The triangular symbol with the number two inside is part of the Resin Identification Code (RIC) system, a standardized method for classifying plastic materials. The number inside the chasing arrows specifically identifies the primary polymer used to make the product, which helps facilities sort plastic for recycling. The number 2 corresponds to High-Density Polyethylene, commonly abbreviated as HDPE. HDPE is one of the most widely produced and utilized plastics globally. Understanding this code provides insight into the material’s properties, common uses, and its journey through the recycling stream.
Defining HDPE 2
High-Density Polyethylene is a thermoplastic polymer synthesized through the polymerization of ethylene monomers. The production process yields a linear molecular structure with very few side branches, which allows the polymer chains to pack tightly together. This close packing is what gives the material its “high density,” typically ranging between 0.941 and 0.965 grams per cubic centimeter.
This structural characteristic results in a material with a high strength-to-density ratio, making it robust yet relatively lightweight. HDPE is also naturally opaque or milky white due to its high crystallinity, a feature that blocks light. The material exhibits substantial resistance to a wide array of chemicals, including many acids, bases, and common solvents.
The minimal branching in the molecular chain contributes to its rigidity and toughness compared to other polyethylene types. HDPE maintains its physical properties across a broad temperature range, which is why it is used in many demanding applications. Its chemical inertness and stability are major factors in its widespread use.
Common Household Applications
The combination of chemical resistance, durability, and low moisture absorption makes HDPE 2 suitable for a vast range of household products. It is the material of choice for containers that hold liquids requiring a strong moisture barrier, such as the opaque plastic milk jug. HDPE’s properties help maintain the product’s integrity and quality.
HDPE’s resistance to solvents and corrosive substances makes it ideal for packaging cleaning products like laundry detergent and bleach. This resistance ensures that these household compounds are safely contained without cracking. Personal care products, such as shampoo and conditioner bottles, also frequently utilize HDPE.
Beyond bottles and containers, HDPE is used in items including food storage containers and certain types of plastic bags. Its toughness and weather resistance extend its use to outdoor goods, such as plastic lumber, patio furniture, and children’s toys. The material’s versatility makes it a fixture in consumer goods and industrial applications like piping systems.
Safety and Reusability
HDPE 2 is considered one of the safest plastics for contact with food and beverages, a designation supported by the U.S. Food and Drug Administration (FDA). This safety profile stems from its non-leaching and chemically inert nature when manufactured as virgin resin. The tight molecular structure prevents substances from migrating from the plastic into the container’s contents under normal conditions of use.
HDPE containers are safe to wash and use again for their original purpose, such as refilling a water bottle. However, avoid exposing the plastic to high heat, such as microwaving, as temperatures above 176°F (80°C) can cause the material to degrade or warp. Degradation compromises the material’s stability.
A significant precaution involves repurposing containers that initially held non-food chemicals, like cleaning solutions or motor oil. Even after thorough rinsing, there is a risk that chemical residues could remain and contaminate any food or drink stored later. For long-term food storage, use containers specifically designated as food-grade and free from any previous chemical exposure.
The Recycling Process
HDPE 2 is one of the most widely accepted and successfully recycled plastics globally, due to its stable composition and clear identification code. The material’s low melting point, typically between 248°F and 284°F (120°C and 140°C), makes it energy-efficient to process. Recycling begins with collection and sorting, where the number 2 code allows facilities to separate it from other plastic types.
A common separation method involves using a float-sink tank, as HDPE’s density is less than that of water, causing it to float while other plastics sink. After sorting, the plastic is thoroughly cleaned to remove residues, such as food debris. Consumers should rinse containers before disposal, as contaminants like residual product or non-HDPE labels can compromise the quality of the final recycled product.
The clean plastic is then shredded into small flakes, melted down, and extruded into uniform pellets, known as post-consumer recycled HDPE (rHDPE). These pellets serve as the raw material for manufacturing new products. Recycled HDPE is commonly transformed into durable goods like plastic lumber for decking and fencing, new non-food bottles, and municipal trash and recycling bins.