Fully biobased epoxy resins from ring opening polymerization of epoxidized pennycress (Thlaspi arvense L.) oil with itaconic and citric acids

Authors: Moser, Bryan; Cermak, Steven - Steve; Evangelista, Roque

Submitted to: Industrial Crops and Products
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/5/2023
Publication Date: 12/8/2023
Citation: Moser, B.R., Cermak, S.C., Evangelista, R.L. 2023. Fully biobased epoxy resins from ring opening polymerization of epoxidized pennycress (Thlaspi arvense L.) oil with itaconic and citric acids. Industrial Crops and Products. 208. Article 117914. https://doi.org/10.1016/j.indcrop.2023.117914.
DOI: https://doi.org/10.1016/j.indcrop.2023.117914

Interpretive Summary: This research describes a sustainable route to a new set of renewable epoxy resins from vegetable oils. Renewable polymers are important because they represent biobased alternatives to existing petrochemically based epoxy resins, which cause negative environmental, ecological, and human health effects. This research discovered that vegetable oils can be easily converted into epoxy resins in high yield using a simple, solvent-free, noncatalytic polymerization method. Field pennycress, which is native to North America, is of interest as a winter cover crop due to its low agricultural inputs and high yield of inexpensive field pennycress oil. In this study, polymers were prepared from field pennycress and soybean oils. The polymers prepared from pennycress oil had similar performance to polymers prepared from soybean oil, thereby indicating that the same performance can be achieved at lower cost. These polymers have potential applications as coatings, sealants, thickening agents, and organogels. This research may ultimately expand markets for biobased polymers, thus reducing the environmental impact of and demand for petroleum-derived products while simultaneously enhancing rural economies by increasing the use of agricultural materials.

Technical Abstract: Fully biobased thermosetting epoxy resins were efficiently synthesized from non-edible field pennycress (Thlaspi arvense L.) oil following a two-step sequence in which the oil was epoxidized by in situ-generated performic acid and then cured with citric and itaconic acids. Ring opening polymerization reactions were self-catalyzed, solvent-free, and conducted at 120°C for 5 - 25 h. Analogous polymers were prepared from epoxidized soybean oil to serve as reference comparisons. The influence of comonomer combination and curing time on properties of the resulting elastomeric, ductile, thermally stable (DTG > 379°C), hydrophobic (contact angle > 70°C) epoxy resins is reported. Crosslink density, storage modulus at the glass transition temperature (6.8 – 14.4 MPa), tensile strength (0.3 – 1.1 MPa), and gel content (87 - 96%) increased with cure time. Citrate-based polymers had higher crosslink densities (317 mol/m3) than itaconate-based polymers (164 - 279 mol/m3) due to the greater functionality of citric acid versus itaconic acid, which resulted in higher glass transitions (> 21°C), tensile strengths (> 0.6 MPa), and storage moduli in the rubbery state (> 2.6 MPa). Finally, the lower oxirane content of EPO versus ESO resulted in lower crosslink density, storage modulus, tensile strength, and elongation at break. Overall, the epoxy networks had promising thermal, mechanical, and viscoelastic properties that were tunable by selection of appropriate comonomer combinations and curing times.