3. Structure

• Homopolymer: standard PS

It is an amorphous polymer with an atactic structure. The average molecular weight of the various commercial products is between 150,000 and 400,000, corresponding to between 1,500 and 4,000 styrene units per macromolecule. Standard PS is transparent, glossy, rigid and brittle.

• PS choc

It's also an amorphous polymer made up of two distinct phases: one continuous (matrix) polystyrene, and the other discontinuous polybutadiene nodules dispersed in the matrix, generally ranging in size from 1 to 5 µm (figure 2 a). Impact PS is opaque, as the two phases do not have the same refractive index. Impact resistance is also a consequence of this...