Developing degradable and self-healable elastomers composed of reusable resources is of great value but is rarely reported because of the undegradable molecular chains. Herein, we report a class of degradable and self-healable vitrimers based on non-isocyanate polyurethane elastomer. Such vitrimers are fabricated by copolymerizing bis(6-membered cyclic carbonate) and amino-terminated liquid nitrile rubber. The networks topologies can rearrange by transcarbonation exchange reactions between hydroxyl and carbonate groups at elevated temperatures; as such, vitrimers after reprocessing can recover 82.9-95.6% of initial tensile strength and 59-131% of initial storage modulus. Interestingly, the networks can be hydrolyzed and decarbonated in the strong acid solution to recover 75% of the pure di(trimethylolpropane) monomer. Additionally, the elastomer exhibits excellent self-healing efficiency (∼88%) and fracture strain (∼1,200%) by tuning the monomer feeding ratio. Therefore, this work provides a novel strategy to fabricate the sustainable elastomers with minimum environmental impact.
Soft, deformable electronic devices provide the means to monitor physiological information and health conditions for disease diagnostics. However, their practical utility is limited due to the lack of intrinsical thermal switching for mechanically transformative adaptability and self‐healing capability against mechanical damages. Here, the design concepts, materials and physics, manufacturing approaches, and application opportunities of self‐healing, reconfigurable, thermal‐switching device platforms based on hyperbranched polymers and biphasic liquid metal are reported. The former provides excellent self‐healing performance and unique tunable stiffness and adhesion regulated by temperature for the on‐skin switch, whereas the latter results in liquid metal circuits with extreme stretchability (>900%) and high conductivity (3.40 × 104 S cm−1), as well as simple recycling capability. Triggered by the increased temperature from the skin surface, a multifunctional device platform can conveniently conform and strongly adhere to the hierarchically textured skin surface for non‐invasive, continuous, comfortable health monitoring. Additionally, the self‐healing and adhesive characteristics allow multiple multifunctional circuit components to assemble and completely wrap on 3D curvilinear surfaces. Together, the design, manufacturing, and proof‐of‐concept demonstration of the self‐healing, transformative, and self‐assembled electronics open up new opportunities for robust soft deformable devices, smart robotics, prosthetics, and Internet‐of‐Things, and human–machine interfaces on irregular surfaces.
Three-layer pipe has many advantages over single layer one, especially for the pipe of glass fiber (GF) reinforced materials. But the hoop strength of the pipe produced via convention extrusion is poor because GFs orient along axial direction. In this work, a self-designed rotation extrusion system was adopted to extrude GF reinforced three-layer polypropylene random copolymer (PPR) pipe, in which a hoop shear field was applied to the polymer matrix and fibers in the middle layer. The structure and performance of pipes were investigated via scanning electronic microscope (SEM) and synchrotron two-dimensional wide-angel X-ray diffraction (2D-WAXD). Due to the hoop shear field, the orientation of GFs in middle layer deviated from axial direction. As a result, PPR pipes with enhanced hoop tensile strength were obtained. Because of the three-layer structure and the production process, the molecular chains of middle layer did not emerge distinct orientation after rotation shear, as shown in 2D-WAXD and SEM experimental results. This three-layer pipe rotation extrusion system offers a novel method for the modification of pipes in manufacture industry.
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