What Is Aramid Fibre And Its Advantage?

1. Good mechanical properties
Interposition aramid is a flexible polymer, breaking strength higher than ordinary polyester, cotton, nylon, etc., elongation is larger, soft to the touch, good spinnability, can be produced into different slenderness, length of short fibers and filaments, in general textile machinery made of different yarn counts woven into fabrics, non-woven fabrics, after finishing, to meet the requirements of different areas of protective clothing.

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2. Excellent flame and heat resistance
The limiting oxygen index (LOI) of m-aramid is 28, so it does not continue to burn when it leaves the flame. The flame retardant properties of m-aramid are determined by its own chemical structure, making it a permanently flame retardant fibre that does not degrade or lose its flame retardant properties with time or washing. The m-aramid is thermally stable and can be used continuously at 205°C and maintains a high strength at temperatures greater than 205°C. The m-aramid has a high decomposition temperature and does not melt or drip at high temperatures, but only starts to char at temperatures greater than 370°C.

3. Stable chemical properties
In addition to strong acids and bases, aramid is virtually unaffected by organic solvents and oils. The wet strength of aramid is almost equal to the dry strength. The stability of saturated water vapour is better than that of other organic fibres.
Aramid is relatively sensitive to UV light. If exposed to the sun for a long time, it loses a lot of strength and should therefore be protected with a protective layer. This protective layer must be able to block the damage to the aramid skeleton from UV light.

4. Radiation resistance
The radiation resistance of interposition aramids is excellent. For example, under 1.72x108rad/s of r-radiation, the strength remains constant.

5. Durability
After 100 washes, the tear strength of m-aramid fabrics can still reach more than 85% of their original strength. The temperature resistance of para-aramids is higher than that of inter-aramids, with a continuous use temperature range of -196°C to 204°C and no decomposition or melting at 560°C. The most significant characteristic of para-aramid is its high strength and high modulus, its strength is more than 25g/dan, which is 5~6 times of high quality steel, 3 times of glass fibre and 2 times of high strength nylon industrial yarn; its modulus is 2~3 times of high quality steel or glass fibre and 10 times of high strength nylon industrial yarn. The unique surface structure of the aramid pulp, which is obtained by surface fibrillation of the aramid fibres, greatly improves the grip of the compound and is therefore ideal as a reinforcing fibre for friction and sealing products. Aramid Pulp Hexagonal Special Fibre I Aramid Pulp, light yellow flocculent, plush, with abundant plumes, high strength, good dimensional stability, non-brittle, high temperature resistant, corrosion resistant, tough, low shrinkage, good abrasion resistance, large surface area, good bonding with other materials, a reinforcing material with a moisture return of 8%, an average length of 2-2.5mm and a surface area of 8m2/g. It is used as a gasket reinforcement material with good resilience and sealing performance, and is not harmful to human health and the environment, and can be used for sealing in water, oil, strange and medium strength acid and alkali media. It has been proven that the strength of the product is equivalent to 50-60% of asbestos fibre reinforced products when less than 10% of the slurry is added. It is used to reinforce friction and sealing materials and other manufactured products, and can be used as an alternative to asbestos for friction sealing materials, high performance heat resistant insulation paper and reinforced composite materials.

Final Advanced Materials has a wide range of aramid products available: threads, tapes, fabrics, packings, sleeves, braided ropes, self-gripping tapes, etc.

What Are Aramid Fibres?

The word 'aramid' is a contraction of 'aromatic polyamide'. The chemical name is para phenylene terephthalamide or PPD-T. Created in the &#;s, aramid fibres consist of yellow filaments of about ten microns in diameter, assembled into threads. There are three main families of polyamides:

• Para-aramids: used in many fields with high-tech applications, they are mainly known under the brand name Kevlar®, from DuPont, and are used for their mechanical properties.

• Para-aramid copolymers: derived from para-aramids, these are also used for their excellent mechanical properties.

• Meta-aramids: these are mainly recognised for their thermal and chemical characteristics and are known under the brand name Nomex® from DuPont. They are mainly used in the fields of technical textiles and protective clothing.

Manufacturing of Aramid Fibres

Paraphenylenediamine is reacted with terephthalyl chloride in an organic solvent to obtain PPD-T. The polymer obtained is dissolved in sulphuric acid. The polymer is then partially oriented into a liquid crystal form. This polymer is extruded in a die and spun. The filaments are cooled by an air jet. The washing, drying and spooling phases are then carried out. The difference between para-aramid and meta-aramid arises from the place the functional groups have on the aromatic rings.

Source : INRS,

General Characteristics of Aramid Fibres

Traction modulus and resistance

The aramid fibres have a tensile strength equivalent to that of steel and a traction modulus that can be up to two times higher than that of glass. These properties make it a balanced material with excellent tensile strength.

