The plastic number is printed on the bottom of plastic products as a triangular recycling symbol, with numbers 1 to 7 corresponding to seven different types of resin materials. Many consumers and buyers often ask when they receive food packaging bags: what does the plastic number mean? Which number is the safest? This article, from the perspective of a flexible packaging factory, explains clearly the material properties, safety levels, and applicable scenarios behind the plastic numbers 1 to 7.
Plastic No. 1: Uses and Limitations of PET Polyester Material
Plastic code 1 represents PET (polyethylene terephthalate), commonly used in mineral water bottles, beverage bottles, and some food packaging films. PET has high transparency, good strength, and is lightweight, but it is not heat-resistant and can deform above 70°C. It is also not suitable for long-term reuse. In flexible packaging, PET film is often used as the outer layer of composite packaging, providing stiffness and a surface for printing. Note that after opening a PET bottled water, it should not be exposed to direct sunlight, and it should not be used to hold hot liquids.
Plastic No. 2: Characteristics of HDPE High-Density Polyethylene
Polyethylene No. 2 represents HDPE (high-density polyethylene), which is relatively rigid, resistant to acids and alkalis, and can withstand low temperatures. It is commonly used for milk containers, shampoo bottles, and some food containers. HDPE has good safety and high chemical stability, but it has relatively low transparency and a waxy feel. In food packaging, HDPE is more commonly used for containers rather than films.
Why is PVC (Plastic No. 3) used less in food packaging?
Plastic number 3 represents PVC (polyvinyl chloride), which was once the primary material used for cling film. PVC requires the addition of plasticizers during production to make it flexible, which is the source of public concern regarding PVC. Food-grade PVC is safe when used within regulatory guidelines, but overall, the use of PVC in food packaging is declining, with many factories switching to safer alternatives such as PE. When purchasing cling film, it is recommended to prioritize PE materials.
Plastic No. 4: LDPE Low Density Polyethylene Applications
Plastic number 4 represents LDPE (Low Density Polyethylene), which is the main material for the plastic bags, food wrap, and bread bags that we commonly use. LDPE is flexible, transparent, resistant to low temperatures, and has good heat sealing properties. It is one of the most widely used materials in the flexible packaging industry. Food-grade LDPE can be in direct contact with food and is commonly used for packaging fresh produce, baked goods, and daily necessities.
Plastic No. 5: Polypropylene (PP) Why Is It the Top Choice for Food Packaging?
Plastic number 5 represents PP (polypropylene), which has excellent heat resistance and can withstand temperatures around 120°C. It is the only common plastic suitable for use in microwave ovens. PP is commonly used in food containers, food transport boxes, and the heat-sealing layers of high-temperature steam bags. In flexible packaging, CPP film is combined with materials such as PA and PET to produce steam bags that can withstand sterilization at 121°C. PP is safe, chemically stable, and is a preferred choice for food contact materials.
Plastic No. 6: Usage Restrictions of Polystyrene (PS)
Plastic number 6 represents PS (polystyrene), commonly found in disposable food containers, cup lids, and foam trays. PS is transparent but brittle, with poor heat resistance. It may release styrene monomers at high temperatures, so it is not recommended for microwave heating. Expanded PS (foam food containers) has been restricted in some applications. When choosing disposable tableware, it is safer to opt for PP material.
Plastic #7: Other Materials and Multi-Layer Composite Structures
Plastic number 7 represents resins other than numbers 1-6, including PC, PA, EVOH, and various multi-layer composite materials. PC is being used less in food containers due to concerns over bisphenol A. PA (nylon) is puncture-resistant and heat-resistant, commonly used in retort packaging. EVOH has excellent barrier properties and serves as a core barrier layer in high-end food packaging. Many flexible packaging bags are multi-layer composite structures and fall under category 7.
How to Choose Plastic Numbers for Food Packaging
Choose packaging based on the plastic code, with the key being to match the usage scenario: select LDPE or PP for short-term storage at room temperature; choose PP or PA composite structure for high-temperature sterilization; opt for composite films containing aluminum foil or EVOH for high barrier freshness preservation. For more details on recycling labels, please refer to our previously published information.Complete Guide to Plastic Recycling Symbols。
Summary and Recommendations
Plastic codes 1-7 are not simply about 0, can we use 1, but rather about 2, how to use 3? The issue is: each material has its own advantages and limitations. As a flexible packaging factory, we recommend that purchasers evaluate material safety, usage scenarios, and compliance testing together. Huashu Packaging specializes in customized food-grade flexible packaging, offering one-stop services from material selection to finished product testing. Welcome to inquire.Contact UsGet material recommendations.
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