Thermal, chemical and morphological properties of carbon fibres derived from chemically pre-treated wool fibres

In this work, the feasibility of using wool fibre as a carbon fibre precursor was explored as well as whether chemical treatments to wool fibre can increase the carbon fibre yield and properties of the produced carbon fibres. Wool fibres were treated with a range of chemicals including lignin, tannic acid, polystyrene sulphonate, and chlorine in conjunction with a polyamide resin. The treated fibres were stabilised in air at 160 C followed by pyrolysis at 800 C under a nitrogen atmosphere. The resulting carbon fibres were characterised in terms of carbon yield, tensile strength, surface roughness, porosity, crystal structure and surface hydrophobicity. The carbon fibre yield was 16.7% for the untreated while the lignin pre-treatment increased the carbon yield up to 25.8%. Generally the surface of the carbon fibre made from both untreated and treated fibre exhibited high hydrophilicity except the lignin and chlorine/polyamide resintreated fibre which showed hydrophobicity. Although the tensile strength achieved for the various produced carbon fibre was poor compared to a commercially available pitch-based carbon fibre, the developed carbon fibre still can be utilised in thermoplastic composite manufacturing

Calculated phase diagrams, iron tolerance limits, and corrosion of Mg-Al alloys

The factors determining corrosion are reviewed in this paper, with an emphasis on iron tolerance limit and the production of high-purity castings. To understand the iron impurity tolerance limit, magnesium phase diagrams were calculated using the Pandat software package. Calculated phase diagrams can explain the iron tolerance limit and the production of high-purity castings by means of control of melt conditions; this is significant for the production of quality castings from recycled magnesium. Based on the new insight, the influence of the microstructure on corrosion of magnesium alloys is reviewed

Sustainable production of carbon fiber: Effect of cross-linking in wool fiber on carbon yields and morphologies of derived carbon fiber

Currently, most of the carbon fibers are made from unsustainable fossil fuel-based precursors including high purity polyacrylonitrile (PAN) and pitch. High purity PAN is not only more expensive than wool fiber but also a limited quantity is produced because of global shortage of its monomer. In this work, various cross-linking pathways are explored as a means of altering the yield and tensile properties of carbon fiber derived from the carbonization of cross-linked wool fiber at 800°C under nitrogen. A range of ionic and covalent-bond-forming cross-linking agents including bifunctional carboxylic acids (succinic acid and sebacic acid), a disulfonic acid (naphthalene disulfonic acid), a dialdehyde (glyoxal), and dianhydrides (succinic anhydride and itaconic anhydride) was investigated. The resulting carbon fibers were characterized in terms of chemical composition, carbon yield, surface topology, crystal structure, hydrophilicity, and tensile properties. It was found that the carbon yield can be increased by 55% by using cross-linking treatments. Carbon fiber produced from untreated and crosslinked wool fibers all exhibited superhydrophilicity. Although the tensile strength of the resulting carbon fiber was relatively low in this preliminary study, the resulting fiber could have applications in the manufacturing of thermoplastic composite materials as low modulus filler

Equilibrium moisture content of a crosslinked epoxy network via molecular dynamics simulations

This study presents molecular dynamics (MD) simulation methods for determining the solubility limit of water in a crosslinked epoxy network. Procedures are first presented for dynamically crosslinking an epoxy network consisting of diglycidyl ether bisphenol A (DGEBA) and isophorone diamine (IPD). Water molecules are then introduced into the crosslinked DGEBA-IPD structure. The excess chemical potential for the absorbed water was determined through combining thermodynamic integration and Widom's test particle insertion methods. The limiting moisture uptake of the epoxy structure was determined through comparing the reduced chemical potential of the water held within the epoxy to that of pure water. The DGEBA-IPD epoxy system was found to have a moisture solubility of 3.50-3.75 wt.% when immersed in water at 300 K

Functional nanofibers in clothing for protection against chemical and biological hazards

Functional nanofibers have great potential to improve protection against chemical and biological warfare agents. This chapter reviews the history of chemical and biological warfare and existing protective technologies. The use of electrospinning to produce nanofibers for protective applications is also introduced. Previous studies demonstrate the applicability of electrospun nanofibers in protective fabric technologies. Advantages of these next generation protective materials include high penetration resistance, excellent breathability, low basis weight, low pressure drop, the potential for the incorporation of surface chemical functionality and simple processing equipment. Finally, the main development issues and potential research directions of electrospun nanofibers in protective applications are discussed

Positive size and scale effects of all-cellulose composite laminates

Negative size effects are commonly reported for advanced composite materials where the strength of the material decreases with increasing volume of the test specimen. In this work, the effect of increasing specimen volume on the mechanical properties of all-cellulose composites is examined by varying the laminate thickness. A positive size effect is observed in all-cellulose composite laminates as demonstrated by a 32.8% increase in tensile strength as the laminate thickness is increased by 7 times. The damage evolution in all-cellulose composite laminates was examined as a function of the tensile strain. Enhanced damage tolerance concomitant with increasing specimen volume is associated with damage accumulation due to transverse cracking and strain delocalisation. A transition from low-strain failure to tough and high-strain failure is observed as the laminate thickness is increased. Simultaneously, scale effects lead to an increase in the void content and cellulose crystallinity at the core, with increasing laminate thickness

Drug release, cytocompatibility, bioactivity, and antibacterial activity of doxycycline loaded Mg-Ca-TiO2 composite scaffold

© 2017 Mg-Ca-TiO2 (MCT) composite scaffolds loaded with different concentrations of doxycycline (DC) with a network of interconnected pores with good compressive strength (5 ± 0.1 MPa) were fabricated via space holder method for the first time. The results showed that MCT-DC scaffolds possess a porosity and pore size in the range of 65–67% and 600–800 μm respectively. The bioactivity results exhibited the apatite formation on the MCT-DC scaffold surface, indicating that DC did not obstruct the bioactivity of MCT. The MCT-DC scaffolds drug release profiles show the initial burst and sustained drug release (55–75%) and the release rate could be adjusted via altering the DC concentration. The MCT loaded with 1 and 5% DC did not indicate cytotoxic behavior against MG63 cells while further DC loading resulted in some toxicity. Antimicrobial properties of MCT-DC scaffolds against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) bacteria were examined and the results reveal oblivious inhibition zone around each MCT-DC scaffold whereas no obvious inhibition is observed around the MCT scaffold. Therefore, MCT-DC composite scaffolds with low concentration of DC could be alternative candidates for infection prevention and bone tissue engineering