Polypropylene is a type of plastic that can be NSF certified, depending on its use and compliance with the relevant NSF standards. NSF International is an organization that develops public health standards and certification programs that help protect the world’s food, water, consumer products, and the environment. For polypropylene to be NSF certified, it must meet specific requirements related to its safety and suitability for use in contact with drinking water or food products. Manufacturers of polypropylene products that are intended for use in these areas often seek NSF certification to demonstrate the safety and quality of their products. There are various NSF standards, such as NSF/ANSI 51 for materials used in the manufacturing of food equipment and NSF/ANSi 61 for products that come into contact with drinking water. Meeting these standards ensures that the polypropylene does not leach harmful chemicals or contaminants into the food or water it comes into contact with.

Plastics are made of polymers due to polymers' unique properties, such as high strength, lightweight, and the ability to be molded into various shapes. Polymers are long chains of molecules, typically made from petroleum-derived substances, that can be engineered to have specific qualities like flexibility, durability, and resistance to water and chemicals. This versatility makes them ideal for a wide range of applications, from packaging and automotive parts to medical devices and household goods. The process of creating plastics involves polymerization, where monomer units are chemically bonded to form polymers, allowing for the customization of plastic properties to suit different needs. This adaptability, combined with relatively low production costs, has made polymers the material of choice for manufacturing plastics.

Comparing the cost of spun yarns to filament yarns, spun yarns are generally less expensive. Spun yarns are made from short staple fibers that are twisted together to form a cohesive thread. This process allows for the use of various types of fibers, including lower-cost options like cotton and synthetic blends. In contrast, filament yarns are made from long continuous fibers, which can be more costly to produce, especially when sourced from high-quality materials such as silk or certain synthetics. Additionally, the manufacturing process for filament yarns is often more complex and energy-intensive, adding to the cost. However, the specific cost can vary widely depending on the type of fiber used, the quality of the yarn, and the production volume.