Mechanical property enhancement in short-fiber composites through the control of fiber orientation during fabrication

The mechanical properties of plastics and elastomers reinforced by short fibers are generally dictated by the selection of matrix and reinforcement. However, the high tensile properties attainable in these systems through laboratory processing techniques are frequently not obtained in conventional fabrication operations. To gain a wider latitude in meeting economic and performance constraints, the control of composite structure in the fabrication step should not be overlooked. Tool geometry and processing conditions can be manipulated specifically to control the fiber orientation distribution in the product. A study of fiber orientation in composite compounds during flow through runners, gates, and dies leads to recommendations for optimizing the directional strength and stiffness according to a kinematic model. Performance data on parts fabricated from various short-fiber composite materials bear out these projections.     

A Fourier-transform infrared study of CO2 and CO2/H2 interactions with caesium-doped copper catalysts

FTIR spectra are reported of CO₂ and CO₂/H₂ on a silica-supported caesium-doped copper catalyst. Adsorption of CO₂ on a “caesium”/silica surface resulted in the formation of CO₂ ⁻ and complexed CO species. Exposure of CO₂ to a caesium-doped reduced copper catalyst produced not only these species but also two forms of adsorbed carboxylate giving bands at 1550, 1510, 1365 and 1345 cm⁻¹. Reaction of carboxylate species with hydrogen at 388 K gave formate species on copper and caesium oxide in addition to methoxy groups associated with caesium oxide. Methoxy species were not detected on undoped copper catalyst suggesting that caesium may be a promoter for the methanol synthesis reaction. Methanol decomposition on a caesium-doped copper catalyst produced a small number of formate species on copper and caesium oxide. Methoxy groups on caesium oxide decomposed to CO and H₂, and subsequent reaction between CO and adsorbed oxygen resulted in carboxylate formation. Methoxy species located at interfacial sites appeared to exhibit unusual adsorption properties.     

The extrusion and performance of plasticized poly(vinyl chloride) hose reinforced with short cellulose fibers

Short fibers of natural cellulose treated to provide dispersability and strong interfacial bonding are ideal reinforcements for plasticized vinyl compounds. The development of substantial strength and stiffness in unidirectional composites indicates the reinforcing potential of these high aspect-ratio fibers in soft compositions. Special extrusion dies developed to control fiber directionality in rubber extrudates are equally applicable to vinyl hose. The unusual expanding geometry of these tools aligns the fibers toward the circumferential direction to provide optimum reinforcement against contained pressure loading. Thus, reinforced poly(vinyl chloride) air and water hoses can be produced in a single extrusion step, since all of the necessary reinforcement is contained in the compound.     

Self Organising Maps for variable selection: Application to human saliva analysed by nuclear magnetic resonance spectroscopy to investigate the effect of an oral healthcare product

SOMs (Self Organising Maps) are derived from the machine learning literature and serve as a valuable method for representing data. In this paper, the use of SOMs as a technique for determining the most significant variables (or markers) in a dataset is described. The method is applied to the NMR spectra of 96 human saliva samples, half of which have been treated with an oral rinse formulation and half of which are controls, and 49 variables consisting of bucketed intensities. In addition, three simulations, two of which consist of the same number of samples and variables as the experimental dataset and a third that contains a much larger number of variables, are described. Two of the simulations contain known discriminatory variables, and the remaining is treated as a null dataset without any specific discriminatory variables added. The described SOM method is contrasted to Partial Least Squares Discriminant Analysis, and a list of the markers determined to be most significant using both approaches was obtained and the differences arising are discussed. A SOM Discrimination Index (SOMDI) is defined, whose magnitude relates to how strongly a variable is considered to be a discriminator. In order to ensure that the model is stable and not dependent on the random starting point of the SOM, one hundred iterations were performed and variables that were consistently of high rank were selected. A variety of approaches for data representation are illustrated, and the main theoretical principles of employing SOMs for determining which variables are most significant are outlined. Software used in this paper was written in-house, allowing greater flexibility over existing packages, and tailored for the specific application in hand.     

High hydrogen production from glycerol or glucose by electrohydrogenesis using microbial electrolysis cells

The use of glycerol for hydrogen gas production was examined via electrohydrogenesis using microbial electrolysis cells (MECs). A hydrogen yield of 3.9 mol-H₂/mol was obtained using glycerol, which is higher than that possible by fermentation, at relatively high rates of 2.0 ± 0.4 m³/m³ d (E_ap = 0.9 V). Under the same conditions, hydrogen was produced from glucose at a yield of 7.2 mol-H₂/mol and a rate of 1.9 ± 0.3 m³/m³ d. Glycerol was completely removed within 6 h, with 56% of the electrons in intermediates (primarily 1,3-propanediol), with the balance converted to current, intracellular storage products or biomass. Glucose was removed within 5 h, but intermediates (mainly propionate) accounted for only 19% of the electrons. Hydrogen was also produced using the glycerol byproduct of biodiesel fuel production at a rate of 0.41 ± 0.1 m³/m³ d. These results demonstrate that electrohydrogenesis is an effective method for producing hydrogen from either pure glycerol or glycerol byproducts of biodiesel fuel production.