GE thermoplastic alloy for ready meal packaging

Related tags Materials science

A new thermoplastic alloy, designed for use in large retort
packaging sterilisation trays, is said to offer ready-meal
manufacturers increased rack/surge capacity for higher output,
double service life, and lower systems costs.

This, says developer GE Advanced materials​, adds up to improved productivity for food processors.

The Noryl PPX 615 resin - an alloy of polyphenylene ether (PPE) and polypropylene (PP) - brings together two incompatible resins via a patent-pending alloying technology. The resulting material benefits from the low-temperature toughness, creep resistance, melt strength, aesthetics and thermal stability of the dispersed PPE phase.

The material is targeted at the large trays used to handle retort pouches during sterilisation and conveyance due to its special balance of broad chemical resistance, excellent thermal and hydrolytic stability, and stiffness with ductility. GE also claims that the new material offers good surface appearance, a wide processing window, and fast cycle times, all of which can help moulders improve their bottom line.

Retort sterilisation uses superheated steam to cook food while killing pathogens. Today, this food-preservation method is most commonly used for ready meals.

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 sterilization 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.

Resistance to common foods and cleaning chemicals are also required properties since the trays must be cleaned after each use and may be exposed to cooking oils and other substances. Common tray materials are metals, wood, or plastics. However, metal trays are typically heavy and can oxidise; wood can be hard to clean and has a limited number of cycles; and, many plastics are limited in that they lack the sufficient mechanical properties needed to resist creep or warpage under the rigorous heat and humidity of retort conditions.

Noryl PPX 615 resin is GE Advanced Materials' answer to these challenges and represents the newest addition to the company's growing family of thermoplastic alloys. These products are available from the company in filled and unfilled resin grades and can replace materials such as olefins, ABS, nylon, wood, and metals in a variety of applications.

"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."

Scott Williams, Allpax​ Products business development manager, said, "Switching to Noryl PPX 615 resin has allowed us to increase the rack capacity in our ovens by 35 per cent, which means we achieve higher food output per cycle. In addition, the service life of our trays has doubled, which is a major cost savings for us."

Thomas Hammoor, GE Advanced Materials' general manager for Engineered Styrenics said: "These new trays are just the tip of the proverbial iceberg in terms of Noryl PPX 615 resin's capabilities. 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."

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