6.02 Quiz: Polymers and Polymerization

Study Notes

Polymers are large molecules made up of many repeating units called monomers. They can be natural materials like cotton fibers, synthetic materials such as nylon, or even biodegradable materials like cornstarch. There are several different categories of polymers based on their chemical composition and structure:

Thermoplastics: These are plastics that become soft when heated and harden when cooled. Examples include PVC, PE, PP, PS, and ABS.
Elastomers: Also known as rubbers, these are elastic materials derived from petroleum products. Their tensile strength is low compared to thermosetting resins but far higher than those of plastics. Some common examples include rubber and silicone.
Fluoropolymer: This type of plastic material has high resistance to heat, oils, solvents, and chemicals. It's most commonly used in nonstick cookware.
Polyurethane foams: These have excellent insulating qualities and are used in furniture cushions and thermal insulation.
Acrylic plastics: These are lightweight, durable, and shatterproof; they also retain color well.
Nitrile rubber: Primarily used as an alternative to standard rubber because it has better resistance against oil-based fluids.
Natural Rubber: Derived from latex produced by trees, predominately in Southeast Asia. Its main uses include tires, balloons, medical gloves, and other various rubber products.

The manufacturing method for creating all polymers involves polymerization — a reaction where two or more monomer units bond together with covalent bonds to form chains or networks. Different processes can be employed depending on the desired end product:

Bulk polymerization occurs within a solid mass. An example is casting polyethylene powder into molds under pressure.
Solution polymerization utilizes liquid solutions instead of bulk reactions. Solvent may evaporate completely, leaving only the pure polymer behind.
Emulsion polymerization creates foam emulsions through agitation, which causes smaller particles to coalesce forming larger ones until finally they reach their final size.
Suspension polymerization forms droplets, suspending them within the reactor vessel, allowing heat transfer between the reactants and the polymerizing mixture.
Dispersion polymerization forms very small droplets dispersed throughout the continuous phase, eventually growing larger as more monomers enter the system.

Some important characteristics of polymers include flexibility, toughness, impact resistance, moisture absorption rates, surface finish, dimensional stability, and thermal expansion. However, one downside to polymers is their susceptibility to deformation due to contact stresses and bending as they stretch easily. Another issue arises during disposal because some polymers aren’t biodegradable making them difficult to recycle. To address this issue, there is currently ongoing work being done towards developing new technologies designed specifically for proper recycling methods.

Description

Test your knowledge on polymers, large molecules made up of repeating units called monomers. Learn about different categories like thermoplastics, elastomers, fluoropolymers, polyurethane foams, acrylic plastics, nitrile rubber, and natural rubber. Discover the manufacturing methods involving polymerization and important characteristics of polymers.