GE says that the new material also offers good surface appearance, a wide processing window and fast cycle times. The firm believes that the resin has the potential to revolutionise retort sterilisation, a complex process that has become increasingly important in food production following the growth of ready to eat meals.
Retort sterilisation, invented in the early 19th century, uses superheated steam to cook food while killing pathogens. This food-preservation method is used today for ready-to-eat meals. Products are often heated via submersion in hot water, and each portioned meal is enclosed in retort packaging, which consists of a heavy-duty multilayer pouch of aluminium and plastic laminate designed to maintain food quality under harsh storage and shipping conditions.
The technical challenges of retort sterilisation can be sizeable. The process involves forcing steam at high pressure and temperatures up to 125C into a chamber containing rigid sterilisation trays, stacked up to 13 high, in which the pouches sit for as long as 90 minutes. This requires that tray materials have excellent heat-distortion performance under load, as well as dimensional and hydrolytic stability, stiffness, and impact strength.
In order to achieve this, Noryl PPX resin brings together two incompatible resins via a patent-pending alloying technology that incorporates PPE particles into a matrix of PP. The company believes that this gives the resin the edge against other materials on the market.
Advantages include lower temperature toughness and better impact strength, higher thermal performance and mechanical property retention and lower mass and generally lower costs than metals. In addition, the trays offer greater processing versatility, so trays can be produced via injection molding or thermoforming.
The new resin is now being used by a number of food packagers, including Allpax.
"Allpax had been experiencing challenges with both short- and long-glass-filled polypropylene, including sagging and breaking in the harsh retort environment," said Vanessa Mirabile, GE Advanced Materials industry manager for performance packaging. "So we introduced them to Noryl PPX 615 resin and the material passed all the criteria they required, including rigorous 1,000-hour heat aging and two-foot drop tests.
"Even after 500 heat cycles, the trays made from Noryl PPX 615 resin experienced minimal warpage."
GE Advanced Materials believes that the new material could revolutionise ready meal packaging. Indeed according to Thomas Hammoor, GE Advanced Materials' general manager for engineered styrenics, these new trays could be just the tip of the iceberg. "We're doing some groundbreaking work with this amazingly rugged and versatile alloy that we expect will continue to offer great benefits to the packaging, food processing, and materials handing industries worldwide," he said.