[article]
| Titre : |
Scaling of rheological properties of hydrogels from polymer blends : PVA-K15M |
| Type de document : |
texte imprimé |
| Auteurs : |
A. El Ghzaoui, Auteur ; P. Ramel, Auteur ; E. Fabrègue, Auteur ; G. Cassanas, Auteur |
| Année de publication : |
1999 |
| Article en page(s) : |
p. 54-59 |
| Note générale : |
Bibliogr. |
| Langues : |
Français (fre) |
| Catégories : |
Alliages polymères
hydrocolloïdes
Hydroxypropyl méthylcellulose
Polyacétate de vinyle
Rhéologie
|
| Index. décimale : |
532.05 Mécanique des fluides et des liquides - Dynamique (cinétique et cinématique) |
| Résumé : |
Polymer blends have been studied to improve the physical properties of the individual applied field, the miscibility of each component polymer is also of interest and importance. One of the driving forces for the thermodynamic miscibility is, for example, interchain cellulosic blends has been extensively studied. Because of the environmental issues for nonbiodegradable polymer wastes have arisen, conventional biodegradable polymers such as cellulose and its derivatives, polyvinyl alcohol have again started to attract attention and interest. The nature of interchain hydrogen bonds in cellulosic blends has been extensively studied. In chemical gelation, a three-dimensional network forms through permanent covalent bonds, therefore the obtained gel is not thermoreversible. A physically gelling material (for example, when the junctions between polymers are hydrogen bonds) also forms a thre-dimensional network. However, the junctions in physical gels are not composed of permanent chemical bonds, and they are of a thermoreversible nature.
In the present investigation, we have chosen a thermoreversible gel composed with PVA (polyvinyl alcohol) and HPMC (hydroxypropylmethylcellulose) as the two component polymers for the solution-cast film blend to investigate the role of interchain hydrogen bonds on the rheological properties of the polymers blend. The entire rheological image of this physically gelling system as a function of the temperature, the molecular weights, the concentration and the ionic strength has been studied. Increasing the concentration of HPMC in the polymer blend induces a decrease of the gel point frequency determined using the crossover of the shear storage modulus G' and loss modulus G''. The same trend is observed when the ionic strength is increased. Useful informations were obtained from the critical frequency of crossover Wc(where G' and G'' are equal). A critical time Tc, is associated with Wc (Tc=1/Wc) which corresponds to a lifetime of the junction of the network at fixed stress. This lifetime seems to be longer as the concentration of HPMC is raised while the concentration of PVA is remained constant. As increasing the ionic strength, the lifetime of the junction increase. Therefore the properties of the gel network are modified and strengthened in the presence of water structure makers like NaCl which was used to range the ionic strength. |
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in LES CAHIERS DE RHEOLOGIE > Vol. XVI, N° 3 (10/1999) . - p. 54-59
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