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Papers by Stewart McGlashan
Rheologica Acta, 1998
Mackay et al. (1995) have presented an approximate technique to determine the elongation viscosit... more Mackay et al. (1995) have presented an approximate technique to determine the elongation viscosity from pressure drop measurements in a simple stagnation flow device. In the present paper we describe experiments using a high viscosity Newtonian oil, aimed at probing some of the assumptions made by Mackay et al. We find that Trouton ratios calculated using the original analysis are well above the value of three expected for Newtonian fluids. Finite element simulations of the flow field show this is due to the net pressure drop having a substantial shear contribution, which should be corrected for before the Trouton ratios are evaluated. Interestingly, most of the shear correction is due to shear on the inside of the orifice near the exit from the central flow region. The shear contribution to the pressure drop occurs for all flow rates, however, at large flow rates there is also an inertial correction to the pressure drop. In this paper we describe an approximate method that corrects for both shear and inertial effects. With these effects recognised and corrected for, the measured Trouton ratios are reduced to around three.
Journal of Non-newtonian Fluid Mechanics, 2000
... Bagley end correction technique [1]. A comparison between the pressure drop derived from this... more ... Bagley end correction technique [1]. A comparison between the pressure drop derived from this correction and that measured from a zero L/D orifice for this LLDPE was shown by McGlashan and Mackay to be ... The simple analysis introduced by Denn [21] and used by Hay et al. ...
... Bagley end correction technique [1]. A comparison between the pressure drop derived from this... more ... Bagley end correction technique [1]. A comparison between the pressure drop derived from this correction and that measured from a zero L/D orifice for this LLDPE was shown by McGlashan and Mackay to be ... The simple analysis introduced by Denn [21] and used by Hay et al. ...
Journal of Non-newtonian Fluid Mechanics, 1999
... 4.1. Instrument details. A device similar in design to one used by Mackay et al. ... The caus... more ... 4.1. Instrument details. A device similar in design to one used by Mackay et al. ... The cause of these instabilities are not investigated here, see such references as Petrie and Denn [38] and Hatzikiriakos and Dealy [39] for a more in depth explanation of this phenomena. Fig. ...
Polymer International, 2003
Different formulations of biodegradable starch–polyester blend nanocomposite materials have been ... more Different formulations of biodegradable starch–polyester blend nanocomposite materials have been film blown on a pilot scale film blowing tower. The physical properties of different films have been examined by thermal and mechanical analysis and X-ray diffraction. The results show that the addition of an organoclay (from 0 to 5 wt%) significantly improves both the processing and tensile properties over the original starch blends. Wide angle X-ray diffraction (WAXD) results indicate that the best results were obtained for 30 wt% starch blends, and the level of delamination depends on the ratio of starch to polyester and amount of organoclay added. The crystallisation temperature of the nanocomposite blends is significantly lower than the base blend. This is probably due to the platelets inhibiting order, and hence crystallisation, of the starch and polyester. The mechanical and thermal properties of the blends are also sensitive to the way the clay particles are dispersed. Copyright © 2003 Society of Chemical Industry
Advances in Colloid and Interface Science, 2003
A review of spontaneous rupture in thin films with tangentially immobile interfaces is presented ... more A review of spontaneous rupture in thin films with tangentially immobile interfaces is presented that emphasizes the theoretical developments of film drainage and corrugation growth through the linearization of lubrication theory in a cylindrical geometry. Spontaneous rupture occurs when corrugations from adjacent interfaces become unstable and grow to a critical thickness. A corrugated interface is composed of a number of waveforms and each waveform becomes unstable at a unique transition thickness. The onset of instability occurs at the maximum transition thickness, and it is shown that only upper and lower bounds of this thickness can be predicted from linear stability analysis. The upper bound is equivalent to the Frenkel criterion and is obtained from the zeroth order approximation of the H3 term in the evolution equation. This criterion is determined solely by the film radius, interfacial tension and Hamaker constant. The lower bound is obtained from the first order approximation of the H3 term in the evolution equation and is dependent on the film thinning velocity. A semi-empirical equation, referred to as the MTR equation, is obtained by combining the drainage theory of Manev et al. [J. Dispersion Sci. Technol., 18 (1997) 769] and the experimental measurements of Radoev et al. [J. Colloid Interface Sci. 95 (1983) 254] and is shown to provide accurate predictions of film thinning velocity near the critical thickness of rupture. The MTR equation permits the prediction of the lower bound of the maximum transition thickness based entirely on film radius, Plateau border radius, interfacial tension, temperature and Hamaker constant. The MTR equation extrapolates to Reynolds equation under conditions when the Plateau border pressure is small, which provides a lower bound for the maximum transition thickness that is equivalent to the criterion of Gumerman and Homsy [Chem. Eng. Commun. 