Curing, gelling, thermomechanical, and thermal decomposition behaviors of anhydride‐cured epoxy (DGEBA)/epoxidized soybean oil compositions

Abstract

The present work was aimed at studying the effects of incorporation of epoxidized soybean oil (ESO) in a standard bisphenol A-type epoxy resin (EP) cured by anhydride hardener. The EP/ESO ratio was set for 100/0, 75/25, 50/50, 25/75 and 0/100 (wt.%/wt.%). The investigations performed covered the curing, rheology (gelling), thermomechanical (TMA) and thermogravimetric analysis (TGA) of the EP/ESO compositions. The results showed that the dilution of EP with ESO was accompanied with marked changes in the curing, gelling behavior and final properties. Differential scanning calorimetry (DSC) revealed that the crosslinking of EP/ESO≥50/50 occurred in two steps. This has been considered for the cure schedule set. The gel time of EP/ESO, determined at T=100, 120, 140 o C, respectively, increased with increasing ESO content. The activation energy of gelling increased with increasing ESO content. The glass transition temperature decreased with increasing ESO content of the transparent samples. According to TMA the coefficient of thermal expansion in the glassy state increased with increasing ESO content but was independent of the latter in the rubbery stage. TGA indicated that with increasing ESO content the thermal degradation started earlier and the char yield decreased. The Ozawa, Flynn and Wall (OFW) approach was adapted to TGA tests to calculate 2 the activation energy of thermal degradation. The activation energy depended on the ESO content of the EP/ESO blends and also on their actual decomposition stage. The latter means a limitation for the OFW approach.

Novel epoxy-benzoxazine water-based emulsions with reactive benzoxazine surfactants for coatings

“…In accordance with the literature [14,15,[30][31][32], epoxy resins, if a proper curing agent is used, usually polymerize at lower temperatures than benzoxazine resins, which is well observed by comparing Figures 7 and 9. The only exception was found for systems with Drapex 39, where no curing process was detected under these conditions.…”

“…We must be aware of the fact that epoxidized soybean oil is a large triglyceride molecule ( Figure 1) with large steric barriers that hinder chemical reactions. In addition, the concentration of epoxy groups per weight of the Drapex 39 molecules is significantly lower compared to synthetic epoxy resins [30]. The heat released during curing reactions (reaction enthalpy, &H) was determined from the area under the exothermic peak in DSC thermograms.…”

Synthesis and Properties of Polyesters from Waste Grapeseed Oil: Comparison with Soybean and Rapeseed Oils

“…Usually an increase in renewable ESBO content leads to greater flexibility in the polymer with a loss in tensile strength (tensile strength; 100% BADGE/MA = 70 MPa, 100% ESBO/MA = 36 MPa) [24]. Unfortunately, replacing petrochemical epoxides (typically containing terminal epoxides) with less reactive plant oil derived internal epoxides leads to increases in cure temperatures by as much as 40°C [25]. Properties of the final plastic are affected by the stoichiometric ratio of epoxide to anhydride functional groups, with values greater or less than the optimum 1:1 ratio leading to a decrease in flexural modulus and hardness of materials due to incomplete curing of the epoxide [26].…”

“…1) is one of the most common vegetable oil feedstocks used in industry, traditionally it has been used as a plasticizer for PVC [22,23], as well as for producing polyesters from anhydrides [24][25][26].…”

Novel high glass temperature sugar-based epoxy resins: Characterization and comparison to mineral oil-based aliphatic and aromatic resins

“…Basically there are four methods: epoxidation with percarboxylic acids; with inorganic or organic peroxides; with halohydrines or with molecular oxygen [11]. Many investigations deal with the mechanical properties of the neat epoxidized plant oils (EPOs) and mixed EPO/ petrol oil based EP (mostly DGEBA -diglycidyl ether of bisphenol A) systems [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26]. According to the literature in these hybrid EP systems usually phase separation was observed [12,20,21].…”