Network toughening of additively manufactured, high glass transition temperature materials via sequentially cured, interpenetrating polymers

Abstract

AbstractVinyl ester and epoxy–amine resins are used to produce polymeric materials for numerous commercial and military applications due to their relatively high moduli (>2 GPa), glass transition temperatures (Tgs) (≥120 °C) and adequate fracture toughness (G1C ≈ 200–250 J m−2). Most commercially available vinyl ester and epoxy–amine resins are typically cured into polymeric materials via traditional manufacturing techniques, such as resin transfer molding and thermal curing. However, additive manufacturing (AM) has gained significant traction as a favorable manufacturing technique over traditional methods due to the ability to create customizable parts with complex geometries on‐demand. Manipulation of polymer network connectivity using a dual‐cure mechanism of methacrylate free radical cure via stereolithography (SLA) and epoxy–amine thermal cure for the in situ creation of interpenetrating polymer networks (IPNs) for AM was investigated. Resins and formulations of individual monomers bearing both vinyl ester and epoxy functionality were either synthesized or formulated to elucidate the effect of interconnecting the two networks at the molecular level. The formation of a multi‐mechanistic, interconnected, sequentially cured IPN via SLA yielded polymeric materials with glass transition temperatures that exceeded 120 °C. Polymer network connectivity was shown to have a minimal impact on thermomechanical and thermogravimetric properties. IPN formation was shown to afford materials with high storage moduli (E′ values as high as 3.2 GPa), tensile strengths (as high as 51 MPa), Young's moduli (exceeding 3.5 GPa) and fracture energies (as high as 790 J m−2). © 2020 Society of Industrial Chemistry