Mechanical properties of SiOx gas barrier coatings on polyester films

Abstract

This paper reports the impressive mechanical properties of 1 μm thick carbon-containing SiO x gas barrier coatings, characterised using the uniaxial fragmentation test. Such coatings have been found to act as excellent barriers to water vapour permeation partly because they can be made so thick without stress induced cracking. The impressive mechanical properties are thought to be due in part to the high amount of carbon they contain, which gives them a more organic character, as well as the fact that they are deposited as a succession of thinner layers. The adhesion of the coatings to the polyester film is good in all cases, reflecting a high density of covalent bonding at the interface. Improvement of the mechanical properties of a SiO x /PET composite can be achieved by altering the substrate. By replacing the PET with a heat-stabilised (HS) PET film, a HS film with an acrylate layer or PEN, it is found that the coating displays improved mechanical properties and adhesive strength (as well as barrier). This is thought to be due to the superior surface thermal and mechanical properties of these substrates. Deposition temperatures are at least 80°C, which causes molecular motion at the surface of a plain PET film and creates defects in the SiO x coating as it grows, making it more brittle and permeable to gas flow.

Models for saturation damage state and interfacial shear strengths in multilayer coatings

“…The topic of multiple cracking of coatings on high elongation substrates (and matrices in composite laminates) has motivated a considerable amount of work, for instance to obtain statistical strength parameters from crack spacing distributions (Hui et al, 1999;Leterrier et al, 1997a,b;Ochiai et al, 2007) and layer toughness (Kim and Nairn, 2000;Nairn, 2000). Prior analyses of experimental data, however, are limited to single coatings (Andersons et al, 2007;Handge, 2002;Handge et al, 2000;Howells et al, 2008;Hsueh and Yanaka, 2003;Leterrier et al, 2004;Tang et al, 2001;Yanaka et al, 1999). In this case, the interfacial shear strength (IFSS, representative of practical adhesion) can be derived from an interfacial stress transfer analysis.…”

Design and fabrication of compositionally graded inorganic oxide thin films: Mechanical, optical and permeation characteristics

“…This reflects the good adhesion of the Al 2 O 3 layer on PES, presumably due to the formation of covalent bonds between the two materials [36]. The IFSS of the SGS layer on the PES substrate was much higher, at 97.0 MPa.…”

Barriers and Chemistry in a Bottle: Mechanisms in Today’s Oxygen Barriers for Tomorrow’s Materials

“…The silica is deposited by physical vapor deposition (PVD) or plasma-enhanced chemical vapor deposition (PECVD) on the inner bottle wall. Both processes lead to a thin layer with a thickness between 10 nm and 100 nm [98,99]. The maximum thickness of the coating is limited with respect to food safety, color and flexibility.…”