The following is an overview of the types and characteristics of plastics most commonly used for food packaging.
1.) Polyethylene terephthalate (PET) – recycling code “01”
PET belongs to the polyester family. It is best known as the material for disposable and recyclable bottles for carbonated drinks. In addition, thin PET films are often used as external packaging for fresh fruit.
PET is resistant to oils, fats, alcohols and diluted acids. It can also be coated with other plastics or aluminum, steamed or used as composite materials.
PET can be crystalline or transparent. In its transparent form, it is used for packaging food products such as ice cream. However, it is not very mechanically resistant. The operating temperature is between -40°C and +60°C.
Semi-crystalline PET is less transparent but more stable. It is harder, more flexible and more resistant to oxygen and carbon dioxide, and its operating temperature is between -20°C and +120°C.
Fully crystalline PET is opaque and is often used for microwave containers.
Pure PET is fully recyclable, which is an ecological advantage over other plastics.
2.) Polyethylene (PE) – recycling codes “02” and “04”
Polyethylene is the most commonly used plastic due to its malleability and relatively low price. One of its advantages is that PE is very resistant to acids, alkalis, oils and fats, which makes it suitable for use as a container for a wide range of products.
Different production methods can be used to produce high-density polyethylene (HD-PE = high-density polyethylene, recycling code “02”) or low-density polyethylene (LD-PE = low-density polyethylene, recycling code “04”).
LD-PE is transparent and much more flexible than HD-PE. LD-PE is widely used in the food industry, mostly in combination with other packaging film materials, such as cling film. In addition, LD-PE is often used, for example, as a sealing layer for the inner lining of milk cartons. HD-PE, on the other hand, is milky white and much stronger than LD-PE. It is mainly used for packaging solid food and for the production of carrier bags.
Depending on the type, polyethylene retains its properties in a temperature range of -60°C to +85°C, making it excellent for the production of freezer bags and containers. On the other hand, it is less used for packaging food that can be heated in a microwave or as cooking bags.
Since polyethylene has a high gas permeability, it can only be used for packaging with a protective gas in a laminated form (in combination with a composite film).
3.) Polyvinyl chloride (PVC) – recycling code “03”
Polyvinyl chloride (PVC) is a plastic that has a very wide range of applications, but above all in the non-food sector. In its original form, it is hard and brittle, but can be made flexible and malleable by adding plasticizers. It is also very resistant to acids, alkalis, alcohol and oil.
Rigid PVC is used in the food industry, among other things, to make cooking oil and vinegar bottles or to package chocolates and sweets. No plasticizing chemicals are added to rigid PVC.
Soft PVC is used, for example, to produce shrink film. This shrinks when heated, thus protecting and stabilizing the contents during transport and storage. It is often used to wrap pallets or PET beverage bottles. PVC films can still be found commercially as packaging for fresh food and as the inner ring of the screw cap of jars.
However, the use of critical hormone-disrupting phthalates as plasticizers is prohibited in the packaging of fatty foods.
The added plasticizers used in food packaging pose a risk because they are not chemically incorporated stably into the plastic structure, so they can evaporate or leach into the food, which has reduced the importance of PVC in the food industry. Nowadays, for example, the fresh-keeping film used in households consists entirely of polyethylene, which does not contain plasticizers, and blue, i.e. PVC-free lids are also available for jars.
4.) Polypropylene (PP) – “05” recycling code
Polypropylene is chemically similar to polyethylene, but stronger and more heat-resistant. Due to its good fat and moisture barrier properties, it is one of the most commonly used plastics in food packaging.
Depending on the manufacturing process, it is used for containers or films, such as in dairy cups, bottle caps, baking films and trays. The application temperature is between 0°C and 100°C. Due to the maximum continuous use temperature, PP can be used to make heat-resistant containers suitable for microwave ovens. However, at temperatures below 0°C, the plastic usually becomes brittle. PP is relatively easy to recycle.
5.) Polystyrene (PS) – recycling code “06”
Polystyrene was previously mainly used for disposable drinking cups, coffee cup lids or disposable cutlery, but is now used for packaging yoghurt pots, honey, coffee cream, pastries and sweets.
As expanded polystyrene (expanded polystyrene foam = ESP) – also known under the brand name Styropor – polystyrene is used for packaging fish, meat, fruit, vegetables and take-away food in restaurants and cafeterias.
Polystyrene is very cheap compared to other plastics. It also has a high water vapor and gas permeability, and is odorless and tasteless, which is particularly beneficial for storing fruit, vegetables, meat and fish. The continuous use temperature is between -10°C and +70°C.
However, polystyrene can release styrene, which is also known as a carcinogen and hormone disruptor.
6.) Other plastics: polycarbonate (PC) and polyamide (PA)
Polycarbonate is formed as a reaction product of carbonic acid dichloride (phosgene), diphenyl carbonate and bisphenol A. It is very strong and hard to break, polycarbonate was used in sterilizable baby bottles until 2011. It can still be found today in water dispensers, drinking bottles, microwave oven containers and kitchen appliances. Due to the hormone-like effect of bisphenol A, its use in the food industry is now declining.
Polyamides are polymers based on peptide bonds. A well-known representative of the polyamide group is nylon. Most polyamides are very strong and tough and can be easily processed industrially. They are used for films, sausage casings and as a sealing material in combination with other plastics, for example as the middle layer of PET beer bottles. Together with polyethylene, multilayer films are produced for the vacuum packaging of oxygen-sensitive foods such as ham, cheese or sausages.
Please feel free to contact us with any questions you may have about food packaging!