1. PS Properties: PS is an amorphous polymer with good flowability 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 coloring power, and high hardness. However, PS products are brittle and prone to internal stress cracking. They also have poor heat resistance (60-80℃), are non-toxic, and have a specific gravity of approximately 1.04 g/cm³ (slightly greater than water).
Molding shrinkage (typically 0.004-0.007 in/in). Transparent PS – this name only indicates resin's transparency, not its crystallinity. (Chemical and Physical Properties: Most commercially available PS is a transparent, amorphous material. PS possesses excellent dimensional stability, thermal stability, optical transmittance, electrical insulation properties, and a very slight tendency to absorb moisture. It is resistant to water and diluted inorganic acids, but can be corroded by strong oxidizing acids such as concentrated sulfuric acid, can swell and deform in some organic solvents.)
2. PS Processing Characteristics: PS has a melting point of 166℃, and optimal processing temperature is generally 185-215℃. Melting temperature is 180-280℃, with an upper limit of 250℃ for flame-retardant materials. Decomposition temperature is approximately 290℃, thus its processing temperature range is relatively wide.
Mold temperature: 40-50℃; Injection pressure: 200-600 bar; Fast injection speed is recommended; All conventional gate types can be used for runners and gates. PS material generally does not require drying before processing unless improperly stored. If drying is necessary, a drying condition of 80℃ for 2-3 hours is recommended.
Because PS has a low specific heat, it can quickly solidify after cooling in molds, resulting in a faster cooling rate than most raw materials and allowing for earlier mold opening. Its plasticizing and cooling times are also shorter, reducing molding cycle time. Gloss of PS products improves with increasing mold temperature.
3. Typical Applications: Packaging products (containers, caps, bottles), disposable medical supplies, toys, cups, knives, magnetic tape reels, windproof windows, and many foamed products—egg cartons. Meat and poultry packaging trays, bottle labels, and foamed PS cushioning materials; product packaging; household goods (tableware, trays, etc.); electrical products (transparent containers, light diffusers, insulating films, etc.).

 

1. HIPS Properties: HIPS is a modified PS material containing 5-15% rubber in its molecules. Its toughness is approximately four times higher than PS, and its impact strength is significantly improved (high-impact polystyrene). Flame-retardant, stress-cracking resistant, high-gloss, extremely high-impact strength, glass fiber reinforced, and low-residual-volatile grades are available.
Other important properties of standard HIPS: Flexural strength 13.8–55.1 MPa; Tensile strength 13.8–41.4 MPa; Elongation at break 15–75%; Density 1.035–1.04 g/ml. It possesses advantages of PS, such as good molding, processing properties and strong coloring power. HIPS products are opaque. HIPS has low water absorption and does not require pre-drying during processing.
2. HIPS Processing Characteristics: Because HIPS molecules contain 5-15% rubber, its flowability is affected to some extent. Therefore, higher injection pressure and molding temperature are preferable. Its cooling rate is slower than PS, therefore requiring sufficient holding pressure, holding time, and cooling time. Molding cycle is slightly longer than PS, and its processing temperature is generally best between 190-240℃.
HIPS resin absorbs moisture slowly, so drying is generally not required. However, sometimes excessive moisture on material surface can be absorbed, affecting final product's appearance. Drying at 160°F for 2-3 hours can remove excess moisture. HIPS parts have a unique "white edge" problem, which can be improved by increasing mold temperature and clamping force, reducing holding pressure and time, etc. Watermarks will be more noticeable in product.
3. Typical Applications: Major application areas include packaging and disposable products, instruments, home appliances, toys and recreational products, and construction industry. Flame-retardant grades (UL V-0 and UL 5-V), impact-resistant polystyrene is already produced and widely used in television housings, commercial machinery, and electrical appliances.