Compressive strength

Aramid fibres have poor compression characteristics, which is a probable consequence of their poor adhesion to resins.

Flexural strength

Aramid fibres have poor compression characteristics, which is a probable consequence of their poor adhesion to resins. 

Elongation at break

The fibre is elastic under a low load and plastic under a heavy load, demons-trating a degree of similarity with metals.

Resistance to UV

Aramid fibres are highly sensitive to UV rays (loss of characteristics and discolouration). It is advisable to store aramid fibre materials away from light.

Thermal characteristics

Aramid fibres have good thermal resistance. The elastic modulus under tension keeps at 300 °C more than 80 % of its value at room temperature. Aramid fibres are used continuously at an average temperature of 200 °C. They have a coefficient of thermal conductivity of around 0.05 W.m-1.K-1.

Benefits of Aramid Fibres

• High tensile resistance
• High elastic modulus
• Excellent vibration damping factor
• Low density
• Excellent thermal stability from &#;70 °C to 200 °C
• Does not sustain combustion, does not melt
• Carbonisation at 425 °C
• Good resistance to fatigue
• Excellent dielectric properties
• Good chemical resistance to fuel and seawater but not strong acids and bases

Comparative Table

Property

Unit

E-Glass

Tensile Resistance

MPa

3,400

2,600

2, 400 to 3,000

990

Traction Modulus* 

 GPa

70

200

45 to 160

5.6

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Allongement à la rupture

%

4.5

2

1.9 to 4.5

18

Density

g/cm3

2.6

7.8

1.44 to 1.47

1.14

Peak Temperature

°C

~700

~800

~300

~170

*Young&#;s tensile modulus: the proportionality factor between pressure and deformation, characterising the elasticity of a given material. //Source: INRS

Applications of Aramid Fibres

• Reinforcement of rubber materials (pneumatic, transport belts, piping, transmission belts)
• Reinforcement of composite materials (sports, aeronautical, naval, protective shielding)
• Reinforcement of cables (rope, telecommunication cables, etc.)
• Protective fire and ballistic clothing
• Friction and sealing (brakes, clutches, seals)

Product Range in Aramid Fibres

Our aramid products are primarily made from continuous fibres to achieve the best possible mechanical properties. We offer different aramid textile formats to suit all requirements:

Threads

We offer two ranges of technical-use threads.

Kevlar® threads can continuously withstand 170 °C. Easier to handle than fibreglass threads, they are used in many technical fields:

• Ballistics (bullet-proof vests)
• Safety shoes
• Protective clothing: heat resistant, flame resistant, cut resistant (gloves, loggers' trousers)
• Composite materials
• Airbags
• Air dust extraction filters (hot gas filtration)
• Tyres (reinforcement)

Nomex® threads are particularly suitable due to their thermal protection, thanks to their self-extinguishing properties and a continuous application temperature of 220 °C. A highly technical thread, they are used for particularly targeted purposes: 

• Heat and flame resistant clothing, textiles and stitching
• Safety shoes
• Protective gloves
• Aircraft seats
• Airbags
• Tapes

Tapes

Our tapes are composed of continuous para-aramid fibres, which gives them excellent mechanical and thermal properties. They are mainly used in the glass industry, valued for their homogeneity and the regularity of their weaving, in the manufacture of fire resistant materials and as conveyor belts.

Braided Ropes

Their properties are similar to tapes. They are mainly used as seals. In order to offer diversified technical solutions, we have a range of ropes available in round or square sections.

Sleeves

Recognised for their resistance to abrasion and their mechanical and thermal characteristics, our sleeves are made with various diameters to suit your requirements. As with our ropes, they are mainly used for thermal sealing, but also in the glass industry and to insulate cables.

Fabrics

Woven in plain weave, 100 % para-aramid fabrics have excellent thermal characteristics. In addition to their good insulating properties, they can reach a peak temperature of 500 °C and a continuous temperature of 350 °C. In addition to this, they have excellent resistance to cuts, abrasion, tearing and acids, as well as excellent mechanical properties. Available in different versions (aluminised, fleece, etc.), they are particularly suitable for the manufacture of protective clothing and thermal insulation.

100% para-aramid (Kevlar®) fabrics always include a cross-twill woven version (two single twills in different directions). Particularly resistant to high temperatures up to 450 °C and cuts, it is mainly used to reinforce protective clothing. Coated versions (silicone, aluminium, flame retardant, etc.) are available.

Packings

Packings are made of a glass-fibre core and of a para-aramid fibre sleeve. The glass-fibre core of the packing improves its thermal and mechanical properties Primarily used as insulation products, they are ideal for industrial furnaces.

Physical variables included in this documentation are provided by way of indication only and do not, under any circumstances, constitute a contractual undertaking. Please contact our technical service if you require any additional information.

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