Polyamide (PA)

日期:2023/1/30 8:33:07 / 阅读: / 来源:本站

2.4 Polyamide
Polyamide (PA) is a thermoplastic polymer compound with acylamide group (- HNCO-1) repeating structural unit on the main chain, which is usually called nylon. PA is the abbreviation of polyamide.
Polyamide is a kind of engineering plastic with a large amount of application and a wide range of uses. There are many varieties of polyamides, which are mainly classified and named according to the number of carbon atoms of synthetic monomers, including PA6, PA11, PA12, PA13, PA66, PA610, PA612, PA1010, etc. Polyamide varieties widely used in plastic products are PA6, PA66, PA610 and PA1010.
(1) Performance and characteristics
Polyamide is a light yellow to amber transparent solid, non-toxic and tasteless. Most polyamides can burn slowly in the fire source, and can self-extinguish after leaving the fire source. When burning, they bubble and emit a burning smell of wool; It has high water absorption, which reduces the strength of the product and affects the stability of the size; It has excellent mechanical properties, good impact strength and tensile strength, good friction resistance and wear resistance; Due to the poor thermal stability of the product, it can only be used under 80~100 ℃; It is resistant to a variety of chemicals and is not affected by weak acids, weak bases, alcohols, esters, hydrocarbons, lubricants, gasoline and grease; Soluble in glycol, glacial acetic acid and chloroethanol at room temperature; The electrical performance is poor, so it is only suitable for power frequency insulation materials.
The performance parameters of several commonly used domestic polyamides are shown in Table 2-93.
(2) Forming method and application
Polyamide can be molded by injection molding, extrusion molding, extrusion blow molding, pouring, molding, rotary molding, foaming, coating, welding, bonding and other methods. The main products include accessories on machinery, instruments and meters, automobiles, textile machinery and other equipment, such as bearings, gears, oil pipes, oil tanks, chemical engineering products, electronic and electrical products, cams, turbines, parts for pumps and valves, gaskets, cable covers, auto parts, fan blades, medical supplies and film for food packaging.
(3) Key points of forming process
The raw material molding products shall be dried before production to make its water content less than 0.06%; In order to prevent the products from being oxidized and brittle under high temperature, carbon black and ultraviolet absorber can be added into the molding raw materials to improve the aging resistance; When forming hose and cable connector products, plasticizers such as aliphatic diols and aromatic chlorosulfonates shall be added into the raw materials; In order to improve the mold filling of the melt and the mold release of the finished product, a small amount of paraffin or metal soap lubricant can be added to the raw material. Adding a certain proportion of glass fiber or mineral fillers and reinforcing modifiers to the raw materials can increase the rigidity of the products, reduce the high temperature creep and shrinkage, reduce water absorption, and improve the dimensional stability, impact strength, wear resistance and flame retardance of the products.


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