July 10, 2025
Plastics Specialist
PS resin, that is, polystyrene (Polystyrene), is a thermoplastic resin polymerized from styrene as the main raw material, is one of the five major general-purpose plastics, with many excellent characteristics, widely used in many fields.
From the point of view of physical properties, PS resin is a glossy, transparent bead or granular solid, density of about 1.04 - 1.09g/cm³, transparency of up to 88% - 92%, refractive index of 1.59 - 1.60 between the appearance of very beautiful. Its melting temperature is 150 - 180 ℃, thermal decomposition temperature of 300 ℃, heat distortion temperature of 70 - 100 ℃, long-term use of 60 - 80 ℃, which makes it in some of the temperature requirements of the scene can play a role in some of the PS resin electrical insulation properties, volume resistivity and surface resistivity are excellent. Volume resistivity and surface resistivity are very high, and is not affected by changes in temperature and humidity, but also not affected by corona discharge, so in the field of electronics and electrical appliances are very useful. At the same time, it also has good processing fluidity, easy to mold, can be injection molding, extrusion, blow molding, foaming, thermoforming, bonding, coating, welding, machining, printing and other methods of processing into a variety of parts, especially suitable for injection molding. In addition, PS resin is easy to color, can be made into colorful products, but also has a good rigidity and chemical resistance, can withstand some mineral oil, organic acids, alkalis, salts, low-grade alcohols and their aqueous solutions. However, it also has some shortcomings, such as brittle and easy to crack, low impact strength, poor heat resistance, not resistant to boiling water, can only be used at lower temperatures and lower loads, poor sunlight resistance, and flammable, combustion will be black smoke and produce a special odor.
In terms of production methods, there are mainly propriety polymerization method and suspension polymerization method. In this method, styrene monomer is sent to pre-polymerization kettle, adding a small amount of additives and initiators, and pre-polymerization is carried out at 95 - 115 ℃, when the conversion rate reaches 20% - 35%, and then sent to the tower reactor to carry out continuous polymerization, and the temperature of polymerization is gradually raised to 170 ℃ or so in order to realize the complete conversion, and the unreacted styrene is recovered from the top of the tower. The unreacted styrene is recovered from the top of the tower, and the polymer is discharged from the bottom of the tower and extruded for pelletizing. Suspension polymerization method is to use styrene as monomer, water as a medium, add gelatin, starch, polyvinyl alcohol and other protective gum, or magnesium carbonate, magnesium silicate and other insoluble inorganic salts as a dispersant, as well as maleic anhydride - styrene copolymer sodium salt as a co-dispersant, to benzoyl peroxide as an initiator, initiating polymerization at about 85 ℃, but also in the high-pressure polymerization autoclave at 100 ℃. It can also be polymerized at high temperature above 100℃ in autoclave, and finally washed, separated and dried to obtain colorless and transparent fine bead resin.
According to the differences in performance and use, PS resin is mainly divided into general-purpose polystyrene (GPPS), high-impact polystyrene (HIPS) and evaporable polystyrene (EPS) and other types. General-purpose polystyrene is a thermoplastic resin, showing a glossy transparent, with good electrical insulation properties, processing fluidity, rigidity, and chemical resistance, but it is brittle and easy to crack, low impact strength, mainly used in the manufacture of injection molded parts, audio-visual products, lighting products, transparent stationery, food and cosmetic display containers and other products. High impact polystyrene is added to polystyrene polybutyl rubber particles and other substances to improve the impact strength, but the product is opaque, commonly used in the production of electronic product shells, cassette recorders shells, daily necessities, home appliances and small power tools shells, and other products that require high impact resistance. Expandable polystyrene is a low boiling point physical blowing agent added to PS resin, processed by heat foaming, light weight, heat insulation, sound insulation, shockproof and other characteristics, widely used in the production of fast-food lunch boxes, construction panels, building thermal insulation materials, fragile cushioning packaging materials and other foam products.
In terms of practical applications, the figure of PS resin can be seen everywhere. In the field of electronic and electrical appliances, due to its excellent electrical insulation, can be used to manufacture connectors, switch parts, small electric cover, etc., to ensure the stable transmission of equipment current; in the field of daily necessities, GPPS easy to process, easy to color the characteristics of the production of transparent cups, tableware, stationery supplies, etc., the ideal material; in the toy industry, PS resin can be made into a variety of lovely shapes, colorful toys; in the field of building materials, EPS can be used for building thermal insulation, reduce building energy consumption, PS resin can also be made into stone, wood-like decorative panels for stone. In the field of building materials, EPS can be used for building insulation and thermal insulation, reduce building energy consumption, PS resin can also be made of imitation stone, imitation wood decorative panels for indoor and outdoor decoration; in the packaging industry, PS resin molding is good, can be made of disposable lunch boxes, food packaging film, packaging containers, etc., to play a role in the protection and display of products; in the medical industry, PS materials in line with health standards can be made of medical equipment shell, disposable syringe parts, etc.. In the medical industry, PS material conforming to hygiene standards can be used to make the shell of medical instruments, disposable syringe parts, etc.
With the continuous progress of science and technology, PS resin is also constantly improving and innovating, through chemical modification or physical modification, to enhance its performance, expand the scope of application to better meet the needs of various industries, and continue to play an important role in modern life.
