Final answer:
Polypropylene forms a covalent bond, not an ionic bond.
Step-by-step explanation:
The correct answer is 2) Polypropylene - Ionic bond. Polypropylene is a polymer that is formed through covalent bonding, not ionic bonding. Covalent bonds are formed when atoms share electrons. In the case of polypropylene, the carbon atoms in the polymer share electrons with each other, forming a strong covalent bond.
Ionic bonding, on the other hand, occurs when atoms transfer electrons to form ions that interact with each other due to their opposite charges. Hydrogen bonding and van der Waals forces are types of intermolecular forces, not the primary types of bonds found within polymers.