polyamide
DATE：2022/9/7 8:49:42 / READ： / SOURCE：This station
polyamide
Polyamide (PA) is a thermoplastic polymer compound with repeating structural units of amido group (HNCO) on the main chain, which is commonly called nylon. PA is the abbreviation of polyamide.Polyamide is a kind of engineering plastic with large application and wide application. 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. PA6, PA66, PA610, PA1010 and other polyamides are widely used in plastic products.
(1) Properties 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 they burn, they bubble and give out a burnt smell of wool; It has high water absorption, which reduces the strength of the product and affects the dimensional stability; 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 below 80 ~ 100 ℃; Resistant to a variety of chemicals, not affected by weak acids, weak bases, alcohols, esters, hydrocarbons, lubricants, gasoline and grease; Soluble in ethylene glycol, glacial acetic acid and chloroethanol at normal temperature; The electrical performance is relatively poor, and it is only suitable for making power frequency insulation materials.
Molding method and application polyamide can be molded by injection molding, extrusion, extrusion blow molding, pouring, molding, rotary molding, foaming, coating, welding, bonding and other methods. The main products are accessories for machinery, instruments, 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 wrapping, automotive parts, fan blades, medical supplies and food packaging films.
Key points of forming process: raw materials and molded products should be dried before production to make their moisture content less than 0.06%; In order to prevent the products from being oxidized and brittle at high temperature, carbon black and ultraviolet absorber can be added to the molding raw materials to improve the aging resistance; Plasticizers such as aliphatic diols and aromatic chlorosulfonates should be added to the raw materials when forming hose and cable connector products; In order to improve the mold filling of the melt and the demoulding property of the finished product, a small amount of paraffin or metal soap lubricants can be added to the raw materials. Adding a certain proportion of glass fiber or mineral filler and reinforcing modifier to the raw materials can increase the rigidity of products, reduce high-temperature creep, shrinkage, reduce water absorption, and improve the dimensional stability, impact strength, wear resistance and flame retardancy of products.
Polyamide 6, also known as polycaprolactam or nylon 6, is a milky white or yellowish transparent or opaque crystalline polymer. Excellent wear resistance and self wetting, good colorability, toughness, small rigidity, low temperature resistance, bacteria resistance, slow burning, and slow extinguishing after leaving the fire source; Molding processability is very good, and products can be molded by injection, extrusion blow molding, pouring, spraying, powder molding, machining, welding, bonding and other methods. The injection molding temperature is 215 ℃, and the mold temperature is about 90 ℃; High water absorption, poor dimensional stability, shrinkage between 1% and 1.5%, and affecting electrical properties; The maximum operating temperature can reach 180 ℃. The pouring temperature of monomer is 160 ~ 170 ℃, and the polymerization time is 20 ~ 30min.
In order to improve the mold filling of the melt and the demoulding property of the finished product, a small amount of paraffin or metal soap lubricants can be added to the raw materials. Adding a certain proportion of glass fiber or mineral filler and reinforcing modifier to the raw materials can increase the rigidity of products, reduce high-temperature creep, shrinkage, reduce water absorption, and improve the dimensional stability, impact strength, wear resistance and flame retardancy of products.
Prepared by polycondensation reaction. Polyamide is a semi transparent or opaque milky white crystalline polymer, which will emit purple white or blue white light when exposed to ultraviolet light. PA66 products have higher strength than other polyamide products, and have better resistance to environmental stress cracking, heat resistance and low temperature (decomposition temperature is 350 ℃, embrittlement temperature is - 30 ℃); It has good chemical resistance and oil resistance, but is easily soluble in polar solvents such as phenol and formic acid: the water absorption is about 2.5%, the dimensional stability of the product is poor, but the molding processability is good. It can be molded by injection, extrusion and blow molding. The injection melt temperature is about 275 ~ 295 ℃. Polyamide 1010 is also called poly (Decanoyl decanediamine) or nylon 1010. Sebacic acid and sebacic diester were prepared from castor oil by polycondensation. PA1010 is a translucent, light and hard crystalline white or yellowish particle with bright surface; The density and water absorption are lower than those of PA6 and PA66; Non toxic, low temperature resistant, mold resistant, brittleness temperature - 60 ℃; High mechanical strength, impact toughness, wear resistance, self lubrication, dielectric and chemical stability, and better cold resistance than PA6; The melt has good fluidity and is easy to form, but the contact between the melt and oxygen is easy to cause thermal oxidation degradation; When the product is exposed to oxygen at 100 ℃ for a long time, it will gradually turn yellowish brown, and the mechanical strength will decrease; It is insoluble in hydrocarbons, lipids and lower alcohols, but soluble in polar solvents such as phenol, concentrated sulfuric acid and formic acid.
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