Abstract
Polyurethane (PU) is a versatile polymer used in a wide range of applications. Recently, imparting PU with self-healing properties has attracted much interest to improve the product durability. The self-healing mechanism conceivably occurs through the existence of dynamic reversible bonds over a specific temperature range. The present study investigates the self-healing properties of 1,4:3,6-dianhydrohexitol-based PUs prepared from a prepolymer of poly(tetra-methylene ether glycol) and 4,4′-methylenebis(phenyl isocyanate) with different chain extenders (isosorbide or isomannide). PU with the conventional chain extender 1,4-butanediol was prepared for comparison. The urethane bonds in 1,4:3,6-dianhydrohexitol-based PUs were thermally reversible (as confirmed by the generation of isocyanate peaks observed by Fourier transform infrared spectroscopy) at mildly elevated temperatures and the PUs showed good mechanical properties. Especially the isosorbide-based polyurethane showed potential self-healing ability under mild heat treatment, as observed in reprocessing tests. It is inferred that isosorbide, bio-based bicyclic diol, can be employed as an efficient chain extender of polyurethane prepolymers to improve self-healing properties of polyurethane elastomers via reversible features of the urethane bonds.
Highlights
Polyurethane (PU) is a very versatile material with a wide range of physical and chemical properties
We investigated Polyurethane elastomer (PUE) based on isosorbide and isomannide, and study the applicability of the reversible properties of the urethane bonds to self-healing polymers using the structural features of 1,4:3,6-dianhydrohexitol
We have synthesized PUEs with biobased isosorbide and isomannide as chain extenders and compared their properties with those of PUE synthesized with a BD chain extender
Summary
Polyurethane (PU) is a very versatile material with a wide range of physical and chemical properties. One self-healing mechanism involves reversible covalent bonding between the isocyanate and active hydrogens in PUs [8,9]. These covalent bonds can be repeatedly formed and dissociated, enabling self-healing in even thermosetting PUs [12,13,14]. To the best of our knowledge, the thermally reversible nature of urethane bonds formed by the chemical reactions between 1,4:3,6-dianhydrohexitol and aromatic diisocyanates was not investigated up to now. We investigated PUEs based on isosorbide and isomannide, and study the applicability of the reversible properties of the urethane bonds to self-healing polymers using the structural features of 1,4:3,6-dianhydrohexitol. The urethane groups formed from isosorbide and isomannide display reversible properties at lower temperature than 1,4-butanediol based urethane groups, allowing reprocessing and thermally self-healing properties at mild temperatures
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