1.Definition of aramid fibres
Aramid fibre is the collective name for aromatic polyamide fibres.
2.Classification of aramid fibres
Aramid fiber according to the molecular structure can be divided into three types: para-aromatic polyamide fiber, inter-aromatic polyamide fiber, aromatic polyamide copolymer fiber. Among them, para-aromatic polyamide fibers are divided into poly-phenylamide (poly-p-aminobenzoyl) fibers, poly-benzenedicarboxamide terephthalamide fibers, inter-position benzodicarbonyl terephthalamide fibers are divided into poly-m-tolyl terephthalamide fibers, poly-N,N-m-tolyl-bis-(isobenzamide) terephthalamide fibers.
3.The characteristics of aramid fibres
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.
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.
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 1414 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.