Oxime–Urethane Structure‐Based Dynamically Crosslinked Polyurethane with Robust Reprocessing Properties

Abstract

Crosslinked polyurethane with excellent mechanical property, solvent resistance, and transparency has become one of the most widely used materials. However, the presence of chemical crosslinks makes it difficult to be reprocessed once molded, which largely restricts its recycling and reusing, resulting in the serious waste problems. Therefore, it is of great significance to prepare a new type of crosslinked polyurethane with reprocessing function. In this work, a novel reprocessable polyurethane (DOPU) based on reversible dibutanone oxime-carbamate bonds is facilely prepared. The gel fraction of DOPUs is all higher than 95%, endowing it with excellent solvent resistance. Meanwhile, the visible light transmittance of DOPUs can reach up to 97.48%. After four thermal recycles, the tensile strength and elongation at break of recycled DOPUs can still remain at 3.21 MPa and 219.09%, respectively. Importantly, the synthesized DOPUs exhibit excellent elastic shape memory and permanent shape reconstruction properties under thermal stimulation. The dibutanone oxime-carbamate bonds can also be degraded under UV irradiation, making this material easily degradable. Hence, this material has potential applications in coatings, elastomers, and some other fields.

Improving Sustainability through Covalent Adaptable Networks in the Recycling of Polyurethane Plastics

“…The route other authors have followed is based on an additional, less-studied type of dynamic covalent bond, the oxime-carbamate bond. This type of bond is of interest, as it is characterised by chemistry that is different from that of classical carbamates and as it is sensitive to UV rays [ 105 ], which can lead to the formation of radicals that can be useful in the reworking phase. Also, the reaction intermediates proposed in this phase, such as isometric nitrone [ 106 ], promote a transcarbamylation different from that of the classical PU.…”

“…Also, the reaction intermediates proposed in this phase, such as isometric nitrone [ 106 ], promote a transcarbamylation different from that of the classical PU. Liu et al [ 106 ], Lei et al [ 105 ], and Zhang et al [ 107 ] worked in this direction. The first one produced a poly(oxime-urethane) (POU), starting from HDI and various dioximes and trioximes without a catalyst.…”

Dynamic covalent polymers enabled by reversible isocyanate chemistry

“…121 Afterwards, a series of PU CANs with OUBs were successfully designed with robust repairable and recyclable properties. [122][123][124][125][126] Recently, a set of self-healing POU elastomers were synthesized by a one-pot catalyst-free polyaddition from DMG, IPDI, PTMG, and glycerol, exhibiting tailorable mechanical properties by regulating the degree of crosslinking to provide mechanical adaptations with different tissues. 127 The self-healing behavior was realized at room temperature because of dynamic OUBs and hydrogen bonds, as well as flexible soft segments and the suppressed crystallization by steric hindrance of IPDI.…”

Developing Reprocessable shape memory thermosetting resins with high thermal resistance and strength through building a crosslinked network based on bismaleimide and epoxy resins

“…[6][7][8] In fact, some thermosetting shape memory polymers (SMPs) with reprocessing ability were prepared, while the majority of which are elastomers. [9][10][11][12][13][14][15] ; some of which are thermosetting resins, [16][17][18][19][20][21][22] but they have significantly lower glass transition temperature (T g = 40-150 C) and lower mechanical strength than traditional thermosetting resins 7,8 (such as epoxy resin and bismaleimide resin), and thus cannot meet the applications that have harsh requirement on high heat resistance and mechanical strength, generally.…”