Polyethylene (PE) is a polymer consisting of long chains of the monomer ethylene (CH2=CH2). Its structure can be represented as [-CH2-CH2-]n, where n indicates the number of repeating units. The physical properties of polyethylene depend on its molecular weight and crystallinity, which are determined by how the chains are organized. There are several types, including Low-Density Polyethylene (LDPE), characterized by branched chains leading to a less dense, more flexible material, and High-Density Polyethylene (HDPE), which has a more linear structure resulting in greater strength and density. The versatility and durability of polyethylene make it widely used in packaging, containers, and piping.

Polypropylene was discovered in 1954 by Italian chemist Giulio Natta and his team, following earlier work by Karl Ziegler who developed the Ziegler-Natta catalyst. Ziegler had already invented a process for polymerizing ethylene into polyethylene. Natta's breakthrough involved applying similar catalytic methodologies to propylene, resulting in the creation of polypropylene, a thermoplastic polymer. This discovery was significant for creating a plastic with high resilience and melting point, making it suitable for a vast range of uses, from packaging to automotive components. The innovative work of Natta and Ziegler fundamentally transformed the plastic industry, earning them the Nobel Prize in Chemistry in 1963.

To fix a hole in PVC pipe, first, turn off the water supply and drain the affected pipe. Clean and dry the area around the hole. You have a few options:

1. **Epoxy Putty**: Knead and apply epoxy putty according to the manufacturer's instructions. Allow it to cure as directed.

2. **Rubber and Hose Clamp**: Place a rubber patch over the hole and secure it tightly with a hose clamp. This is a quick, temporary fix.

3. **PVC Slip Coupling**: For a more permanent solution, cut out the damaged section. Use a PVC slip coupling (which doesn’t require the pipe to be movable for installation) for the repair. Glue the coupling with PVC primer and cement as per the instructions.

Remember to let any adhesive or repair material fully set or cure before turning the water back on.