The material classification of food packaging bags is diverse to adapt to different types of food protection, preservation and display needs. Here are some of the main types of food packaging materials:
1. Polyethylene (PE)
Low density polyethylene (LDPE) : soft, transparent, often used to make frozen food packaging, bread bags, etc.
High-density polyethylene (HDPE) : hard texture, usually used to make supermarket shopping bags, dairy packaging.
2. Polypropylene (PP)
Amorphous polypropylene (APP) : good transparency, heat resistance, often used in hot and cold food packaging.
Oriented polypropylene (OPP) : Stretched polypropylene, high strength, often used in dry food packaging.
Cast polypropylene (CPP) : good flexibility, strong heat resistance, suitable for heat sealing packaging.
3. Polyester (PET)
Temperature resistance, high strength, good transparency, usually used in bottled beverages, ready meals and baked goods packaging.
4. Polyvinyl chloride (PVC)
High transparency, good flexibility, but due to health and environmental issues, its use is increasingly limited.
5. Polystyrene (PS)
Good transparency, but brittle, often used in lunch boxes, yogurt boxes and other packaging.
6. Biodegradable plastics
Polylactic acid (PLA) : Derived from plant-based materials, degradable.
Starch-based plastics: Contain biodegradable starch.
7. Aluminum foil material
Excellent barrier property, suitable for food with high shelf life requirements.
8. Metallized film
Usually a metallized form of PET or other plastic film, with both plastic and metal properties, used for snack packaging such as potato chips.
9. Composite materials
Films of different materials are combined through adhesives or extrusion composite processes to achieve better barrier properties, mechanical properties and processing properties.
10. Paper materials
Kraft paper: high strength, can be used for dry food packaging.
Coated paper: The surface has a plastic coating to provide a certain barrier.
11. Glass
Mainly used for bottled food, such as sauces, drinks, etc., the advantages are good transparency, strong sealing, non-toxic.
12. Metal cans
Usually made of tin or aluminum, it is used to preserve food for a long time, such as canned meat, vegetables, etc.
Composite structures are widely used in food packaging, the most common including double-layer composite and three-layer composite.
Double-layer composite involves two different layers of materials, each of which provides specific protective properties and functions. The following are some common double-layer composite structure methods in food packaging:
PE/PET
Polyethylene (PE) : As an inner layer, mainly provides good heat sealing, flexibility and low cost material.
Polyethylene terephthalate (PET) : As an outer layer, provides rigidity and strength, as well as good gas and moisture barrier properties.
PE/OPP
Polyethylene (PE) : Commonly used as a sealing layer.
Oriented polypropylene (OPP) : Commonly used as an outer layer, it provides high strength and good transparency, as well as some degree of moisture barrier capability.
PE/CPP
Polyethylene (PE) : Used as an inner layer to provide heat sealing and flexibility.
Cast polypropylene (CPP) : Used as an outer layer, it has high heat and tear resistance and is suitable for packaging that requires heat sealing.
PET/AL
Polyethylene terephthalate (PET) : provides structural strength and good chemical resistance.
Aluminum (AL) : provides excellent gas, moisture and light barrier, greatly extending the shelf life of the product.
PET/PE
Polyethylene terephthalate (PET) : As an outer layer, provides strength and stability.
Polyethylene (PE) : As the inner layer, ensuring good heat sealing properties.
PA/PE
Polyamide (PA, nylon) : As an outer layer, provides excellent mechanical strength and puncture resistance, as well as good oxygen and oil barrier properties.
Polyethylene (PE) : As the inner layer, provides heat sealing and flexibility.
PET/MPET
Polyethylene terephthalate (PET) : provides high strength and good chemical stability.
Metallized PET (MPET) : provides enhanced gas and light barrier properties, as well as a unique metallic luster.
Three-layer composite structures are typically composed of two or more different materials, with the aim of using the properties of each material to achieve higher levels of protection, barrier and mechanical properties. In food packaging, three-layer composite packaging can provide excellent barrier properties, mechanical strength, heat sealing properties and processing properties. Here are some common three-layer composite ways in food packaging:
PET/AL/PE
AL (Aluminum foil) : Intermediate layer that provides excellent gas and moisture barrier properties, as well as light barrier properties.
PE (polyethylene) : Inner layer for heat sealing, providing flexibility and tightness.
PET/MPET/PE
PET (polyethylene terephthalate) : As the outermost layer, it provides mechanical strength, a good printing surface and chemical stability.
MPET (metallized PET) : The intermediate layer, which is thinner than the pure aluminum layer, provides good barrier and reflection, but is cheaper than aluminum foil.
PE: Inner layer for heat sealing, providing flexibility and tightness.
OPP/AL/PE
OPP (Oriented polypropylene) : Outer layer that provides rigidity and clarity.
AL (Aluminum foil) : Intermediate layer that provides excellent gas and moisture barrier properties, as well as light barrier properties.
PE (polyethylene) : Inner layer for heat sealing, providing flexibility and tightness.
PA/AL/PE
PA (Nylon) : The outer layer, which adds strength and puncture resistance to the package, while also providing a certain gas barrier.
AL (Aluminum foil) : Intermediate layer that provides excellent gas and moisture barrier properties, as well as light barrier properties.
PE (polyethylene) : Inner layer for heat sealing, providing flexibility and tightness.
PET/PA/PE
PET (polyethylene terephthalate) : As the outermost layer, it provides mechanical strength, a good printing surface and chemical stability.
PA: Intermediate layer that provides additional gas and odor barriers.
PE (polyethylene) : Inner layer for heat sealing, providing flexibility and tightness.
PET/EVOH/PE
PET (polyethylene terephthalate) : As the outermost layer, it provides mechanical strength, a good printing surface and chemical stability.
EVOH (ethylene-alcohol copolymer) : An intermediate layer that provides very good oxygen and odor barrier properties.
PE (polyethylene) : Inner layer for heat sealing, providing flexibility and tightness.
These structures are common because they combine the advantages of multiple materials to meet the stringent requirements of food packaging. For example, the aluminum foil layer provides unmatched barrier properties, while the PET and PA layers increase strength and durability, and the PE layer ensures the sealing and heat sealing properties of the package. With a carefully designed three-layer structure, packaging can maintain food safety while also withstanding stress and impact during transportation, and can present a look that appeals to customers on the shelf.
