Polystyrene has a higher Tg than polyethylene.

Amorphous polymers do not exhibit a melting temperature.

The Tg of poly(methyl methacrylate) (PMMA), which is typically used to fabricate shatter-proof screens, is lower than room temperature.

Molecular weight of the polymer does not affect its Tg.

the crosslinked material has a constant modulus above the glass transition temperature

there is crystallinity in the crosslinked sample

the crosslinks degrade at low temperatures

there is crystallinity in the amorphous thermoplastic sample

rotation around the carbon-carbon bond

bending of the carbon-carbon-hydrogen bond angle

stretching of the carbon-carbon bond

strong secondary bonds between chains

polymer chains absorb all colours and white light is reflected

polymer chains are naturally white in colour

the crystallites scatter light

the refractive index of crystallites and the amorphous region is the same

poly(vinyl alcohol) is less polar

poly(vinyl alcohol) is more polar

the hydroxyl group in poly(vinyl alcohol) is less bulky than a hydrogen group

the hydroxyl group has a strong dipole and thus causes stronger bonding between chains

a series of crosslinks leading to a high melting point

less polar monomers leading to a lower melting point

more branches in the chains, leading to a lower melting point

much shorter molecules with weaker covalent bonds

polyethylene

natural rubber

polypropylene

polyethylene terephthalate

Polypropylene

Nylon

High density polyethylene

Low density polyethylene

They are liquids with low volatility.

They decrease the glass transition temperature of the material.

They may leach out of the plastic.

They increase the glass transition temperature of the material.

an increase in the rigidity of the material

a decrease in the glass transition temperature of the material

an increase in the material's melt viscosity

an increase in the glass transition temperature of the material