Facts about aluminium foil!
*Info from The European Aluminium Foil Association e.V. (EAFA)*
Aluminium foil is a very thin aluminium sheet(up to 200 µm or 0.2 mm).
Approximately 75% of the European production is used for packaging and household foil and 25% is used in technical applications.
Aluminium foil, commonly used in packaging and laminates, offers packaged goods:
1. absolute barrier properties,
2. guaranteed quality by preventing the loss of valuable aromas,
3. protection of contents against light, oxygen, moisture and contamination.
Aluminium foil saves far more resources than are consumed in its production throughout the supply and valuechain.
Aluminium: today’s material:
Aluminium has been used commercially for over 100 years. Since the late nineteenth century, its plentiful availability and its characteristics have increasingly shaped our modern way of life. Think of aircrafts and cars without it, or space exploration, electricity transmission, modern buildings, cooking pans and, today, high quality packaging of many sorts. More than 43 million tons of primary aluminium is now produced annually around the world. Thanks to recycling, an increasingly large amount comes from metal which has been used at least once before.
How aluminium is made?
Aluminium, the third most abundant element on the earth’s crust, after oxygen and silicon, is extracted from an ore called Bauxite. The ore is refined to make ‘alumina’, a pure aluminium oxide. The aluminium metal is then produced from alumina by passing an electric current through it in a process called ‘electrolytic reduction’. The resulting silvery metal is the basis of a wide range of alloys made by adding small amounts of other metals to provide the specific characteristics needed for each application. For most alufoil packaging virtually pure aluminium is used but increasingly alloys are being ‘tailored’ in order to add strength and allow for reductions in thickness for the same performance.
Making aluminium foil:
Alufoil is a very thin sheet of aluminium ranging from about 0.006mm to the upper ISO defined limit of 0.2mm (200µm). It is produced by first rolling heated ingots (hot rolling) down to coils of thickness between 2 and 4mm. The coils are then successively cold rolled to the required foil thicknesses.
A second foil rolling method, continuous casting, bypasses the ingot stage and converts molten metal directly into a thick strip which is immediately rolled into the coil from which the foil is then rolled.
To obtain the very thinnest foils, two layers are rolled simultaneously. This ‘double rolling’ results in the difference between the two surfaces – matt and polished – the matt side being the inner side during double rolling. The two layers of alufoil are then separated. The resulting large reels are slit to the widths needed for further processing for the required end use – flexible packaging, foil containers, lidding foils, household foil, heat exchanger foil, laminations for heat insulation materials, etc.
Converting aluminium foil:
From plain aluminium foil many material specifications are produced. Packaging converting companies make an enormous variety of alufoil-based products by coating and laminating with other materials, printing, embossing, etc. By using plain foil in thicker gauges, specialist manufacturers produce containers for fresh and cooked foods. Plain foil is also familiar in most domestic and professional kitchens. Its unique combination of properties – impermeability, flexibility, strength, ductility, recyclability, corrosion resistance, conductivity and compatibility with other materials – qualify aluminium foil for an infinite variety of uses.
Aluminium foil: Characteristics and properties
Aluminium foil is a versatile and effective material, involved in many applications – in particular for packaging and technical products. See Facts if you are interested in facts about alufoil or Markets to see where it is used.
Net Saver of Resources
Aluminium foil in food and drink packaging applications saves more resources than are needed in its production. Various Life Cycle Assessments (LCAs) show that alufoil packaging and household foil contribute less than 10% of the environmental impact in a product‘s lifecycle – Sustainable production and consumption.
Barrier Protection
Alufoil’s total barrier to light, gases and moisture is the principal reason for its use in flexible laminates for food, drink and technical applications. Even when very thin it provides perfect protection and preservation of aroma and product characteristics. It can help to extend the viable life of sensitive products for many months, even years, fully retaining original aromas. By enabling products to be preserved for long periods without the need for refrigeration, alufoil packaging helps to prevent spoilage and can provide large energy savings.
Mechanical Properties
Light yet strong, alufoil has unique deadfold characteristics which make it ideal for wrapping and re-wrapping many different products and product shapes, while minimising the need for sealants. Because it is very malleable it can be easily deformed without losing its barrier integrity, making it an ideal material for use in combination with other flexible substrates to create very thin laminates for a variety of markets and consequently, again, save resources.
