PA - polyamide, also known as nylon, is a general term for a large class of amide polymers. The most common are PA6, PA66 and PA1010. Recently, with the development of I T industry, the use of a new type of polyamide - PA46 has increased dramatically. It is used to replace LCP (liquid crystal polymer) in the production of computer plug-ins. Because PA has good mechanical properties, good toughness, impact resistance, wear resistance, self-lubrication, flame retardant, insulation and other characteristics, it is widely used in automotive, mechanical, electronic, instrumentation, chemical and other fields, such as gears, pulleys, bearings, impellers, bushings, containers, brushes, zippers and so on.
PA6, PA66 and PA46 belong to aliphatic polyamides and are linear polymers. The molecular structure of PA6, PA66 and PA46 has very strong polar amide groups, so they have high crystallization ability. The properties of PA products depend on their crystalline morphology and crystallinity. The processing conditions have an effect on the crystalline morphology and crystallinity. The crystallization of PA products can change up to 40% under different processing conditions. The products have slow cooling, high crystallinity and large size crystalline morphology. Water absorption also affects its crystallinity.
In addition, due to the flow and shear action, PA will produce a certain degree of orientation during processing, which leads to the anisotropy of product performance. The strength along the orientation direction is better than that in the non-orientation direction. Orientation is also conducive to the crystallization process. This factor should be considered in die design.
Performance of PA
No_, tasteless, mildew, translucent or transparent appearance, milky white or light yellow, density 1.04-1.36, when burning, it emits a special protein flavor, the flame is blue and the upper end is yellow.
It has good rigidity and toughness, resistance to repeated impact and vibration, and use temperature is - 40 - 100 C. It has good resistance to friction, wear and self-lubrication, but poor creep resistance and poor dimensional stability. It can be overcome by adding glass fiber reinforced or blending with other materials.
Chemical resistance and weatherability
PA has few organic solvents and good chemical properties. The organic solvents of PA are formic acid and phenolic compounds. Different concentrations of inorganic acids, alkalis and salts can cause PA to swell, dissolve or hydrolyze. Under the condition of not being exposed to sunlight, its aging resistance is good, but under the conditions of heat, light and radiation, the aging speed is fast, the product discoloration and the performance is reduced.