Room-Temperature Self-Healable and Mechanically Robust Thermoset Polymers for Healing Delamination and Recycling Carbon Fibers
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ABSTRACT:
SUBMITTER: Feng X
PROVIDER: S-EPMC8587616 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:The design of self-healing agents is a topic of important scientific interest for the development of high-performance materials for coating applications. Herein, two series of copolymers of 2-hydroxyethyl methacrylate (HEMA) with either the hydrophilic N,N-dimethylacrylamide (DMAM) or the epoxy group-bearing hydrophobic glycidyl methacrylate were synthesized and studied as potential self-healing agents of waterborne polyurethanes (WPU). The molar percentage of DMAM or GMA units in the P(HEMA-co-DMAMy) and P(HEMA-co-GMAy) copolymers varies from 0% up to 80%. WPU/polymer composites with a 10% w/w or 20% w/w copolymer content were prepared with the facile method of solution mixing. Thanks to the presence of P(HEMA-co-DMAMy) copolymers, WPU/P(HEMA-co-DMAMy) composite films exhibited surface hydrophilicity (water contact angle studies), and tendency for water uptake (water sorption kinetics studies). In contrast, the surfaces of the WPU/P(HEMA-co-GMAy) composites were less hydrophilic compared with the WPU/P(HEMA-co-DMAMy) ones. The room-temperature, water-mediated self-healing ability of these composites was investigated through addition of water drops on the damaged area. Both copolymer series exhibited healing abilities, with the hydrophilic P(HEMA-co-DMAMy) copolymers being more promising. This green healing procedure, in combination with the simple film fabrication process and simple healing triggering, makes these materials attractive for practical applications.
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Project description:Nature builds numerous structurally complex composites with fascinating mechanical robustness and functionalities by harnessing biopolymers and amorphous calcium carbonate (ACC). The key to successfully mimicking these natural designs is efficiently stabilizing ACC, but developing highly efficient, biodegradable, biocompatible, and sustainable stabilizing agents remains a grand challenge since anhydrous ACC is inherently unstable toward crystallization in the wet state. Inspired by the stabilized ACC in crustacean cuticles, we report the efficient stabilization ability of the most abundant biopolymer-cellulose nanofibrils (CNFs) for ACC. Through the cooperative stabilizing effect of surface carboxyl groups and a rigid segregated network, the CNFs exhibit long-term stability (more than one month) and achieved a stabilization efficiency of 3.6 and 4.4 times that of carboxymethyl cellulose (CMC) and alginate, respectively, even higher than poly(acrylic acid). The resulting CNF/ACC dispersions can be constructed into transparent composite films with the high strength of 286 MPa and toughness up to 28.5 MJ/m3, which surpass those of the so far reported synthetic biopolymer-calcium carbonate/phosphate composites. The dynamic interfacial interaction between nanocomponents also provides the composite films with good self-healing properties. Owing to their good wet stability, the composite films present high humidity sensitivity for monitoring respiration and finger contact.
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Project description:Natural fibers can be attractive reinforcing materials in thermosetting polymers due to their low density and high specific mechanical properties. Although the research effort in this area has grown substantially over the last 20 years, manufacturing technologies to make use of short natural fibers in high volume fraction composites; are still limited. Natural fibers, after retting and preprocessing, are discontinuous and easily form entangled bundles. Dispersion and mixing these short fibers with resin to manufacture high quality, high volume fraction composites presents a significant challenge. In this paper, a novel pneumatic design for dispersion of natural fibers in their original discontinuous form is described. In this design, compressed air is used to create vacuum to feed and convey fibres while breaking down fibre clumps and dispersing them in an aerosolized resin stream. Model composite materials, made using proof-of-concept prototype equipment, were imaged with both optical and X-ray tomography to evaluate fibre and resin dispersion. The images indicated that the system was capable of providing an intimate mixture of resin and detangled fibres for two different resin viscosities. The new pneumatic process could serve as the basis of a system to produce well-dispersed high-volume fraction composites containing discontinuous natural fibres drawn directly from a loosely packed source.
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Project description:The development of soft electronics and soft fiber devices has significantly advanced flexible and wearable technology. However, they still face the risk of damage when exposed to sharp objects in real-life applications. Taking inspiration from nature, self-healable materials that can restore their physical properties after external damage offer a solution to this problem. Nevertheless, large-scale production of self-healable fibers is currently constrained. To address this limitation, this study leverages the thermal drawing technique to create elastic and stretchable self-healable thermoplastic polyurethane (STPU) fibers, enabling cost-effective mass production of such functional fibers. Furthermore, despite substantial research into the mechanisms of self-healable materials, quantifying their healing speed and time poses a persistent challenge. Thus, transmission spectra are employed as a monitoring tool to observe the real-time self-healing process, facilitating an in-depth investigation into the healing kinetics and efficiency. The versatility of the fabricated self-healable fiber extends to its ability to be doped with a wide range of functional materials, including dye molecules and magnetic microparticles, which enables modular assembly to develop distributed strain sensors and soft actuators. These achievements highlight the potential applications of self-healable fibers that seamlessly integrate with daily lives and open up new possibilities in various industries.
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Project description:Although significant advances have been achieved in dynamic reversible covalent and non-covalent bonding chemistries for self-healing polymers, an ultimate goal is to create high strength and stiffness commodity materials capable of repair without intervention under ambient conditions. Here we report the development of mechanically robust thermoplastic polyurethane fibers and films capable of autonomous self-healing under ambient conditions. Two mechanisms of self-healing are identified: viscoelastic shape memory (VESM) driven by conformational entropic energy stored during mechanical damage, and surface energy/tension that drives the reduction of newly generated surface areas created upon damage by shallowing and widening wounds until healed. The type of self-healing mechanism is molecular weight dependent. To the best of our knowledge these materials represent the strongest (Sf = 21 mN/tex, or σf ≈ 22 MPa) and stiffest (J = 300 mN/tex, or E ≈ 320 MPa) self-healing polymers able to repair under typical ambient conditions without intervention. Since two autonomous self-healing mechanisms result from viscoelastic behavior not specific to a particular polymer chemistry, they may serve as general approaches to design of other self-repairing commodity polymers.
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Project description:To date delamination of organo-clays is restricted to highly charged, vermiculite-type layered silicates (e.g. n-butylammonium vermiculites) while - counterintuitively - low charged, smectite-type layered silicates do not delaminate although their Coulomb interactions are much weaker. Guided by previous findings, we now identified organo-cations that allowed for extending the delamination of organo clays to charge densities in the regime of low charged smectites as well. Upon intercalation of protonated amino-sugars like N-methyl-d-glucamine (meglumine) robust delamination of 2 : 1 layered silicates via repulsive osmotic swelling in water is achieved. This process is stable over a wide range of charge densities spanning from smectites (layer charge x ∼ 0.3 charges per formula unit Si4O10F2, p.f.u.) to vermiculites (x ∼ 0.7 p.f.u.). It is evidenced that a combination of first, a sufficiently large charge equivalent area (bulkiness) of meglumine with second, a significant hydrophilicity of meglumine leads to swelling above a threshold d-spacing of ≳17.5 Å in moist air (98% r.h.). Hereby, electrostatic attraction is critically weakened, causing the onset of repulsive osmotic swelling which leads to utter delamination. Moreover, meglumine renders delamination tolerant to charge heterogeneities typically found in natural and synthetic clays.
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