Investigation of the Fabrication Suitability, Structural Performance, and Sustainability of Natural Fibers in Coreless Filament Winding

Coreless filament winding is an emerging fabrication technology in the field of building construction with the potential to significantly decrease construction material consumption, while being fully automatable. Therefore, this technology could offer a solution to the increasing worldwide demand for building floor space in the next decades by optimizing and reducing the material usage. Current research focuses mainly on the design and engineering aspects while using carbon and glass fibers with epoxy resin; however, in order to move towards more sustainable structures, other fiber and resin material systems should also be assessed. This study integrates a selection of potential alternative fibers into the coreless filament winding process by adapting the fabrication equipment and process. A bio-based epoxy resin was introduced and compared to a conventional petroleum-based one. Generic coreless wound components were created for evaluating the fabrication suitability of selected alternative fibers. Four-point bending tests were performed for assessing the structural performance in relation to the sustainability of twelve alternative fibers and two resins. In this study, embodied energy and global warming potential from the literature were used as life-cycle assessment indexes to compare the material systems. Among the investigated fibers, flax showed the highest potential while bio-based resins are advisable at low fiber volume ratios.

Solubility, thermal and photoluminescence properties of triphenyl imidazole-containing polyimides

In this paper, three kinds of triphenyl imidazole-containing diamines including 2-phenyl-4,5-bis(4-(4-amino-2-trifluoromethylphenoxy)phenyl)imidazole (PBAI), 2-(4-methylphenyl)-4,5-bis(4-(4-amino-2-trifluoromethyl phenoxy)phenyl)imidazole (MPBAI) and 2-(4-trifluoromethylphenyl)-4,5-bis(4-(4-amino-2-trifluoromethylphenoxy)phenyl)imidazole (TFPBAI) were synthesized. Then, a series of polyimide (PI) films were prepared by the solution polymerization of the three diamines and various dianhydrides, such as 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), 1,2,4,5-pyromellitic dianhydride (PMDA) and 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA), followed by thermal imidization. The effects of chemical structures on the solubilities and thermal, optical and electrochemical properties of polyimides were explored. All the polyimides exhibited higher glass transition temperatures around 300 °C and excellent solubilities in common polar solvents. The polyimide films derived from CBDA or 6FDA showed better optical properties with light color and transparent characteristics. The fluorescence test showed that the photoluminescence color of CBDA-based polyimide films is in the blue range in the CIE 1931 spectrum, while the polyimide film based on PMDA and 6FDA presented black or weak yellow light. However, all these polyimides in solution exhibited similar blue luminescence. Electrochemical tests indicated that the HOMO and LUMO values of these films were around −6.5 and −3.6 eV, and the energy gap difference was about 3.0 eV. Therefore, the triphenyl imidazole-containing polyimides exhibit comprehensive performance, which will be expected as a new kind of functional material for certain application in the optical and optoelectronics fields.

The triphenyl imidazole-containing polyimide films exhibit excellent solubility and thermal and photoluminescence properties.

Graphene-Encapsulated Co9 S8 Nanoparticles on N,S-Codoped Carbon Nanotubes: An Efficient Bifunctional Oxygen Electrocatalyst

An inexpensive and efficient bifunctional electrocatalyst for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) is central to the rechargeable zinc-air battery. Herein, a nanohybrid, in which N,S-codoped carbon nanotubes were decorated with Co₉ S₈ nanoparticles encapsulated in porous graphene layers, was fabricated by a one-step heat-treatment process. The N,S dopant species were the major active sites for the ORR, and Co₉ S₈ nanoparticles were mainly responsible for the OER. Compared with commercial 20 wt % Pt/C and Ir/C electrocatalysts, this nanohybrid exhibited a comparable ORR half-wave potential (0.831 V vs. reversible hydrogen electrode) and OER potential (1.591 V at 10 mA cm^-2 ), better long-term stability in an alkaline medium, and a narrower potential gap (0.76 V) between ORR and OER. Furthermore, as air electrode of the rechargeable zinc-air battery, it delivered a low charge-discharge voltage gap (0.65 V at 5 mA cm^-2 ), high open-circuit potential (1.539 V), good specific capacity (805 mA h g - 1 Zn at 5 mA cm^-2 ), and excellent cycling stability (48 h), superior to those of commercial Pt/C and Ir/C catalysts, and thus showed promise for applications in renewable energy conversion devices.

An Oligoimide Particle as a Pickering Emulsion Stabilizer

A pyromellitic dianhydride (PMDA) and 4,4'-oxydianiline (ODA)-based oligoimide (PMDA-ODA) was synthesized by a one-step procedure using water as a solvent. The PMDA-ODA particles showed excellent partial wetting properties and were stably dispersed in both water and oil phases. A stable dispersion was not obtained with comparison PMDA-ODA particles that were synthesized by a conventional two-step method using an organic solvent. Both oil-in-water and water-in-oil Pickering emulsions were prepared using the oligoimide particles synthesized in water, and the size of the emulsion droplet was controlled based on the oligoimide particle concentration. The oligoimide particles were tested to prepare Pickering emulsions using various kinds of oils. The oil-in-water Pickering emulsions were successfully applied to prepare microcapsules of the emulsion droplets. Our new Pickering emulsion stabilizer has the advantages of easy synthesis, no need for surface modification, and the capability of stabilizing both oil-in-water and water-in-oil emulsions.

Ternary memory property of novel polyimide with backbone carbazole moiety and pendant triphenylamine moiety

The polyimide (TPA-Cz PI) was synthesized by the reaction of 9-(4′-(4′-diphenylamino)phenylbenzyl)-3,6-diaminocarbazole with 2,2′,3,3′-biphenyltetracarboxylic dianhydride through a classical two-step polymerization process. It exhibited excellent organo-solubility and self-extinguishing property. The synthesized TPA-Cz PI shown excellent film formation. The TPA-Cz PI film sandwiched between an indium tin oxide bottom electrode and Al top electrode. And the fabricated memory device exhibited ternary rewritable storage property in the bias with good data retention and the current ratio of 104:102:1 for ON2, ON1, and OFF states. Its current conduction mechanism by the I-V curves of different conduction models based on the experimental data was analyzed and used to illuminate the physical nature of resistance switching effects. The experimental result indicates that field-induced conformational ordering of the TPA-Cz PI chains and charge-transfer interaction between electron-donor and electron-withdrawing are responsible for the switching behavior. This work can provide a sketch for the design and selection of ternary state resistance random access memory materials in future research.