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With China Plastic Machinery
With China Plastic Machinery
PAR is polyarylate, also known as aromatic polyester, which refers to a thermoplastic special engineering plastic with aromatic rings and ester bonds on the main chain of the molecule. PAR is a transparent polymer with good heat resistance, wide operating temperature, good flame retardancy, and good mechanical properties. PAR is widely used in aerospace, electronics, automobiles and machinery, medical supplies and daily necessities.
The study of PAR began in the 1950s. The earliest research report was that in 1957, Belgians first used terephthalic acid and isophthalic acid with bisphenol A to prepare polyarylate by interfacial polymerization. In 1973, Unitika Company in Japan first industrialized polyarylate. Subsequently, the United States, Germany and Japan put into production different brands of polyarylate. In China, Shenyang Chemical Research Institute conducted a pilot test in 1967. Guangzhou Chemical Research Institute and Chenguang Chemical Research Institute also conducted research on polyarylate. A few companies have carried out commercial production of polyarylate. The main methods for synthesizing polyarylates include the acyl chloride method, the phenyl ester method, the acetylation method, the silylation method and the direct ester exchange method.
¢±It is a transparent amorphous thermoplastic engineering plastic with excellent heat resistance, flame retardancy and non-toxicity. It can be directly processed into products by ordinary thermoplastic molding methods.
¢²It has excellent thermal properties. Under a load of 1.86MPA, its heat deformation temperature is as high as 175 degrees and its decomposition temperature is 443 degrees. Its various mechanical properties are less affected by temperature.
The notable characteristics of polyarylate (PAR) are excellent transparency, excellent heat resistance without glass fiber reinforcement, and good flame retardancy without adding flame retardants. In addition, it also has excellent UV shielding resistance, impact resistance, surface hardness and creep resistance. Polyarylate is a non-crystalline polymer compound that can be molded by thermoplastic methods, but has poor melt fluidity. Polyarylate is acid and oil resistant, but its alkali resistance, stress cracking resistance, aromatic hydrocarbon and ketone resistance are not ideal.
1. Physical and mechanical properties
Polyarylate has excellent creep resistance, impact resistance, strain recovery, wear resistance, as well as high mechanical strength and rigidity. Polyarylate shows high tensile strength in a wide temperature range.
2. Thermal properties
Polyarylate has dense benzene rings in the main chain of the molecule, so it has excellent heat resistance. Under a load of 1.82MPa, the heat deformation temperature of polyarylate U-100 reaches 175¡æ. The temperature of its initial weight loss is 400¡æ and the decomposition temperature is 443¡æ as measured by differential scanning calorimetry (DSC method). The glass transition temperature of polyarylate is 193¡æ, which is about 50¡æ higher than polycarbonate and 3 to 4¡æ higher than polysulfone. Therefore, the various properties of polyarylate are less affected by temperature than polycarbonate and polysulfone, and the linear expansion coefficient is small and the dimensional stability is better.
Polyarylate is a self-extinguishing plastic and non-flammable. In the absence of flame retardants, a sample with a thickness of 1.6mm can reach the UL94 V-0 level.
The oxygen index of polyarylate is 36.8. In addition to being lower than that of halogen-containing polyvinyl chloride, polyvinylidene chloride, polytetrafluoroethylene, polyphenylene sulfide, etc., it is higher than the oxygen index of other plastics, including those containing flame retardants.
3. Electrical properties
The electrical properties of polyarylate are similar to those of polyoxymethylene, polycarbonate and polyamide, and its voltage resistance is particularly good.
4. Chemical properties
As a non-crystalline engineering plastic, polyarylate is easily corroded by halogenated hydrocarbons, aromatic hydrocarbons or ester solvents, but it has good acid resistance and oil resistance. Cohesive energy density of polyarylate in some organic solvents and critical strain value for solvent cracking. Relationship between critical cracking strain and time of polyarylate at different temperatures. Generally, the smaller the molecular weight of polyarylate and the higher the ambient temperature, the shorter the time for solvent cracking.
5. Other properties
Polyarylate has excellent transparency, with a refractive index of 1.61, which is higher than that of polycarbonate and polymethacrylate, and its light transmittance is 87% at a thickness of 2mm, which is roughly the same as that of polycarbonate.
Polyarylate has excellent resistance to ultraviolet radiation. Polyarylate with a thickness of 0.1mm can completely block light with a wavelength below 350nm.
Polyarylate is one of the engineering plastics with excellent weather resistance. Its weather resistance is significantly better than that of polycarbonate.
¢± As the wall thickness of the product increases, the molding shrinkage increases.
¢² The hygroscopicity is small, about 0.1-0.3%, but trace amounts of water during injection molding will cause polyaromatic resin to decompose. Therefore, the material must be dried before molding. Make its moisture content less than 0.02%.
¢± Suitable for making electrical parts with high heat resistance, flame resistance and dimensional stability. Connectors, coil frames, relay housings.
¢² Lighting parts. Can be made into transparent lampshades, illuminators, car reflectors, etc.
¢³ In terms of application, the use of automobiles and machinery tends to increase, while that of electrical appliances tends to decrease slightly. Automobiles use the inner lens of the direction lamp, the diffuser mirror of the rear lamp, the interior lamp lens, and other types of automotive lamp lenses, and the turn lamp reflector.
FL fuses and other electronic products, as well as searchlight bodies, lenses, hydraulic torque converter indicators, etc. In the electrical and electrical fields, there are switches, relays, LED reflective lampshades, etc. In the OA business machine field, there are FDD collets, CFD wheel shells, sliders for fax machines, etc. In the mechanical field, there are clocks, AV machine gears, pumps, bearing retainers, etc. In the medical field, it is used in eye drops containers, inspection medicine containers, etc. In addition, the use of heat-resistant beverage bottles using multi-layer and insertion methods is also expanded. The bottom of the golf club is also a new use.
Its glass transition temperature is 193¡æ, which is higher than polycarbonate. Because it is non-crystalline, it belongs to the glass state within the practical temperature range. In terms of dynamic loss, it can be considered as another peak value at -60¡æ, so it is also very cold-resistant.
UL temperature parameters are 140¡æ in electrical properties and 130¡æ in mechanical properties.
Because it is a non-crystalline plastic, it will be corroded by aromatics, esters, chlorinated carbon aqueous solutions, etc. It is resistant to low concentrations of acids.
Because it is a polyester, it will undergo hydrolysis.
It has good transparency, and the light transmittance of 2mm thickness is 87%, which is the same level as polycarbonate. Ultraviolet rays below 350mu can hardly pass through a thickness of 0.1mm. On the other hand, those below 400mu have a transmittance of nearly 90%. This ultraviolet shielding is superior to polycarbonate.
The deformation range that can restore elasticity is large, and the recovery of deformation is good.
The limiting oxygen index is about 37%
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