Synergy between fillers in organomontmorillonite/graphene–PLA nanocomposites

• Mixtures of two fillers (OMt and graphene) were used to enhance the PLA's properties.
• Better dispersion of hybrid Cloisites®/graphene in the PLA matrix was achieved.
• The barrier properties of PLA were enhanced by adding OMt/graphene mixtures.
• The storage moduli of ternary nanocomposites show a synergy between OMt and graphene.

Polylactic acid (PLA) nanocomposites filled with two organomontmorillonites (Cloisite® 15A and 30B), graphene functionalized epoxy (Gr) and montmorillonites–graphene mixtures were prepared via melt blending method. The main objective of this research was to study the synergetic effect of organically modified layered silicates with graphene when they are incorporated together into a PLA matrix. For this purpose, the rheological, morphological, barriers, and mechanical properties of elaborated materials were investigated. In contrast to binary composites containing different amounts of graphene (Gr–PLA), the addition of 3 phr of Cloisites® into Gr–PLA systems improved their elasticity and a secondary plateau was observed at the low frequencies in rheological measurements. Transmission electronic microscopy (TEM) images showed an enhancement of dispersion and exfoliation of two nanofillers (organomontmorillonite and graphene) in ternary nanocomposites attributed to a right combination of repulsive and attractive interactions between Cloisite® 15A-graphene and Cloisite® 30B-graphene systems, respectively. Dynamical Mechanical property (storage modulus) and water vapor permeability (WVP) were significantly improved by the microstructure development of materials; hence very interesting values of elastic modulus (G′) and WVP coefficient were obtained in the case of organomontmorillonite/graphene-PLA systems and particularly for Cloisite® 15A/graphene-PLA nanocomposites.

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