${\mathrm{H}}_3\mathrm{C}-{\mathrm{CH}}_3\stackrel{\mathrm{Py}ro\mathrm{lysis}}{\to } \mathrm{A} \underset{\mathrm{RCOOOCOR}}{\overset{1000-200\mathrm{atm}}{\to }}\mathrm{B}.$

$\mathrm{A} \underset{\mathrm{catalyst}}{\overset{\mathrm{ziegler}-Natta}{\to }}\mathrm{C}.$ 

Here B and C are respectively 

${\mathrm{H}}_3\mathrm{C}-{\mathrm{CH}}_3\stackrel{\mathrm{Py}ro\mathrm{lysis}}{\to } C{H}_2 =C{H}_2 \underset{\mathrm{RCOOOCOR}}{\overset{1000-200\mathrm{atm}}{\to }}LDPE.$

$C{H}_2 =C{H}_2 \underset{\mathrm{catalyst}}{\overset{\mathrm{ziegler}-Natta}{\to }}HDPE.$

LDPE= low density polyethylene 

HDPE= High density polyethylene