Which polymer is used in orthopedic devices and in controlled drug-release capsules?

The structure of the monomer unit of natural rubber is:

Identify the polymer obtained by heating $n$ moles of isobutylene with $n$ moles of isoprene at $100^{\circ} C$ in the presence of anhydrous $AlCl_{3}$.

Major product of the following reaction is

Which of the following polymers is used to obtain plastic dinnerware?

Identify the urea-formaldehyde resin from the following polymers: