Improvement of Thermal Processability and Recyclability of Cellulose Mixed Esters via Introducing Long Side Chains

The improvement of thermal processability for cellulosic material is still a tough challenge in practical production. Cellulose mixed esters were synthesized by introducing long acyl groups onto cellulose diacetate (degree of substitution, DS = 2.3) to improve its thermal processability and demonstrate the effect of these long side chains on polymer properties under a low DS (0.7). The introduced long side chains can act as internal plasticizers to reduce the melting point from 261 to 170 °C and improve the thermal plasticity of the product, avoiding the risk of deterioration and biosafety caused by bleeding. Importantly, the glass transition temperature remained above 125 °C despite the introduction of long side chains. Hot-pressing and injection molding were performed to evaluate the thermal processability of the synthesized polymers. The obtained materials exhibited transparency and controllable mechanical properties by adjusting the length of the introduced side chains. The mechanical recyclability of the hot-pressed films and injection-molded specimens was also studied, and the polymers showed unchanged physical properties and usage stability after 3 cycles of processing. The results confirmed that the synthesized cellulose mixed esters exhibited improved thermal processability, usage stability, and recyclability for practical production and applications as cellulosic bioplastics.