1. SA Properties: Chemical and Physical Properties: SA is a hard, transparent material, resistant to stress cracking. It has high transparency, its softening temperature and impact strength are higher than PS. Styrene component makes SA hard, transparent, and easy to process; acrylonitrile component provides chemical and thermal stability. SA has strong load-bearing capacity, resistance to chemical reactions, resistance to heat deformation, and geometric stability.
Adding glass fiber additives to SA can increase its strength and resistance to heat deformation, and reduce its coefficient of thermal expansion. Vicat softening temperature of SA is approximately 110℃. Flexural deformation temperature under load is approximately 100℃, and shrinkage rate of SA is approximately 0.3~0.7%.
2. SA Processing Characteristics: Processing temperature of SA is generally suitable at 200-250℃. This material is hygroscopic and requires drying for at least one hour before processing. Its fluidity is slightly lower than PS, therefore injection pressure should be slightly higher (injection pressure: 350~1300 bar). Injection speed: High-speed injection is recommended. Mold temperature should be controlled between 45-75℃. Drying treatment: SA has some hygroscopic properties if not stored properly.
Recommended drying conditions: 80℃, 2~4 hours. Melting temperature: 200~270℃. For processing thick-walled products, a melting temperature below lower limit can be used. For reinforced materials, mold temperature should not exceed 60℃. Cooling system must be well-designed, as mold temperature directly affects appearance, shrinkage, and bending of product. Runners and gates: All conventional gates can be used. Gate size must be appropriate to avoid streaks, burnt spots, and voids.
3. Typical applications: Electrical (sockets, housings, etc.), daily necessities (kitchen appliances, refrigerator units, TV stands, cassette cases, etc.), automotive industry (headlight housings, reflectors, dashboards, etc.), household goods (tableware, knives, etc.), cosmetic packaging safety glass, water filter housings, and faucet knobs.
Medical products (syringes, blood aspiration tubes, renal osmosis devices and reactors). Packaging materials (cosmetic cases, lipstick sleeves, mascara caps, covers, caps, spray nozzles, etc.), specialty products (disposable lighter housings, brush substrates and bristles, fishing gear, dentures, toothbrush handles, pen barrels, musical instrument nozzles, and oriented monofilaments), etc.

1. Properties of ABS: ABS is synthesized from three chemical monomers: acrylonitrile, butadiene, and styrene. (Each monomer possesses different properties: acrylonitrile exhibits high strength, thermal stability, and chemical stability; butadiene possesses toughness and impact resistance; and styrene possesses ease of processing, high gloss, and high strength. Polymerization of these three monomers produces a two-phase terpolymer: a continuous styrene-acrylonitrile phase and a polybutadiene rubber dispersion phase.)
Morphologically, ABS is a non-crystalline material with high mechanical strength and excellent overall properties of being strong, tough, and resilient. It is an amorphous polymer and a general-purpose engineering plastic, available in various varieties and with wide applications; it is also known as a "general-purpose plastic" (MBS is called transparent ABS). ABS is hygroscopic, with a specific gravity of 1.05 g/cm³ (slightly heavier than water), low shrinkage (0.60%), dimensional stability, and ease of molding and processing.
Properties of ABS mainly depend on ratio of three monomers and molecular structure of two phases. This allows for great flexibility in product design, resulting in hundreds of different qualities of ABS materials on market. These materials of varying qualities offer different properties, such as medium to high impact resistance, low to high smoothness, and high-temperature torsion characteristics. ABS material boasts excellent processability, superior appearance, low creep, excellent dimensional stability, and high impact strength.
ABS is a light yellow, granular or bead-like opaque resin. It is non-toxic, odorless, and has low water absorption. It possesses excellent comprehensive physical and mechanical properties, such as good electrical properties, abrasion resistance, dimensional stability, chemical resistance, surface gloss, is easy to process and mold. Its disadvantages include poor weather resistance, poor heat resistance, and flammability.

 

2. Processing Characteristics of ABS
2.1 ABS has high hygroscopicity and moisture sensitivity. Before molding, it must be thoroughly dried and preheated (at least 2 hours at 80-90℃) to control moisture content below 0.03%.
2.2 Melt viscosity of ABS resin is less sensitive to temperature (unlike other amorphous resins).
While injection temperature of ABS is slightly higher than that of PS, it doesn't have same wide heating range. Blindly increasing temperature cannot lower its viscosity; instead, increasing screw speed or injection pressure can improve its flowability. A processing temperature of 190-235℃ is generally suitable.
2.3 ABS has a medium melt viscosity, higher than PS, HIPS, and AS, requiring higher injection pressure (500-1000 bar) for injection.
2.4 ABS material responds better to medium-high injection speeds (unless shape is complex or part is thin-walled requiring a higher injection speed). Air bubbles are prone to appear at sprue.
2.5 ABS has a relatively high molding temperature; its mold temperature is generally adjusted between 25-70℃.
When producing larger products, temperature of stationary mold (front mold) should generally be about 5℃ higher than that of moving mold (rear mold). (Mold temperature affects surface finish of molded part; lower temperatures result in lower surface finish.)
2.6 ABS should not remain in high-temperature barrel for too long (less than 30 minutes), otherwise it is prone to decomposition and yellowing.
3. Typical applications: Automobiles (dashboards, tool compartment doors, wheel covers, rearview mirror boxes, etc.), refrigerators, high-strength tools (hair dryers, blenders, food processors, lawnmowers, etc.), telephone housings, typewriter keyboards, recreational vehicles such as golf carts and snowmobiles, etc.

