Are you holding a phone? Are you in a car or riding a bus? Chances are, you are surrounded by plastic. Plastic is created into a variety of different products that have shaped the world we live in today
Polymers
A plastic is anything naturally occurring or synthetic that is composed of polymers. Naturally occurring polymers include cellulose (derived from plants), tortoiseshell, and latex (from tree sap). Synthetic polymers are usually made from crude oil to create plastic bottles, plastic food wrap, and Zip-Lock bags. The word polymer comes from the two Greek words: “poly” (many) and “mer” (unit). Chemically speaking, plastic is simply a bunch of carbon chains strung together. Within a piece of plastic, there are thousands or possibly millions of carbon units linked together.
Plastics are not Created Equal
Although all plastics stem from the same key ingredients, the way that the plastic is made affects its chemical structure and properties. There are two common ways to create plastic: addition polymerization and condensation polymerization.
Addition polymerization adds one more chemical unit at a time to make longer and longer carbon chains. Plastics made using this technique are often called thermoplastics that are soft when heated but rigid and firm when cooled. These types of plastics are much easier to recycle or reprocess. The other method, condensation polymerization, removes a molecule connected to the carbon chain before adding the following chain of polymers. The plastics created like this can be thermoplastic or thermosetting, which means that once the plastic has cooled, it will retain the shape it was formed.
Additionally, varying levels of pressure can be used in the plastic forming process to produce unique properties. For example, plastic can be developed to be very strong if the process incorporates lots of pressure and heat. Other properties include flexibility, durability, transparency, low conductivity. The range of possibilities allows plastic to be useful in a variety of industrial applications. Someone might call this “plasticity.”
Types of Plastic
Based on the properties of the plastic, the most common plastics will fall into seven groups. Whenever you see a plastic item, check to see if there is a recycling symbol with a number in the middle. That number identifies the type of plastic. You will find the descriptions of each plastic below:
1 – Polyethylene Terephthalate (PET): lightweight, transparent, and tough
Examples: Single-Use Plastic bottles, condiment bottles
DOWNCYCLABLE
2 – High-Density Polyethylene (HDPE): strong, colorful, food-safe, waterproof
Examples: Laundry Detergent Bottles, Bottle Caps
RECYCLABLE
3 – Polyvinyl Chloride (PVC): hard, rigid, chemically resistant, weatherproof
Examples: Outdoor Siding, Plumbing Pipes
NOT RECYCLABLE
4 – Low-Density Polyethylene (LDPE): flexible, colorful, soft
Examples: Cling wrap, storage tubs, garbage bags
RECYCLABLE
5 – Polypropylene (PP): heat resistant, strong, flexible
Examples: Food containers, straws, DVD cases
RECYCLABLE (But Difficult)
6 – Polystyrene (PS): lightweight, rigid,
Example: Styrofoam Cups, egg cartons, insulation
NOT RECYCLABLE
7 – Other: (Everything else)
Examples: Cutlery, electronics
NOT RECYCLABLE
References
https://www.sciencedirect.com/topics/medicine-and-dentistry/polymer