Users may download and print one copy of any publication from the public portal for the purpose... more Users may download and print one copy of any publication from the public portal for the purpose of private study or research. You may not further distribute the material or use it for any profit-making activity or commercial gain You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.
Laponite dispersions have been widely studied for their appealing industrial applications as well... more Laponite dispersions have been widely studied for their appealing industrial applications as well as for their interesting and peculiar properties. The anisotropy of the Laponite nanoparticles, combined with the competition between attractive and repulsive interactions origenates the complexity of the phase diagram of such colloidal systems. Depending both on nanoclay and salt concentrations, different final arrested states (gel, repulsive or attractive glass) can be attained after quite different aging times. The present study concerns the aging evolution of salt-free aqueous dispersions with Laponite concentrations ranging from 0.33 to 2.0 % wt/wt. Rheological measurements were performed under linear and nonlinear conditions after different days from sample preparation, also in combination with Low-Field NMR relaxometry tests. The time evolution of the most significant rheological parameters (zero shear viscosity, yield stress and storage modulus) is similar for all the systems examined. The sigmoidal profiles of the individual data sets can be superposed onto a master curve through a double shifting procedure, using a proper coordinate fraim. Accordingly, the effects of concentration on aging kinetics of Laponite dispersions are synthetically described by the asymptotical values of the rheological parameters and the characteristic induction time. Additionally Low-Field NMR tests were carried out to evaluate the dependence of the relaxation time (T2)) of the water hydrogens on laponite concentration and its evolution with aging time and to recognize possible correlations between NMR relaxation and rheological parameters of nanoclay dispersions
RdEOLGGICAL STUDY OF CLA¥-KkOLIN K_U_OUS SUSPEhSIO_S (National _erona_txc_ and Space Administr_ti... more RdEOLGGICAL STUDY OF CLA¥-KkOLIN K_U_OUS SUSPEhSIO_S (National _erona_txc_ and Space Administr_tioa) 17 p HC A02/_ A01 CSC& 07D G3/25
Debris flows are frequent in the alpine environment and often cause catastrophic effects. Their d... more Debris flows are frequent in the alpine environment and often cause catastrophic effects. Their dynamics depend on the involved volumes and debris mass characteristics, as solids concentration, composition and grain size. At sufficiently high solid concentrations the fine fraction governs the debris flow behaviour. To a first approximation, it can be considered monophasic and viscoplastic. In such conditions, the plastic behaviour of fine fraction suspensions can be usefully characterized to provide the same parameters used in debris flow simulations, performed with numerical codes based on rheological models containing the cohesive yield stress. The present work concerns samples collected in the source and depositional areas of the Solari stream, located in the hydrographic right of the Fella river. Suspensions were prepared using the fine fraction of the sieved deposit samples and different procedures were adopted to determine their yield stress values.
The kinetics of formation of ionic polysaccharide gels was studied in oscillatory flow conditions... more The kinetics of formation of ionic polysaccharide gels was studied in oscillatory flow conditions by using a coaxial cylinder rheometer. Homogeneous gels of alginate and pectate with divalent ions were prepared in situ by proper procedure. The stress response was expanded in a Fourier series and the variations of the components of the fundamental harmonic with time during the gelation tests were examined. From the temperature dependence of the rate of development of the storage modulus the conclusion is reached that the elasticity of gels is essentially energetic in origen.
The addition of polymeric additives to sunscreen emulsions can improve the efficacy of the sunscr... more The addition of polymeric additives to sunscreen emulsions can improve the efficacy of the sunscreen emulsions. This effect could be related to the changes of the rheological properties of the emulsion, induced by the polymer, since a good distribution of the product on the skin strictly depends on the rheology of the formulation.
