7 Polymers Free Online FlashCards

What are polymers made of?

Polymers are materials made of very large molecules: long chains built from repeating smaller units called monomers.

How do branches affect polymer-chain packing?

Branches tend to hinder close packing of polymer chains.

What does semicrystalline mean for a polymer?

A semicrystalline polymer has both ordered, tightly packed regions and disordered regions.

What happens to amorphous regions around the glass-transition temperature?

Below its glass-transition temperature, amorphous portions tend to be hard and glassy; above it, they become more flexible or rubbery.

How do thermoplastics respond to heating and cooling?

Thermoplastics soften when heated and harden when cooled; their chains can move past one another when sufficiently heated.

Name three processes used to shape thermoplastics.

Thermoplastics can be shaped by injection molding, extrusion, and thermoforming.

Why can cured thermosets generally not be remelted and reshaped?

Thermosets form a cross-linked network as they cure. Once cured, they generally cannot be remelted and reshaped.

What are common uses of epoxy?

Epoxy is used in strong adhesives, protective coatings, and fiber-reinforced components.

What mechanical behavior defines an elastomer?

Elastomers can undergo large, mostly recoverable deformation.

How do elastomer chains respond to stretching and release?

Stretching aligns their flexible chains; when the force is removed, the chains tend to return toward a less ordered, coiled state.

How do limited connections help elastomers recover after stretching?

A small number of cross-links or equivalent physical connections helps prevent elastomer chains from sliding permanently past one another.

Can an elastomer be a thermoplastic or a thermoset?

Elastomer describes a rubber-like mechanical response, so an elastomer can be either a thermoset or a thermoplastic.