With increasing requirements on recyclability, interest in mono-materials is rapidly growing. Machine Direction Oriented Polyethylene film – or MDO-PE film – is playing a key role at the production of easy-to-recycle mono-material structures for flexible packaging.
“Due to its properties, MDO-PE film is an ideal solution when it comes to replace PET in PET-PE laminates, which were used for a variety of flexible packaging products as a standard so far”, Elias Mayrhofer, Product Manager at extrusion line manufacturer SML explains. Application areas of MDO-PE film range from mono-material tubular bags for food packaging to side gusset bags, and from sealed bags to different types of pouches.
Straight-forward further processing
MDO-PE film manufactured on SML’s latest cast film lines with integrated MDO unit provide excellent optical, mechanical and barrier properties. The film can be easily laminated to mono-material structures, for example with CPE sealent film on a FlexPack line from SML. “Cast MDO-PE films exhibit excellent printability and have been successfully tested on both Flexographic and Rotogravure printing systems. Metallisation is possible without any complications even with ultra-thin MDO-PE films”, Elias Mayrhofer states.
Wide variety of different film properties
The cast MDO technology allows the production of a wide variety of different types of MDO-PE film:
Ultra-thin film down to 15 µm SML cast film lines are ready to manufacture MDO-PE film as thin as 15 μm. “It goes without saying, that even at the most ultra-thin film the process is completely stable. There are no compromises when it comes to performance, functionality and printability,” Elias Mayrhofer says. A market-ready 15 µm MDO-PE film developed at SML in close cooperation with its polymer supplier and long-term partner Dow Packaging & Specialty Plastics has the following structure:
17 µm film with an EVOH barrier layer of less than 1 µm This ultra-thin barrier film was developed by SML in collaboration with Dow Packaging & Specialty Plastics and EVAL Europe N.V. (a Kuraray company). It comes with this layer distribution:
The film has been extensively tested and is ready for the market. It is characterised by the following barrier properties, given a stretching ratio of 1:5:
OTR: 1 – 3 cm³/m²/24hr * * Oxygen transmission rate at 23 °C; 50 % RH, testing method: ASTM F1927-07
WVTR: 5 – 8 g²/m²/24hr *
* Water vapour transmission rate at 38 °C; 90 % RH, testing method: ASTM F1249-06
Up to 65 µm MDO-PE film for extended application areas
The production of ultra-thin MDO-PE films of the highest quality is by no means the only possible application at the latest generation of SML cast film lines. The achievable thickness range for fully stretched MDO-PE films goes up to 65 µm which opens up a variety of other possibilities for film manufacturers. Especially with regard to packaging goods that require higher barrier functions or enhanced mechanical properties.
Integrated sealing layer: Ready-to-use film straight from the line
A further functional advantage of manufacturing MDO-PE film in the cast process is the option to directly integrate a sealing layer. This makes it possible to produce a completely ready-to-use film straight off the line, for example for products such as stand-up pouches.
Cast technology for unparalleled film quality
Generally, MDO-PE films produced in a cast process attain an excellent level of transparency. A superior film quality is reached through optimum flatness and the ideal distribution of thickness during production.