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3: materials


Different tray materials are used for a number of reasons:
  • The process may dictate which material must be used e.g. for a frozen, chilled, or cooked in the pack product
  • The product contained in the tray may mean one material is more suitable than another
  • The choice may be dictated by the cost of the tray material
  • Marketing and consumer perception may influence the choice because of the aesthetic qualities of the material
For a list of suppliers for a specific material, please click on its name.

material abbreviation         uses
Polypropylene PP
  • Microwaveable, freezable, suitable for MAP.
  • Available in any colour as well as clear.
  • Can be surface printed.
  • Relatively cheap.
Crystallised polyester terephthalate C-PET
  • Ovenable, microwaveable, freezable, suitable for MAP.
  • Colours offered are limited to white, black and brown.
  • Can not be surface printed.
  • Relatively expensive.
Amorphous polyester terephthalate A-PET
  • Not suitable for use in the microwave or oven
  • Freezable and suitable for MAP.
  • Available in any colour as well as clear.
  • Can be surface printed.
  • More expensive than PVC.
Polyvinyl chloride PVC
  • Not suitable for use in the microwave, oven or freezer.
  • Suitable for MAP, but performance will be improved with a PE coating.
  • Available in any colour as well as clear.
  • Can be surface printed.
  • Relatively cheap.
  • Environmental issues are making this a less popular choice than A-PET.
Polystyrene PS
  • Not suitable for use in the microwave, oven or freezer.
  • Not suitable for MAP
  • Very brittle material
  • Available in any colour
  • Cheap
High impact polystyrene HIPS
  • Not suitable for use in the microwave or oven
  • Suitable for freezing
  • Not suitable for MAP
  • Available in any colour
  • Cheap
  • Not as brittle as PS
High density polyethylene HDPE
  • Not suitable for use in the microwave or oven
  • Suitable for freezing
  • Suitable for MAP, very high gas barrier properties
  • Limited to white, black or clear
  • Can be surface printed
  • Fairly expensive
Aluminium foil - crinkle wall -
  • Suitable for freezing
  • Not suitable for MAP
  • Cannot be surface printed
  • Fairly cheap
  • Cannot be sealed hermetically - mostly used with board lids and crimping
Aluminium foil - smooth wall -
  • Suitable for use in the oven and most microwaves
  • Suitable for freezing
  • Suitable for MAP
  • Available in different colours
  • Cannot be surface printed
  • Can be difficult to seal unless lacquered
  • Product contamination checks have to be carried out with an x-ray machine
  • Expensive
Board (pressed, folded, pulp) -
  • Suitable for use in the oven, microwave and freezer
  • Not suitable for MAP
  • Can be surface printed
  • Require a sealant layer to enable sealing
  • Fairly cheap

These are some of the common heat sealing applications and the tray materials used:

application materials
Microwaveable ready meals
 PP, C-Pet, Board
Ovenable ready meals C-Pet, Smooth wall foil, Crinkle wall foil, Board
Salads A-Pet, PVC
Vegetables PP, Smooth wall foil, Crinkle wall foil
Desserts A-Pet, PVC
Puddings PP, C-Pet
Dairy products PP, PS
Confectionery PVC, PS
Fish Smooth wall foil, PP, PVC, A-Pet
Meat A-Pet, PVC, Smooth wall foil
Soup PP, A-Pet

These are the common lidding materials used in heat sealing:
  • Polyester (PET)
    This is the most common base material used and is the most heat resistant material (up to 235oc). It offers excellent clarity and can be supplied printed.
  • Nylon (OPA)
    This is technically known as "Orientated Polyamide". It is heat resistant up to 190oc and has to be laminated to Polyethylene. It is tear resistant, slightly opaque and can be supplied printed.
  • Polypropylene (OPP)
    This is technically known as "Orientated Polypropylene". It is heat resistant up to 160oc and has to be laminated to cast polypropylene. It will only seal to polypropylene. It can be supplied printed.
  • Aluminium foil
  • Board

click here to view a list of lidding materials suppliers and links to their websites

Heat sealing films are manufactured in two different ways

  • mono layers - which are a single layer of material with an adhesive coating. Different adhesives used include A-Pet (used for high temperatures e.g. for cooking), Vinyl Acetate (EVA) (used for microwave products only), and Polyethylene (PE).
  • laminates - which are multi layer films formed from two or more different substrate materials
    The sealant layer is dictated by the tray material, the type of seal needed (e.g. weld or peel) and cost.
 
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