Performance
PS is an amorphous polymer with good fluidity and low water absorption (less than 0.2%). It is a transparent plastic that is easy to mold and process. Its products have a light transmittance of 88-92%, strong tinting strength, and high hardness. However, PS products are brittle, prone to internal stress cracking, and have poor heat resistance (60-80℃). They are non-toxic, with a specific gravity of approximately 1.04 g/cm³ (slightly higher than water). Mold shrinkage (typically 0.004-0.007 in/in). Transparent PS—this name refers only to transparency of resin, not its crystallinity.
(Chemical and Physical Properties: Most commercially available PS is a transparent, amorphous material. PS exhibits excellent geometric stability, thermal stability, optical transparency, electrical insulation, and minimal hygroscopicity. It is resistant to water and dilute inorganic acids, but can be corroded by strong oxidizing acids such as concentrated sulfuric acid and can swell and deform in some organic solvents.)
Processing Characteristics
PS has a melting point of 166℃, optimal processing temperature is generally between 185℃ and 215℃. Its melting point is 180℃ to 280℃, with an upper limit of 250℃ for flame-retardant materials. Its decomposition temperature is approximately 290℃, resulting in a wide processing temperature range. Mold temperatures are 40℃ to 50℃, and injection pressures are 200 to 600 bar. A fast injection speed is recommended, all conventional runner and gate types can be used.
PS materials generally do not require drying prior to processing unless improperly stored. If drying is required, drying at 80℃ for 2-3 hours is recommended. Because PS has a low specific heat, it can quickly solidify and condense after dissipating heat in molds. Its cooling rate is faster than that of standard raw materials, allowing for earlier mold opening. Its plasticizing and cooling times are both shorter, reducing molding cycle times. Gloss of PS products improves with increasing mold temperature.
Typical Applications: Packaging products (containers, covers, bottles), disposable medical supplies, toys, cups, knives, tape reels, windshields, and many foam products, such as egg cartons. It can also be used in meat and poultry trays, bottle labels, foamed PS cushioning materials, product packaging, household goods (tableware, trays, etc.), and electrical products (transparent containers, light diffusers, insulating films, etc.).

 

Performance: HIPS is a modified PS material containing 5-15% rubber in its molecule. Its toughness is approximately four times greater than PS, and its impact strength is significantly improved (high-impact polystyrene). Available grades include flame retardant, stress crack resistant, high gloss, ultra-high impact strength, glass fiber reinforced, and low residual volatiles.
Other key properties of standard HIPS include: flexural strength of 13.8-55.1 MPa; tensile strength of 13.8-41.4 MPa; elongation at break of 15-75%; and density of 1.035-1.04 g/ml. It shares advantages of PS in terms of processability and tinting strength. HIPS products are opaque and have low water absorption, so pre-drying is not required during processing.
Processing Characteristics
Because HIPS molecules contain 5-15% rubber, which somewhat affects its fluidity, higher injection pressure and molding temperature are recommended. Its cooling rate is slower than that of PS, so sufficient holding pressure, holding time, and cooling intervals are required. Molding cycle is slightly longer than that of PS, and processing temperature is generally between 190-240℃.
HIPS resin absorbs water slowly, so drying is generally not required. However, excessive surface moisture can sometimes be absorbed, affecting final product's appearance. Excess moisture can be removed by drying at 160°F for 2-3 hours. HIPS parts present a unique "white edge" problem. This can be addressed by increasing mold temperature and clamping force, reducing holding pressure and time. However, water lines will become more noticeable in finished product.
Typical Applications
Major applications include packaging and disposable products, instrumentation, household appliances, toys and entertainment products, and construction industry. Flame-retardant (UL V-0 and UL 5-V) high-impact polystyrene is currently available and widely used in TV cases, commercial machines, and electrical appliances.

Properties
SA is a hard, transparent material that is not susceptible to internal stress cracking. It offers high transparency and a higher softening temperature and impact strength than PS. Styrene component makes SA hard, transparent, and easy to process; acrylonitrile component provides chemical and thermal stability.
SA exhibits strong load-bearing capacity, resistance to chemical reactions, resistance to thermal deformation, and geometric stability. Adding glass fiber additives to SA increases strength and thermal deformation resistance, while reducing coefficient of thermal expansion. SA's Vicat softening temperature is approximately 110℃. Its flexural deflection temperature under load is approximately 100℃, and its shrinkage is approximately 0.3-0.7%.
Processing Characteristics
SA's processing temperature is generally between 200-250℃. This material is hygroscopic and requires drying for at least one hour before processing. Its fluidity is slightly lower than that of PS, so injection pressure is slightly higher (350-1300 bar). Injection speed: High-speed injection is recommended. Mold temperature control between 45-75℃ is recommended. Drying: If improperly stored, SA can absorb some moisture. Drying at 80℃ for 2-4 hours is recommended.
Melting Temperature: 200-270℃. For thick-walled parts, a melt temperature below lower limit can be used. For reinforced materials, mold temperatures should not exceed 60℃. Cooling system must be carefully designed, as mold temperature directly affects part's appearance, shrinkage, and warpage. Runners and Gates: All conventional gates can be used. Gate size must be precisely dimensioned to avoid streaks, smears, and voids.
Typical Applications
Electrical (sockets, housings, etc.), consumer goods (kitchen appliances, refrigerator units, TV bases, cassette cases, etc.), automotive (headlight housings, reflectors, instrument panels, etc.), household goods (tableware, food knives, etc.), safety glass for cosmetic packaging, water filter housings, and faucet knobs.
Medical products (syringes, blood aspiration tubing, renal dialysis devices, and reactors). Packaging materials (cosmetic cases, lipstick tubes, mascara bottles, covers, caps, sprayers, and nozzles, etc.), specialty products (disposable lighter housings, brush bases and bristles, fishing gear, dentures, toothbrush handles, pen barrels, musical instrument nozzles, and oriented monofilament).

