Plastic Sheet Catagories

The word "plastic" comes from the Greek word "plastikos," which means moldable. This is a fitting name for a material that can be formed into a countless variety of shapes. Plastics are also commonly referred to as "polymers," another Greek word with roots, in this case 'poly' and 'meros,' which translate to many "many parts."

What do "many parts" have to do with plastic? It's simple, really, once you understand the chemistry behind this amazing substance. Plastics, or polymers, are synthetic (chemically fabricated) materials derived mostly from fossil fuels, such as oil, coal or natural gas. Think of polymers as chains of many molecules. Each link of the chain is made of elements such as carbon, hydrogen, oxygen and/or silicon.

To make the chain, individual links are joined together through a process called polymerization. The polymerization process is similar in theory to the linking together of many strips of construction paper to make paper garlands. The type of atoms in the chain and the way they are linked together is what gives the plastic that is created different characteristics, such as strength, melt temperature, or resistance to hear of cold.
This means that there are hundreds of differnt varieties of plastics, each with very different properties and suitable for diverse uses. Each of these different types of plastics fit into one or two main plastics catagories: thermosets and thermoplastics.

A thermoset is a polymer that solidifies or "sets" irrreversibly when heated. Much like an egg, which, once it is heated (cooked), can't be softened again and returned to its original form. Thermosets are valued for their durability and strength and are used primarily in automobiles and construction. Other applications for thermosets include adhesives, links and coatings for wires or coat hangers. Some common examples of thermoset plastics and their products are:

Polyurethanes

Mattresses
Cushions
Insulation
Ski Boots
Toys

Thermoplastics can be heated, melted and reshaped countless times. After being heated and softened they are shaped by putting the plastic under pressure through a variety of processes so that it flows into a mold or through a die. The plastic then cools and sets into its shape. Some of the most common types of plastics are thermoplastics:

Polyethelelene Teraphathalate (PET)
Soft dink bottles
Salad dressing containers
Peanut butter jars

High Density Polyethelene (HDPE)
Mik Bottles
Crinkly plastic shopping bags
Freezer bags
Shampoo bottles

Polycarbontate (PC)
Sunglass lenses
CDs
Cell phones and pagers
Football and bicycle helmets

Polyvinyl Chloride (PVC)
Vinyl siding
Plumbing pipes
Watch straps
Garden hose