Kevlar (Poly-p-phenylene Terephthalamide) Fiber Production

The aramid fiber five times stronger than steel by weight

Materials Science & Polymers Commercial Production $3.5 billion

Overview

Kevlar is a para-aramid fiber produced by the polycondensation of p-phenylenediamine and terephthaloyl chloride in solution, followed by dry-jet wet spinning. Invented by Stephanie Kwolek at DuPont in 1965, Kevlar has a tensile strength-to-weight ratio five times that of steel. Its liquid crystalline behavior in solution enables production of highly oriented fibers with exceptional mechanical properties. Applications include body armor, cut-resistant gloves, tire reinforcement, aerospace composites, and fiber-optic cables.

Chemical Process

p-Phenylenediamine is dissolved in N-methyl-2-pyrrolidone (NMP) with CaCl2 at -10 degrees C. Terephthaloyl chloride in NMP is added rapidly with vigorous stirring, producing the polymer as a gel. The polymer is dissolved in concentrated sulfuric acid (19.4% w/w) to form a liquid crystalline dope, which is extruded through a spinneret into an air gap and then a water coagulation bath (dry-jet wet spinning).

nH2N-C6H4-NH2 + nClOC-C6H4-COCl -> -[NH-C6H4-NH-CO-C6H4-CO]n- + 2nHCl (low-temperature polycondensation)

Raw Materials

  • p-Phenylenediamine (C6H4(NH2)2) — Reduction of p-nitroaniline (Diamine monomer)
  • Terephthaloyl chloride (ClOC-C6H4-COCl) — Chlorination of terephthalic acid (Diacid chloride monomer)
  • Concentrated sulfuric acid (H2SO4) — Contact process (Spinning solvent for liquid crystalline dope)

End Products

  • Kevlar fiber (poly-p-phenylene terephthalamide) — Body armor, tire cord, cut-resistant gloves, composites (Tensile strength 3.6 GPa, modulus 130 GPa)
<path stroke-linecap="round" stroke-linejoin="round" d="M12 9v3.75m-9.303 3.376c-.866 1.5.217 3.374 1.948 3.374h14.71c1.73 0 2.813-1.874 1.948-3.374L13.949 3.378c-.866-1.5-3.032-1.5-3.898 0L2.697 16.126zM12 15.75h.007v.008H12v-.008z" />

Environmental Impact

The use of concentrated sulfuric acid as spinning solvent and NMP in polymerization generates hazardous waste requiring careful recovery. HCl byproduct is captured and neutralized. Kevlar fibers are extremely durable and persist indefinitely in the environment, but the small production volume limits overall impact.

Safety Considerations

Recent Innovations

DuPont has developed solvent-free Kevlar processing for certain applications.
Recycled Kevlar pulp from end-of-life body armor is used in brake pads and gaskets.
New copolymer aramids offer improved dyeability and UV resistance.

Production Scale

70000

tons/year

$3.5 billion

market value

More in Materials Science & Polymers

Carbon Fiber Manufacturing from Polyacrylonitrile

Commercial Production

Epoxy Resin Production from Bisphenol A

Global Industrial Scale

Glass Fiber Composite Manufacturing

Global Industrial Scale

Nylon 6,6 Production via Polycondensation

Global Industrial Scale

Polyethylene Synthesis via Ziegler-Natta Catalysis

Global Industrial Scale

Silicone (PDMS) Manufacturing via Direct Process

Global Industrial Scale

Vulcanization of Rubber with Sulfur Cross-Linking

Global Industrial Scale

Frequently Asked Questions

What industry uses Kevlar (Poly-p-phenylene Terephthalamide) Fiber Production?
Kevlar (Poly-p-phenylene Terephthalamide) Fiber Production is used in the materials science & polymers sector at commercial production scale.
What process is involved in Kevlar (Poly-p-phenylene Terephthalamide) Fiber Production?
p-Phenylenediamine is dissolved in N-methyl-2-pyrrolidone (NMP) with CaCl2 at -10 degrees C. Terephthaloyl chloride in NMP is added rapidly with vigorous stirring, producing the polymer as a gel. The polymer is dissolved in concentrated sulfuric acid (19.4% w/w) to form a liquid crystalline dope, wh
What is the economic significance of Kevlar (Poly-p-phenylene Terephthalamide) Fiber Production?
Kevlar (Poly-p-phenylene Terephthalamide) Fiber Production has a market value of $3.5 billion and annual production of 70,000 tons.
What is the environmental impact of Kevlar (Poly-p-phenylene Terephthalamide) Fiber Production?
The use of concentrated sulfuric acid as spinning solvent and NMP in polymerization generates hazardous waste requiring careful recovery. HCl byproduct is captured and neutralized. Kevlar fibers are extremely durable and persist indefinitely in the environment, but the small production volume limits
What raw materials are used in Kevlar (Poly-p-phenylene Terephthalamide) Fiber Production?
The main raw materials include: p-Phenylenediamine (C6H4(NH2)2), Terephthaloyl chloride (ClOC-C6H4-COCl), Concentrated sulfuric acid (H2SO4).