A type
of polyurethane elastomer with excellent self-healing ability
has been fabricated through digital light processing 3D printing.
First, a type of polyurethane acrylate containing disulfide bonds
is synthesized and then compounded with reactive diluent and photoinitiators
to get a photopolymer resin. Due to the good fluidity and high curing
rate, the photopolymer resin can be applied in DLP 3D printing, and
various 3D objects with complicated structures, high printing accuracy,
and remarkable self-healing ability have been printed. The tensile
strength and elongation at break of the polyurethane elastomer are
3.39 ± 0.09 MPa and 400.38 ± 14.26%, respectively, and the
healing efficiency can get to 95% after healing at 80 °C for
12 h and can be healed for multiple times. With the ease of fabrication
and excellent performance, the polyurethane elastomers from DLP 3D
printing have great potential applications in flexible electronics,
soft robotics, and sensors.
Four-dimensional printing, a new process to fabricate active materials through three-dimensional (3D) printing developed by MIT's Self-Assembly Lab in 2014, has attracted more and more research and development interests recently. In this paper, a type of epoxy-acrylate hybrid photopolymer was synthesized and applied to fabricate shape memory polymers through a stereolithography 3D printing technique. The glass-to-rubbery modulus ratio of the printed sample determined by dynamic mechanical analysis is as high as 600, indicating that it may possess good shape memory properties. Fold-deploy and shape memory cycle tests were applied to evaluate its shape memory performance. The shape fixity ratio and the shape recovery ratio in ten cycles of fold-deploy tests are about 99 and 100%, respectively. The shape recovery process takes less than 20 s, indicating its rapid shape recovery rate. The shape fixity ratio and shape recovery ratio during 18 consecutive shape memory cycles are 97.44 ± 0.08 and 100.02 ± 0.05%, respectively, showing that the printed sample has high shape fixity ratio, shape recovery ratio, and excellent cycling stability. A tensile test at 62 °C demonstrates that the printed samples combine a relatively large break strain of 38% with a large recovery stress of 4.7 MPa. Besides, mechanical and thermal stability tests prove that the printed sample has good thermal stability and mechanical properties, including high strength and good toughness.
A series of photosensitive resins suitable for the production of silicone elastomers through digital light processing 3D printing are reported. Based on thiol− ene click reaction between a branched mercaptan-functionalized polysiloxane and different-molecular-weight vinyl-terminated poly(dimethylsiloxane), silicone elastomers with tunable hardness and mechanical properties are obtained. Printed elastomeric objects show high printing resolution and excellent mechanical properties. The break elongation of the silicone elastomers can get up to 1400%, which is much higher than the reported UV-cured elastomers and is even higher than the most stretchable thermocuring silicone elastomers. The superstretchable silicone elastomers are then applied to fabricate stretchable electronics with carbon nanotubes-doped hydrogel. The printable and processable silicone elastomers have great potential applications in various fields, including soft robotics, flexible actuators, and medical implants.
Zn2+ is an essential regulator of coagulation and is released from activated platelets. In plasma, free Zn2+ concentration is fine-tuned through buffering by human serum albumin (HSA). Importantly, the ability...
In the present research, a type of cycloaliphatic silicone–epoxy resin is synthesized and then compounded with acrylates as well as photoinitiators to obtain hybrid photopolymers. The photocuring rate of the hybrid photopolymers, the morphology, thermal and mechanical properties of the cured samples with different silicone–epoxy/acrylate ratios are studied in detail. Scanning electron microscopy images prove that interpenetrating polymer network structure is formed. To improve the mechanical properties, diglycidyl ether of bisphenol A is added and finally a type of hybrid photopolymer suitable for stereolithography 3D printing is obtained. Fourier‐transform infrared spectroscopy and photo‐differential scanning calorimeter measurements show that the hybrid photopolymer has a high curing rate, while thermal property tests prove that the cured sample has high thermal stability. Mechanical property tests show that the cured samples have a tensile strength of 40.3 MPa with a break elongation of 6.7%. The objects printed with the hybrid photopolymer exhibit high resolution and dimension accuracy.
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