Polyamide (PA) is a general name for a family of synthetic polymers. First produced in February 1935 by Wallace Carrots at DuPont. Because this polymer is produced by the binding of repetitive peptamide (amide bond) units, it was also called polyamide.
Moisture absorption property
All polyamides or nylons (Polyamide-PA) more or less tend to absorb moisture. For this reason, in using these materials, their technical information (information related to dry state and information related to 50% humidity) should be considered. Moisture absorption is also effective in dimensional changes of parts produced with polyamide. Therefore, attention to this issue in design issues should be considered.
It should be noted that in practice, moisture acts as a softening agent (plasticizer) in polyamides or nylons (Polyamide-PA) and reduces the tensile modulus and increases the impact strength.
Due to the sensitivity of polyamides or nylons (Polyamide-PA) to moisture absorption, these materials need dehumidification before the injection process. If the dehumidification operation is not done well, on the surface of the manufactured parts, the adverse effect of moisture-induced streaks is observed. In addition, due to the point increase in temperature in the mold and the effect of water on oxidation, the produced parts will have weaker mechanical properties due to material degradation.
Thermal and electrical resistance
In addition to thermal resistance, these materials have a high electrical resistance and due to their crystalline structure, they show good chemical resistance. Other properties for polyamides or nylons (Polyamide-PA) include impermeability. At the same time, by combining, the ignition resistance of these materials can be easily increased. Polyamides or nylons (Polyamide-PA) are widely used in the automotive and transportation industries, electricity and electronics, textiles, packaging and household products.
By adding glass fibers and increasing the strength of these materials, they can be used as suitable alternatives to metal parts. Therefore, polyamides or nylons (Polyamide-PA) can be considered as the first and most important engineering polymer.
The commercial use of polyamides or nylons (Polyamide-PA) first began in 1938 in the production of toothbrush filaments. Then in 1940 the fibers of this material were used in the production of women’s socks.
Although the production of fibers from this material has a longer history, but since 1950, its applications in the field of production of plastic parts has expanded to about 25% of the total consumption of polyamides or nylons (Polyamide-PA) in 2000. Or has reached 65.1 million tons per year. The annual growth of 8 to 9 percent of consumption in the field of production of plastic parts compared to its growth of 1.5 percent in the use of fibers indicates the new fields of application of this category of materials.
The following types of polyamide or nylon (Polyamide-PA) are available in the form of sheets and rods: