Isoconversional cure kinetics of a novel thermosetting resin based on linseed oil
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Isoconversional cure kinetics of a novel thermosetting resin based on linseed oil Günter Wuzella1 · Arunjunai Raj Mahendran1 · Christopher Beuc1 · Herfried Lammer1 Received: 30 August 2019 / Accepted: 7 March 2020 © Akadémiai Kiadó, Budapest, Hungary 2020
Abstract In the current work, the thermal curing process of maleinated acrylated epoxidized linseed oil (MaAELO) mixed with reactive diluent, initiator, and accelerator was studied by using isothermal differential scanning calorimetry (DSC) and dynamic rheology. The investigations encompassed (1) the determination of the whole set of apparent kinetic parameters, Ea(α), A(α), and f(α) by using two accurate isoconversional kinetic analysis methods and the compensation effect, (2) the prediction of cure conversion curves, α(t), at arbitrary processing temperatures with all three kinetic parameters in comparison with the prediction based on Ea(α) alone, and (3) the determination of molecular and macroscopic gelation during the thermal cure of MaAELO resin mixture. The thermal cure of MaAELO resin mixture did not start immediately but after a remarkable induction period. It was possible to determine the kinetic parameters and use them to predict the induction period for arbitrary process temperature. In addition, the glass transition temperature, Tg, of thermally cured MaAELO resin mixture was measured by thermomechanical analysis and dynamic DSC. Keywords Bio-based thermosetting resin · Isoconversional cure kinetics · Induction period · Gel Point · DSC · Multiwave rheology
Introduction Over the past decades, there has been a growing interest in the use of polymers based on renewable resources because of diminishing petroleum resources and environmental issues. Vegetable oils are triglyceride oils based on different fatty acids that are responsible for making them a versatile natural and renewable resource for a variety of polymeric materials [1]. The routes to synthesize unsaturated polyester resins (UPR) from a broad range of renewable resources including vegetable oils have been reviewed recently by Ma et al. [2] and in more detail, including the synthesis routes to achieve bio-based reactive diluents for UPR, by Li et al. [3]. In the current work, we followed the synthesis route of epoxidation of linseed oil (ELO) which was acrylated (AELO) afterward and finally reacted with Maleic anhydride (MaAELO). Wool and his team first proposed this synthesis route in order to * Günter Wuzella g.wuzella@wood‑kplus.at 1
Competence Center for Wood Composites and Wood Chemistry, Wood K Plus, Altenberger Straße 69, 4040 Linz, Austria
achieve a bio-based UPR with improved mechanical properties for composite applications. They investigated the mechanical and thermomechanical properties of completely cured bio-based UPR based on soybean oil, linseed oil and canola oil and presented their work in several scientific papers [4–8]. The crosslinking, or curing, of an UPR is characterized by a free radical polymerization mechanism. For this purpose, UPR is normally mixed with a
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