Effect of Nanoclay Hydration on Barrier Properties of PLA/Montmorillonite Based Nanocomposites

Abstract

Incorporating Cloisite 30B (C30B) in poly(lactic acid) (PLA) matrix was investigated as functions of the content and of the hydration state of nanoclays. Two series of PLA based nanocomposites were prepared by melt compounding using nanoclays in hydrated state (undried C30B) or preliminary dried (dried C30B). Their structure was characterized by transmission electron microscopy (TEM) observations and X-ray diffraction (XRD) measurements which highlighted the coexistence of exfoliated, intercalated, and aggregated structures. Rheological measurements put forward better degrees of dispersion and of exfoliation for nanocomposites containing undried C30B. From differential scanning calorimetry (DSC) measurements, a slight change in crystallinity was measured owing to the nucleating effect induced by the nanoclays. The transport properties were analyzed from permeation and sorption kinetics. A significant improvement of the water and oxygen barrier properties was obtained, especially for nanocomposites with undried C30B, while a reduction in diffusion was evidenced. This peculiar behavior was correlated to the presence of water molecules included in C30B contributing to a better dispersion and orientation of the nanoplatelets into the PLA matrix.

A review of the water barrier properties of polymer/clay and polymer/graphene nanocomposites

“…It is found that the classical model of Nielsen [14] is most often fitted to water vapour permeability data of polymer/clay nanocomposites. If nanofiller exfoliation is incomplete or the orientation is not perpendicular to the diffusion direction, then the model due to Bharadwaj [22] can be successfully applied [50,56,62]. Other models are claimed to be more suitable for predicting behaviour at high filler aspect ratios.…”

“…However, as shown in Table 1, there are a number of other studies where Cloisite 30B has been used very successfully to reduce water vapour permeability in PLA [16,[60][61][62].…”

“…Bharadwaj [22] can be successfully applied [50,56,62]. Other models are claimed to be more suitable for predicting behaviour at high filler aspect ratios.…”

“…The formation of clusters during the penetration of water has been observed in many polymer systems [4,12,41,52,53,62,68,113,114]. The presence of water clusters often causes a reduction in water diffusivity.…”

Nanoamphiphilic Chitosan Dispersed Poly(lactic acid) Bionanocomposite Films with Improved Thermal, Mechanical, and Gas Barrier Properties

“…2,[4][5][6][7] It is biodegradable, biocompatible, non-toxic, hydrophobic in nature and fully industrially viable. 2,[7][8][9][10] It has commendable thermal, mechanical and barrier properties with superior transparency in the processed materials which increases its utility in food packaging and medical applications.…”