Polyaryl esters

1. Introduction to polyaryl esters
Polyaryl ester, also known as aromatic polyester or polyphenolic ester, is a thermoplastic composed of aromatic rings and ester bonds on the molecular backbone, abbreviated as PAR. There are hundreds of varieties of PAR synthesis monomers, among which bisphenol A, terephthalyl chloride and isophthaloyl chloride synthesis of bisphenol A type PAR are the most commonly used.
PAR has excellent heat resistance and can be used in the temperature range of -70~180°C. It has good mechanical properties and is close to the price of general engineering plastics, which is a very promising heat-resistant plastic.
2. Structural performance
(1) PAR is a linear amorphous polymer, and the comprehensive result of intermolecular interaction makes PAR show great rigidity, certain polarity, and certain flexibility.
(2) Transparency The light transmittance can reach 87%, and the refractive index is 1.61, which is higher than PC and PMMA, and only slightly lower than PES.
(3) Mechanical properties PAR has good creep resistance, wear resistance, impact resistance and elastic recovery, and has good mechanical strength retention in a wide range of temperatures.
(4) Thermal performance The glass transition temperature is 193 °C, the load heat deflection temperature is 175 °C, and the heat decomposition temperature is 443 °C. It is flame retardant and has an oxygen index of 36.8. The coefficient of linear expansion is small, and the solder resistance is good.
(5) Electrical properties Due to the polarity of PAR, its insulation at high frequencies is affected, but it has excellent insulation properties in the medium and low frequency range. PAR has good arc resistance, and its electrical properties are less affected by temperature and humidity.
(6) Environmental performance: Good ultraviolet resistance, resistance to most solvents, not resistant to halogenated hydrocarbons, acetone, banana water, aromatic hydrocarbons, ammonia, hot water, alkali and concentrated sulfuric acid.
3. Molding processing
(1) Processing characteristics The melt viscosity of PAR is high, which is 10 times higher than that of PC, and the flow characteristics are close to Newtonian fluid, and the viscosity is more affected by temperature than by shear rate.
The processing temperature of PAR is very close to the decomposition temperature, and the melting processing temperature range is narrow, which brings certain difficulties to the processing, and it is generally necessary to add heat stabilizers. It is dried before processing. The molding shrinkage is small, only 0.05%, and the processing accuracy of the product is high.
PAR can be molded using traditional processing methods such as injection molding and extrusion.
4. Scope of application
(1) Electronic appliances can be used as H-class heat-resistant insulating materials, specifically: switch operation keyboards, knobs, etc., electrical shafts, covers, sockets, winding tubes, relays, light-emitting diodes and lighting parts, etc.
(2) Auto parts are mainly used for automotive transparent parts, such as lenses, mirrors, lampshades, etc.
(3) Mechanical parts of plastic pump impellers, housings, machine housings, various sliding friction parts such as gears, bearings and pulleys, etc.
(4) Other medical equipment, daily necessities, etc.