What is Heat Sealing of Aluminum Foil?
Heat sealing is a process that uses heat and pressure to fuse together overlapping surfaces of aluminum foil or foil laminates. It works by melting a layer of thermoplastic resin or coating on the foil which then bonds and seals the overlapped edges upon cooling and solidification. Common thermoplastic resins used in heat-seal coatings for foil include polyethylene, polypropylene, ethylene vinyl acetate, and ionomers. The heat is typically applied using a heated seal jaw or welding bar that presses down onto the foil overlap area. Precise heat and pressure are applied for a set dwell time to achieve a strong, hermetic seal between the foil surfaces that withstands peeling, puncturing or other stresses during transport and storage of packaged foods.
Heat sealing transforms standard aluminum foil into a highly functional packaging material for various food types. It allows foil to be formed into bags, pouches, trays or other container shapes simply by cutting, creasing and sealing the foil laminate accordingly. The resulting foil package encases and protects the food product from the external environment while the heat-sealed seam keeps air and contaminants out, aiding shelf life extension. Heat sealing is a critical process in the conversion of aluminum foil rolls into finished flexible packaging formats like those commonly found on supermarket shelves today.
Heat sealing aluminum foil specifications
| Type | Heat Sealing Aluminium Foil |
| Application | To be used for food contact lid,by heatseal with PET |
| Alloy | 801,112,358,079 |
| Temper | O |
| Thickness | 0.025mm-0.05mm |
| Width | 150mm-1000mm |
| Surface | One side bright,One side matt |
| Packaging | Free Fumigated wooden box |
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Common Aluminum Foil Alloys for Heat Sealing
There are two predominant alloys of aluminum that are widely used in heat-sealable foil for food packaging - 8079 alloy and 8011 alloy. These alloys provide ideal mechanical and thermal properties for heat sealing applications.
8079 Alloy
8079 alloy contains 99% pure aluminum with trace amounts of magnesium and chromium. The magnesium content enhances mechanical properties and foil strength. It allows foil to be rolled very thin - as thin as 5-7 microns for some applications - while maintaining good handling properties prior to packaging. 8079 alloy also features excellent formability which enables complex shapes to be stamped or formed from the foil sheet. Its ability to be made into ultra thin yet durable foil makes 8079 alloy ideal for many food contact applications where a minimal material barrier is desired. An example would be very thin overwraps that provide visibility into packaged products but offer a lightweight protective layer. 8079 alloy heat seals well within the common temperature range of 350-450°F (175-230°C).
8079 alloy has gained widespread usage as the predominant heat-sealing aluminum for food packaging foil since its development in the 1960s. Estimates suggest it accounts for over 70% of the total heat-sealable aluminum foil market. Its versatility and formability advantages have made 8079 alloy a mainstay for flexible food packaging formats like bags, pouches and trays. Manufacturers favor 8079 alloy for its consistent heat sealing properties across a broad set of processing parameters.
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Influence of Foil Coatings on Heat Sealing
In addition to aluminum alloy composition, the coatings applied to heat-sealable foil surfaces also impact sealing performance and suitability for different packaging needs. Common heat-seal coating types include:Polyethylene (PE): Provides very effective sealing over a wide temperature range. PE is the most prevalent sealing resin and lends good clarity to allow product visibility. It is economical but not as heat resistant as other options.
Polypropylene (PP): Has enhanced temperature and chemical resistance over PE. PP seals offer greater puncture resistance but lack some of PE's clarity. It is preferable for retort applications.
Ethylene Vinyl Acetate (EVA): Delivers high clarity, flexibility and hot-tack strength straight from the sealing jaw. EVA forms strong initial seals immediately upon cooling. However, it has limited heat resistance.
Ionomer: These materials are polyethylene copolymers that contain ionizing groups. Ionomers offer heat, abrasion and chemical resistance above other options and are suited to demanding retort packaging. However, they are more expensive than standard PE or PP.
Foil converters tailor sealant coatings based on the processing requirements and end-use demands of packaged foods. For example, PE may suffice for chilled or frozen food pouches while PP or ionomer would be needed for retorted items. In some cases, foil laminates employ multiple coatings - one on each side - to capitalize on distinct benefits. One surface may utilize PE for effective sealing while the other uses EVA for strong hot-tack adhesion. Selection of compatible resin layers allows packaging designs to satisfy specific application needs.
Examples of Heat-Sealed Foil Food Packaging
Heat-sealed aluminum foil finds widespread deployment across various food types and product formats. Here are some representative examples:
Tea Bags
Individual serve tea bags are a classic application of heat-sealed foil laminates. Ultra thin 8079 alloy foil provides a protective yet delicate barrier layer for tea leaves. Tea bags are sealed by fusing overlapping foil edges coated with materials like PE or EVA that withstand brewing temperatures. Heat sealing forms convenient single-serve pouches for on-the-go tea enjoyment.
Snack Bags
Many salty and sweet snack foods like potato chips, crackers, cookies and candies are packaged in foil-based stand-up pouches or quad-seal bags. 8079 alloy foil laminated with PEinnersealant layers allows efficient production of bags on form-fill-seal equipment. Dense, multiple overlaps around bag bases enable bags to maintain their shape during shelf life.
Coffee Packets
Individual coffee creamer or sugar packets resemble tear-open sachets made by heat sealing 8079 alloy foil laminated with EVA or PE. These coatings form seals capable of withstanding the thermal shock of being added to hot coffee or tea without leaking.
Retort Pouches
Sheets of 8011 alloy foil are processed on high-speed equipment to produce rigid preformed trays or fully formed flexible pouches for retorted foods like soup, broth, sauce and infant formula. PP or ionomer liner resins on the foil enable it to withstand industrial sterilizing temperatures upwards of 275°F during retort processing.
Meat Trays
Modified atmosphere packaged (MAP) meats for grocery deli counters often utilize multilayer trays made from aluminum foil lidding laminated to a semi-rigid support substrate. 8011 alloy foil lidding sealed with ionomer creates an effective oxygen and moisture barrier to extend unopened tray shelf life for up to 3-4 weeks.
If you are interested in heat-sealing aluminum foil or you need heat-sealing aluminum foil, you can contact us and HTMM will answer your questions with the best service.
In summary, heat sealing provides aluminum foil with core functionality for a broad spectrum of food packaging applications. Through selection of the proper alloy, gauge, coating materials and sealing parameters, heat-sealed foil satisfies the performance requirements for countless packaged food types whether destined for industrial processing, retail shelves or direct foodservice use. Its combination of barrier properties, formability, cost effectiveness and heat sealing adaptability cement aluminum foil's status as a packaging substrate supporting modern food manufacturing and distribution worldwide.
