Static tensile and dynamic mechanical properties of hydroxypropylcellulose films prepared under various conditions

Abstract

AbstractThe films of hydroxypropyl cellulose (HPC), which is a lyotropic and thermotropic liquid crystal, were cast under various conditions of temperature and concentration. The effects of the casting conditions on the static tensile and dynamic mechanical properties of the cast films were determined, and the results were compared with those of films prepared by means of hot compression. The tensile properties of the films prepared by both processes (cast and hot compression) were unsatisfactory in comparison with other liquid crystalline polymers, and this was partly due to water absorbed during the test. In dynamic properties, two distinct transitions were detected. The higher one, around 110°C, was associated with the rotation of an unhydroglucose ring and the lower one, around 25°C, was associated with the Tg. There were no marked differences in the properties between cast films and hot‐compressed films, except the disappearance of the Tg for hot‐compressed film prepared at a relatively higher temperature. The basis for defining the liquid crystalline structure in cast and hot‐compressed films are not directly given in this preliminary paper. However, judging from the dynamic mechanical properties and refractive index data for films prepared by both processes, it appears that dimethylacetamide‐cast films and films compressed at 180 and 200°C may have some structures related to liquid crystalline phase and that inter‐ and intramolecular hydrogen bonding play an important role in lyotropic and thermotropic liquid crystalline behavior for HPC.