Biosourced blends based on poly (lactic acid) and polyamide 11: Structure-properties relationships and enhancement of film blowing processability

The purpose of the present work is to develop a new biomaterial with suitable melt strength, stiffness-to-toughness balance, and the required thermal performance for food packaging applications. The study is dedicated to investigating a new physical compatibilization approach of biosourced materials as well poly (lactic acid) (PLA) and polyamide 11 (PA11) in comparison with the chemical compatibilization through addition of a multifunctionalized epoxide. For this reason, this paper deals with gaining better understanding physical compatibilization in the biosourced blend with the incorporation of an acrylic melt strength enhancer into PLA/PA11 blend. The main focus of this paper is studying how physical compatibilization improves melt strength in comparison with chemical approach. Hitherto, the chain extension-branching balance was demonstrated to be difficult to be controlled and decoupled from chemical compatibilization at the polymer-polymer interface. Hence, the physical approach is presented as an original route in this work to develop a PLA-based blend with good film blown processability and engineering properties. Morphological, rheological and thermomechanical properties of the new obtained biosourced blends were studied. The physical compatibilization effect was confirmed by the tuning interfacial properties. The extensional rheology highlighted that melt strength for the physical blends was also improved without any pronounced strain hardening in comparison with reactive blends. Besides, a great enhancement of the blowing processing windows of physically PLA-PA11 compatibilized blend was highlighted while higher blow-up ratio and take-up ratio values were obtained. Overall, a correlation between the obtained thermal and crystalline properties was performed for the optimal biosourced blown film.