1. Properties of BS: BS is a butadiene-styrene copolymer. It has certain toughness and elasticity, low hardness (relatively soft), and good transparency. Specific gravity of BS material is 1.01 f/cm³ (similar to water). This material is easy to color, has good fluidity, and is easy to mold.
2. Processing characteristics of BS: Processing temperature range for BS is generally 190-225℃, and mold temperature is better at 30-50℃. This material should be dried before processing. Due to its good fluidity, injection pressure and injection speed can be lower.

1. Properties of PMMA: PMMA is an amorphous polymer, commonly known as plexiglass. It has excellent transparency, good heat resistance (heat distortion temperature 98℃), and good impact resistance. Its products have moderate mechanical strength and low surface hardness, making them easily scratched by hard objects. Compared to PS, it is less brittle and has a specific gravity of 1.18 g/cm³.
PMMA possesses excellent optical properties and weather resistance. Its white light transmittance is as high as 92%. PMMA products have very low birefringence, making them particularly suitable for manufacturing DVDs, etc. PMMA exhibits room temperature creep. With increased load and time, stress cracking can occur.
2. Processing Characteristics of PMMA: PMMA has strict processing requirements. It is very sensitive to moisture and temperature, and must be thoroughly dried before processing (recommended drying conditions: 90℃, 2-4 hours). Its melt viscosity is relatively high, requiring molding at higher temperatures (225-245℃) and pressures. A mold temperature of 65-80℃ is preferable.
PMMA has poor stability; exposure to high temperatures or prolonged exposure to high temperatures will cause degradation. Screw speed should not be too high (around 60%). Thicker PMMA parts are prone to "voids," requiring a large gate and a "low material temperature, high mold temperature, slow injection" method.
3. Typical Applications: Automotive industry (signal lights, dashboards, etc.), pharmaceutical industry (blood containers, etc.), industrial applications (DVDs, light diffusers), consumer goods (beverage cups, stationery, etc.).

