linseed and castor oil cured with citric acid

Abstract

Bio‐based epoxy resins were synthesized from nonedible resources like linseed oil and castor oil. Both the oils were epoxidized through in situ method and characterized via Fourier transform infrared and 1H‐NMR. These epoxidized oils were crosslinked with citric acid without using any catalyst and their properties compared with diglycidyl ether of bisphenol A‐epoxy. The tensile strength and modulus of epoxidized linseed oil (ELO) were found to be more than those of epoxidized castor oil (ECO)‐based network. However, elongation at break of ECO was significantly higher than that of both ELO and epoxy, which reveals its improved flexibility and toughened nature. Thermogravimetric analysis revealed that the thermal degradation of ELO‐based network is similar to that of petro‐based epoxy. Dynamic mechanical analysis revealed moderate storage modulus and broader loss tangent curve of bio‐based epoxies confirming superior damping properties. Bioepoxies exhibit nearly similar contact angle as epoxy and display good chemical resistant. The preparation method does not involve the use of any toxic catalyst and more hazardous solvents, thus being eco‐friendly.

Polymerization kinetic pathways of epoxidized linseed oil with aliphatic bio‐based dicarboxylic acids

“…A comparison with the work of Sahoo et al show that the use of citric acid, which is a triacid, as hardener results in a 10 times higher cross‐link density. [ 25 ] From Table 2, it can be concluded that the T α and the crosslink density of ELO/suberic and ELO/sebacic systems are very similar. The T α is much lower for these two systems in comparison with ELO/succinic system, while the differences in crosslink density are weak.…”

“…This degradation phenomenon can be attributed to ester and ether chain scissions formed thanks to the reaction between dicarboxylic acids and ELO. [ 25 ] The last degradation step at around 530°C corresponds to the carbonization. These steps occur in the same T range as reported by Ding et al [ 17 ] and Falco et al [ 49 ] for ELO cured with aliphatic diacids.…”

“…[ 24 ] Sahoo et al also studied the crosslinking of ELO in a fully bio‐based way thanks to the use of citric acid as a hardener. [ 25 ]…”

Recent Advancement in Plant Oil Derived Polyol‐Based Polyurethane Foam for Future Perspective: A Review

“…Recently, epoxidation is the most preferred process for hydroxyl functionalization of plant-based oils. [55][56][57] Since the conversion of double bonds into epoxide ring is done using various methods such as i) in situ epoxidation using peracids such as peracetic acid or perbenzoic acid in the presence of an acid catalyst, ii) epoxidation of double bond with organic and inorganic peroxides, including transition metal catalysts, iii) epoxidation with halohydrins using hypohalous acids and their salts, and iv) epoxidation with molecular oxygen. Figure 5 depicts the reaction of epoxidation using acetic acid and hydrogen peroxide in the presence of an acid catalyst.…”

Cardanol‐Based Epoxy Monomers for High Thermal Properties Thermosets

“…In an environmental context, concerns about the reduction of the carbon footprint is growing rapidly with the development of bio‐based polymers. Many epoxy networks based on renewable resources have been developed recently from epoxidized natural oils, such as soybean oil, linseed oil, and castor oil . However, all of these triglycerides exhibit similar structures with long flexible chains which provide low thermal or mechanical properties induced by a low crosslinking density and T g .…”