Kevlar (para-aramid) is a strong, heat-resistant synthetic fiber, related to other aramids such as Nomex and Technora. Developed by Stephanie Kwolek at DuPont in 1965, the high-strength material was first used commercially in the early 1970s as a replacement for steel in racing tires. It is typically spun into ropes or fabric sheets that can be used as such, or as an ingredient in composite material components.

Kevlar has many applications, ranging from bicycle tires and racing sails to bulletproof vests, all due to its high tensile strength-to-weight ratio; by this measure it is five times stronger than steel. It is also used to make modern marching drumheads that withstand high impact; and for mooring lines and other underwater applications.

Kevlar, a lightweight and strong fiber, was invented by chemist Stephanie Kwolek at DuPont in anticipation of a gasoline shortage. It is synthesized from monomers 1,4-phenylene-diamine and terephthaloyl chloride through a condensation reaction. Kevlar is available in various grades for diverse applications, including industrial use, cables, ropes, and ballistic protection. The fiber has a high tensile strength and a molecular structure that includes inter-chain bonds and aromatic stacking interactions. However, Kevlar is vulnerable to UV degradation and is not commonly used outdoors without protection. Its thermal properties allow it to maintain strength and resilience in extreme temperatures, although prolonged exposure to high temperatures can reduce its strength.

Kevlar is widely used in various applications due to its strength, low thermal conductivity, and high-performance characteristics. In science, it is employed for suspension purposes in cryogenics and as a thermal standoff. It is a crucial component in personal armor, including combat helmets, ballistic face masks, and vests. Kevlar is also used in protective clothing, gloves, and sports equipment such as racing canoes, bicycle tires, and tennis racquets.

Additionally, Kevlar is utilized in the manufacturing of loudspeaker cones, musical instrument parts, and fiber optic cables. In motor vehicles, it serves as a structural component and replacement for asbestos in brake pads. Kevlar is also found in fire-dancing wicks, non-stick frying pans, ropes, cables, and cell phone backplates. The material is often used to reinforce composite materials, such as in aircraft construction, high-performance composites, and sports equipment.