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HOW TO SELECT HEAT SEAL COATINGS FOR LIDDING APPLICATIONS

Home HOW TO SELECT HEAT SEAL COATINGS FOR LIDDING APPLICATIONS

Selection of the appropriate peelable heat seal coating for any lidding application is a challenging process and is influenced by a multitude of parameters.

We present here some of the major parameters that a converter must consider in selecting a heat seal coating for lidding applications.


Major Parameters

Lid film or lamination

Coating can be applied to a variety of substrates

  • Aluminum foil (AF)
  • Polyester film (PEST)
  • Oriented polypropylene (OPP)
  • Polyethylene (PE)
  • Paper or paperboard
  • Polyvinylidene chloride (PVDC)
  • Tyvek
  • Vinyl

Cup stock, tray stock, or bottom web

A variety of rigid materials are used as cup or tray stock


  • Aluminum foilPolyester (PET OR PETG)
  • Polyvinyl chloride (PVC)
  • Polystyrene (PS)
  • High impact polystyrene (HIPS)
  • Cast polypropylene (PP)
  • High density Polyethylene (HDPE)
  • XT polymer
  • Barex
  • Aclar

Food, Pharmaceutical, or medical products

The heat seal must be compatible with the contents or the cup or tray


Service Conditions

The heat seal coating must be selected to withstand one or more of the following conditions.  

Hot fill

Jellies, jams, syrup, sauces are often filled at 170-200 F the heat seal must have adequate hot tack at this temperature to resist leaking.

Refrigerated or freezing temperatures

citrus juices and concentrates are refrigerated or frozen. The heat seal must maintain its flexibility and adhesion to both surfaces at low temperatures.

Heat resistance

This property is important for retortable, autoclaavable, or oven able products. The heat seal must have bond integrity up to 350 – 450 F

Chemical resistance

The coating may be in contact with greasy, oily, acidic, or corrosive food products, perhaps at elevated temperatures.

Vacuum resistance

The sealed package may be exposed to a vacuum during sterilization or another process.

Porosity

Disposable medical devices are often sterilized by ethylene oxide gas. The heat seal coating must have adequate oxide gas. The heat seal coating must have adequate porosity to permit entry and exit of the gas and not react with it.

Stability to radiation

For certain medical devices or pharmaceutical uses, the heat seal coating must not degrade or react under gamma radiation.

FDA status

Heat seal coating must comply with the pertinent Food and Drug Administration (FDA) regulation for the lidding substrate, food type, and services conditions.

Type of bond

The packager must be specified low, moderate, or high peel strengths as well as the amount of coating transfer desired. Sometimes a destruct bond is required.

Seal Conditions

The coating must function within the limits imposed by available heat. Pressure, and dwell time at the bond line. This also includes considerations of sealing equipment.

Application equipment

The converters equipment – gravure, flexo, roller coater will have a strong influence on coating selection.

EPA considerations

Sometimes the choice between a solvent or water based heat seal has more influence than all of the others. Solvent recovery equipment can also dictate the solvent to be used.

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