2 (1975) 27]. The relative accuracy of either bound is thought to be dependent on the amplitude of the hydrodynamic corrugations, and a semi-empirical correlation is also obtained that permits the amplitude to be calculated as a function of the upper and lower bound of the maximum transition thickness. The relationship between the evolving theoretical developments is demonstrated by three film thickness master curves, which reduce to simple analytical expressions under limiting conditions when the drainage pressure drop is controlled by either the Plateau border capillary pressure or the van der Waals disjoining pressure. The master curves simplify solution of the various theoretical predictions enormously over the entire range of the linear approximation. Finally, it is shown that when the Frenkel criterion is used to assess film stability, recent studies reach conclusions that are contrary to the relevance of spontaneous rupture as a cell-opening mechanism in foams.
Polymer Engineering and Science, 2006
Maleic anhydride (MA) and dicumyl peroxide (DCP) were used as crosslinking agent and initiator re... more Maleic anhydride (MA) and dicumyl peroxide (DCP) were used as crosslinking agent and initiator respectively for blending starch and a biodegradable synthetic aliphatic polyester using reactive extrusion. Blends were characterized using dynamic mechanical and thermal analysis (DMTA). Optical micrographs of the blends revealed that in the optimized blend, starch was evenly dispersed in the polymer matrix. Optimized blends exhibited better tensile properties than the uncompatibilized blends. X-ray photoelectron spectroscopy supported the proposed structure for the starch–polyester complex. Variation in the compositions of crosslinking agent and initiator had an impact on the properties and color of the blends. POLYM. ENG. SCI. 46:248–263, 2006. © 2006 Society of Plastics Engineers
Rheologica Acta, 1998
Mackay et al. (1995) have presented an approximate technique to determine the elongation viscosit... more Mackay et al. (1995) have presented an approximate technique to determine the elongation viscosity from pressure drop measurements in a simple stagnation flow device. In the present paper we describe experiments using a high viscosity Newtonian oil, aimed at probing some of the assumptions made by Mackay et al. We find that Trouton ratios calculated using the original analysis are well above the value of three expected for Newtonian fluids. Finite element simulations of the flow field show this is due to the net pressure drop having a substantial shear contribution, which should be corrected for before the Trouton ratios are evaluated. Interestingly, most of the shear correction is due to shear on the inside of the orifice near the exit from the central flow region. The shear contribution to the pressure drop occurs for all flow rates, however, at large flow rates there is also an inertial correction to the pressure drop. In this paper we describe an approximate method that corrects for both shear and inertial effects. With these effects recognised and corrected for, the measured Trouton ratios are reduced to around three.
Journal of Non-newtonian Fluid Mechanics, 2000
... Bagley end correction technique [1]. A comparison between the pressure drop derived from this... more ... Bagley end correction technique [1]. A comparison between the pressure drop derived from this correction and that measured from a zero L/D orifice for this LLDPE was shown by McGlashan and Mackay to be ... The simple analysis introduced by Denn [21] and used by Hay et al. ...
... Bagley end correction technique [1]. A comparison between the pressure drop derived from this... more ... Bagley end correction technique [1]. A comparison between the pressure drop derived from this correction and that measured from a zero L/D orifice for this LLDPE was shown by McGlashan and Mackay to be ... The simple analysis introduced by Denn [21] and used by Hay et al. ...
Journal of Non-newtonian Fluid Mechanics, 1999
... 4.1. Instrument details. A device similar in design to one used by Mackay et al. ... The caus... more ... 4.1. Instrument details. A device similar in design to one used by Mackay et al. ... The cause of these instabilities are not investigated here, see such references as Petrie and Denn [38] and Hatzikiriakos and Dealy [39] for a more in depth explanation of this phenomena. Fig. ...
