Temperature dependency of gas barrier properties of biodegradable PP/PLA/nanoclay films: Experimental analyses with a molecular dynamics simulation approach

Abstract

Polypropylene (PP)/poly(lactic acid) (PLA)/clay nanocomposite films with various compositions (PP‐rich and PLA‐rich) were prepared. Their structural and barrier properties against CO2, O2, and N2 were investigated. The microstructure of the nanocomposites was studied by scanning electron microscopy, transmission electron microscopy, and wide angle X‐ray scattering. The PP‐rich with 75/25 composition revealed the best barrier properties against all the gases which could be justified according to its microstructure. Selectivity of O2/N2 and CO2/N2 was also measured. It was found that the addition of nanoclay as a gas barrier component reduced the permeability in both systems. The permselectivity was also reduced in the PP‐rich films while it was increased in the PLA‐rich system. Moreover, the temperature dependency of permeability, selectivity, and permselectivity for PP, PLA, and PP/PLA (75/25) samples was examined. The results showed that the temperature dependence of permeability obeyed an Arrhenius equation and order of activation energy of permeability for O2, CO2, and N2 gases was found to be EP < EP/PLA < EPLA. According to solubility measurements, the order of solubility coefficient for gases was as follows: CO2 > O2 > N2. Finally, the molecular dynamics (MD) simulation was performed to estimate the diffusivity coefficients of the gases and showed that solubility increases with increasing temperature, which was in accordance with the experiments. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46665.

A Theoretical and Experimental Analysis of the Effect of Nanoclay on Gas Perm‐Selectivity of Biodegradable PLA/EVA Blends in the Presence and Absence of Compatibilizer

“…The name, composition, filler content and compatibilizer loading of samples are reposted in Table 1. It should be mentioned that according to the previous studies on the similar blend nanocomposite systems [2,3] only a set of optimized systems with a fixed clay loading of 5 wt% were chosen to investigate the role of blend composition, clay, and compatibilizer on the gas perm-selectivity of the developed blend nanocomposites. Higher loadings of clay lead to server reduction in gas permeability of these materials.…”

“…Considering fossil fuel consumption and environmental contaminants, packaging industry tends to use biodegradable and eco-friendly polymers instead of petroleum-based conventional plastics such as polyethylene (PE), polypropylene (PP), polyvinyl-chloride (PVC), and polyamide (PA) that are widely employed in the packaging industry. [1][2][3][4] Bio-based, semicrystalline poly(lactic-acid) (PLA) is one of the widespread materials which is used as the biodegradable polymer in the packaging application, tissue engineering, drug delivery systems, etc. [5][6][7][8][9] PLA, due to its low cost of polymerization, appropriate thermal behavior, excellent barrier properties, high strength, and stiffness, is richly applicable but have noticeable drawbacks such as brittleness and hydrolysis.…”

“…of PLA with various biodegradable or non-biodegradable (co) polymers. [2,6,11,12] Among them ethylene-co-vinyl acetate (EVA) is a suitable material for blending with PLA, since it compensates the brittleness of PLA due to its high toughness and flexibility. [6,13,14] It is thought that the blend of PLA/EVA is generally immiscible, but the compatibility of the blend depends on the vinyl acetate (VA) content which increases with respect to the VA content.…”

“…Furthermore, the permeability of N 2 as an inert gas helps to reduce the degeneration rate of the food. [2] One of the commonly used manners to promote gas barrier performance of a polymer is to add platelet nanofillers like nanoclay. [20][21][22][23] Clay has a high aspect ratio owing 2D platelet-like structure, which can prolong the gas diffusion pathway by a mechanism known as tortuosity.…”

“…[9,30] In a crystalline polymer, gas molecules cannot easily diffuse or dissolve into the crystalline domain, so the solubility and diffusion coefficient are small. [2] Also, it has been reported that with rise of VA content in EVA, polarity increases which positively affects clay dispersion and improves its degree of exfoliation/or intercalation. Moreover, the degree of intercalation or exfoliation of clay directly affects the in situ aspect ratio of clay which itself can be affected by mixing method [15] .…”