The Seven Deadly (Re)sins

Have you ever wondered what various numbers in the triangular symbols on plastic products mean?

In 1988, the Resin Identification Code system was implemented, highlighting seven main types of plastic resins and creating a classification construct that remains in use to this day. Under this system, each of the major types of plastics have a numerical code from 1 to 7 associated with them, which can tell us about the material properties of a given plastic product.

For those concerned with plastic flooding into our world, it’s vital to understand the nuanced environmental implications of these seven different types of plastics, their uses, and how easily each of them are recycled. The following list will arm you with that understanding:

1. Polyethylene Terephthalate (PET or PETE)

• Uses: Commonly used for water and soda bottles, food containers, and synthetic fibers (like polyester in clothing)

• Properties: Durable, moisture resistant, versatile

• Recyclability: Easily recyclable, typically coded as #1 in recycling symbols. Recycled PET can be used to make new bottles, containers, carpeting, and fabric for clothing. However, recycled PET often goes through a downcycling process, meaning it is converted into lower-quality products.

2. High-Density Polyethylene (HDPE)

• Uses: Often used for milk jugs, detergent bottles, agricultural pipe, grocery bags, and playground equipment.

• Properties: Strong, thick, durable, and temperature tolerant

• Recyclability: Highly recyclable, coded as #2. HDPE can be recycled into products like pipes, plastic lumber, picnic tables, pens, bottles, and bins. It maintains its quality well through recycling.

3. Polyvinyl Chloride (PVC)

• Uses: Found in pipes, flooring, wire and cable insulation, medical devices, kayaks

• Properties: Durable, inexpensive, white, corrosion / chemical resistant, inflammable, lightweight

• Recyclability: Most PVC can be recycled up to 6 or 7 times, via both mechanical and chemical means. That said, PVC can release harmful chemicals if not managed properly, making it challenging to recycle safely

4. Low-Density Polyethylene (LDPE)

• Uses: Used for plastic bags, cling wrap, and squeezable bottles

• Properties: Thin and ultra-flexible; innexpensive and easy to produce

• Recyclability: Less commonly recycled, often coded as #4. LDPE recycling programs are limited, though some facilities turn LDPE into bin liners, piping, sheeting, and films

5. Polypropylene (PP)

• Uses: Found in food containers (i.e., tupperware), bottle caps, automotive parts, and textiles

• Properties: Hard, sturdy, durable, temperature tolerant

• Recyclability: Recycling is possible but more difficult than other types of plastics and is not widely accepted in all programs. When recycled, it can be used to make products like dishware, storage racks and bins, containers, gardening materials, etc.

6. Polystyrene (PS)

• Uses: Known for use in disposable coffee cups, plastic food containers, and packing foam (often called Styrofoam)

• Properties: Inexpensive, easy to create, lightweight, widespread and versatile, inflammable, susceptible to leaching chemicals into contents of containers

• Recyclability: Coded as #6, PS is challenging to recycle due to its low density and high volume. Some facilities recycle PS into items like picture frames and various packing materials.

7. Other (Often Polycarbonate or Mixed Plastics)

• Uses: Includes polycarbonate and other less common plastics, often used in products like eyewear lenses, skylights, face shields, and car parts.

• Properties: (Polycarbonate) tough, transparent, durable, and stiff

• Recyclability: Coded as #7, recycling is often challenging and depends on the exact plastic type. Polycarbonate, for instance, is sometimes recycled for use in automotive parts, electronics, and construction materials

The continued production of each of these plastic types holds implications for our world. It’s important to note that while recycling is possible for all types of plastic, in practice it is really only #1 and #2 that are able to be reliably recycled at scale. It is up to us, the consumers, to limit consumption of plastics that are difficult to recycle where possible and support efforts to transition away from these polymers toward more sustainable alternatives.

As strongly as we must each guard against the seven deadly sins from creeping into our lives, we as a people would do well to similarly prevent these seven deadly resins from sullying the natural world.

Sources: American National Standards Institute, Plastics for Change, Curbell Plastics, Omnexus, Oceana, Accel Polymers, Clean River, MLive, EDL Packaging, Palmetto Industries, Intco Recycling, Everyday Recycler