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Need LDPE for film clarity or improved processability? Not anymore

Plastic film processors are finding they can reduce the use of LDPE in their film, or even stop adding it entirely, while maintaining similar clarity and processability. Some, in fact, are seeing a big uptick in mechanical properties, even a doubling of impact strength, with a recently introduced metallocene polyethylene from ExxonMobil Chemical.

The supplier introduced its Enable brand of metallocene polyethylene (mPE) in 2008, and since then the material has met rapid success in the market, says David McConville, global PE market development manager. ExxonMobil also supplies Exceed-brand mPE and its Vistamaxx propylene-based elastomer. This last material is finding "a very nice fit" in the stretch hood market, he says, with it also seeing use in applications as varied as raffia, tape and surface protection films and even in cast polypropylene. "We're still finding new applications (for it) and so are our customers," he says.

Enable mPE was in the spotlight on some high-layer lines running at the recent K show in Düsseldorf, including on a 9-layer film running there which included EVOH in its core. McConville says processors are using the new mPE to replace or simplify the blends they use, downgauge, improve processability, and improve output—almost anything a films processor could want. "Using (Enable mPE) lets you run with less LDPE, or even not use it at all," he says.

Processors often add low-density polyethylene (LDPE) to their film recipes to increase a film's clarity and to improve processability. "But in the past year we've shown quite successfully that with the use of Enable mPE you can get rid of LDPE, run your line at the same speed and get much better tear resistance. It's one of the focuses of our marketing effort right now," he explains. "(With Enable mPE) there is a significant increase to mechanical performance, even a doubling of dart impact strength...Customers are latching onto this very quickly. Everyone is working to take cost out of film, and this has been a real winner." It's even helped his own company, which has switched to an Exceed mPE for the bags it uses to ship its resin to processors, without need for LDPE in those bags.

In addition to this mPE development, McConville says he and his colleagues also are excited about the growing trend among some processors to run dedicated 5-layer polyolefin film lines. With his company's materials running on such lines, "We're getting added performance even in the pure form. You get more stiffness, so you can downgauge...It's still early in the development phase [for these lines] but it's intriguing as you can really increase the mechanical properties. We believe these lines will be the next step-change in downgauging." Most 5-layer lines, he explains, are for barrier films and are not dedicated to extrusion of PE film. On one of these dedicated lines, instead of blending more high-density PE in the core, the HDPE would be added in the B layers in an A-B-A-B-A structure. Two such lines were in operation at the K show.

McConville, who works out of the company's Singapore offices, has global marketing responsibility. Despite globalization's strong influence on packaging, there still remain significant differences in polyolefin film design among different regions, he says. Most of the difference can be traced to the great variance in what defines "fitness for use" in the different markets. For example, pallet wrapping in Asia is almost all hand wrap whereas in Europe or North America, it typically is automated. Stand-up pouches have a strong market presence in Asia but have not been as popular in Europe or the Americas. Bucking the trend is heavy-duty bag design, he says, with its design similar all around the world.

McConville, his colleagues and the extruder manufacturing OEMs with which they closely partner see a bright future for the plastic films industry, he says. "Look at our portfolio of advanced mPE, and couple that with the advances in multilayer extrusion lines, and we and the OEMs are pretty excited."

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