How to distinguish some common types of plastics

Nowadays, plastic bags are in their “golden age,” appearing everywhere. However, few people know that some of them are made from plastics harmful to human health. In general, PP, PE, and PS are non-toxic plastics, commonly used to produce fixed food containers such as trays, boxes, and plates. PVC, on the other hand, is toxic and therefore not used to produce food storage bags or containers.

To identify whether a plastic is toxic or not, cut a small piece of the food bag with scissors, place it in the fire, and observe.

Physical properties of plastics

Flexibility: Easily molded, pressed, or shaped.
Lightweight: Low density, much lighter than metals or ceramics.
Water and vapor resistance: Good barrier properties to moisture.
Corrosion resistance: Withstand chemicals and acids, suitable for harsh environments.
Electrical and thermal insulation: Excellent insulators, preventing electricity and heat conduction.
Mechanical strength: Can achieve high strength depending on the resin type and additives.

Chemical properties

Flame resistance: Some plastics are flame-retardant or burn slowly.
Chemical resistance: Withstand many chemicals and acids, ideal for industrial applications.
Solubility: Certain plastics dissolve in specific solvents, aiding processing and recycling.

Environmental properties

Recyclability: Many plastics can be recycled, reducing waste and saving resources.
Biodegradability: Some bioplastics can decompose under microbial activity.
Environmental impact: Improper production and disposal of plastics can harm ecosystems.

👉 With these characteristics, you can better recognize the types of plastics used in everyday products and evaluate their safety and environmental impact.

How to distinguish and safely use common plastics

Plastics such as PE, HDPE, and PP belong to the same family and have very similar chemical structures. If their molecular weight is low, they are quite similar to paraffin wax. When burned with a lighter, if there is no acrid odor, the plastic is likely PE, HDPE, or PP.

PET, ABS: burn with black smoke and emit a strong acrid odor.
PVC: does not form a flame when burned.

⚠️ Toxicity if used improperly

All plastics used for liquid food packaging from reputable domestic or international brands are safe, since manufacturers must comply with legal standards for food-grade plastic packaging.

The real danger comes from reusing plastic containers that previously held toxic chemicals.
👉 For example, using paint buckets to pickle vegetables is highly unsafe. Harmful chemicals can leach into the acidic liquid, posing health risks.

When storing edible liquids such as cooking oil, fish sauce, vegetable oil, or medicinal alcohol, PET bottles (polyethylene terephthalate)—especially those originally made for drinking water—are the safest option.

🚫 Hazards of unsafe plastic use

Environmental pollution: Plastics take hundreds of years to decompose, contaminating soil, water, and air.
Health risks: Some plastics contain harmful chemicals (BPA, phthalates, lead, cadmium…) that may cause cancer, cardiovascular disease, hormonal disorders, and reproductive problems.
Food poisoning: Using plastic containers for hot or acidic foods may release toxic chemicals into food.

✅ Safe plastic use practices

Limit single-use plastics: Replace with fabric bags, glass bottles, or metal food containers.
Use the right plastic for the right purpose: Avoid storing hot or acidic food in unsuitable plastics.
Recycle responsibly: Sort and recycle plastics properly to reduce waste.
Raise community awareness: Promote responsible use of plastics to protect health and the environment.

👉 In daily life, the most common plastic is PE (polyethylene). Transparent or colored plastic bags often called “nylon bags” are actually made from PE, not nylon (nylon is polyamide, a completely different material).
👉 Bottles for milk, soft drinks, and other liquid foods are usually made from HDPE (high-density polyethylene) or specialized PVC for food use.