Polymers I $(15$ P$)$

Today, polypropylene $($PP$)$ is a widely used material for the manufacture of shaped parts.

a$)$ Knowing that PP belongs to the group of semi$-$crystalline thermoplastics, please decide, which of the following designations for PP are correct. Highlight your answer with a tick $[$Caution: Wrong ticks are counted $-1$; minimum total points $=0$

PP$...$

does not melt, but softens upon heating

has a slightly crosslinked structure

in the liquid state is not transparent

has its preferred service temperature at below $T_g$

with its crystalline domains is difficult to recycle

b$)$ For the production of PP$,$ monomer propylene $($propene$)$ is used:

Would you expect chain growth or step growth to be the predominant polymerization mechanism for PP $?$ Please explain. $(2$P$)$