1. PE Properties: PE is the most produced plastic, characterized by its softness, non-toxicity, low price, ease of processing, good chemical resistance, resistance to corrosion, and difficulty in printing. PE is a typical crystalline polymer.
There are many types, commonly including LDPE (low-density polyethylene) and HDPE (high-density polyethylene), which are semi-transparent plastics with low strength and a specific gravity of 0.94 g/cm³ (less than water); and very low-density LLDPE resin (density below 0.910 g/cc; density of both LLDPE and LDPE is between 0.91 and 0.925).
LDPE is softer (commonly known as soft plastic), while HDPE, commonly known as rigid soft plastic, is harder than LDPE. It is a semi-crystalline material with a higher shrinkage rate after molding, ranging from 1.5% to 4%. It has poor light transmittance, high crystallinity, and is prone to environmental stress cracking. Cracking can be mitigated by using materials with very low flow properties to reduce internal stress. While it readily dissolves in hydrocarbon solvents at temperatures above 60℃, its resistance to dissolution is better than that of LDPE.
HDPE's high crystallinity results in high density, tensile strength, high-temperature torsion temperature, viscosity, and chemical stability. It also exhibits stronger impermeability than LDPE. PE-HD has lower impact strength. Its properties are primarily controlled by density and molecular weight distribution.
HDPE suitable for injection molding has a narrow molecular weight distribution. For densities of 0.91–0.925 g/cm³, we refer to it as Type I PE-HD; for 0.926–0.94 g/cm³, Type II HDPE; and for 0.94–0.965 g/cm³, Type III HDPE.
This material has excellent flow properties, with an MFR between 0.1 and 28. Higher molecular weight LDPE exhibits poorer flow properties but better impact strength. HDPE is prone to environmental stress cracking. Cracking can be mitigated by using materials with very low flow properties to reduce internal stress. HDPE is easily soluble in hydrocarbon solvents at temperatures above 60℃, but its resistance to dissolution is better than that of LDPE.
LDPE is a semi-crystalline material with a high shrinkage rate after molding, ranging from 1.5% to 4%.
LLDPE (linear low-density polyethylene) has higher tensile strength, puncture resistance, impact resistance, and tear resistance, making it suitable for film production. Its excellent resistance to environmental stress cracking, low-temperature impact, and warpage makes LLDPE attractive for pipe, sheet extrusion, and all molding applications. The latest application of LLDPE is as a lining for landfills and wastewater treatment plants.
2. Processing Characteristics of PE: The most significant characteristic of PE parts is their high molding shrinkage, making them prone to shrinkage and deformation. PE material has low water absorption and does not require drying. PE has a wide processing temperature range and is not easily decomposed (decomposition temperature is 320℃). With high pressure, part density is high, and shrinkage rate is relatively low.
PE has medium fluidity, requiring strict control of processing conditions and maintaining a constant mold temperature (40-60℃). Degree of crystallinity in PE is related to molding process conditions; it has a high solidification temperature, and lower mold temperatures result in lower crystallinity. During crystallization, anisotropic shrinkage causes internal stress concentration, making PE parts prone to deformation and cracking.
Placing the product in an 80℃ hot water bath can provide some pressure relief. During molding, a slightly higher material and mold temperature is preferable, while injection pressure should be kept relatively low to ensure part quality. Rapid and uniform mold cooling is crucial, as product will be quite hot upon demolding.
HDPE drying: No drying is necessary if stored properly. Melting temperature: 220~260℃. For materials with larger molecules, a melting temperature range of 200~250℃ is recommended.
Mold temperature: 50~95℃. Higher mold temperatures should be used for parts with wall thicknesses below 6mm, and lower mold temperatures for parts with wall thicknesses above 6mm. Part cooling should be uniform to minimize shrinkage differences. For optimal cycle time, cooling channel diameter should be no less than 8 mm, and distance from mold surface should be within 1.3d (where "d" is diameter of cooling channel).
Injection pressure: 700~1050 bar. Injection speed: High-speed injection is recommended. Runners and gates: Runner diameter should be between 4 and 7.5 mm, and runner length should be as short as possible. Various types of gates can be used, but gate length should not exceed 0.75 mm. This is particularly suitable for hot runner molds.

 

"Softness when stretched" characteristic of LLDPE is a disadvantage in blown film production; LLDPE blown film bubbles are not as stable as LDPE. Die gap must be widened to avoid reduced output due to high back pressure and melt fracture. Typical die gap dimensions for LDPE and LLDPE are 0.024–0.040 in and 0.060–0.10 in, respectively.
3. Typical Applications: LLDPE has penetrated most traditional polyethylene markets, including films, molding, pipes, and wires and cables. Leak-proof mulch films are a newly developed market for LLDPE. Mulch films, large extruded sheets, are used as liners for landfills and waste ponds to prevent leakage or contamination of surrounding areas.
For example, production of bags, garbage bags, elastic packaging, industrial liners, towel liners, shopping bags utilizes advantages of this resin after improvements in strength and toughness. Transparent films, such as bread bags, have traditionally been dominated by LDPE due to its superior turbidity.
However, blends of LLDPE and LDPE improve strength, puncture resistance, and stiffness of LDPE films without significantly affecting their transparency.
HDPE Applications: Refrigerator containers, storage containers, household kitchenware, sealing caps, etc.

