What are Nylon 6 and Nylon 66

Nylon 6 and nylon 66 are the main products of nylon. Nylon is strong and wear-resistant, and its strength is even comparable to that of steel wire of the same thickness; 15% nylon mixed into wool can increase its wear resistance by 3.5 times; except for polypropylene, nylon is the lightest synthetic fiber; nylon has strong fatigue resistance; its flatness is second only to polyester; its bending and winding resistance is 7-8 times higher than that of cotton fiber; nylon has excellent chemical stability.

The elongation at break of nylon varies with the variety; among synthetic fibers, nylon is a fiber that is easier to dye. Nylon does not have advantages in light resistance, moisture absorption, and heat resistance. Nylon was developed by DuPont in the United States, and nylon 66 was synthesized for the first time. Later, nylon 6 was made by German chemists.

The Difference Between Nylon 66 and Nylon 6

1. Structure

Nylon 66 is polyhexamethylene adipate, and its industrial abbreviation is PA6. Nylon 6 is polycaprolactam, and its industrial abbreviation is PA66. The two contain different numbers of carbon atoms. In a single molecule, 66 contains nine carbon atoms and 6 contains six carbon atoms.

2. Strength and hardness

In terms of single fiber, nylon 66 is thinner than nylon 6. Because nylon 66 is thinner, the fabric it forms is soft and delicate, feels good, and has good strength. It is the most suitable fiber for engineering and is generally used as military material. Nylon 66 is 12% harder than nylon 6. In theory, the higher the hardness, the more brittle the fiber is and the easier it is to break. But in the use of carpets, this tiny difference cannot be distinguished.

3. Feel

Nylon 66 feels dense, while nylon 6 feels soft. In addition, nylon 66 is less affected by ozone and laughing gas (nitrous oxide), while nylon 6 is prone to fading under the influence of ozone and laughing gas (nitrous oxide).

4. Specific gravity and molding shrinkage

Specific gravity: PA6 1.14 g/cm3, PA66 1.15 g/cm3. Molding shrinkage: PA6 0.8-2.5%, PA66 1.5-2.2%.

5. Combustion identification method

The flame is yellow at the top and blue at the bottom. After burning, the molten plastic drips and bubbles appear. After leaving the fire, it smells like special wool, burnt nails and celery.

6. Mechanical properties

Nylon 66 has high fatigue strength and rigidity, good heat resistance, low friction coefficient, good wear resistance, but high hygroscopicity and insufficient dimensional stability. It has good corrosion resistance, is not moldy, is not afraid of moths, has alkali resistance, but is not resistant to acids and oxidants.

7. Cleanability and antifouling properties

The two properties are affected by the cross-sectional shape of the fiber and the subsequent antifouling treatment, while the strength and hardness of the fiber itself have little effect on cleaning and antifouling properties.

8. Melting point and elasticity

The melting point of nylon 6 is 220°C, and the melting point of nylon 66 is 260°C. However, this is not a difference in terms of the temperature conditions of carpet use. The lower melting point makes nylon 6 have better resilience, fatigue resistance and thermal stability than nylon 66.

9. Wear resistance and dust resistance

Clemson University in the United States conducted a two-and-a-half-year experiment at Tampa International Airport using nylon 6 carpet and nylon 66 carpet. The carpet was exposed to extremely high traffic, and the results showed that nylon 6 was slightly better than nylon 66 in terms of color retention and pile wear resistance. There was no difference in the dust resistance of the two yarns.

10. Impact resistance

Nylon 6 has a high impact strength. In order to improve its impact resistance, synthetic rubber such as EPDM and SBR can be added.

11. Shrinkage

The shrinkage of nylon 6 plastic raw materials is between 1% and 1.5%. Adding glass fiber additives can reduce the shrinkage to 0.3%.

12. Color fastness

Color fastness is not a property of nylon. It is the dye in the nylon that fades under light, not the nylon itself. Nylon 6 is easy to dye, while nylon 66 is difficult to dye.

In short, apart from the obvious differences in structure, the intuitive feeling given by the two is that nylon 66 is softer; nylon 6 has better moisture absorption.