Recycling Polymer Plastics Guide


What should be done with those old items that aren’t needed anymore? Several decades ago, the most practical option was to throw them out. Throwing out old plastic just adds to growing landfills. While the issue of waste is one that must be approached cautiously, the stream of plastic can be addressed by everyone in their own way. Plastic accounts for about one-fifth of all waste, and therefore recycling it would result in up to 20% less waste overall. Unfortunately only 3.5% of plastics are recycled. This statistic is troubling.

Plastics vs. Polymers

Plastic has no one specific molecular structure. It is merely a general term for certain resins and polymers. As a result of this association, people often use the word “polymer” synonymously with plastic. However, polymers are not always plastic (though all plastics are polymers). Polymers generally exist as compound materials classified by their development and properties. There are two basic types. Thermoplastic polymers can be formed when they are heated. If they are heated again, then they can be reformed. The reason for this is that the molecules flow when they are melted. The other type of polymers is Thermoset polymers. When these polymers are heated, instead of changing structure they actually undergo a chemical change. Once they form the first time, they can never be reformed even when heated. Thermoplastic polymers are easy to recycle. Thermosets can be recycled, but not nearly as easily.

Polymer Coding System

The Society of the Plastics Industry has established a numerical coding system to identify which types of plastic are which. This system is necessary for recycling because certain types of plastics are only safe or useful for certain types of products. There are six main types. The number 1 denotes PETE, or Polyethylene Terephthalate. PETE is mostly found in beverage containers because it is waterproof. It can be spun into carpets, pillows or jackets. Number 2 is HDPE, or High-Density Polyethylene. It is most commonly found in plastic bags, oil and detergent bottles, and toys. It is one of the simplest polymers to recycle. It is broken down into flakes, decontaminated and then reused for pipes, flower pots or reused as (non-food) bottles. Number 3 is PVC, or Vinyl/Polyvinyl Chloride. It is found in food wrappers and vegetable oil bottles. Number 4 is LDPE, or Low-Density Polyethylene. It has similar properties to HDPE so it is no surprise that it can also be found in some plastic bags as well as shrink wrap. When it is recycled, it is grinded into a thin film and then reused for trash bags, agricultural film and plastic tubing. Number 5 is PP, or Polypropylene. It is found in re-sealable refrigerator wares, bottle tops and carpeting. The sixth and final type of polymer plastic is PS, or Polystyrene is used for meat packaging and plastic silverware. The numbers are NOT assigned based on a polymer’s recyclability, but HDPE and PETE are most commonly recycled nonetheless. If an item is labeled with a 7, it is not recyclable. Plastics that are not identified by code numbers are generally not recycled either because they often do not fit neatly into a single category. However, some offer great recyclability.

Issues with Recycling Certain Plastics

Glass, paper and aluminum can be recycled time and time again. However, plastic can only be recycled once. That is why it is imperative that the plastic is used for an item with a longer lifespan. Soda bottles are not reshaped into soda bottles, but rather they are used as carpeting. It also takes longer to recycle polymer plastics because they need to be sorted by the six types. Even after they are sorted once, they are usually sorted again because some types so closely resemble other types. The constant resorting can be cumbersome. PVC has caused a particular problem in that it was, and is still being used for short-life products. When it is done in its stage of life, it does not burn well. In fact, it takes so much energy to incinerate PVC, and emits so much carbon dioxide into the atmosphere, that it is actually safer to hold on to it. Unfortunately, once PVC pipes, frames and furnishings are no longer of use, they pile up. Many countries including Denmark, the United States, Japan and nations in Latin America are experiencing serious PVC landfill problems. 


Reduce, Reuse, Recycle

Information on Plastic

Plastics & Polymers

Plastics that can be Recycled

Exploring Polymers