Efficient and sustainable ultraviolet (UV)-blocking materials are of great interest in many fields. Herein, novel cellulose-based UV-blocking films are developed via surface modification using the Biginelli reaction. The resulting films exhibited excellent visible transparency (80%) at 550 nm and superhigh UV-blocking performance, which can shield almost 100% UVA and UVB. These features are very stable even the materials are being subjected to solvents, UV irradiation, and thermal treatment. This work provides a novel and facile strategy to fabricate functional cellulose-based films with superhigh anti-ultraviolet performance.
The catechol groups of mussel-inspired polydopamine (PDA) act as the active sites to induce in-situ polymerization of 3,4-ethylenedioxythiophene (EDOT) on the surface of tunicate sulfated nanocellulose (TSN) to prepare PEDOT:PDA:TSN (PPTSN) conductive nanofiber with a core-sheath structure. The abundant negative sulfate groups on the surface of TSN endow PPTSN with outstanding dispersion stability. The flexible self-supporting PPTSN nanocomposite films formed by solution casting, inheriting the excellent mechanical properties of the TSN core and electrical conductivity of the PEDOT sheath, exhibit decent thermoelectric properties for thermoelectric material applications. Furthermore, based on the humidity responsiveness of PPTSN, the obtained nanocomposite films have great application prospects in constructing respiratory monitoring and non-contact sensors for sensing human humidity-related behaviors.
Electroconductive fibers composed of cellulose and carbon nanotubes (CNTs) were spun using aqueous alkaline/urea solution. The microstructure and physical properties of the resulting fibers were investigated by scanning electron microscopy, Raman microscopy, wide-angle X-ray diffraction, tensile tests, and electrical resistance measurements. We found that these flexible composite fibers have sufficient mechanical properties and good electrical conductivity, with volume resistivities in the range of about 230-1 Ohm cm for 2-8 wt % CNT loading. The multifunctional sensing behavior of these fibers to tensile strain, temperature, environmental humidity, and liquid water was investigated comprehensively. The results show that these novel CNT/cellulose composite fibers have impressive multifunctional sensing abilities and are promising to be used as wearable electronics and for the design of various smart materials.
Abstract The pulp and paper industry growingly paid attention to the recycling and maintenance of waste paper products. Each paper-making cycle would lead to a sharp drop in the mechanical properties of the cellulosic paper, which was related to the hornification effect. Here, the recycling performance of the holocellulose paper was studied, compared with that of the cellulosic paper. Holocellulose fibers from sisal were fabricated by a gentle delignification method, and the well-preserved cellulose and hemicellulose components hindered the cocrystallization and aggregation of cellulose fibril. Holocellulose paper exhibited much more favorable recycling properties, compared with cellulosic paper. After 5 runs of recycling, holocellulose paper still shown an ultimate strength as high as 25 MPa (reduced from 35 MPa), a decrease of 27.1 %. However, cellulosic paper experienced a substantial loss in ultimate strength from 35 MPa to 9 MPa, a decrease of about 74 %. This can be attributed to the core-shell structure from cellulose and hemicellulose to weaken the hornification effect.
Surface micro-crystalline coatings were prepared on Ni-20Cr and Ni-20Cr-Ce alloys by high-energy pulse plasma treatment (HEPP).After oxidation at 1000°C in air for 200h, it was shown that both oxidation resistance and the Cr content in the oxide scales on these four alloys increased in the order of Ni-20Cr < Ni-20Cr-Ce < Ni-20Cr (HEPP) < Ni-20Cr-Ce (HEPP).The results indicated that the selective oxidation of Cr in Ni-20Cr alloys can be improved either by adding Ce or surface micro-crystallisation.The synergistic effects have been discussed based on Wagner's selective oxidation theory, together with the reactive element effects, short circuit diffusion, oxide nucleation and growth processes, and stress release in the oxide scales.
Excessive exposure to ultraviolet (UV) light is harmful to human health. However, the traditional preparation of anti-UV films through the doping of UV absorbers leads to unstable products. Chemical modification of polyvinyl alcohol (PVA) to fabricate functional derivatives expand the application of these materials. Herein, a 1,4-dihydropyridine (DHP) fluorescent ring with a conjugated structure as a strong UV-absorber group was introduced onto a polyvinyl alcohol acetoacetate (PVAA) film to improve its UV-blocking performance. Firstly, PVAA was prepared via transesterification using tert-butyl acetoacetate (t-BAA). Then, the Hantzsch reaction was carried out on the surface of the PVAA film at room temperature. The resulting film showed high transparency, bright fluorescence emission, good mechanical properties, and outstanding stability. The introduction of the hydrophobic carbon chain reduced the hydrophilicity and swelling capacity of the PVAA film. In addition, the conjugated structure endowed the fluorescent film with excellent UV-blocking performance, where almost 100% UVA and UVB spectra could be shielded. The UV-blocking properties of the prepared films were persistent when they were exposed to UV irradiation, solvents, and subjected to thermal treatment. This work presents a facile and environmentally-friendly strategy by which to fabricate a multifunctional PVA-based film, which holds great potential for application in the anti-counterfeiting and UV-blocking fields.
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