Dual-ovenable tray

DFMA design for manufacmrability/ assembly DOT dual-ovenable tray... 

With the increase in the market of dual-ovenable and microwaveable trays there has been an increase in the demand for special lidding material, as the lid has to provide an oxygen barrier and a 100% hermetic steal to prevent food spoilage, besides being easy to remove. Grades of Du Pout s Mylar OL polyester lidding can be used to seal CPET, thermoset polyesters, and paper-board trays. 

Formed multilayer barrier packages, eg, trays, bowls, and cans from coextruded PP/PVDC/ PP, are being developed for soups and entrees that can be stored at ambient temperatures and heated to serving temperature in a microwave oven. Coextrusions of high performance, high temperature polymers, such as polyether-imide and polysulfone, for dual-oven containers capable of withstanding conventional bake-oven temperatures of 204-232°C are being tested. 

Wheel machines are designed specifically for dedicated products, such as picnic plates, dual-ovenable food trays, and takeaway coffee lids [8]. The wheel is a horizontal cylinder that contains dozens to hundreds of female or negative molds. The sheet is continuously extruded through the sheet die directly onto the slowly turning wheel. Vacuum pulls the sheet into the cool molds. As the wheel turns, the formed products are cooled. When the products are sufficiently cooled, the sheet containing the products is stripped from the wheel and fed to a conventional in-hne trimmer. 

Another use of microscopy is the study of competitive materials, which is similar to doing failure analysis as the full nature of the material is not known. In this example, the question was to learn the nature of the process used to make a dual ovenable food tray. Transmission electron microscopy cross sections, stained with... 

Figure 5.90. Transmission electron microscopy cross section of a dual ovenable food tray reveals a bilayer construction with neat PET (left side) at the shiny surface and submicrometer modifier particles with a sharp interface outlined by the stain formed by coextruding a multilayer construction. (From Wood [52] unpublished.)...

Attention has been paid to the possible use of multilayer coextrusion of engineering resins for dual ovenable containers, as multilayer packaging could increase shelf stability and thus eliminate the need for freezing or refrigeration. One multilayer combination in commercial use is a sheet of Lexan polycarbonate sandwiched between layers of Ultem polyetherimide. Thermoformed trays of this material are reported to have better break resistance at lower temperatures and higher stiffness at temperatures up to 232°C, as compared to CPET. They are also insert, compatible with polyester lidding materials, and have lower oxygen permeability than PET materials. 

Other plastics that, like PP, are not formable (or easy to form) have undergone similar changes. These plastics inherently have performance and cost characteristics that make them desirable materials for forming. An example that has involved large production quantities is PET from Goodyear Tire and Rubber. To make it formable, researchers produced CPET (crystallized PET). One major user of thermoformed CPET is Campbell Soup Co., where dual-use CPET trays (for conventional ovens and microwaves) replaced aluminum TV dinner trays. 

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