Multilayer films | materials feature
Multi-layer films are beneficial for a multitude of reasons – and could soon be getting even thinner and more effective. Lou Reade reports
Building a barrier over many layers
At AMI’s Multilayer Packaging Films USA conference – held in Chicago, USA in late June – delegates heard about a wide range of developmental materials that could soon be used to create more effective barrier packaging.
Lindsay Corcoran, product and application develop-
ment researcher at LyondellBasell in the US, told delegates about a developmental resin that can improve film performance – by boosting water vapour barrier and film toughness, while allowing downgauging. The resin, called Alathon M6020SB, is one of a number
of resins that the company is developing. The HDPE grade promises higher water vapour barrier through increased nucleation. At the same time, its enhanced toughness is achieved by co-extruding it with LLDPE. “Development of PE nucleation led to further barrier
improvement in some HDPE by modifying crystal orientation,” she said. Corcoran said that the new resin was 50% more
effective as a water vapour barrier than the existing M6020 grade. In experiments, the company produced three-layer
co-extruded film which included a 15% skin layer of sealant, 55-70% HDPE core layer and a 15-30% barrier HDPE layer. For a 2.2 mil film, a structure with 25% M6020 had a WVTR of 0.16g/100in2
/day. Replacing it with 15% M6020SB reduced this to 0.11g//100in2 /day. At
the same time, machine direction (MD) tear increased from around 37 to 52g. There was also the option to downgauge by around
20%, from 2.2 to 1.8 mil. In this case, M6020 content was raised from 15 to 30%. The thinner film had comparable haze and MD modulus to its thicker alternative. When the core HDPE layer was replaced with LLDPE, MD tear improved more than threefold. Corcoran said that the new film could be a cheaper barrier than alternative materials, and could help packagers to strike a balance between WVTR, optics and strength.
www.filmandsheet.com
Transparent barrier At the same time, Hiroshi Suzuki, chief engineer at Toppan USA, revealed details of a new transparent barrier film technology. The product, called Besela, is an addition to its
global GL Film line – which has high oxygen and moisture barrier properties. GL Film comprises a PET base film, an AlOx/SiOx deposition and a patented ‘guard layer’. It is used in applications such as trans- parent retort pouches – as its properties can be retained at high temperature – as well as coffee capsules and for bakery products. Besela is a high barrier PET film that is coated with
organic resin – and demonstrates a high oxygen barrier by reacting to the moisture and the heat, said Suzuki. “It is an ideal film for boil and retort,” he said. He expect it to find use in applications such as
vacuum pouches, for products such as sweetcorn or boiled beans. The structure of such as film would typically be Besela/OPA/CPP. A typical Besela film comprises a 12 micron PET film with a 1 micron organic resin coating. Toppan is also developing a thermoformable version of Besela, consisting largely of a PP layer to maintain structural stiffness, and incorporating a barrier layer.
October 2016 | FILM & SHEET EXTRUSION 33
Toppan says that its new Besela film
could be used in vacuum pouches, for
products such as sweetcorn
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