Polypropylene is a synthetic thermoplastic polyamide. It is a performance fiber that can be manufactured in filament yarn with different structures and can be used as a breathable fiber or for heat retaining. Polypropylene is hydrophobic and lipophilic, which means it can only be solution dyed and printed with oil-based paint. Untreated polypropylene can be easily degraded by light. With added flame retardants, polypropylene is applicable for outdoor upholstery. The melting point is relatively lower than other thermoplastic fibers, which may limit finishing options. The fabric resists abrasion, water-based stains, and diluted bleach, which makes it ideal for indoor upholstery, area rugs, and doormats. It is often used as a backing for commercial carpet as well. Polypropylene nonwovens can be treated with static to filter air, and it is a common material used for disposable surgical masks and medical textiles.