TY - JOUR
T1 - Biobased, Reprocessable Non-isocyanate Polythiourethane Networks with Thionourethane and Disulfide Cross-Links
T2 - Comparison with Polyhydroxyurethane Network Analogues
AU - Chen, Yixuan
AU - Chen, Boran
AU - Torkelson, John M.
N1 - Publisher Copyright:
© 2023 American Chemical Society
PY - 2023/5/23
Y1 - 2023/5/23
N2 - Here, we report the first study of the reprocessability and properties of non-isocyanate polythiourethane (NIPTU) networks in which the cross-links are of two types, thionourethane and disulfide, the latter obtained by auto-oxidation of pendant thiol groups. Our two NIPTU networks are biowaste based because starting materials can be derived from cashew nutshells or rice husks. We use dynamic mechanical analysis, tensile testing, and water sorption studies to compare our NIPTU networks with structurally analogous polyhydroxyurethane (PHU) networks, which are non-isocyanate polyurethanes (PUs). With significant advantages in reactivity, mechanical properties, and cross-link density, NIPTU networks can be favorable alternatives to PHU networks. Our biobased NIPTU networks also exhibit better water resistance, with a factor of ∼3 reductions in water sorption relative to their PHU analogues. Due to their dynamic covalent cross-links, our NIPTUs show excellent reprocessability with complete recovery of cross-link density after multiple reprocessing steps as well as potential as self-healing polymers. Although their creep viscosity activation energies differ by a factor of 2, both NIPTU networks exhibit excellent creep resistance up to 80-100 °C. Thus, with elevated-temperature creep resistance and significant advantages in reactivity, mechanical properties, and water resistance, in many applications, e.g., water-resistant coatings, biobased NIPTU networks are favored as non-isocyanate substitutes for PU networks.
AB - Here, we report the first study of the reprocessability and properties of non-isocyanate polythiourethane (NIPTU) networks in which the cross-links are of two types, thionourethane and disulfide, the latter obtained by auto-oxidation of pendant thiol groups. Our two NIPTU networks are biowaste based because starting materials can be derived from cashew nutshells or rice husks. We use dynamic mechanical analysis, tensile testing, and water sorption studies to compare our NIPTU networks with structurally analogous polyhydroxyurethane (PHU) networks, which are non-isocyanate polyurethanes (PUs). With significant advantages in reactivity, mechanical properties, and cross-link density, NIPTU networks can be favorable alternatives to PHU networks. Our biobased NIPTU networks also exhibit better water resistance, with a factor of ∼3 reductions in water sorption relative to their PHU analogues. Due to their dynamic covalent cross-links, our NIPTUs show excellent reprocessability with complete recovery of cross-link density after multiple reprocessing steps as well as potential as self-healing polymers. Although their creep viscosity activation energies differ by a factor of 2, both NIPTU networks exhibit excellent creep resistance up to 80-100 °C. Thus, with elevated-temperature creep resistance and significant advantages in reactivity, mechanical properties, and water resistance, in many applications, e.g., water-resistant coatings, biobased NIPTU networks are favored as non-isocyanate substitutes for PU networks.
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U2 - 10.1021/acs.macromol.3c00220
DO - 10.1021/acs.macromol.3c00220
M3 - Article
AN - SCOPUS:85161040900
SN - 0024-9297
VL - 56
SP - 3687
EP - 3702
JO - Macromolecules
JF - Macromolecules
IS - 10
ER -