Structural characteristics defining high barrier properties in polymeric materials

Abstract

The packaging industry has dramatically increased the number of packaging systems and designs made of plastics over recent decades. Plastics, in contrast with more traditional packaging materials such as glass and metals, are permeable systems that permit the exchange of low molecular weight compounds, e.g. gases and vapours, between the inner and the outer atmosphere. Despite this drawback, the availability of shapes and forms in which they can be manufactured, their ease of processing and handling, low price, excellent chemical resistance, etc., have made them very attractive in many packaging elds. Consequently, much industrial and academic research has been devoted to understanding the mechanisms of mass transport in polymers, to enable design of materials with improved barrier properties. The present paper reviews some of these developments, and highlights the structural factors that cause polymers to behave as high barrier materials, taking as benchmark the properties of one of the most widely used family of high barrier materials, the ethylene -vinyl alcohol copolymers.MST/5992

Nanocellulose in Thin Films, Coatings, and Plies for Packaging Applications: A Review

“…As a general rule, plasticizers tend to hurt the cohesive energy density of a material. As a result, they tend to hurt resistance to permeation (Lagaron et al 2004). Positive effects of plasticizers on oxygen or water vapor barrier performance have been reported by some authors (Bayati et al 2014; Arrieta et al 2015).…”

“…The general subject area of packaging materials involving biomaterials has been the focus of numerous review articles and monographs (Lagaron et al 2004;Rhim and Ng 2007;Chiellini 2008;Johansson et al 2012;Tang et al 2012;Paunonen 2013a). For example, Krochta and DeMulderJohnston (1997) reviewed research related to edible and biodegradable films for packaging applications.…”

“…In addition, there is fastaccumulating information regarding the performance of nanocellulose-containing packaging structures relative to end-use requirements such as barrier properties, appearance, and strength. Some general directions for the development of barrier films already had been well established before nanocellulose films were even considered for such applications (Lagaron et al 2004), and these goals have been extended to systems that can involve cellulosic nanomaterials (Moon et al 2011;Paunonen 2013b). The subsections below further expand upon such aspects.…”

“…Both oxygen and nitrogen gases are non-polar compounds, whereas cellulose is rich in polar, hydrogen-bonding -OH groups. The other key factor noted by Lagaron et al (2004) is a high cohesive energy density, which again can be attributed to the hydrogen bonding. According to Lagaron et al (2004), resistance to gas permeation through a solid film is often correlated with the glass transition temperature; a high Tg value implies a generally immobile nature of molecular segments, so that gas diffusion through the material is not facilitated.…”

“…The performance of various nanocellulose-based films to resist permeation by oxygen is summarized in Some key factors accounting for the ability of nanocellulose films to block gas transport will be summarized. As noted already by Lagaron et al (2004), one of the essential principles underlying resistance to diffusion of gases through packaging materials is to have a very low solubility of the gas in the material. In general terms, very low solubility implies a large difference in factors such as hydrogen bonding ability.…”