Glass-rubber transitions of cellulosic polymers by dynamic mechanical analysis.

The glass-rubber transition temperatures (Tg) of several cellulosic polymers [hydroxypropyl methylcellulose (HPMC), hydroxypropyl cellulose (HPC), hydroxyethyl cellulose (HEC)] have been examined using dynamic mechanical analysis (DMA). The melting temperatures of the above polymers were examined using a hot stage melting point apparatus. The primary Tg of three different grades of HPMC (3, 6, and 15 cps) were determined to be 160, 170, and 175 degrees C, respectively. The primary Tg of the HEC film was determined as 120 degrees C. The HPC film did not indicate a primary Tg. These cellulosic polymers also displayed secondary transitions. Hot stage melting of HPMC and HPC was observed at 225 to 254 degrees C and 190 to 195 degrees C, respectively. The HEC powder did not exhibit a melting temperature, but became darker at temperatures greater than 150 degrees C.