Jackie Y. Cai

Modifying Surface Resistivity and Liquid Moisture Management Property of Keratin Fibers through Thiol–Ene Click Reactions

This paper reports on a new method for improving the antistatic and liquid moisture management properties of keratinous materials. The method involves the generation of thiols by controlled reduction of cystine disulfide bonds in keratin with tris(2-carboxyethyl) phosphine hydrochloride and subsequent grafting of hydrophilic groups onto the reduced keratin by reaction with an acrylate sulfonate or acrylamide sulfonate through thiol-ene click chemistry. The modified substrates were characterized with Raman spectroscopy and scanning electron microscopy and evaluated for their performance changes in liquid moisture management, surface resistivity, and wet burst strength. The results have revealed that the thiol-acrylate reaction is more efficient than the thiol-acrylamide reaction, and the keratinous substrate modified with an acrylate sulfonate salt exhibits significantly improved antistatic and liquid moisture management properties.

Novel immobilization of a quaternary ammonium moiety on keratin fibers for medical applications

This paper introduces a new approach for immobilizing a quaternary ammonium moiety on a keratinous substrate for enhanced medical applications. The method involves the generation of thiols by controlled reduction of cystine disulfide bonds in the keratin, followed by reaction with [2-(acryloyloxy)ethyl]trimethylammonium chloride through thiol-ene click chemistry. The modified substrate was characterized with Raman and infrared spectroscopy, and assessed for its antibacterial efficacy and other performance changes. The results have demonstrated that the quaternary ammonium moiety has been effectively attached onto the keratin structure, and the resultant keratin substrate exhibits a multifunctional effect including antibacterial and antistatic properties, improved liquid moisture management property, improved dyeability and a non-leaching characteristic of the treated substrate.

Enhanced mechanical performance of CNT/Polymer composite yarns by γ -irradiation

Multiwall carbon nanotube (CNT) spun yarns were subjected to γ-irradiation in an oxygen rich environment, followed by the application of epoxy to form CNT/epoxy composite yarns with a high CNT fraction. The method for fabrication of the CNT/polymer composite yarns was presented, and the effect of γ-irradiation on the mechanical performance of the pure CNT spun yarns and their epoxy composite yarns were studied. The γ-irradiated CNT yarns were also characterized by X-ray Photoelectron Spectroscopy and Raman spectroscopy. The results of this study have demonstrated that the γ-irradiation is an effective micro-engineering tool to improve mechanical properties of the CNT spun yarn and its epoxy composite yarn.

Formation of a chrome-free and coloured conversion coating on AA6063 aluminium alloy

A new passivation process has been developed for producing a chrome-free and coloured conversion coating on aluminium alloy AA6063. The method is based on the reaction of the aluminium alloy with a potassium hexafluorozirconate based solution at room temperature. The conversion coating obtained has a grey colour, which enables visual assessment of the coating development and coating quality during processing. The colouring effect is a significant advantage over the zirconium and titanium based conversion coatings currently used in the industry, which are largely colourless. The new treatment process is simple and allows a uniform coating to be formed within a few minutes. The composition and the surface morphology of the coatings were characterized. The corrosion resistance of the coated samples was evaluated by electrochemical tests. The results have shown that the treatment yields a zirconium based conversion coating with a microcrystalline structure, which is desirable for paint adhesion, and substantially improves the corrosion resistance of the aluminium alloy.

Insulation properties of the monolithic and flexible aerogels prepared at ambient pressure

This paper reports a method for scale-up fabrication of hydrophobic and flexible aerogels derived from a combined precursor methyltrimethoxysilane and vinyltrimethoxysilane. The method developed enables the preparation of large pieces of monolithic aerogels at ambient pressure drying conditions. The thermal and acoustic insulation properties of the flexible aerogels were investigated and compared with the commercially available insulation materials.

Click chemistry modification of natural keratin fibers for sustained shrink-resist performance.

This paper introduces a novel chemical treatment for achieving sustained shrink-resist performance on natural keratin fibers. The new treatment involves the controlled reduction of keratin in the cuticle region of the fiber, and the application of a water soluble diacrylate, namely glycerol 1,3-diglycerolate diacrylate (GDA), on the reduced keratin substrate. The acrylate groups of the GDA react with cysteine residues in the reduced keratin through thiol-ene click reactions at room temperature, leading to GDA grafting and the formation of GDA crosslinks in the keratin structure. The modified substrates were characterized by infrared spectroscopy and scanning electron microscopy, and assessed for its shrink-resistance and wet burst strength. This chemical modification has shown to alter the fiber surface morphology and hydrophilicity, resulting in substantially improved shrink-resistance with good fiber strength retention. Possible shrink-resistance mechanisms were also discussed.

Dyeing Wool with Metal-free Dyes – The Use of Sodium Borohydride for the Application of Vat Dyes to Wool

Vat dyestuffs are pigments that must be pre-treated with a reducing agent, such as sodium hydrosulphite, to make them water-soluble immediately before they are used for dyeing (Latham, 1995; Trotman, 1984). The reduction step converts the pigment form into a leuco compound. This owes its name to the Greek word for colourless, because many vat dyes are very pale in colour when in the reduced state, due to the lower level of conjugation of double bonds. A schematic of this reaction for the dyestuff Vat Red 1 is shown in Figure 1.

Protecting keratin fiber with water soluble N-substituted maleimides in high temperature processes

This paper reports a facile method for protecting keratin fiber with water soluble N-substituted maleimides during high temperature processing in aqueous solutions. Three water soluble N-substituted maleimides, including aliphatic and aromatic maleimides, were synthesized and applied. Their treatment effects were characterized by Raman spectroscopy and evaluated on the fiber’s physical and mechanical properties. An aliphatic maleimide, 3-maleimidopropanoic acid, was demonstrated to be an excellent protective agent for keratin fiber, as evidenced by the significantly reduced permanent set and improved wet burst strength of the protected substrate.

A Practical Approach for Producing Hydrophobic and Elastic Aerogels by Ambient Pressure Drying

Hydrophobic and elastic aerogels derived from methyltrimethoxysilane (MTMS) precursor were prepared by ambient pressure drying under various processing conditions, and their morphology and physical and mechanical properties were characterised and evaluated. The results of this study demonstrated that for inherently hydrophobic gels like MTMS based gels, high temperature ageing is a practical and effective means to reduce volume shrinkage and produce low bulk density monolithic aerogels at ambient pressure, without the need of any solvent exchange and surface modification. By using this simple method, we were able to produce an aerogel with a bulk density as low as 0.064g/cm3. The results also revealed a significant difference from that previously reported in the literature.