13 Chemistry of Polymers

Covalent Bonds

A chemical attraction between two atoms that are sharing electrons.

Hydrocarbons

A chemical made only of carbon and hydrogen. Many polymers, including polyethlene, are hydrocarbons.

Plastic

A common term that is frequently used interchangeably with the word polymer. Some people attempt to restrict it only to thermoplastic polymers.

Polymer

A long, chain-like molecule made of repeating units.

Specific Gravity

A measurement of how many times more dense a material is than water. In the metric system, the value for the specific gravity is the same as density.

Condensation Polymerization

A method of forming molecules between two different types of mers. In the process, a smaller molecule (usually water) is formed for each bond that takes place. This is also called a step reaction.

Trimer

A molecule composed of three monomers.

Dimer

A molecule composed of two monomers.

Crystallinity

A property of polymers where there exists areas of regularity called crystallites. This results in a stronger and more opaque material.

Addition Polymerization

A rapid chain reaction where molecular units are added to one another - usually by breaking double bonds.

Monomer

A simple molecule that can be used as the repeating unit to form a polymer.

Initiator

A substance that speeds up or begins the polymerization process.

Amorphous

A substance whose molecules have no definite regularity or order.

Vinyl

A synthetic resin whose repeating unit has a side group replacing one of the hydrogen atoms on the ethylene repeating unit. If that side group is chlorine, then polyvinyl chloride (PVC) is produced.

Site

A term used in chemistry to represent an are where a chemical reaction can occur.

Polyethylene

A tough thermoplastic made solely of ethylene. Major uses include making plastic bags, other plastic films, and milk bottles.

Elastomer

A type of polymer that is usually able to double its length easily in the direction that it is stretched and then return to its original shape when the stress is released. Elastomers usually possess a small amount of cross-linking.

Thermoplastic

A type of polymer that softens when heated and resolidifies when cooled. It is the primary type of polymer used for recycling.

Thermoset

A type of polymer that, when heated, sets into a solid form permanently and cannot be softened by heat.

Polycarbonate

An extremely tough and highly transparent type of polymer that is classified as a thermoplastic.

Crazing

Fine cracks which usually occur under the surface of a polymer. They may be produced either chemically or by mechanical forces such as bending.

Alkenes

Hydrocarbons that contain double covalent bonds.

Alkanes

Hydrocarbons that contain only single covalent bonds.

Synthetic

Not occurring in nature - human-made.

Plasticity

The ability to change shapes when stress is applied and retain the new shape when the stress is removed.

Cross-Linking

The joining of adjacent polymer molecules by forming chemical bonds.

Mer

The part or unit that repeats itself in a long chain molecule.

Polymerization

The process of putting smaller repeating units called mers together to form extremely long molecules called polymers.

Elasticity

The property that measures a material's ability to return to its original shape when deformed.

Set

To form a solid by curing

Synthesize

To make or create

Translucent

Transmission of light but not with a distinct image.

Transparent

Transmission of light that gives a distinct image.

Van Der Waals Forces

Weak forces of attraction between molecules due to temporary electrical charges.

Opaque

Will not transmit light.