Polymer International, 2003
Different formulations of biodegradable starch–polyester blend nanocomposite materials have been ... more Different formulations of biodegradable starch–polyester blend nanocomposite materials have been film blown on a pilot scale film blowing tower. The physical properties of different films have been examined by thermal and mechanical analysis and X-ray diffraction. The results show that the addition of an organoclay (from 0 to 5 wt%) significantly improves both the processing and tensile properties over the original starch blends. Wide angle X-ray diffraction (WAXD) results indicate that the best results were obtained for 30 wt% starch blends, and the level of delamination depends on the ratio of starch to polyester and amount of organoclay added. The crystallisation temperature of the nanocomposite blends is significantly lower than the base blend. This is probably due to the platelets inhibiting order, and hence crystallisation, of the starch and polyester. The mechanical and thermal properties of the blends are also sensitive to the way the clay particles are dispersed. Copyright © 2003 Society of Chemical Industry
Advances in Colloid and Interface Science, 2003
A review of spontaneous rupture in thin films with tangentially immobile interfaces is presented ... more A review of spontaneous rupture in thin films with tangentially immobile interfaces is presented that emphasizes the theoretical developments of film drainage and corrugation growth through the linearization of lubrication theory in a cylindrical geometry. Spontaneous rupture occurs when corrugations from adjacent interfaces become unstable and grow to a critical thickness. A corrugated interface is composed of a number of waveforms and each waveform becomes unstable at a unique transition thickness. The onset of instability occurs at the maximum transition thickness, and it is shown that only upper and lower bounds of this thickness can be predicted from linear stability analysis. The upper bound is equivalent to the Frenkel criterion and is obtained from the zeroth order approximation of the H3 term in the evolution equation. This criterion is determined solely by the film radius, interfacial tension and Hamaker constant. The lower bound is obtained from the first order approximation of the H3 term in the evolution equation and is dependent on the film thinning velocity. A semi-empirical equation, referred to as the MTR equation, is obtained by combining the drainage theory of Manev et al. [J. Dispersion Sci. Technol., 18 (1997) 769] and the experimental measurements of Radoev et al. [J. Colloid Interface Sci. 95 (1983) 254] and is shown to provide accurate predictions of film thinning velocity near the critical thickness of rupture. The MTR equation permits the prediction of the lower bound of the maximum transition thickness based entirely on film radius, Plateau border radius, interfacial tension, temperature and Hamaker constant. The MTR equation extrapolates to Reynolds equation under conditions when the Plateau border pressure is small, which provides a lower bound for the maximum transition thickness that is equivalent to the criterion of Gumerman and Homsy [Chem. Eng. Commun. 2 (1975) 27]. The relative accuracy of either bound is thought to be dependent on the amplitude of the hydrodynamic corrugations, and a semi-empirical correlation is also obtained that permits the amplitude to be calculated as a function of the upper and lower bound of the maximum transition thickness. The relationship between the evolving theoretical developments is demonstrated by three film thickness master curves, which reduce to simple analytical expressions under limiting conditions when the drainage pressure drop is controlled by either the Plateau border capillary pressure or the van der Waals disjoining pressure. The master curves simplify solution of the various theoretical predictions enormously over the entire range of the linear approximation. Finally, it is shown that when the Frenkel criterion is used to assess film stability, recent studies reach conclusions that are contrary to the relevance of spontaneous rupture as a cell-opening mechanism in foams.
Polymer Engineering and Science, 2006
Maleic anhydride (MA) and dicumyl peroxide (DCP) were used as crosslinking agent and initiator re... more Maleic anhydride (MA) and dicumyl peroxide (DCP) were used as crosslinking agent and initiator respectively for blending starch and a biodegradable synthetic aliphatic polyester using reactive extrusion. Blends were characterized using dynamic mechanical and thermal analysis (DMTA). Optical micrographs of the blends revealed that in the optimized blend, starch was evenly dispersed in the polymer matrix. Optimized blends exhibited better tensile properties than the uncompatibilized blends. X-ray photoelectron spectroscopy supported the proposed structure for the starch–polyester complex. Variation in the compositions of crosslinking agent and initiator had an impact on the properties and color of the blends. POLYM. ENG. SCI. 46:248–263, 2006. © 2006 Society of Plastics Engineers