Polypropylene, first created in 1954 is one of the most commercially significant plastic resins. It has a relatively low melting temperature for ease of manufacturing and is a relatively inexpensive polymer to synthesize. Additionally, polypropylene is resistant to degradation from most organic solvents, acids and bases making it ideal in a wide range of applications. Polypropylene is subject to degradation from Ultraviolet radiation and heat, and appropriate UV absorbers and anti-oxidation additives effectively prevent degradation.

The resin can be processed through injection molding to create many different solid parts such as containers, cups and plastic silverware. It can also be melt molded into many complex shapes and melt-extruded into fibers. The melt extrusion process can create both melt-blown and spun-bond fibers. Spun-bond fibers are converted into sheets of fabric used in applications ranging from masks, air and water filters, diapers and even car covers.

Due to the balance of properties, polypropylene makes for excellent protective covers. Spun-bond fibers are soft, resistant to degradation from most chemicals, create a good filtration barrier and can be finished to have a hydrophobic surface to repel water.

In addition to melt-extruding polypropylene into fibers, polypropylene can be extruded into a film. Through a mechanical and chemical process, as the film cools microscopic cracks form in the film. These cracks are large enough for water vapor to pass through the fabric, while still preventing liquid water from penetrating. By including these extruded films inside multilayer materials, car covers can have increased waterproof performance, while maintaining breathability. Breathability allows water vapor to breathe through fabrics preventing a buildup of moisture under the cover, and ultimately mold and mildew.