Ionic liquid aided solution-precipitation method to prepare polymer blends from cellulose with polyesters or polyamide
Cellulose is commonly regarded unsuitable for melt blending. Therefore, direct use of cellulose in thermoplastic applications is still a challenge without further modification, and limited compatibility may result in poor mechanical performance of melt compounded polymer/cellulose composites. In this study, blends of various synthetic polymers and cellulose with thermoplastic properties were successfully produced using an ionic-liquid based solution-precipitation process and subsequent hot-pressing. Dimethyl sulfoxide was used in the presence of 1-ethyl-3-methylimidazolium acetate as an appropriate co-solvent for cellulose dissolution and as the sole solvent for poly(e-caprolactone), poly(butylene succinate), poly(lactic acid), poly(hydroxyl alkanoate) and polyamide 6 prior to solution blending. Both blended solutions as well as single polymer solutions were precipitated with an anti-solvent. A slight decrease in molecular weight was detected for poly(butylene succinate) as well as the cellulose regenerates. Precipitated and dried materials were thermomechanically formed into platelets, investigating their thermoplastic behavior. Depending on their polymeric nature and the ability to interact with the polymer chains, different compatibility behavior of the regenerated blends was observed during precipitation as well as thermomechanical forming. Promising interactions were detected for polyamide 6 and poly(lactic acid), expressed via melting point depression (polyamide 6), hydrogen bonding (poly(lactic acid)) and homogeneous morphology of the transparent blend films.