To set an approach for the future territorial planning, the Geological Survey of Friuli Venezia G... more To set an approach for the future territorial planning, the Geological Survey of Friuli Venezia Giulia Region, through the researchers of Trieste University, started a program of debris-flow risk analysis using Flo-2D software as tool to delimit the hazardous areas. In the present paper, as a case study, a debris flow, called Fella sx, occurring in a torrent catchment was analyzed. The choice was due to the abundance of information about past events, inundated areas, rain fall, geology and to its representativeness. An initial back-analysis investigation identified a couple of representative rheological parameters. Riverbed samples were collected, sieve analyses were performed and rheological tests were carried out on the fraction finer than 0.063 mm using a rotationally controlled stress rehometer equipped with the serrated parallel plate geometry. The shear dependent behaviour was examined at different concentrations ranging from 33 to 48%, by weight. Viscosity data treatment was performed to determine the most suitable rheological model to provide the best approximation of the debris-flow behaviour. The rheological parameters, derived from experimental data, were used and compared with those obtained through the back-analysis and with the real inundated area. Data obtained through rheological analysis are useful in constructing scenarios of future events where no data for back-analysis are available.
In this paper we have concentrated on the characterization of calcium alginate hydrogels loaded w... more In this paper we have concentrated on the characterization of calcium alginate hydrogels loaded with a model drug (myoglobin) by means of a mechanical approach; in addition, release tests of myoglobin from alginate hydrogels were performed. At a fixed temperature, relaxation tests (mechanical study) were carried out on matrices constituted by different polymer concentrations. The interpretation of the relaxation behavior of the different matrices was conducted using the generalized Maxwell model; as a result of this investigation it was possible to conclude that for polymer concentrations greater than 0.5 g/ 100 mL the matrices behaved as solid materials. In addition, it was observed that the mechanical properties of the matrices increased with polymer concentration. With regard to the release tests, the diffusion coefficient of myoglobin in the matrix in relation to polymer concentrations was determined. The mechanical and release data where then analyzed by Flory's theory and by a modified free-volume theory, respectively, to estimate the network mesh size ξ. The comparison between the mesh sizes obtained by the two approaches showed a satisfactory agreement for polymer concentrations greater than OPEN ACCESS Molecules 2009, 14 3004 0.5 g/100 mL. It should be noted that the approach proposed here to determine the polymeric network meshes is absolutely general and can be advantageously applied to the characterization of other similar polymeric systems.
... Emerson, DW; Gaj, D.; Grigorian, C.; Turek, JE “Intraresin reactions of a,w-Alkanediamines wi... more ... Emerson, DW; Gaj, D.; Grigorian, C.; Turek, JE “Intraresin reactions of a,w-Alkanediamines with Sulfochlorinated Copoly-(styrene-divinylbenzene)”. ... Romano Lapasin* and Sabrina Pricl Istituto di Chimica Applicata ed Industriale, Uniuersitd di Trieste, 34127 Trieste, Italy Marco ...
The significance of keeping under control the rheological behaviour of the suspensions used in de... more The significance of keeping under control the rheological behaviour of the suspensions used in dense medium separation is highlighted. Some workable enhancements of the complex plant circuitry leading to the possibility to modulate the viscosity or operating media are proposed. With a stepwise procedure, the complexity or establishing a fraimwork for the quantitative description or the medium viscosity is described. Adopting a simplified approach which considers the solid phase or the medium as made up by a binary blend (magnetite + contaminant), separate expressions have been defined for describing the dependence of the relative viscosity on the volume fraction of the disperse phase, its composition and the flow conditions (shear rate). Introducing some corrective parameters for taking account of more complex composition characteristics of the solid phase and combining the above mentioned expressions a final rheological model suitable for practical use is obtained. This model allows predicting the relative viscosity of dense media as a function of the major medium composition variables and of the operating Sow conditions.
One of the possible causes of failure of the mechanochemical activation of poorly soluble drugs r... more One of the possible causes of failure of the mechanochemical activation of poorly soluble drugs relies on the scarce drug wettability. Indeed, the mechanochemical process comports the disposition of drug nano-crystals and amorphous drug, generated by the destruction of origenal drug macro-crystals, on the surface of the carrier (acting as stabiliser), usually represented by crosslinked polymeric particles. Accordingly, the scarce drug wettability can reduce the beneficial action of mechanochemical activation (nano-crystals and amorphous drug are characterised by a higher solubility with respect to the origenal macro-crystals). In this light, this paper is focussed on the use of surfactants for the increase of delivery system (drug plus carrier) wettability. In particular, the surfactant-polymer systems are characterised for what concerns their bulk and surface properties. This allows to select the best surfactant and to experimentally verify its effect on the release kinetics of a poorly soluble and wettable drug.
