Differentiating Plastics

Plastic Types

Plastic containers typically contain an identification number surrounded by arrows -- the plastic packaging resin identification code. These numbers are:

• 1: Polyethylene Terephthalate (PET, PETE)
• 2: High-Density Polyethylene (HDPE)
• 3: Polyvinyl Chloride (PVC, vinyl)
• 4: Low-Density Polyethylene (LDPE)
• 5: Polypropylene (PP)
• 6: Polystyrene (PS)
• 7: Other

Polyethylene Terephthalate (PET, PETE)

Polyethylene terephthalate (PET) is clear, tough, and shatterproof. It provides a barrier to oxygen, water, and carbon dioxide. PET can be semi-rigid to rigid, depending on its thickness, and it is very lightweight. It is strong and impact-resistant. It is naturally colorless with a high transparency. Easily recyclable.

High-Density Polyethylene (HDPE)

High-density polyethylene (HDPE) is used to make many types of bottles. HDPE has good barrier properties; it's well suited for packaging products with a short shelf life and has good chemical resistance. It is also harder and more opaque and can withstand somewhat higher temperatures than LDPE and higher tensile strength than LDPE.

Low-Density Polyethylene

Low-density polyethylene (LDPE) is used for its toughness, flexibility, and relative transparency. It can withstand temperatures of 80 °C continuously and 95 °C for a short time. Made in translucent or opaque variations, it is quite flexible, and tough but breakable

Polyvinyl Chloride

Polyvinyl chloride (PVC or vinyl) can be manufactured to be either rigid or flexible. It is biologically and chemically resistant.

Polypropylene (PP)

Polypropylene (PP) is known for its high melting point and is break-resistant. Polypropylene is reasonably economical, and can be made translucent when uncolored but is not as readily made transparent. It is often opaque or colored using pigments. Food containers made from it will not melt in the dishwasher. This material is often chosen for its resistance to corrosion and chemical leaching, its resilience against most forms of physical damage, including impact and freezing, and its ability to be joined by heat fusion rather than gluing.

Polystyrene (PS)

Polystyrene provides greater rigidity and strength. Polystyrene is a colorless, hard plastic with limited flexibility. It can be cast into molds with fine detail. Polystyrene can be transparent or can be made to take on various colors. Polystyrene is easily recycled.

Oriented Polystyrene (OPS)

Oriented polystyrene (OPS) is produced by stretching extruded polystyrene film, improving visibility through the material by reducing haziness and increasing stiffness. This is often used in packaging where the manufacturer would like the consumer to see the enclosed product. Some benefits to OPS are that it is less expensive to produce than other clear plastics such as PP, PET and HIPS, and it is less hazy than HIPS or PP. The main disadvantage to OPS is that it's brittle. It will crack or tear easily.

Acrylonitrile Butadiene Styrene (ABS)

Acrylonitrile Butadiene Styrene is impact resistant and tough. ABS is light weight and can be injection molded and extruded.