The steady shear and extensional rheology of aqueous guar gum solutions was studied for concentrations, C, ranging from 1 g/L to 20 g/L. Extensional rheometry measurements were made using the Cambridge Trimaster filament-stretching device. The steady shear tests indicated a transition between a semi-dilute regime, below 10 g/L, and an entangled regime at higher concentrations. The solutions were shear-thinning solutions and obeyed the unmodified Cox-Merz rule in the dilute regime, but deviated from Cox-Merz and exhibited strongly viscoelastic behaviour at higher concentrations. The surface tension at higher concentration also deviated from the Szyszkowski model, exhibiting behaviour consistent with entanglement. The filament-thinning data did not fit the model for polymer solution behaviour presented by Entov and Hinch (1997), but gave a good fit to a modified form where time was normalized by the time for filament break-up. This scaling was independent of concentration effects, as reported by Chesterton et al. (2011) for cake batters. The modified model parameters approached asymptotic values for entangled solutions. The estimated apparent extensional viscosity exhibited a peak at unit strain followed by a constant value. The former increased as C n , where n > 1, while the latter increased linearly with C.
Life cycle assessment has been used to investigate the environmental impacts associated with using ethylene produced from biomass, rather than from the processing of crude oil, in the production of polyethylene terephthalate (PET). The cases investigated were for polymer production and distribution facilities located either (i) in the United Kingdom (UK) or (ii) in the United States of America (USA). For these cases, the ethylene was assumed to be made in Brazil, starting from ethanol made from sugar cane, and subsequently converted to ethylene glycol before shipping. A further comparison was made for the UK-based plant in which ethylene glycol was produced from a hypothetical plant based in the UK using willow as the feedstock. Using the Brazilian ethylene glycol, the net reduction of greenhouse gas emissions, over a process using ethylene glycol from petroleum processing, was ∼28% when the final product was a 500 mL PET bottle. The accompanying reduction in total use of fossil fuel was ∼16%. Using ethylene glycol derived from willow biomass in the UK produced similar fossil fuel savings, however, a smaller 3.6% reduction in the greenhouse gases. Comparisons have also been made using other environmental impacts, e.g. acidification and eutrophication, for which the biomass systems are at a disadvantage. An economic assessment of the bioethanol to ethylene conversion process has demonstrated significant dependence on the feedstock cost and product price margin; the analysis suggests that such a process is unprofitable without incentives.
The shear and extensional behavior of two aqueous gum solutions, namely (1) 1–20 g/L guar gum (Torres et al., Food Hydrocolloids. 2014;40:85–95) and (2) κ/ι‐hybrid carrageenan solutions (5–20 g/L), are shown to exhibit Giesekus‐fluid behavior when in the semidilute regime. In this regime, a common set of Giesekus fluid parameters described both shear and extensional behavior. A new analytical result describing the extension of a Giesekus fluid in the filament stretching geometry is presented. This also gave reasonable predictions of the Trouton ratio. Higher concentration guar solutions, in the entangled regime, yielded different Giesekus fluid parameters for extension to those for simple shear. The extensional data for all concentrations of both gums collapsed to a common functional form, similar to that reported for cake batters (Chesterton et al., J Food Eng. 2011;105(2):332–342); the limits of the new filament thinning expression provide insight into this behavior. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3902–3915, 2014
Herein we describe the preparation of a novel continuous flow multi-channel microreactor in which the internal surface has been functionalised with a palladium coating, enabling its use in catalytic heterogeneous liquid-phase reactions. Simple chemical deposition techniques were used to immobilise palladium(0) on the channel wall surface of a polymeric multi-capillary extrudate made from ethylenevinyl alcohol copolymer. The Pd coating of the microcapillaries has been characterised by mass spectrometry and light and electron microscopy. The functional activity of the catalytic Pd layer was tested in a series of transfer hydrogenation reactions using triethylsilane as the hydrogen source.
Microcapillary film (MCF) is a new material, produced by a continuous extrusion process, that has hybrid product characteristics linked to polymer foam, polymer film and single hollow‐fibre extrusions. MCFs have unique properties which, combined with their ease of production, may lead to exciting new developments and applications in the physical and engineering sciences, medicine and the life sciences.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.