Polyethylene (PE) and polypropylene (PP) are both common plastics with diverse applications, from packaging to automotive parts. Generally, PE tends to be less expensive than PP. This price difference can be attributed to PE's simpler polymerization process and the fact that it is produced in larger quantities worldwide, which scales down its cost. However, prices can fluctuate based on market demand, oil prices (as both are petroleum-derived products), and the specific type or grade of the polymer. Polyethylene is preferred for its flexibility and durability, making it ideal for products like plastic bags and containers. Polypropylene, while slightly more costly, offers higher melting points, making it suitable for applications requiring resistance to heat, such as microwaveable containers. Ultimately, the choice between the two materials depends on the intended application's specific requirements and the budget constraints of the project.

To prevent yarn from tangling, start by winding it into a ball or cake, which allows it to unwind smoothly as you work. Use a yarn bowl or a container with a hole to guide the yarn and minimize movement. Additionally, employing tools like yarn winders and yarn swifts can keep your yarn organized and prevent kinks and knots. If working with multiple colors, keeping each skein in a separate baggie with the end fed through a small hole can also prevent tangling. For projects in progress, butterfly clips or yarn bobbins can manage multiple working ends, ensuring they don't intertwine. Regularly pausing to untwist your work can also mitigate tangling issues. By implementing these practices, your yarn should remain tangle-free, allowing for a smoother knitting or crocheting experience.

PVC, or Polyvinyl Chloride, is not a conductor but rather an insulator. It is a synthetic plastic polymer widely used in construction for pipes, cables, and other applications. Its electrical insulation properties make it ideal for coating wires and cables to prevent electrical accidents. PVC's insulation capability is attributed to its high resistance to electricity. This keeps the current flow strictly within the wires, ensuring safety and efficiency in electrical systems. It's important to differentiate between the material of wires and their coating; while metals inside the wires conduct electricity, PVC coating around them serves to protect and insulate.