Design and Synthesis of Epoxidized Hemicellulose Polyether from Viscose Fiber Waste as Efficient Plasticizer for Ethyl Cellulose

Ethyl cellulose (EC) has been widely used in pharmaceutical and food packaging aspects due to its biodegradability and antimicrobial properties; however, it suffers from excessive brittleness, which must be plasticized to meet the requirement of industry. Herein, hemicellulose polyether glycidyl ether (EPPG) was developed as a plasticizer for EC using viscose waste liquor as feedstock through etherification and epoxidation. When 40 wt % EPPG (based on the weight of EC) was blended with EC, the elongation at break was increased from 3.0% (Neat EC) to 54.5% (EC/EPPG), while the glass transition temperature of EC/EPPG decreased from 137.5 °C (Neat EC) to 73.1 °C, which were better than those of EC plasticized by 40 wt % DOP (dioctyl phthalate) (EC/DOP). Comprehensive characterization through XRD, FT-IR spectroscopy, and quantum chemical calculations provides molecular-level evidence of strong intermolecular interactions between EPPG and the EC matrix, imparting excellent compatibility and plasticization. The EPPG-plasticized EC films exhibit decent stability characteristics, showing only 15.5% mass loss in n-hexane migration tests and maintaining thermal stability up to 276.9 °C (T5%). In contrast, the migration rate of EC/DOP films is as high as 25.0%, and the T5% is only 254.2 °C. This work represents a significant advancement in sustainable material design, simultaneously addressing two critical challenges: the valorization of viscose waste stream components and the development of high-performance, biobased alternatives to conventional plasticizers.