Capillary effects in vacuum‐assisted resin transfer molding with natural fibers

The study of the capillary flow developed during the processing of composite materials is key because it acts as an important driving force for the impregnation of the fiber tows. It is also the main mechanism of void formation during infiltration of the fibers. In this work, capillary pressure of jute/vinylester composites was measured and the impact of capillary forces on fabric permeability was analyzed. It was found that the capillary pressure was significantly higher in vegetal than in synthetic fiber fabrics. In addition, the permeability of the fibers was characterized using various fluids. The resulting permeability was influenced by the nature of fluid and its polar property. Finally, the capillary pressure measured by this work was used to correct the experimental permeability in order to obtain a property independent of the test fluid. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Urban form, biodiversity potential and ecosystem services

Using data from selected areas in five UK cities, we studied the relationships between urban form and the following measures of ecosystem performance: availability and patch characteristics of tree cover, gardens and green space; storm-water run-off; maximum temperature; carbon sequestration. Although most measures of ecosystem performance declined with increasing urban density, there was considerable variability in the relationships. This suggests that at any given density, there is substantial scope for maximising ecological performance. The social status of residents was related to measures of tree cover. Housing type was significantly associated with some types of ecosystem service provision, indicating that the type of development may be important independent of its density. These findings have implications for understanding the distribution of ecosystem services and biodiversity across urban landscapes, and the management of development aimed at meeting UK government housing density targets.     

Chemical Kinetics and Heat Transfer Issues for a Safe Bench Scale Production of Partially Triazole Substituted Glycidyl Azide Polymer (GAP)

The reaction of azido polymers with double and triple bonds of light olefins can lead to triazole and aziridine cycles formation on the azide bearing sites of the polymer. An experimental investigation of the burning behaviour of these modified polymers has shown that triazole substituted GAPs exhibit a higher burning rate at low pressure, which may be a desirable characteristic for ducted rocket applications. However, the chemical reaction of interest is highly exothermic and as such, it represents a significant safety risk when conducted in bulk. In order to reduce this risk, we have assessed the chemical kinetics of triazole formation by NMR spectroscopy and linked this information with DSC measurements to produce a safe procedure for the synthesis of GAP‐triazole polymer in a chemical reactor.