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What are the functions and characteristics of Nomex fibers?

6,607 Published by Pure Technology Co., Ltd 1 月 03,2020

What is Nomex?

Meta-amide, or meta-phenylene isophthalamide, is made from meta-phenylenediamine and isophthaloyl chloride in an amide solution. It is a long chain of polyamide on which at least 85% of the amide bonds are connected to two benzene rings.

The meta-oriented phenylene forms a bend in the polymer chain, which reduces rigidity compared to the para-amide bonds of the chemically similar para-aramid.

This compliant polymer molecule chain gives meta-aramid more wearable fabric properties while retaining the high-temperature resistance similar to para-aramid.

Nomex is an intermediate aramid that has good heat resistance and high possession properties. At 250°C, the material properties can remain stable for a long time.

nomex

Properties of Nomex Fiber:

1. Temperature resistance: the maximum temperature resistance is 280℃, and the material properties can be kept stable for a long time under an environment of 250℃.

2. Dimensional stability: at 250℃, Nomex has a thermal shrinkage rate of less than 1%, which has good high-temperature stability

3. Fire resistance: Nomex will not decompose and carbonize until 400℃. As a representative of inherently flame-retardant materials, Nomex has a limiting oxygen index of 28 and can self-extinguish after removing the fire source without the need for added flame retardants.

This property makes it an ideal choice for protective clothing.

4. Chemical resistance: low concentration of acid-base and most hydrocarbons will not affect Nomex, and even a small amount of fluoride will not significantly corrode Nomex.

5. Excellent electrical insulation, the insulation paper made of it can withstand a breakdown voltage of up to 20kV/mm.

Uses of Nomex Fiber:

In addition, it has also been widely used in other industrial fields, such as optical fiber protection, high-temperature filter bags, automotive hoses, tires, audio elastic cloth, power transmission belts, conveyor belts, transfer printing blankets, rubber shoe soles, etc.

In the field of personal protection, aramid can be made into bulletproof vests, bulletproof helmets, bulletproof armor, fire suits, fire masks, military and police training uniforms, anti-cut gloves, etc.

In the civilian field, aramid can be made into flame-retardant interiors and fabrics for aircraft, automobiles, and high-speed railways. It can be made into fire blankets, escape ropes, flame-retardant curtains, bedspreads, pajamas, tablecloths, aprons, microwave gloves, etc. Aramid can also be made into aramid paper for insulation of motors, transformers, and electronic appliances, and can be further processed into honeycomb structure materials for secondary receiving parts of aircraft, yachts, high-speed railways, and motor vehicles.

In the field of special equipment such as flight suits, Nomex IIIA fabric has enhanced its burst resistance by blending 5% Kevlar and has been widely used in aviation protective clothing and racing equipment.

 

nomex felt roller

Nomex felt roller sleeve applied to large Tonnage extrusion machine Saw Table, made of Nomex and Polyester fiber acupuncture. Size can be customized.

nomex felt belt

Nomex felt belt applied to Low-temp cooling bed. The thickness is 6mm-12mm and the length is 1.5m-20m, or a specific size can be customized.

For more information about Nomex products, please move to the product catalog.

Nomex fiber product type

NOMEX 430 type

NOMEX 430 aramid fiber type is a high crystallinity, primary color filament yarn, which has higher strength and better chemical resistance than spun yarn. Type 430 is used as a filament yarn that emphasizes both beauty and performance.

 Type 430 is used in the outer material and lining of firefighters’ fire uniforms, coated fabrics, electrical insulators, automotive hoses, heating pipes, industrial filtration, protective sleeves, and industrial ironing boards.

Usually, primary colors are used because it is difficult to ensure the consistency of printed and dyed products.

NOMEX 450 Type

NOMEX 450 is a staple fiber in its original color. It has a higher crystallinity and strength than the fibers of types 455 and 462. It is sold as a 100% meta-aramid staple fiber in various cut lengths.

