Composition-property relationship of polyurethane networks based on polycaprolactone diol
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Composition‑property relationship of polyurethane networks based on polycaprolactone diol Ivan S. Stefanović1 · Jasna V. Džunuzović1,2 · Enis S. Džunuzović3 · Aleksandra Dapčević3 · Sanja I. Šešlija2 · Bojana D. Balanč4 · Monika Dobrzyńska‑Mizera5 Received: 2 April 2020 / Revised: 7 September 2020 / Accepted: 6 November 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract This work was focused on the synthesis of polyurethane networks (PUNs) based on polycaprolactone (PCL) as soft segment (SS) and Boltorn® aliphatic hyperbranched polyester of the second pseudo generation and 4,4′-diphenylmethane diisocyanate (MDI) as the parts of the hard segments (HS), by a two-step solution polymerization. In order to find the best ratio between HS and SS to achieve good thermal and mechanical properties, suitable hydrophobicity and morphology of the PUNs, various experimental analyses were conducted. The obtained results revealed that features of the PUNs highly depend on the PCL content. The increase in the PCL content leads to the increase in thermal stability, hydrophobicity and appearance of the microphase separation, but on the other side, it also leads to the decrease in storage modulus in the rubbery plateau, crosslinking density and glass transition temperatures of PUNs. This work shows that features of PUNs can be easily adjusted for a specific application by careful selection of the SS and HS ratio. Keywords Polyurethane networks · Polycaprolactone · Hyperbranched polyesters · Thermal properties · Mechanical properties · Morphology
Introduction Segmented polyurethanes (PUs) represent a wide range of polymeric materials that have been constructed of alternating rigid urethane parts (hard segments, HS) and flexible polyol parts (soft segments, SS). By appropriate selection of reactants that includes different diisocyanates, polyols with a defined molecular weight, as well as chain extenders, it is possible to obtain PUs with different chemical and physical properties, customized for a variety of applications [1–3]. In order to improve * Ivan S. Stefanović [email protected]; [email protected] Extended author information available on the last page of the article
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their mechanical properties, thermal and chemical resistance, polyurethane networks (PUNs), can be prepared using adequate multifunctional reactants [4, 5]. PUNs are, compared to the linear PUs, polymeric materials with a three-dimensional chemically crosslinked structure which is insoluble in any solvent. The features of the PUNs depend on the degree of crosslinking, molecular weight between crosslinks (Mc), type and functionality of reactants, intermolecular forces between polymer chains, etc. [6–8]. Crosslinked structure of PUNs leads to the improvements in tensile strength, storage and loss modulus, as well as increase in Tg value, but on the other hand induces deterioration of their elongation at break [9]. Hyperbranched polyesters (HBPs) are multifunctional
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