Thermal and mechanical properties of anhydride‐cured epoxy resins with different contents of biobased epoxidized soybean oil

Abstract

Thermosetting resins were synthesized by the partial replacement of the synthetic epoxy prepolymer based on diglycidyl ether of bisphenol A (DGEBA) with increasing amounts of epoxidized soybean oil (ESO) with methyltetrahydrophthalic anhydride as a crosslinking agent and 1-methyl imidazole as an initiator. Calorimetric studies showed a drop in the reaction heat with ESO content; this was associated with the lower reactivity of oxirane rings in ESO due to steric constrains. The effects of the replacement of increasing amounts of synthetic DGEBA with ESO on the network properties, such as the storage modulus (E 0 ) in the glassy and rubbery regions, glass-transition temperature (T g ), and impact and compressive properties were examined. All formulations were transparent, although phase-separated morphologies were evidenced by scanning electron microscopy observations. The intensity of the transmitted light passed to a minimum at a short reaction time associated with the cloud point and then increased continuously until the refractive index of the dispersed phase approximated that of the continuous phase at complete conversion. The combination of DGEBA with 40 wt % ESO resulted in a resin with an optimum set of properties; E 0 in the glassy state was 93% of that of the neat DGEBA resin, T g decreased only about 11 C, and the impact strength increased about 38% without a loss of transparency. V C 2010 Wiley Periodicals, Inc.J Appl Polym Sci 120: [789][790][791][792][793][794][795][796][797][798] 2011

Vegetable oil-derived epoxy monomers and polymer blends: A comparative study with review

“…The saturated component in ESO thus plays a significant role in reducing the crosslink density. Though crosslink density has been reported to not be changed by the replacement of DGEBA by ESO using mechanical analysis of the rubbery plateau [52], an artificially larger modulus can result for the inherently heterogeneous DGEBA-ESO-anhydride network due to a broadened glass transition temperature range. As heterogeneity will broaden the modulus signal in the rubbery region, a shear storage modulus value near the glass transition in the rubbery region can be artificially increased resulting in an inflated value for the calculated crosslink density.…”

“…The exothermic peaks were characteristic of the epoxy and anhydride curing reaction [52,53]. Integration of the peaks allows the determination of the enthalpy of curing reaction ("H), cure onset temperature (T o ) and peak exothermic (T p ).…”

“…The DGEBA-ESO system generally has a heterogeneous structure [52] and, not surprisingly, a nonuniform crosslinked structure will lead to a poorer mechanical performance compared to a more homogeneous structure. Cured aromatic DGEBA polymers are much more rigid compared to cured aliphatic ESO, which behave as weak points or flaws when applying load.…”

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].…”

Study of the Properties of Thermoset Materials Derived from Epoxidized Soybean Oil and Protein Fillers

“…In addition, it seems to be that the microcracks starts in the grains of cured ovalbumin, because there is the possibility that has a lower modulus of rupture compared with the ESBO matrix. The uniformity of the dispersed particles causes crack growth from ovalbumin particles to find the ESBO matrix, which acts as center of dissipation of mechanical energy and offers the maximum in the impact test value [35] . When the ESBO matrix can´t absorb more energy, it breaks, thus resulting in the grooves on the surface of the matrix [ Fig.…”