Solving the difficult recyclability of conventional thermosetting polyurea elastomers based on commercial raw materials in a facile way

Abstract

Great efforts have been devoted to solving the hot issues that t covalent hermosetting polymers or its composites, unlike thermoplastic polymers, cannot be secondary melting reprocessed or recycled through injection...

A dynamic polyurea network with exceptional creep resistance

“…Unlike dynamic urea networks reported previously which are mainly based on catalysts and hindered urea bonds, 42–46 the unique properties of A-PU 1.2 should be originated from its special structure with both immobile inner “cores” and mobile outer branches. Due to the high reactivity between isocyanate and amino groups, and the short alkyl chain of twelve methylenes, the immobile inner “cores” are highly crosslinked and account for a large proportion in the A-PU 1.2 polymer.…”

“…2 and other recyclable CANs in terms of temperature and applied stress. 12,24,25,28,29,31,32,37,[39][40][41][42]…”

“…2 (a) Creep curves of A-PU 1.2 under stress of 1 MPa at different temperatures. (b) Creep curves of A-PU 1.2 under different levels of stresses at 140 C. (c) A comparison of creep behavior among A-PU 1.2 and other recyclable CANs in terms of temperature and applied stress 12,24,25,28,29,31,32,37,[39][40][41][42]. (d) SR, and (e) GR of A-PU 1.2 fragments immersed in different solvents for a month.…”

Dynamic covalent polymers enabled by reversible isocyanate chemistry

“…As discussed above, urea bonds are usually more stable than urethane bonds, leading to the requirement of high temperatures, extra nucleophiles, or catalysts to promote reversibility. 72,80,[149][150][151][152] Interestingly, the dynamicity of urea bonds can be dramatically expedited by delicately regulating the structures of nucleophilic moieties. Therefore, hindered urea bonds (HUBs), 55,153 pyrazole-urea bonds (PzUBs), 71 acylhydrazide-urea bonds 154 have been developed for the design of dynamic covalent polymers.…”

Humidity-Responsive Shape Memory Polyurea with a High Energy Output Based on Reversible Cross-Linked Networks

“…Thermo-triggered shape memory polymers (SMPs) are one of the most popular smart materials owing to their controllable shape transformation, large deformation, and hysteresis-free shape recovery. Furthermore, heat energy can be generated by an electric field, light, and a magnetic field to implement remote control of the shape-changing module; therefore, thermo-triggered SMPs are applied in space-inflatable structures, left atrial appendage occluders, organic electronic devices, , and artificial muscles . However, most SMPs are not competitive in energy density (<1 MJ/m 3 ) and shape recovery stress (<5 MPa), limiting their use in mechanical work applications .…”