HDPE Resin Allows Converters to Create Mono-Material Barrier Film
ExxonMobil grade replaces multi-material structures in blown film packaging
It wasn’t so long ago that resin producers and converters were developing multilayer film structures to enhance barrier packaging. Five-, seven- and nine-layer packages were not uncommon on retail shelves, and some packaging had even more layers.
Now, however, resin producers and converters are looking at flexible packaging structures that provide barrier protection with mono-material layers. The reason, of course, is sustainability: multi-material packaging is difficult to mechanically recycle, and since mechanical recycling reportedly accounts for around 90 percent of all recycling in the U.S. (see Aug. 17 post: New Polyolefin Recycling Technology Has Commercial Promise), mono-material structures would be easier to collect and process.
HDPE Resin Designed for Use in MDO Polyethylene Film
One of the latest developments in this area comes from ExxonMobil, which has announced what it describes as a “novel high-density polyethylene (HDPE) grade” for machine-direction oriented (MDO) polyethylene film. The grade, HD7165L, reportedly allows converters to create mono-material laminates to replace multi-material laminate structures in packaging and applications including cast film, cast stretch film, shrink film, heavy-duty bags, agricultural film and standup pouches, among others uses.
Grade HD7165L is formulated to allow blown film converters to produce MDO-PE films with 60 to 70 percent HDPE for enhanced stiffness and high heat resistance. Output rates exceeding 400 kilograms (880 pounds) per hour are possible, while bubble stability is maintained, the company says.
High Optical Properties and Printability
According to performance data, MDO stretch ratios as high as 7:1, with high stiffness (1 percent secant modulus up to >200 kilopounds per square inch) can be achieved. With haze less than 10 percent and gloss higher than 60 percent, ExxonMobil says Grade HD7165L offers excellent optical properties. Used as a print web of a PE/PE laminate, the resin offers, in addition to heat resistance, stiffness for a lack of extensibility and high printability for optimum brand promotion.
In blown MDO-PE film, Grade HD7165L is formulated to provide uniform orientation, gauge stability and low gels for easy processability.
ExxonMobil says that compared to a market reference HDPE grade with density of 0.962 grams/cubic centimeter, Grade HD7165L, with density of 0.961 grams/cubic centimeter, delivers greater shear-thinning behavior and extrudability, high melt strength for bubble stability, and high orientability and gauge uniformity.
Additional properties include peak melt temperature of 274°F; tensile strength at yield in machine direction (MD) of 5,000 psi; tensile strength at break in MD of 11,000 psi; and elongation at break MD of 460 percent.
The resin is available in North America, Latin America and Europe.