Formability and Strength
When pressed into a shaped dish, the aluminium foil memorises its shape, particularly where the folds and rims occur. Shape, thickness, alloy and temper can be selected to create exactly the performance characteristics required.
Lightweight and Space Efficient
Economies in both transport and storage result from lightness, flat or reeled format of empty packs and, in the case of alufoil containers, their nesting shapes which are particularly suited to filling machine magazines. Alufoil helps save resources during packaging, product and waste transportation. By enabling products to be preserved for long periods without the need for refrigeration, alufoil packaging provides large energy savings. Their shape can make them very ‘space efficient’ in storage and display, enabling further energy and cost savings. Alufoil is weight saving, versatile and minimises the amount of packaging material needed.
Structural Stability
In light honeycomb structures aluminium foil introduces the necessary stiffness and stability enabling architects to lighten building structures and foundations; and engineers to save weight in all types of transport – ships, planes, trucks and cars.
Recycling
Aluminium is fully recyclable, endlessly, without any loss of quality. The recycling process for aluminium requires 95% less energy compared to its primary production, which corresponds to enormous emission savings. Modern separation techniques allow aluminium foil in household waste to be extracted and recycled at a fraction of its original energy cost.
Recovery
If aluminium foil is not collected for recycling but processed in incinerators the thin, laminated foil material is oxidised and releases energy, which can be recovered. In addition, the remaining non-oxidised aluminium can be extracted from the bottom ashes of the incinerator and subsequently used for recycling purposes.
Heat Performance
Alufoil is very conductive to heat. It stands up to all temperature variations encountered in the processing and use of packaging – from well below blast-freezing to the extremes of baking and grilling- without distorting, melting or the risk of sudden cracking. Alufoil also dissipates heat quickly – ideal for autoclaving and heat-sealing processes. It can help minimise sealing times and evens out the temperature gradient within both containers and flexible packaging, helping to protect product quality and energy economy. Its heat conductivity can help minimise processing, chilling and reheating times.
Vital to the efficient operation of a vehicle’s power plant and to the comfort of driver and passengers, alufoil-finned heat exchangers provide both cooling and heating as required. Thanks to its light weight alufoil has become the automatic choice.
Multi-mode Heating or Cooking
Food in alufoil dishes can be cooked, re-heated or heated by convection, microwave or fan oven or in ‘bain-marie’ systems. Alufoil packaging helps to save time and resources during preparation.
Hygiene
Once produced, alufoil is completely sterile due to the high temperature annealing process. It is safe for use in contact with foodstuffs and it does not harbour or promote the growth of bacteria.
Safety and Product Security
Alufoil is safe for use in contact with foodstuffs. Uncoated aluminium foil will not react with the vast majority of foods. In many applications alufoil is not in contact with the product as it is used in association with other materials within a laminate. In addition it is an ideal protection against product tampering and can support anti-counterfeiting features.
Decorative Potential
Alufoil’s bright or matt metallic finish plus its compatibility with all printing technologies provides designers with enormous scope to create packs with stunning graphic design, shelf presence and brand identity.
Reflectivity
Aluminium foil reflects up to 98% of light and infrared heat. The bright surface also has low heat emissivity. This helps to save energy in insulation. Its insulation role extends into fire protection. In ‘fire walls’ for vehicles and ships, for fire-resistant doors and building panels, aluminium foil dissipates heat and stops access to the oxygen required to support flames.
Electrical Conductivity
Alufoil shields against magnetic and radio frequency emissions. Used in fibre-optic cables, alufoil acts as a ‘tracer’ to enable testing of the integrity of cable links. In cable wrap, electrical conductivity enables the integrity of the cable circuit to be verified.
Physical characteristics:
Density: 2.7 g/cm³;
Alufoil specific weight: 6.35 µm foil weighs 17.2 g/m2;
Melting point: 660°C;
Electrical conductivity: 64.94% IACS (IACS: International Annealed Copper Standard);
Electrical resistivity: 26.5 nΩm;
Thermal conductivity: 235 W/m K;
Thickness: Foil is defined as measuring less than 0.2mm (<200 µm).
*Info from The European Aluminium Foil Association e.V. (EAFA)*
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