Aggregation and gelation in hydroxypropylmethyl cellulose aqueous solutions

Silva, Sérgio M.C.; Pinto, Fátima; Antunes, Filipe E.; Miguel, Maria G.; Sousa, João; Pais, Alberto A. C. C.

doi:10.1016/j.jcis.2008.08.056

Cited by 116 publications

(82 citation statements)

References 31 publications

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“…With a G 0 value of *10 5 Pa and s el * 10 Pa, the semi-solid binder is likely to impart considerable strength to the paste under ambient conditions. The G 0 and G 00 values are considerably larger than values for other VE gel materials reported in the literature [19,[37][38][39][40][41] (see Table 3). These other gel materials are commonly based on cellulose derivatives and contain aqueous binders, in contrast to the alcohol/biopolymer mixture in this study.…”

Section: Rheological Propertiescontrasting

confidence: 63%

Influence of visco-elastic binder properties on ram extrusion of a hardmetal paste

Ferstl

Barbist²,

Rough

et al. 2012

J Mater Sci

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The influence of the viscous and elastic components of a visco-elastic binder phase on the extrusion behaviour of a tungsten carbide-cobalt hardmetal paste was investigated by studying the paste over a range of temperatures, 30-42°C, where the binder changed from a semi-solid gel to a viscous liquid. The extrusion behaviour of the paste was studied by ram extrusion and quantified by the Benbow-Bridgwater (BB) method. The elastic and viscous components of the binder were studied separately by means of oscillatory and steady shear techniques in a controlled stress rheometer using rough parallel plates. The paste behaviour fitted the four parameter BB model well: the initial bulk yield stress parameter, r 0 , increased linearly with the binder elastic modulus, G 0 , while both the velocity dependence parameters a and b were linearly related to the binder steady shear viscosity. Analysis of paste-wall slip parameters gave estimated slip layer thicknesses of 2-5 particle diameters. List of symbols Roman APre-exponential factor in Eq. (6) (Pa s) C Carreau relaxation time constant (s) d 10 10 % of the population are smaller than this diameter (m) d 50 50 % of the population are smaller than this diameter (m) d 90 90 % of the population are smaller than this diameter (m) d [4,3] Volume moment (De Brouckere) mean diameter (m) D Die land diameter (m) D 0 Barrel diameter (m) E Activation energy in Eq. (6) (J mol -1 ) G 0 Elastic shear modulus (Pa) G 0 B Elastic shear modulus of unloaded binder (Pa) G 00 Viscous shear modulus (Pa) [k] Intrinsic viscosity (-) K Herschel-Bulkley consistency (Pa s k ) L Die land length (m) m Benbow-Bridgwater die entry velocity index (-) n Benbow-Bridgwater wall slip velocity index (-) pCarreau power law index (-) P ex Extrusion pressure (Pa) P 1 Component of extrusion pressure associated with die entry flow (Pa) P 2 Component of extrusion pressure associated with die land flow (Pa) R Universal gas constant (J mol -1 K -1 )Mean extrudate velocity (m s -1 )Greek a Benbow-Bridgwater extensional deformation velocity coefficient (Pa s m m -m ) bBenbow-Bridgwater wall slip velocity coefficient (Pa s n m -n ) _ cShear rate (s -1 ) _ c app Apparent shear rate (s -1 )

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Section: Rheological Propertiescontrasting

confidence: 63%

Influence of visco-elastic binder properties on ram extrusion of a hardmetal paste

Ferstl

Barbist²,

Rough

et al. 2012

J Mater Sci

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“…Interestingly, the development of moduli in aqueous MC is dramatically different to that in aqueous HPMC during the sol-gel transition. [29][30][31][32] For HPMC solutions, as temperature is raised, a sudden drop in the storage modulus is observed followed by an increase as gelation occurs. In contrast for MC solutions no sharp drop appears, the solutions merely thicken as temperature is increased.…”