It is used in areas that require high tensile properties and chemical and thermal stability, such as sewing thread, zipper tape, and firefighters’ combat jackets.

It is also used in its original color for knitted products such as headbands and underwear. Although it can be dyed, it is less dyeable than types 455 and 462 and does not belong to the category of dyed staple fibers.

NOMEX 455 (NOMEX Ⅲ)

NOMEX 455 staple fiber is a patented brand of NOMEX and KEVLAR blends, developed to meet the needs of better high-performance thermal protective clothing. Fabrics made from NOMEX 455 staple fibers are commercial NOMEX Ⅲ.

It has many improvements over yarns or fabrics made from 450 staple fibers. However, due to its low crystallinity, the yarns or fabrics made from it are slightly weaker than those made from 450 staple fibers.

The advantages of NOMEX 455 over 450 include:

l Improved crack resistance under thermal load. 5% KELVAR inhibits thermal shrinkage, which reduces the possibility of cracking and the resulting loss of protective function.

l Easier to dye. NOMEX 455 can be uniformly yarn-dyed or piece-dyed into a variety of colors according to the requirements of civilian protective clothing. NOMEX 455 is sold as a dyeable staple fiber.

l Fabric appearance. Autoclaving pressed garments at 30 psig steam pressure imparts wrinkle retention and wrinkle resistance to NOMEX Ⅲ or NOMEX ⅢA.

Although not as good as the memory of heat-set polyester, this memory gives it many advantages in appearance and ease of maintenance over many competing materials or untreated garments.

Testing of Aramids:

Flame Test

NOMEX has a limiting oxygen index of about 28. In a normal air environment, at room temperature, NOMEX will stop burning when exposed to flames and away from the fire source. When the temperature exceeds 427°C, NOMEX will carbonize and become a hard block.

Ordinary polyester and cotton fabrics will burn immediately when exposed to fire until a 12-inch-long sample is completely burned. Fabrics made of synthetic fibers such as polypropylene, polyester, or nylon will melt and produce flaming liquid drips when burning. The melting and dripping phenomenon, when clothes burn, is very dangerous because the dripping liquid will transfer more heat to the person, aggravating the degree of burns.

In contrast, NOMEX fabrics will not burn melt, and drip. This fabric can form a protective layer to reduce the area of human burns. When NOMEX fabrics pass the industry vertical burning test, the char length does not exceed 6 inches and the time to completely stop burning does not exceed 2 seconds.

In contrast, NOMEX fabrics will not ignite, continue to burn, or melt droplets. So they do not increase the hazard but provide a protective layer that reduces burns.

NOMEX fabrics pass industry vertical flammability standards with a char length of no more than 4 or 6 inches and a complete burn time of no more than 2 seconds.

Superior to conventional flame retardant treated polyester-cotton blends, this inherently flame retardant material remains stable in high-temperature fluororubber decomposition environments and is suitable for industrial scenarios that require long-term exposure to heat and flames.

Friction

Abrasion resistance is an important consideration for both protective clothing and filter materials. Friction during wear and laundering is the primary cause of garment wear, and filter bag failure is often caused by friction from exposure to dust and wear in dewatering cages.

NOMEX staple yarn woven fabrics consistently demonstrate significantly better abrasion resistance than comparable, and in some cases even heavier weight, polyester/cotton blends, and 100% cotton construction fabrics.

Chemical resistance

Generally speaking, NOMEX fibers have good resistance to many chemical agents, especially to most hydrocarbons and organic solvents. In addition, NOMEX’s acid resistance is better than nylon, but not as good as polyester.

However, as the temperature rises, NOMEX’s resistance to acid gases is better than polyester. At room temperature, NOMEX has excellent alkali resistance, but at high temperatures, it will be decomposed by strong alkali.

NOMEX 430 and 450 have excellent resistance to sodium hypochlorite bleach, but 455 and 462 have moderate (35%) strength loss in this case. At high temperatures, NOMEX can resist the decomposition of fluoro rubber, resin, and moderators.

 

 

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