Understanding and Controlling the Multistep Crystallization of Fatty Acid Cellulose Esters

Fatty acid cellulose esters (FACEs) have great potential as biogenic alternatives to petroleum-based plastics. Nevertheless, their thermal property profiles have been the subject of controversial discussion, particularly with respect to their crystallization behavior. A thorough understanding of the crystallization behavior of FACEs is fundamentally important for gaining deep insights into their solid-state characteristics and thermal properties. This systematic study succeeds in elucidating the crystallization behavior of FACEs as bulk materials. Differential scanning calorimetry combined with rheological analysis and X-ray diffraction of cellulose esters bearing side chains with varying numbers of fatty acid residues (C-12-C-20) and degrees of substitution (ranging from partial to full esterification, i.e., 0.1-3.0) revealed that crystallization of FACEs occurs in multiple stages. These stages involve the distinct crystallization of inter and intramolecular side chains and polysaccharide backbones. A quantitative multistep crystallization mechanism is proposed based on the study findings.