Morphological, Mechanical and Barrier Properties of Polylactic Acid/Cellulose Nanocrystal/Nanoclay Composite Films

The aim of this study was to develop the biodegradable nanocomposite films based on polylactic acid (PLA) reinforced with cellulose nanocrystal and nanoclay. Nanocomposite films with different loads of nanocrystal and nanoclay (0, 3 and 5 wt%) were prepared using a solvent casting method and their morphological, mechanical and barrier properties were tested. The study of nanoparticles dispersion quality in a PLA matrix has been examined using X-ray diffraction (XRD). For evaluating the mechanical and barrier properties of films, tensile strength, water vapor permeability and oxygen transmission rate were measured. XRD patterns showed that pure PLA has a semi-crystalline structure and addition of cellulose nanocrystal into this polymer would produce a more regular structure which results in improved crystallization. Also, the morphological findings revealed the formation of intercalation structure in nanocomposite films at all nanoclay loadings. The results indicated that the presence of cellulose nanocrystalls in the polymer matrix increased the tensile strength and elastic modulus of nanocomposite compared to those of pure PLA. Moreover, the mechanical properties of composite films increased with the increase of nanoclay up to loading fraction of 3%, but decreased using higher (5%) nanoclay loading fraction. The positive effect of nanofillers on mechanical properties is related to their high aspect ratio, crystalline structure and modulus. Furthermore, the decrease in mechanical properties at higher clay content levels is probably due to the formation of clay agglomeration, and its uneven distribution. Besides, the adding of cellulose nanocrystal and nanoclay improved barrier properties, by reduction of water vapor permeability and oxygen transmission of nanocomposite films.