Miscibility and dynamical properties of cellulose acetate/plasticizer systems

• We study the miscibility and dynamical properties of secondary cellulose acetate plasticized by diethyl phthalate (DEP).
• Partial miscibility (characterized by differential scanning calorimetry) is observed above 25 wt% of DEP content.
• The α-relaxation of the system and its VFT/WLF behavior are studied over a broad frequency range.
• A new secondary relaxation is found for DEP-plasticized cellulose acetate system.

Due to its biodegradability and renewability, a great interest has been devoted to investigating cellulose acetate in order to expand its potential applications. In addition, secondary cellulose acetate (CDA) could also be considered as a model system for strongly polar polymer system. The dynamical behavior of CDA is supposed to be governed by H-bonding and dipolar interaction network. Due to their high glass transition temperature, cellulose acetate-based systems are processed when blended with plasticizers. It is thus of utmost importance to study the miscibility and plasticizing effects of various molecules. We prepared CDA films via solvent casting method with diethyl phthalate as the plasticizer. Miscibility diagrams were established by calorimetry and thermo-mechanical (DMTA) experiments. Dynamical properties were analyzed by DMTA and broadband dielectric spectroscopy. We could identify the α-relaxation of these CDA-plasticizer systems in the frequency range from 0.06 Hz to 106 Hz, which allowed for describing the dynamics in the so-called Williams-Landel-Ferry/Vogel-Fulcher-Tammann regime.