What are the properties of aramid fibers?

The general characteristics of aramid fibers that distinguish them from other synthetic fibers are as follows:

• Fiber structure: Amide fibers contain a series of synthetic polymers which have repeating units containing large phenyl rings linked together by amide groups. Due to these strong amide bonds, amide fibers are resistant to solvents and heat.
• Densities: Aramid fibers are characterized by medium to low elongation and moderately high to ultra-high-modulus with densities ranging from 1.38g/cm3 to 1.47g/cm3.
• Resistance towards heat: Aramid fibers are heat-resistant and flame-resistant because they contain a high proportion of meta-oriented phenylene rings.
• Resistance towards acids and organic solvents: Due to the amide links present in aramid fibers, the fibers are hydrophilic in nature. And aramid fibers have very good resistance to many organic solvents and salt, but there is a substantial loss of strength with strong acids.
• Dyeing ability: Aramid fibers have a very high glass transition temperature due to which they are difficult to dye.
• Reaction towards UV light: When exposed to UV light there is a change in color and loss of some strength. This is mainly due to the aromatic nature of para-aramid which is responsible for oxidative reactions.
• Thermal properties: Aramid fibers have high crystallinity due to which even at 300 degrees Celsius, they can still retain about 50% of their strength with negligible shrinkage. They don’t melt and burn easily because they have higher Limited Oxygen Index (LOI) values. These fibers are self-extinguishing.
• Breaking Strength: Aramid fibers tend to have medium to ultra-high strength. The breaking tenacity of aramid fibers is around 3045 MPa. In simple words, the strength of aramid fibers is more than 5 times this of steel and twice that of glass fiber or nylon fiber. Even the underwater strength of aramid fibers is 4 times stronger than steel. This higher strength is mainly due to its aromatic and amide group and high crystallinity.
• Bending strength: Non-linear plastic deformation is created when severe bending strength is applied to aramid fibers.
• Cutting resistance: Aramid fibers have very good resistance to abrasion and cutting and they are difficult to cut even by scissors.