Aramid fibers are a class of strong heat-resistant and electrical insulating synthetic fibers. They are used in aerospace, military, and industrial applications. They can come in the form of compressed fiber sheets, high temperature insulating papers, and woven textiles to name a few.
The name "Aramid" is a compound of aromatic polyamides which were first introduced in commercial applications in the early 1960s, produced by DuPont under the trade names Nomex® and Kevlar®. The fibers are characterized by their excellent resistance to heat, as they neither melt nor ignite in normal levels of oxygen. Additionally aramid fibers are inherently flame resistant by having the flame resistance that can never be worn away or washed out built into their chemical structures. In the case of DuPont Nomex®, when exposed to flame, the aramid fiber swells and becomes thicker, forming a protective barrier between the heat source and the skin.
Aramid fiber gaskets are used extensively for thermal and electrical insulation applications, as well as in many high temperature industrial applications such as pumps, valves, and compressors.
Aramid fiber characteristics
Aramids share a high degree of orientation with other fibers such as ultra-high-molecular-weight polyethylene, a characteristic that dominates their properties.
- good resistance to abrasion
- good resistance to organic solvents
- no melting point, degradation starts from 500 °C
- low flammability
- good fabric integrity at elevated temperatures
- sensitive to acids and salts
- sensitive to ultraviolet radiation
- prone to electrostatic charge build-up unless finished
- para-aramid fibers, such as Kevlar®, provide outstanding strength-to-weight properties
- high Young's modulus
- high tenacity
- low creep
- low elongation at break (~3.5%)
- difficult to dye – usually solution-dyed
Vulcanized Fiber, also known as Fish Paper, is a laminated plastic composed of only cellulose. The material is a tough, resilient, hornlike material that is lighter than aluminum, tougher than leather, and stiffer than most thermoplastics. It is used as electrical insulation in many applications due to pure cellulose having outstanding electrical properties. Cellulose is a good isolator and is also polar, having a dielectric constant significantly greater than one. Electrical paper products are classified by their thickness, with tissue considered papers less than 1.5 mils (0.0381 mm) thickness, and board considered more than 20 mils (0.508 mm) thickness.
Polypropylene (PP), also known as polypropene, is a thermoplastic polymer used in a wide variety of applications including thermal and electrical insulation.
Formex™ electrical insulation products, crafted of durable, flexible polypropylene material, offer superior protection for sensitive electronic components and serve as a barrier to prevent consumers and service workers from experiencing electric shock. Its superior dielectric strength, dimensional stability and resistance to moisture and chemicals make it the top choice for engineers and designers. Unlike other heat insulating materials, Formex™ electrical heat insulation materials provide lightweight, flame retardant protection that meets strict safety and environmental standards at a low cost. It is also used to prevent unintended contact between circuit boards and housings and between circuit boards themselves. Formex™ electrical insulation is also used as a low-cost, lightweight barrier to protect sensitive parts or energized components from contact with fingers or other objects.