 

Properties
ABS is synthesized from three chemical monomers: acrylonitrile, butadiene, and styrene. (Each monomer has distinct properties: acrylonitrile offers high strength, thermal stability, and chemical stability; butadiene offers toughness and impact resistance; styrene offers easy processing, high gloss, and high strength.
Polymerization of these three monomers produces a two-phase terpolymer: a continuous phase of styrene-acrylonitrile and a dispersed phase of polybutadiene rubber.) Morphologically, ABS is a non-crystalline material with high mechanical strength and a good combination of "toughness, toughness, and steel."
As an amorphous polymer, ABS is a general-purpose engineering plastic with a wide variety of applications. It is also known as "general-purpose plastic" (MBS is transparent ABS). ABS is highly hygroscopic, with a specific gravity of 1.05 g/cm³ (slightly heavier than water), low shrinkage (0.60%), dimensionally stable, and easy to mold. ABS's properties are primarily determined by ratio of three monomers and molecular structure of two phases.
This allows for great flexibility in product design, resulting in hundreds of different ABS grades on the market. These different grades offer varying properties, such as moderate to high impact resistance, low to high glossiness, and high-temperature distortion resistance.
ABS material offers exceptional processability, aesthetic appeal, low creep, excellent dimensional stability, and high impact strength.
ABS is a light yellow, opaque resin in granular or beaded form. It is non-toxic, odorless, and has low water absorption. It possesses excellent overall physical and mechanical properties, including excellent electrical properties, wear resistance, dimensional stability, chemical resistance, surface gloss, is easy to process and mold. However, its disadvantages include poor weather and heat resistance, and flammability.
Processing Characteristics: ABS is highly hygroscopic and moisture-sensitive. Therefore, it must be thoroughly dried and preheated (at 80-90℃ for at least two hours) before molding to keep moisture content below 0.03%.
Melt viscosity of ABS resin is less sensitive to temperature (unlike other amorphous resins). Although injection temperature of ABS is slightly higher than that of PS, it lacks same wide temperature range as PS. Therefore, blindly increasing temperature should not be used to reduce its viscosity. Instead, increasing screw speed or injection pressure can be used to improve its fluidity. A typical processing temperature is between 190℃ and 235℃.
ABS has a medium melt viscosity, higher than PS, HIPS, and AS, requiring higher injection pressures (500-1000 bar) for injection molding.
ABS material performs best when injected at medium- to high-speed injection speeds (unless complex shapes or thin-walled parts require higher injection speeds). However, air marks are more likely to form at the sprue.
ABS molding temperatures are relatively high, generally maintained between 25℃ and 70℃. When producing larger parts, fixed mold (front mold) temperature should generally be approximately 5℃ higher than movable mold (rear mold). (Mold temperature affects finish of plastic part; lower temperatures result in lower finish.)
ABS should not be left in a high-temperature barrel for extended periods (less than 30 minutes), as this can cause decomposition and yellowing.
Typical Applications
Automobiles (instruments, tool compartments, wheel covers, mirror boxes, etc.), refrigerators, high-strength tools (hair dryers, blenders, food processors, lawn mowers, etc.), telephone housings, typewriter keyboards, and recreational vehicles such as golf carts and jet skis.

Properties
BS is a butadiene-styrene copolymer. It exhibits moderate toughness and elasticity, low hardness (softness), and good transparency. BS has a specific gravity of 1.01 f/cm³ (similar to water). It is easy to color, has good flowability, and is easily molded.
Processing Characteristics
Processing temperature range for BS is generally between 190-225℃, with a mold temperature of 30-50℃ being optimal. This material should be dried before processing. Due to its excellent fluidity, injection pressure and speed can be lower.

Performance
PMMA is an amorphous polymer, commonly known as organic glass. It has excellent transparency, good heat resistance (heat deformation temperature of 98℃), and good impact resistance. Its mechanical strength is medium, its surface hardness is low, and it is easily scratched by hard objects. Compared with PS, it is less prone to brittle cracking and has a specific gravity of 1.18 g/cm³.
PMMA has excellent optical properties and weathering resistance. It has a white light transmittance of up to 92%. PMMA products have very low birefringence, making them particularly suitable for making video discs, etc. PMMA exhibits room temperature creep properties. With increasing load and time, stress cracking can occur.
Processing Characteristics: PMMA has stringent processing requirements. It is very sensitive to moisture and temperature, must be thoroughly dried before processing (recommended drying conditions are 90℃ for 2-4 hours). Its high melt viscosity requires molding at high temperatures (225-245℃) and high pressure, with a mold temperature of 65-80℃ being ideal. PMMA is not very stable and can degrade when exposed to high temperatures or when held at high temperatures for extended periods. Screw speed should not be too high (approximately 60% is sufficient), as thicker PMMA parts are prone to cracking.