Polyamide, referred to as polyamide pa for short, is commonly known as nylon. It is a kind of crystalline thermoplastic plastic formed by the polymerization of binary amines and diacid or lactam. There are many kinds of PA, according to the number of carbon atoms in the monomer involved in the polymerization reaction, and different kinds of PA with different performances can be formed, such as PA6, PA66, PA612, PA1010, PA11, PA12, PA46, PA9, PA1212, etc. PA6 and PA66 are mostly used, accounting for 90% of the total production.
Polyamid pa6 has the polarity, which is non-toxic, tasteless and easy to be colored;
Crystalline type (50 to 60%), translucent milky white or light yellow granule;
Newtonian fluids (Newtonian fluids refer to fluids where the stress is proportional to the strain rate);
Density: 1.02 to 1.20g/cm³;
High water absorption, hydrolysis reaction will happen at 230 degrees Celsius;
Water absorption PA46 > PA6 > PA66 > PA1010 > PA11 > PA12 > PA1212;
Large shrinkage rate of molding. PP, PE > PA > PS, ABS. Medium barrier property and strong barrier to air.
The mechanical properties of polyamid pa6 are generally related to crystallinity: The higher the crystallinity, the higher the strength and the stronger the rigidity. In terms of strength, PC > PA66 > PA6 > POM > ABS.
Strength is greatly affected by hygroscopicity, the higher the temperature, the higher the hygroscopicity, the lower the tensile strength and other properties.
The impact toughness is greatly affected by the hygroscopic performance. With the increase of temperature, the water absorption increases and the toughness increases. (Usually, toughness is poor in a dry state and low temperature, and it is likely to have stress cracking with metal products and the brittle fracture at 0℃.
Polyamid pa6 has good self lubricity and good wear resistance.
Excellent resistance to oil, eg. petrol.
The fatigue strength is high, generally 20% to 30% of the tensile strength. The fatigue strength of PA6 and PA66 can reach about 22MPa, second only to POM (35MPa) and higher than PC (10-14MPa). The sequence in terms of fatigue strength: POM > PBT, PET > PA66 > PA6 > PC > PSF > PP.
High hardness, PA66: 108 to 120HRR; PA6120HRR.
Poor Creep resistance: Better than PP and PE, and worse than ABS and POM.
Poor stress cracking resistance: Annealing or humidification treatment should be carried out after processing products.