What are the differences in chemical bonding between PVC and polypropylene molecules?

The chemical bonding in PVC (polyvinyl chloride) and polypropylene molecules differs significantly due to their distinct molecular structures. PVC contains a chlorinated backbone, where each repeating unit has a chlorine atom attached to every other carbon in the carbon chain. This creates polar carbon-chlorine bonds, making PVC more rigid and less flexible. In contrast, polypropylene consists of a simple hydrocarbon chain with alternating carbon and hydrogen atoms, resulting in non-polar carbon-hydrogen bonds.

The presence of chlorine in PVC leads to stronger intermolecular forces (dipole-dipole interactions) compared to polypropylene's weaker van der Waals forces. This difference affects their physical properties: PVC is denser, more flame-resistant, and has higher chemical stability, while polypropylene is lighter, more flexible, and resistant to fatigue. Additionally, the carbon-chlorine bonds in PVC make it less thermally stable than polypropylene, which degrades at higher temperatures.

These bonding variations explain why PVC is commonly used for pipes, cables, and construction materials, while polypropylene is preferred for packaging, textiles, and reusable containers. Understanding these molecular differences helps in selecting the right polymer for specific applications.