Curing of epoxidized linseed oil: Investigation of the curing reaction with different hardener types

Abstract

The effect of the hardener type and amount on the curing reaction and the resulting thermal and mechanical performance characteristics of epoxidized linseed oil are studied in detail. The analysis of the curing mechanism reveals that due to steric hindrance, side reactions and/or fast gelation, the optimal mixing ratio of bio‐based epoxy resins and hardeners has to be determined experimentally and cannot be calculated. The investigated thermosets exhibit a glass transition temperature of 12, 54, and 145°C after curing. The overall mechanical performance of the resulting resin ranges from soft and flexible to stiff and rigid, depending on the hardener type applied, which can be utilized in the formation of epoxy composites and coatings.

Influence of Keratin on Epoxidized Linseed Oil Curing and Thermoset Performances

“…On studying the FT-IR spectra of the ELO/DDSA thermoset (Figure ), we can highlight the disappearance of the peak at 3050 cm –1 (present in the ELO spectrum), which is characteristic of the C–H stretching of the methylene group of the epoxy ring, and the increase in the intensity of the peaks in the absorption region between 3000 and 2850 cm –1 attributed to the CH 2 and CH 3 aliphatic group stretching vibrations. Based on the literature, the first result can be associated with epoxy ring-opening, while the second one can be assigned to the epoxy-anhydride group reaction. ,− The absorption bands at 1738 cm –1 (CO stretching vibration of the ester group) and 1154 cm –1 (C–O stretching vibration of the ester group) increased considerably in the thermoset, which can indicate the occurrence of the esterification reactions through the cross-linking of ELO with DDSA. The intensity of the peaks at 795–820 cm –1 (C–O stretching vibration of the epoxy ring) decreases almost to extinction, showing the consumption of the epoxy group during copolymerization.…”

“…An important vegetable oil used for the synthesis of thermoset resins is linseed oil (LO) due to not only the high content of double bonds but also its multitude of natural properties such as inherent biodegradability, low toxicity toward environment and humans, low price, and abundant availability . Various academic studies have been developed to investigate the chemical reactivity of epoxidized LO (ELO) according to different initiators or hardeners to develop new polymeric resins with properties comparable to those of commercial epoxy resins. ,− Grauzeliene et al combined photo- and thermal polymerization of acrylated epoxidized soybean oil (ESO) and ELO with thiols, obtaining new biorenewable resins for 3D printing with good properties making them suitable biobased alternatives to bisphenol A diglycidyl ether (DGEBA). Pin et al developed biobased materials based on ELO copolymerized with methyl hexahydrophthalic anhydride (MHHPA) or benzophenone-3,3′,4,4′-tetracarboxylic dianhydride (BTDA).…”

Recent development on bio‐based thermosetting resins

“…By altering the curing agent, the properties of epoxidized linseed oil (Scheme 1(A)) could be adjusted within a certain range. For example, the glass transition temperature (T g ) of cured materials can be regulated from 12 to 145 C. 6 Because of its soft character and good processability, epoxidized castor oil has also been successfully used to prepare composite materials. [7][8][9] Khundamri et al 10 developed a soybean oil-based material enhanced by epoxidized mangosteen tannin in order to improve its compressive strength.…”

Development of renewable thermosetting polymers based on grape seed oil derivatives

“…Their reaction with epoxide rings has been extensively investigated for various applications 22‐25 . Some papers have studied the reaction between epoxidized vegetable oils and anhydrides, such as phthalic, 25 dodecenylsuccinic, 26 and others 27‐29 . Other papers used maleinized vegetable oils together with other epoxidized monomers as hardeners 30‐34 .…”