Rheological characteristics of gelation

Abstract

Hydrogels have become increasingly important in various areas such as pharmaceutical, biological and food industry. Hydroxypropyl methylcellulose hydrogels are thermally reversible physical hydrogels that are widely used in recent years. The gelation process is initiated by the change of temperature and it is highly related to the polymeric mechanism of the hydrogel that involves hydrophobic association and network forming of the polymeric chain. During the process of gelation, many physical properties of the hydrogel are affected. The purpose of this project is to investigate three main properties of hydroxypropyl methylcellulose hydrogels, which are: surface tension, shear and extensional rheological behaviour. These three properties are selected as their variations during the gelation process are closely linked to the rheological behaviour of the gel that will greatly affect the use of hydrogels in various industries. Many past works have been done on the surface tension and shear rheological behaviour of the hydrogel but few of them analysed the extensional rheological behaviour of the hydrogel. Henceforth, the investigation of extensional rheological behaviour and connecting it with the other two properties will be done in detail on this project.