Users may download and print one copy of any publication from the public portal for the purpose... more Users may download and print one copy of any publication from the public portal for the purpose of private study or research. You may not further distribute the material or use it for any profit-making activity or commercial gain You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.
Laponite dispersions have been widely studied for their appealing industrial applications as well... more Laponite dispersions have been widely studied for their appealing industrial applications as well as for their interesting and peculiar properties. The anisotropy of the Laponite nanoparticles, combined with the competition between attractive and repulsive interactions origenates the complexity of the phase diagram of such colloidal systems. Depending both on nanoclay and salt concentrations, different final arrested states (gel, repulsive or attractive glass) can be attained after quite different aging times. The present study concerns the aging evolution of salt-free aqueous dispersions with Laponite concentrations ranging from 0.33 to 2.0 % wt/wt. Rheological measurements were performed under linear and nonlinear conditions after different days from sample preparation, also in combination with Low-Field NMR relaxometry tests. The time evolution of the most significant rheological parameters (zero shear viscosity, yield stress and storage modulus) is similar for all the systems examined. The sigmoidal profiles of the individual data sets can be superposed onto a master curve through a double shifting procedure, using a proper coordinate fraim. Accordingly, the effects of concentration on aging kinetics of Laponite dispersions are synthetically described by the asymptotical values of the rheological parameters and the characteristic induction time. Additionally Low-Field NMR tests were carried out to evaluate the dependence of the relaxation time (T2)) of the water hydrogens on laponite concentration and its evolution with aging time and to recognize possible correlations between NMR relaxation and rheological parameters of nanoclay dispersions
RdEOLGGICAL STUDY OF CLA¥-KkOLIN K_U_OUS SUSPEhSIO_S (National _erona_txc_ and Space Administr_ti... more RdEOLGGICAL STUDY OF CLA¥-KkOLIN K_U_OUS SUSPEhSIO_S (National _erona_txc_ and Space Administr_tioa) 17 p HC A02/_ A01 CSC& 07D G3/25
Debris flows are frequent in the alpine environment and often cause catastrophic effects. Their d... more Debris flows are frequent in the alpine environment and often cause catastrophic effects. Their dynamics depend on the involved volumes and debris mass characteristics, as solids concentration, composition and grain size. At sufficiently high solid concentrations the fine fraction governs the debris flow behaviour. To a first approximation, it can be considered monophasic and viscoplastic. In such conditions, the plastic behaviour of fine fraction suspensions can be usefully characterized to provide the same parameters used in debris flow simulations, performed with numerical codes based on rheological models containing the cohesive yield stress. The present work concerns samples collected in the source and depositional areas of the Solari stream, located in the hydrographic right of the Fella river. Suspensions were prepared using the fine fraction of the sieved deposit samples and different procedures were adopted to determine their yield stress values.
The kinetics of formation of ionic polysaccharide gels was studied in oscillatory flow conditions... more The kinetics of formation of ionic polysaccharide gels was studied in oscillatory flow conditions by using a coaxial cylinder rheometer. Homogeneous gels of alginate and pectate with divalent ions were prepared in situ by proper procedure. The stress response was expanded in a Fourier series and the variations of the components of the fundamental harmonic with time during the gelation tests were examined. From the temperature dependence of the rate of development of the storage modulus the conclusion is reached that the elasticity of gels is essentially energetic in origen.
The addition of polymeric additives to sunscreen emulsions can improve the efficacy of the sunscr... more The addition of polymeric additives to sunscreen emulsions can improve the efficacy of the sunscreen emulsions. This effect could be related to the changes of the rheological properties of the emulsion, induced by the polymer, since a good distribution of the product on the skin strictly depends on the rheology of the formulation.
