Polypropylene (PP) is a thermoplastic polymer, appreciated for its unique combination of properties. It boasts a low density (0.855-0.946 g/cm³), making it lighter than most plastics. Its melting point is relatively high, around 160°C, which contributes to its excellent thermal resistance. Polypropylene is also known for its resistance to chemicals, making it a popular choice for containers and pipework in the chemical industry. Despite its toughness and flexibility, it does have a weakness in terms of UV resistance; prolonged exposure to sunlight can degrade the material unless it is specially treated or stabilized. Another key attribute is its electrical insulating property, which makes it ideal for electronic components. The versatility of PP is further enhanced by its ability to be easily modified through copolymerization, improving characteristics like impact resistance, especially at low temperatures.

Polypropylene, a common plastic material, can exist in two forms: totally crystalline and totally amorphous. The density of totally crystalline polypropylene is typically around 0.946 g/cm3. This high density is due to the ordered arrangement of polymer chains, which pack closely together. On the other hand, the totally amorphous form of polypropylene has a lower density, around 0.855 g/cm3, because its polymer chains are arranged in a random, less organized way, resulting in more space between them. The significant difference in density between these two forms is crucial for applications requiring specific material properties, such as rigidity, flexibility, or transparency. For instance, high-density, crystalline polypropylene is desirable for making rigid containers, while lower-density, amorphous polypropylene is better suited for flexible applications.

Once PVC cement is applied and set, removing it is challenging because it chemically bonds PVC materials together, creating a virtually inseparable joint. However, for excess cement or spills, you can try using acetone or a similar solvent to soften and remove it. Firstly, apply the solvent to a cloth and gently rub the affected area. This method is more effective on fresh spills. For hardened cement, mechanical means like sanding or scraping might be necessary, but this could damage the PVC surface. Always wear protective gear and work in a well-ventilated area when using solvents.