A comparison of mechanical properties of recycled high-density polyethylene/waste carbon fiber via injection molding and 3D printing

Recycled high-density polyethylene (r-HDPE) was combined with waste carbon fiber by loading 6 k, 12 k, and 24 k tows through an extruder to create thermoplastic/carbon pellets with fiber volume fractions of 11.2%, 18.9%, and 29.5%, respectively. Tensile and flexural coupons were subsequently produced via injection molding and novel 3D printing. The addition of carbon into r-HDPE in all cases showed increased mechanical properties. Maximum increases were observed through the inclusion of 29.5% fiber volume fraction. Increases in tensile and flexural modulus of up to 2.9 GPa (+505.9%) and 5.8 GPa (+711.0%) respectively were observed for r-HDPE/carbon fiber (CF) samples. Increases in tensile and flexural strengths of up to 57.9 MPa (+311.8%) and 47.7 MPa (+188.0%) respectively were observed for 29.5% r-HDPE/CF samples. Some variance in mechanical performance between injection molded and 3D printed samples was observed indicating production methodology might influence final material performance

A high value application of reclaimed carbon fibers: Environmental remediation and redeployment in structural composites

This paper describes the use of reclaimed milled carbon fibers in a non-traditional application of pollutant removal and redeployment in a composite material. Commercially available milled reclaimed carbon fibers were able to remove 78% of perfluorinated and polyfluorinated alkyl substance pollutants from water. Modification of the reclaimed milled carbon fiber surface to model fibers ‘saturated’ with pollutant was undertaken and a comparison made between the modified sample and control materials. Aging these samples in water at 35 °C for 2 months, and periodically determining weight gain, flexural strength, and flexural modulus showed no significant difference between control fibers and those possessing a fluorinated surface. More aggressive aging, by boiling these samples in water for 48 h, again shows no meaningful difference between fiber types. Moreover, analysis of the water used for aggressive aging of samples by 19F NMR shows that no leaching of the fluorinated species occurs

Applications of nano-porous graphene materials-critical review on performance and challenges

The design and fabrication of 2D nano-porous architectures with controllable porosity and pore structure, as well as unique properties at the nanoscale are critical for applications such as separation, sensing, energy and catalysis. Perforation strategies across 2D materials, primarily graphene, have shown promising opportunities to develop nanostructures with tunable ranges of pore size distribution, pore density and uniformity. In addition, the perforated graphene structures exhibit improved properties in terms of plasmonic diffusion, catalytic activity and thermo-electrical properties compared to dense 2D materials and are opening new avenues for the development of responsive or reactive materials. This review presents and discusses the very recent developments in the synthesis of perforated graphene-based materials and correlates the morphology and other properties of such 2D nano-porous materials to their performance in applications such as separation, sensing and energy. Challenges related to the controlled engineering and manufacturing of such nanostructures particularly from a scalability point of view, as well as potential avenues for performance improvements through alternative 2D perforated materials are also critically evaluated

Solvent-free surface modification of milled carbon fiber using resonant acoustic mixing

Resonant Acoustic Mixing (RAM) is used to rapidly modify the surface of milled carbon fiber using diazonium salts in solvent free conditions. This novel method allows tuning of the surface properties of this material and reduces the environmental footprint usually associated with surface modification of carbon fiber (discontinuous or otherwise). As a proof of concept, fluorine-containing diazonium salts were successfully grafted as determined by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX) and an increase in water contact angle (WCA) of the milled carbon fiber samples (+15°). Atomic Force Microscopy (AFM) together with SEM revealed the surface structure and integrity of the milled carbon fibers could be maintained despite vigorous mixing conditions. Using RAM proved more efficient than positive controls produced under thermal conditions in solvent

Mixed Surface Chemistry on Carbon Fibers to Promote Adhesion in Epoxy and PMMA Polymers

Carbon fibers were surface modified using mixed grafting solutions of methyl methacrylate and glycidyl (epoxy) methacrylate in ratios of 0:100; 25:75; 50:50; 75:25; and 100:0, respectively. When evaluated in an epoxy resin, all modified fibers showed significant improvement in fiber-to-matrix adhesion. Notably, the surface-grafted polymer with blends of methyl methacrylate:glycidyl methacrylate of 0:100 and 25:75, respectively, showed a >200% improvement in adhesion relative to control fibers. When evaluated in PMMA, again significant adhesion improvements were observed, though fibers grafted with ≥25% methyl methacrylate were statistically indistinguishable. This shows that by correctly tuning the surface chemistry an optimal covalent sizing can be developed for thermoplastic and thermoset resins. As an additional benefit, a significant improvement in the treated fiber's tensile strength and modulus was also observed

Inducing liquid crystallinity in dilute MXene dispersions for facile processing of multifunctional fibers

Inducing liquid crystallinity in dilute MXene dispersions for facile processing of multifunctional fiber

Reinterpreting the Fate of Iridium(III) Photocatalysts-Screening a Combinatorial Library to Explore Light-Driven Side-Reactions

Photoredox catalysts are primarily selected based on ground and excited state properties, but their activity is also intrinsically tied to the nature of their reduced (or oxidized) intermediates. Catalyst reactivity often necessitates an inherent instability, thus these intermediates represent a mechanistic turning point that affords either product formation or side-reactions. In this work, we explore the scope of a previously demonstrated sidereaction that partially saturates one pyridine ring of the ancillary ligand in heteroleptic iridium(III) complexes. Using highthroughput synthesis and screening under photochemical conditions, we identified different chemical pathways, ultimately governed by ligand composition. The ancillary ligand was the key factor that determined photochemical stability. Following photoinitiated electron transfer from a sacrificial tertiary amine, the reduced intermediate of complexes containing 1,10-phenanthroline derivatives exhibited long-term stability. In contrast, complexes containing 2,2′-bipyridines were highly susceptible to hydrogen atom transfer and ancillary ligand modification. Detailed characterization of selected complexes before and after transformation showed differing effects on the ground and excited state reduction potentials dependent on the nature of the cyclometalating ligands and excited states. The implications of catalyst stability and reactivity in chemical synthesis was demonstrated in a model photoredox reaction