Increasing the Gas Barrier Properties of Polyethylene Foils by Coating with Poly(methyl acrylate)-Grafted Montmorillonite Nanosheets.

Judith E Rauschendorfer,Philipp Vana

doi:10.3390/polym13193228

Abstract

Low-density polyethylene (LDPE) foils were coated with a thin film of polymer-grafted Montmorillonite (MMT) nanosheets, which form a barrier against gas diffusion due to their unique brick-and-mortar arrangement. The MMT nanosheets were grafted with poly(methyl acrylate) (PMA), a soft and flexible polymer. Already very thin films of this nanocomposite could reduce gas permeability significantly. The impact of the topology of the surface-grafted polymer on gas permeability was also studied. It was found that grafting MMT nanosheets with a mixture of star-shaped and linear PMA and with PMA that is cross-linked via hydrogen bonds further decrease gas permeability. The presented strategy is quick and simple and allows for the easy formation of effective gas barrier coatings for LDPE foils, as used in food packaging.

Highlights

Multilayer systems are omnipresent in modern high-performance materials
Low-density polyethylene (LDPE) foils were coated with a thin film of polymer-grafted Montmorillonite (MMT) nanosheets, which form a barrier against gas diffusion due to their unique brick-and-mortar arrangement
It was found that grafting MMT nanosheets with a mixture of starshaped and linear poly(methyl acrylate) (PMA) and with PMA that is cross-linked via hydrogen bonds further decrease gas permeability

Summary

Introduction

Multilayer systems are omnipresent in modern high-performance materials. For example, polymer-based food packaging is a highly sophisticated layer system with usually at least one layer providing a barrier against gas diffusion [1]. We showed that by addition of a hydrogen-bonding comonomer to the grafted linear PMA the properties of the composites can be further enhanced [14] We demonstrated that these changes in the grafted polymer allow for an increase in mechanical stability of the arranged polymer/nanosheet structure. As this structure is crucial for the formation of a gas barrier, these novel matrix-free hybrid nanosheets are adapted to form coatings for LDPE foils and are for the first time analyzed for their gas barrier properties. The polymer-grafted MMT nanosheets—without any additional matrix polymer—are cast to the surface of LDPE forming a μm-thin coating, which effectively decreases gas diffusion

Materials

Synthesis of Polymer-Grafted MMT Nanosheets

Coating of LDPE Foils with Polymer Grafted Nanosheets

Sample Preparation

Analysis of the Gas Barrier Properties