J. Y. Cai, J. Min, J. McDonnell, J. S. Church, C. D. Easton, B. Humphries, S. Lucas, A. Woodhead

We report a method for modifying carbon nanotube (CNT) spun yarns with aryldiazonium salts that involves the pH controlled application of the diazonium salts to CNTs both during and after the yarn formation process. This largely facilitates the chemical accessibility to CNTs within the yarn, potentially enabling a more extensive and uniform modification. The modified CNT yarns were characterised by X-ray photoelectron spectroscopy, Raman spectroscopy and scanning electron microscopy, and also examined for their mechanical properties. The results demonstrated that a CNT spun yarn was effectively modified by this method without impairing the yarn integrity. The formation of oligomerised polyene structures on the CNT surfaces was observed. This modification resulted in an increase in tensile strength and Young’s modulus of the CNT yarn. The functional groups grafted on CNTs also provide opportunities to form crosslinks in the yarn to further improve mechanical properties.

J. A. Schutz, J. S. Church

People who work in hazardous Environments under high physiological stress often have to weigh up the benefits and difficulties of wearing respiratory protection. By developing filter materials that provide comparable smoke particle protection at a significantly lower breathing Resistance, exposure to physiological stress may be reduced without jeopardizing protection. In this paper, we investigate to this end the use of stationary electrostatic surface Charges, which are known to dramatically improve the efficiency of filter media to fine particles at next to no change in breathing resistance. Filtration test results presented show that some high temperature polymer fiber materials commonly used for personal protective equipment can in fact reach best practice filtration performance if combined with a suitable fiber counterpart. Tribo-electric fiber blends made from combinations of polypropylene with poly-imide-amide, poly(m-phenylene benzimidazole), meta-polyaramid or para-polyaramid have been found to generate significant electrostatic enhancements in nonwoven needle felts that are stable over time. Results suggest that polypropylene is an essential component of fiber blends that reach best practice electrostatic performance with the exception of a meta-aramid fiber blended with wool that appears to work as well. As a result, it is possible to manufacture heat resistant garments for respiratory protection against smoke particles, which could be similar to a bandana and provides protection at a reduced breathing resistance.

E. P. Schokker, J. S. Church, J. P. Mata, E. P. Gilbert, A. Puvanenthiran, P. Udabage

A problem associated with micellar casein (MC) powders is their poor reconstitution properties. In this study, we prepared MCs with different salt and protein compositions and having different reconstitutabilities directly after production. Reconstitutability further decreased during storage at 30 °C. Differential scanning calorimetry, infrared spectroscopy, and small angle X-ray scattering showed that the powders were very similar on a molecular or sub-micellar level, indicating that the loss of reconstitutability is probably controlled by higher order structural changes, such as cross-linking between casein micelles, possibly involving intermolecular β-sheet formation. The reconstitutability of MC could be improved by adding sodium caseinate to the concentrated milk before spray drying. This novel approach to improve reconstitutability can easily be incorporated into the existing processing protocol. We propose two possible mechanisms for the protecting effect of the non-micellar caseins.

A. J. Poole, R. E. Lyons, J. S. Church

Feather keratin has been widely studied for use as a bio-based material. In this paper, we dissolve feather keratin using industrial sodium sulfide to investigate the yield, dissolved keratin characteristics, and properties of regenerated products to assess the potential of using sodium sulfide as a means of converting waste feathers into a biopolymer. Optimal conditions appeared to require short incubation times in order to give maximum strength in the regenerated product. This limits the yield to approximately 55%. Air-dried films and acid-precipitated samples are all readily re-crosslinked, suggesting the re-crosslinking process is robust. Minimizing exposure to the highly alkaline conditions appears favorable to final product strength through minimizing alkaline chain damage. The β-sheet structure of the parent keratin is largely maintained. The regenerated keratin was shown to have potentially attractive physical properties for use as a bio-polymer.

M. S. Islam, J. S. Church, M. Miao

Natural fibre/polypropylene thermoplastic composites are often produced by compression moulding of a blended preform of polypropylene fibre and natural fibre treated by chemicals or enzymes. Two preform processing routes may be adopted: (1) treating the natural fibre first and then blending it with the polypropylene fibre (the pre-treatment route), and (2) forming a blended preform of the natural fibre and polypropylene fibre first and then carrying out the chemical/enzyme treatment on the blended preform (the post-treatment route). The kenaf/polypropylene composites produced according to the post-treatment route show up to 36% higher flexural strength and up to 63% higher flexural modulus than the composites produced according to the corresponding pre-treatment route. These differences were attributed to the chemical surface finishes of the polypropylene fibre, which have been removed in the post-treatment processing route, but persisted into the final composites in the pre-treatment processing route.

S. L. Edwards, J. S. Church, D. L. J. Alexander, S. J. Russell, E. Ingham, J. A. M. Ramshaw, J. A. Werkmeister

In this study we present a novel approach for predicting tissue growth within the pores of fibrous tissue engineering scaffolds. Thin nonwoven polyethylene terephthalate scaffolds were prepared to characterize tissue growth within scaffold pores, by mouse NR6 fibroblast cells. On the basis of measurements of tissue lengths at fiber crossovers and along fiber segments, mathematical models were determined during the proliferative phase of cell growth. Tissue growth at fiber crossovers decreased with increasing interfiber angle, with exponential relationships determined on day 6 and 10 of culture. Analysis of tissue growth along fiber segments determined two growth profiles, one with enhanced growth as a result of increased tissue lengths near the fiber crossover, achieved in the latter stage of culture. Derived mathematical models were used in the development of a software program to visualize predicted tissue growth within a pore. This study identifies key pore parameters that contribute toward tissue growth, and suggests models for predicting this growth, based on fibroblast cells. Such models may be used in aiding scaffold design, for optimum pore infiltration during the tissue engineering process.

M. G. Huson, E. V. Strounina, C. S. Kealley, M. K. Rout, J. S. Church, I. A. M. Appelqvist, M. J. Gidley, E. P. Gilbert

The effects of moisture and thermal denaturation on the solid-state structure and molecular mobility of soy glycinin powder were investigated using multiple techniques that probe over a range of length and time scales. In native glycinin, increased moisture resulted in a decrease in both the glass transition temperature and the denaturation temperature. The sensitivity of the glass transition temperature to moisture is shown to follow the Gordon-Taylor equation, while the sensitivity of the denaturation temperature to moisture is modeled using Flory's melting point depression theory. While denaturation resulted in a loss of long-range order, the principal conformational structures as detected by infrared aremaintained. The temperature range over which the glass to rubber transition occurred was extended on the high temperature side, leading to an increase in the midpoint glass transition temperature and suggesting that the amorphous regions of the newly disordered protein are less mobile. ¹³C NMR results supported this hypothesis.

S. Weisman, V. S. Haritos, J. S. Church, M. G. Huson, S. T. Mudie, A. J. W. Rodgers, G. J. Dumsday, T. D. Sutherland

Transgenic production of silkworm and spider silks as biomaterials has posed intrinsic problems due to the large size and repetitive nature of the silk proteins. In contrast the silk of honeybees (Apis mellifera) is composed of a family of four small and non-repetitive fibrous proteins. We report recombinant production and purification of the four full-length unmodified honeybee silk proteins in Escherichia coli at substantial yields of 0.2–2.5 g/L. Under the correct conditions the recombinant proteins self-assembled to reproduce the native coiled coil structure. Using a simple biomimetic spinning system we could fabricate recombinant silk fibers that replicated the tensile strength of the native material.