Exploring the Six Marvelous Characteristics and Applications of Nylon Fiber

Specific Gravity

Among the main synthetic fibers (polyester, nylon, acrylic, vinylon), nylon has the lightest specific gravity-1.14. Because of its light specific gravity, nylon is suitable for high altitude and alpine work materials, plus the high strength of nylon, so it can be made into ropes, fishing nets and so on, and can be spun into fine yarn or made into "hollow fiber".

Thermal Performance

When processing nylon, the effect of temperature on fiber properties must be taken into account. In hot air above 100°C, the loss of nylon strength is obvious, because of the oxidative cleavage of the fiber molecules under the action of heat. If no oxygen is present for heating, the loss of strength is minimal. In general, the lower the temperature, the higher the strength of nylon. Because the temperature is low, the ability of molecular thermal movement is small, and the intermolecular force is strong. Therefore, the fiber strength is high at low temperatures.

The strength of nylon staple fiber can reach 57.33~66.15cN/tex at room temperature, and the strength of nylon strong wire can reach 83.8cN/tex, which is 2~3 times higher than the strength of cotton fiber. In addition, the increase of temperature will make the nylon shrink, near the melting point when the shrinkage is serious, the fiber becomes yellow.

Electrical Performance

The electrical conductivity of nylon is very low, and it is prone to electrostatic build-up due to friction during the production process. However, when the relative temperature of the environment increases, the conductivity increases as an exponential function. For example, when the relative humidity changes from 0 to 100%, the electrical conductivity of nylon 66 increases by a factor of (10 to the sixth power).

Moisture Absorption Dyeing Performance

Nylon is a hydrophobic fiber, but nylon macromolecules contain a large number of weakly hydrophilic groups -C=O-NH-, and there are -NH2, -COOH hydrophilic groups at both ends of the molecule. Therefore, the hygroscopicity of nylon is higher than that of all synthetic fibers except vinylon. Nylon 6 has slightly higher moisture absorption than nylon 66 due to the presence of residual oligomers.

This is probably due to the fact that the nylon skin structure limits the expansion in the cross-sectional direction, while the length of the fiber is affected by the stretching of the molecules in the amorphous part, which results in the elongation of the nylon weave after moisture absorption.

The dyeability of nylon is not as good as natural fibers, but it is easy to dye in synthetic fibers. From the molecular structure of nylon, the macromolecule contains a considerable number of -CH - hydrophobic chains, so nylon can be dyed with hydrophobic disperse dyes.

The nylon macromolecule contains amino-NH2 and carboxy-COOH at the end and imino-NH- in the chain.

Nylon macromolecules have dyeing properties similar to wool. In acidic medium, nylon macromolecules are cationic and can be dyed with anionic dyes; in alkaline medium, nylon macromolecules are anionic and can be dyed with cationic dyes, but the soaping and sun fastness are poor after dyeing, so they are less used.

Chemical Properties                     

The chemical stability of nylon is good, especially the alkali resistance is more outstanding. In 10% NaOH solution, the fiber strength is only reduced by 5% when treated at 85℃ for 10h.

The more active group in nylon macromolecule is amide group, which will be hydrolyzed under certain conditions.

Acid can make the nylon macromolecule hydrolysis, causing the reduction of fiber polymerization, and the nylon macromolecule hydrolysis will occur in water above 150℃. Acid and heat play a catalytic role in the hydrolysis of fibers.

Strong oxidizing agents can destroy nylon, such as bleaching powder, sodium hypochlorite, hydrogen peroxide, etc. can cause the breakage of fiber molecular chains and reduce the strength of fiber. And bleaching with these oxidizing agents after the fabric is easy to turn yellow, so nylon if you need to bleach, generally use sodium chlorite (NaCLO2) or reduced bleaching agent.