Richard A. Pethrick

Bio: Richard A. Pethrick is an academic researcher from University of Strathclyde. The author has contributed to research in topics: Dielectric & Epoxy. The author has an hindex of 38, co-authored 410 publications receiving 6918 citations. Previous affiliations of Richard A. Pethrick include Defence Research Agency & Osmania University.

Tensile Testing of Cellulose Based Natural Fibers for Structural Composite Applications

Abstract: A series of tensile tests were conducted on a Lloyd LRX tensile testing machine for numerous natural fibers deemed potential candidates for development in composite applications. The tensile tests were conducted on the fibers jute, kenaf, flax, abaca, sisal, hemp, and coir for samples exposed to moisture conditions of (1) room temperature and humidity, (2) 65% moisture content, (3) 90% moisture content, and (4) soaked fiber. These seven fibers were then tested for the four conditions and the mechanical properties of tensile strength, tensile strain to failure, and Young's modulus were calculated for the results. These results were then compared and verified with those from the literature, with some of the fibers showing distinctly promising potential. Additionally, a study on the effect of alkalization using 3% NaOH solution was carried out on flax, kenaf, abaca, and sisal to observe impact that this common fiber pre-treatment process has on fiber mechanical properties. The result of the investigation indicated that over treatment of natural fibers using NaOH could have a negative effect on the base fiber properties. It is consequently apparent that a treatment time of less than 10 min is sufficient to remove hemicelluloses and to give the optimum effect.

A dielectric, mechanical, rheological and electron microscopy study of cure and properties of a thermoplastic-modified epoxy resin

Abstract: The effect of varying the proportion of a blended thermoplastic, poly(ether sulfone), on the cure and properties of an epoxy resin system, an aromatic diamine cured trifunctional aromatic epoxide, was studied. The initial mixture, prepared by solution casting, is homogeneous, but phase separation occurs rapidly in the initial stages of curing. Analysis of the dielectric data from the cured material shows the existence of a relaxation process which can be ascribed to polarization of a conducting occluded phase. Correlation of these data with the electron micrograph data indicates that the type of phase structure changes with thermoplastic content

Surface Topography and Composition of Deuterated Polystyrene-Poly(bromostyrene) Blends

Abstract: Surface structure, obtained from atomic force microscopy and X-ray reflectivity, and surface chemical analysis data, obtained from X-ray photoelectron and static secondary ion mass spectroscopy, are reported for blends of poly(p-bromostyrene) with poly(deuteriostyrene). When high speeds are used in the spin-coating process, the atomic force microscopy measurements reveal that the surface structure consists of islands, the distribution and number changing with the poly(bromostyrene) content. A ribbon structure is observed at just above 50% (w/w) poly(bromostyrene) in the mixture. These ribbons merge to form more continuous structures, leaving voids at higher concentrations. X-ray reflectivity data from the films were consistent with the topographical features observed with the AFM. At low spinning speeds, continuous films with little or no topographical structure are formed. The islands observed at high spinning speeds are predominately poly(bromostyrene) and reflect the importance of thermodynamic and kin...

Applications of nanotechnology in food packaging and food safety: Barrier materials, antimicrobials and sensors

Abstract: In this article, several applications of nanomaterials in food packaging and food safety are reviewed, including: polymer/clay nanocomposites as high barrier packaging materials, silver nanoparticles as potent antimicrobial agents, and nanosensors and nanomaterial-based assays for the detection of food-relevant analytes (gasses, small organic molecules and food-borne pathogens). In addition to covering the technical aspects of these topics, the current commercial status and understanding of health implications of these technologies are also discussed. These applications were chosen because they do not involve direct addition of nanoparticles to consumed foods, and thus are more likely to be marketed to the public in the short term.