The goal of this research was to study the kinetics of the reaction of diglycidyl ether of bisphenol A (DGEBA)-based epoxy resin cured with sebacic acid as a biobased hardener in the presence of three different loadings of epoxidized soybean oil (ESO) (i.e., 10, 20, 30 wt %). Nonisothermal differential scanning calorimetric (DSC) and model-free isoconversional method was used to analyze the curing kinetic data and determine the activation energy of the reactions. It was found that the biobased hardener increased the enthalpy of reaction as well as the activation energy of reaction in comparison to the amine hardeners that are currently used for epoxy curing. The addition of epoxidized soybean oil increased the enthalpy of reaction, maximum exothermic temperature, and activation energy of the system. Kissinger–Akahira–Sunose (KAS) and Starink methods were used to determine the activation energy of the studied systems. It was also found that the curing reaction of epoxy with 30 wt % of ESO is diffusion controlled in comparison with other counterparts.

Poly(propylene carbonate) (PPC) polyol derived from carbon dioxide has been used to make a tough biobased interpenetrating polymer network (IPN). PPC polyol (10, 20, and 30 phr) was added to an epoxy/poly(furfuryl alcohol) IPN, and the effect of PPC polyol on the tensile modulus, tensile strength, tensile toughness, and notched Izod impact strength was determined. Dynamic mechanical analysis (DMA) was used to investigate the effect of PPC polyol on the glass-transition temperature. Loss area (LA) as a characteristic of IPN damping properties was evaluated using DMA. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to obtain more information on the morphology of IPNs on the micro- and nanoscale. It was found that the incorporation of PPC polyol improved the notched Izod impact strength and tensile toughness up to 190 and 220%, respectively. The damping factor peak was broadened with the addition of PPC polyol, and the glass-transition temperature was decreased as the amount of PPC polyol increased. The IPN with 20 phr PPC polyol exhibited better damping properties than neat epoxy and the epoxy/PFA IPN. SEM and AFM images revealed that PPC polyol domains were dispersed in the epoxy phase with an average diameter of around 280 nm.

A novel biobased thermoset interpenetrating network was introduced in this study. Epoxidized soybean oil (ESO) and poly(furfuryl alcohol) (PFA) were added to a commercial biobased epoxy resin. It was hypothesized that addition of ESO and PFA can decrease brittleness of bioepoxy resin and also increase biobased content. Mechanical properties of samples were evaluated using tensile and impact test. It was found that the addition of ESO and PFA increased notched Izod impact energy by 76.6%. This significant increase was related to incorporation of long flexible chains of ESO into the matrix. Hybridization of ESO and PFA in bioepoxy reduced tensile strength (around 70%), tensile modulus (around 90%), and glass transition temperature in comparison to neat bioepoxy. Tensile strength and modulus of hybridized system can be further improved by addition of natural fibers and the resultant composite may be considered as a good candidate for applications in which damping properties are important. Crosslink density was calculated using dynamic mechanical analysis and a decrease in crosslink density was observed in hybridized system. PFA domains were observed in the matrix using atomic force microscopy in peak force quantitative nano‐mechanical mode and it revealed inhomogeneity in the crosslinked structure. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 44352.

Epoxy composites are typically petroleum based and prone to fracture. Increasing concerns about climate change have motivated scientists to find green alternatives. To address both drawbacks, effect of addition of poly(propylene carbonate) polyol (PPC), a polyol derived from carbon dioxide, and biochar, a byproduct of pyrolysis in an epoxy/poly(furfuryl alcohol) (PFA) network was studied. It is hypothesized that addition of PPC will increase impact strength while addition of inexpensive biochar will offset cost of final product. In addition, incorporation of PFA, PPC, and biochar can increase biobased content of thermoset. A statistical approach was used to find a systematic correlation between constituent contents and mechanical properties of biocomposites. Mixture design of experiment and backward elimination regression were used to model mechanical properties of biocomposites. The fitted models showed a great ability to predict mechanical properties of new formulations. Addition of 10% biochar increased tensile strength and toughness by 13% and 34%, respectively. Biochar also increased modulus while it had adverse effect on impact strength. Promising effect of PPC on toughening of matrix was proved and it was found that addition of 30% of PPC increased impact strength by fivefolds.