Section: Introductionmentioning

confidence: 99%

Interplay between Gelation and Phase Separation in Aqueous Solutions of Methylcellulose and Hydroxypropylmethylcellulose

et al. 2012

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Thermally-induced gelation in aqueous solutions of methylcellulose (MC) and hydroxypropyl methylcellulose (HPMC) has been studied by rheological, optical microscopy and turbidimetry measurements. The structural and mechanical properties of these hydrogels are dominated by the interplay between phase separation and gelation. In MC solutions, phase separation takes place almost simultaneously with gelation. An increase in the storage modulus is coupled to the appearance of a bicontinuous structure upon heating. However, a thermal gap exists between phase separation and gelation in the case of HPMC solutions. The storage modulus shows a dramatic decrease during phase 2 separation, and then rises in the subsequent gelation. A macroporous structure forms in the gels via "viscoelastic phase separation" linked to "double phase separation".

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“…This syneresis allows hydrophobic interactions between the respective macromolecules accompanied with the formation of polymer clusters, which further associate in a three-dimensional network. This specific mechanism of gelation is supported by the results obtained from several experimental techniques including: differential scanning calorimetry, IR attenuated total reflectance spectroscopy, UV/VIS and fluorescence spectroscopy, polarized light microscopy, and oscillatory rheometry [22,26,[68][69][70][71].…”

Section: Colloidal Dissolution and Gelation As Processes Involved In mentioning

confidence: 60%

“…Thus, the additives that impart a solubilizing effect (i.e., ethanol, propyleneglycol, PEG 400) raise the gel point of HPMC, whereas the additives that exhibit a coagulant effect (i.e., glycerol, sorbitol, and most electrolytes) lower the gel temperature. In the past decade, numerous studies on thermoreversible gelation behavior of HPMC solutions have been carried out [22][23][24][25][26].…”

Section: Specific Property Hydroxyethylcellulosementioning

confidence: 99%

Cellulose-Derivatives-Based Hydrogels as Vehicles for Dermal and Transdermal Drug Delivery

Vlaia¹,

Coneac²,

Olariu³

et al. 2016

Emerging Concepts in Analysis and Applications of Hydrogels

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The use of water-soluble polymers of natural, semisynthetic, and synthetic origin for dermal and transdermal drug delivery systems is manifold. Among the most used biopolymers in the formulation of skin preparations, the cellulose ether derivatives as representatives of semisynthetic polymers distinguish through their specific physicochemical properties, by which the pharmacist can select the appropriate cellulose derivative for a particular purpose. The hydrogels containing cellulose derivatives as gelling agents are widely used as water-soluble ointment bases, because they usually associate the characteristics of both conventional and innovative hydrogels, including especially safety, biocompatibility, biodegradability, and a relatively easy way of preparation and low price. The present chapter describes the following issues: the physicochemical properties of water-soluble cellulose derivatives in relationship with their type and grade; physical and chemical properties of cellulose-derivatives-based hydrogels and their compatibility with other auxiliary substances commonly used in the formulation of pharmaceutical hydrogels; the development and manufacturing of these hydrogels on both small and large scales; the characterization of cellulose derivatives hydrogels as pharmaceutical dosage forms through different compendial and noncompendial methods; and well-recognized and novel applications of cellulosederivatives-based hydrogels for dermal and transdermal drug delivery.

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Aggregation and gelation in hydroxypropylmethyl cellulose aqueous solutions

Cited by 116 publications

References 31 publications

Influence of visco-elastic binder properties on ram extrusion of a hardmetal paste

Influence of visco-elastic binder properties on ram extrusion of a hardmetal paste

Interplay between Gelation and Phase Separation in Aqueous Solutions of Methylcellulose and Hydroxypropylmethylcellulose

Cellulose-Derivatives-Based Hydrogels as Vehicles for Dermal and Transdermal Drug Delivery

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