Thermoplastics
The polymers are uncross-linked and held together by intermolecular forces. When exposed to heat, the chains weaken and the plastic can be molded. Thermoplastics can repeatedly be molded into new shapes. When force is applied, the material changes until it breaks.
Polyethylene is made up of ethylene monomers and is a thermoplastic. In places, the molecules cross-link several times to form more stable structures known as crystalline thermoplastics.
Polystyrene is also sometimes known as Styrofoam. It features a benzene ring, consisting of carbon atoms connected in a ring shape. The material is foamed into white beads during production, making it a lightweight plastic. That’s why it’s very commonly used in packaging.
Thermosets
Molecules are arranged in three dimensions, close-meshed, and firmly bonded together with many cross-links. They cannot be melted and remolded by applying heat. Even when subjected to force, they only deform slightly.
Bakelite was the first entirely synthetic plastic. It is dark, hard, and still used today for insulation.
Elastomers
Wide-meshed cross-linked molecules that can be shaped or stretched, sometimes considerably, by applying force, but return to their original configuration when the force is removed. We’ve seen this ourselves in rubber bands and bicycle tires.
Isoprene can be found in many different objects, for example as synthetic rubber in car tires.
Related Topics
GlossaryMolecule Atoms Polymers Intermolecular forces Thermoplastics Polyethylene Polystyrene Styrofoam Benzene ring Carbon Bakelite Synthetic Isoprene Synthetic rubber