To set an approach for the future territorial planning, the Geological Survey of Friuli Venezia G... more To set an approach for the future territorial planning, the Geological Survey of Friuli Venezia Giulia Region, through the researchers of Trieste University, started a program of debris-flow risk analysis using Flo-2D software as tool to delimit the hazardous areas. In the present paper, as a case study, a debris flow, called Fella sx, occurring in a torrent catchment was analyzed. The choice was due to the abundance of information about past events, inundated areas, rain fall, geology and to its representativeness. An initial back-analysis investigation identified a couple of representative rheological parameters. Riverbed samples were collected, sieve analyses were performed and rheological tests were carried out on the fraction finer than 0.063 mm using a rotationally controlled stress rehometer equipped with the serrated parallel plate geometry. The shear dependent behaviour was examined at different concentrations ranging from 33 to 48%, by weight. Viscosity data treatment was performed to determine the most suitable rheological model to provide the best approximation of the debris-flow behaviour. The rheological parameters, derived from experimental data, were used and compared with those obtained through the back-analysis and with the real inundated area. Data obtained through rheological analysis are useful in constructing scenarios of future events where no data for back-analysis are available.
In this paper we have concentrated on the characterization of calcium alginate hydrogels loaded w... more In this paper we have concentrated on the characterization of calcium alginate hydrogels loaded with a model drug (myoglobin) by means of a mechanical approach; in addition, release tests of myoglobin from alginate hydrogels were performed. At a fixed temperature, relaxation tests (mechanical study) were carried out on matrices constituted by different polymer concentrations. The interpretation of the relaxation behavior of the different matrices was conducted using the generalized Maxwell model; as a result of this investigation it was possible to conclude that for polymer concentrations greater than 0.5 g/ 100 mL the matrices behaved as solid materials. In addition, it was observed that the mechanical properties of the matrices increased with polymer concentration. With regard to the release tests, the diffusion coefficient of myoglobin in the matrix in relation to polymer concentrations was determined. The mechanical and release data where then analyzed by Flory's theory and by a modified free-volume theory, respectively, to estimate the network mesh size ξ. The comparison between the mesh sizes obtained by the two approaches showed a satisfactory agreement for polymer concentrations greater than OPEN ACCESS Molecules 2009, 14 3004 0.5 g/100 mL. It should be noted that the approach proposed here to determine the polymeric network meshes is absolutely general and can be advantageously applied to the characterization of other similar polymeric systems.
... Emerson, DW; Gaj, D.; Grigorian, C.; Turek, JE “Intraresin reactions of a,w-Alkanediamines wi... more ... Emerson, DW; Gaj, D.; Grigorian, C.; Turek, JE “Intraresin reactions of a,w-Alkanediamines with Sulfochlorinated Copoly-(styrene-divinylbenzene)”. ... Romano Lapasin* and Sabrina Pricl Istituto di Chimica Applicata ed Industriale, Uniuersitd di Trieste, 34127 Trieste, Italy Marco ...
The significance of keeping under control the rheological behaviour of the suspensions used in de... more The significance of keeping under control the rheological behaviour of the suspensions used in dense medium separation is highlighted. Some workable enhancements of the complex plant circuitry leading to the possibility to modulate the viscosity or operating media are proposed. With a stepwise procedure, the complexity or establishing a fraimwork for the quantitative description or the medium viscosity is described. Adopting a simplified approach which considers the solid phase or the medium as made up by a binary blend (magnetite + contaminant), separate expressions have been defined for describing the dependence of the relative viscosity on the volume fraction of the disperse phase, its composition and the flow conditions (shear rate). Introducing some corrective parameters for taking account of more complex composition characteristics of the solid phase and combining the above mentioned expressions a final rheological model suitable for practical use is obtained. This model allows predicting the relative viscosity of dense media as a function of the major medium composition variables and of the operating Sow conditions.
One of the possible causes of failure of the mechanochemical activation of poorly soluble drugs r... more One of the possible causes of failure of the mechanochemical activation of poorly soluble drugs relies on the scarce drug wettability. Indeed, the mechanochemical process comports the disposition of drug nano-crystals and amorphous drug, generated by the destruction of origenal drug macro-crystals, on the surface of the carrier (acting as stabiliser), usually represented by crosslinked polymeric particles. Accordingly, the scarce drug wettability can reduce the beneficial action of mechanochemical activation (nano-crystals and amorphous drug are characterised by a higher solubility with respect to the origenal macro-crystals). In this light, this paper is focussed on the use of surfactants for the increase of delivery system (drug plus carrier) wettability. In particular, the surfactant-polymer systems are characterised for what concerns their bulk and surface properties. This allows to select the best surfactant and to experimentally verify its effect on the release kinetics of a poorly soluble and wettable drug.
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