Polypropylene (PP) is manufactured primarily through two processes: the slurry process and the gas-phase process. Both methods rely on the polymerization of propylene, a byproduct of oil refining and natural gas processing. In the slurry process, propylene is polymerized in a solvent, typically hexane, using a catalyst. The resulting polymer is then separated from the liquid and dried. The gas-phase process involves flowing propylene gas through a bed of powdered catalyst in a reactor, where polymerization occurs. The polymer powder is continuously removed and granulated. Catalysts play a crucial role in controlling the polymer's properties, such as its molecular weight and crystallinity. Advancements in catalyst technology have significantly improved the efficiency and versatility of PP manufacturing, enabling the production of a wide range of polypropylene types for various applications.

PVC pipes themselves do not freeze; rather, it is the water inside them that freezes. Water freezes at 32°F (0°C). However, the temperature at which the water in the PVC pipes will freeze depends on several factors, including the pipe's insulation, exposure to wind chill, and whether the water is flowing or stagnant. Better insulated and buried pipes might resist freezing longer, even as ambient temperatures drop below the freezing point. To prevent freezing, ensure your pipes are properly insulated, consider using heat tape in particularly vulnerable areas, and keep a trickle of water running through pipes during extremely cold spells.

Polyethylene (PE) is a versatile polymer used widely across various industries. Its molecular mass, or molar mass, varies greatly depending on its type and manufacturing process. Essentially, PE is made from the polymerization of ethylene (C2H4). The molecular mass of a single ethylene monomer is about 28 g/mol. However, polyethylene can range significantly in molecular size - from low molecular weight (5000-20,000 g/mol for LDPE) to high molecular weight (up to 1-5 million g/mol for HDPE or UHMWPE). Factors such as the degree of polymerization and branching affect the molecular mass. Higher molecular masses are generally associated with properties like increased strength, toughness, and chemical resistance. Therefore, specifying the type of PE is crucial when discussing its molecular mass.