X-fiper

X-Fiper is a registered trademark of aramid fiber (formally aromatic polyamide fiber) developed by SRO Group (China) in 2007. It is very similar to Dupont's Nomex as both share very similar specification and application.

History

Aromatic polyamides were first introduced in commercial applications in the early 1960s, with a meta-aramid fiber produced by DuPont under the tradename Nomex. This fiber, which handles similarly to normal textile apparel fibers, is characterized by its excellent resistance to heat, as it neither melts nor ignites in normal levels of oxygen. It is used extensively in the production of protective apparel, air filtration, thermal and electrical insulation as well as a substitute for asbestos.

Aramid Fibers

Aramid fibers are a class of heat-resistant and strong synthetic fibers. They are used in aerospace and military applications, for ballistic rated body armor fabric, and as an asbestos substitute. The name is a shortened form of "aromatic polyamide". They are fibers in which the chain molecules are highly oriented along the fiber axis, so the strength of the chemical bond can be exploited. The Federal Trade Commission definition for aramid fiber is: A manufactured fiber in which the fiber-forming substance is a long-chain synthetic polyamide in which at least 85% of the amide linkages, (-CO-NH-) are attached directly to two aromatic rings.

Polymer preparation

Aramids are generally prepared by the reaction between an amine group and a carboxylic acid halide group. Simple AB homopolymers may look like:

nNH₂-Ar-COCl → -(NH-Ar-CO)_n- + nHCl

The most well-known aramids (Nomex, X-fiper) are AABB polymers. Nomex, X-fiper contain predominantly the meta-linkage and are poly-metaphenylene isophtalamides (MPIA).

Spinning After production of the polymer, the aramid fiber is produced by spinning the solved polymer to a solid fiber from a liquid chemical blend. Polymer solvent for spinning PPTA is generally 100% (water free) sulfuric acid (H2SO4).

Aramid fiber characteristics

Aramids share a high degree of orientation with other fibers such as Ultra high molecular weight polyethylene, a characteristic which dominates their properties.

General

• good resistance to abrasion
• good resistance to organic solvents
• nonconductive
• no melting point, degradation starts from 390°C
• low flammability
• good fabric integrity at elevated temperatures
• sensitive to acids and salts
• sensitive to ultraviolet radiation
• prone to static build-up unless finished

Para-aramids

• para-aramid fibers such as Kevlar and Twaron, provide outstanding strength-to-weight properties
• high Yung's modulus
• high tenacity
• low creep
• low elongation at break (~3.5%)
• difficult to dye - usually solution dyed

Major industrial uses

• flame-resistant clothing
• heat protective clothing and helmets
• body armor