1. Properties of PP: PP is a crystalline polymer. Among commonly used plastics, PP is the lightest, with a density of only 0.91 g/cm³ (less than water). Among general-purpose plastics, PP has the best heat resistance, with a heat distortion temperature of 80-100℃, allowing it to be boiled in water. PP has good stress cracking resistance and a high flexural fatigue life, commonly known as "unbreakable rubber."
PP's overall performance is superior to PE. PP products are lightweight, have good toughness, and good chemical resistance. PP's disadvantages include low dimensional accuracy, insufficient rigidity, poor weather resistance, and susceptibility to "copper damage." It exhibits post-shrinkage, and after demolding, it is prone to aging, becoming brittle, and deforming. PP has always been a major raw material for fiber manufacturing due to its colorability, wear resistance, chemical resistance, and favorable economic conditions.
PP is a semi-crystalline material. It is harder and has a higher melting point than PE. Because homopolymer PP becomes very brittle above 0℃, many commercial PP materials are random copolymers with 1-4% ethylene or block copolymers with higher ethylene content. Copolymer-type PP materials have lower heat distortion temperature (100℃), lower transparency, lower gloss, and lower rigidity, but higher impact strength. Strength of PP increases with increasing ethylene content.
PP has a Vicat softening temperature of 150℃. Due to its high crystallinity, this material has excellent surface stiffness and scratch resistance.
PP does not suffer from environmental stress cracking. Typically, PP is modified by adding glass fibers, metal additives, or thermoplastic elastomers. Melt flow rate (MFR) of PP ranges from 1 to 40. Low MFR PP materials have better impact resistance but lower tensile strength. For materials with same MFR, copolymer-type PP has higher strength than homopolymer-type PP.
Due to crystallization, PP has a relatively high shrinkage rate, typically 1.8% to 2.5%. Furthermore, directional uniformity of shrinkage is much better than materials like HDPE. Adding 30% glass fiber additives can reduce shrinkage rate to 0.7%.
Both homopolymer and copolymer PP materials possess excellent resistance to moisture absorption, acid and alkali corrosion, and solvents. However, they are not resistant to solvents containing aromatic hydrocarbons (such as benzene) or chlorinated hydrocarbons (carbon tetrachloride). PP also does not retain its antioxidant properties at high temperatures like PE.
2. Processing Characteristics of PP: PP exhibits good fluidity and molding performance at its melting temperature. PP processing has two main characteristics:
Firstly, viscosity of PP melt decreases significantly with increasing shear rate (with relatively little influence from temperature);
Secondly, its high degree of molecular orientation results in a large shrinkage rate. Optimal processing temperature for PP is 220-275℃, ideally not exceeding approximately 275℃. It has good thermal stability (decomposition temperature is 310℃), but at high temperatures (270-300℃), prolonged exposure in injection barrel may lead to degradation. Because viscosity of PP decreases significantly with increasing shear rate, increasing injection pressure and injection speed will improve its fluidity, reduce shrinkage and indentation. Mold temperature (40~80℃), 50℃ is recommended.
Degree of crystallinity is mainly determined by mold temperature and should be controlled within range of 30-50℃. PP melt can pass through very narrow mold gaps, resulting in burrs. PP absorbs a large amount of heat of fusion during melting (high specific heat), making product quite hot after demolding.
PP material does not require drying during processing. PP has lower shrinkage and crystallinity than PE. High injection speed is generally used to minimize internal pressure. If surface defects appear on product, low-speed injection at a higher temperature should be used. Injection pressure: up to 1800 bar.
Runners and gates: For cold runners, typical runner diameter range is 4~7mm. A fully circular sprue and runner are recommended. All types of gates can be used. Typical gate diameter range is 1~1.5mm, but gates as small as 0.7mm can also be used. For edge gates, minimum gate depth should be half wall thickness; minimum gate width should be at least twice the wall thickness. PP materials can fully utilize hot runner systems.
PP has always been a primary raw material for fiber manufacturing due to its colorability, abrasion resistance, chemical resistance, and favorable economic conditions.
3. Typical Applications: Automotive industry (primarily using PP with metal additives: mudguards, ventilation ducts, fans, etc.), equipment (dishwasher door liners, dryer ventilation ducts, washing machine frames and covers, refrigerator door liners, etc.), consumer goods (lawn and garden equipment such as lawnmowers and sprinklers, etc.).
Injection molding is the second largest market for PP homopolymers, including containers, seals, automotive applications, household goods, toys, and many other consumer and industrial end uses.

1. PA Properties: PA is also a crystalline plastic (nylon is a tough, angular, translucent or milky-white crystalline resin). As an engineering plastic, nylon typically has a molecular weight of 15,000-30,000, there are many varieties. Commonly used in injection molding are nylon 6, nylon 66, nylon 1010, and nylon 610.
Nylon possesses toughness, wear resistance, and self-lubricating properties. Its advantages include high organic mechanical strength, good toughness, fatigue resistance, smooth surface, high softening point, heat resistance, low coefficient of friction, wear resistance, self-lubrication, shock absorption and sound damping, oil resistance, resistance to weak acids, alkalis and common solvents, good electrical insulation, self-extinguishing properties, non-toxicity, odorless, and good weather resistance.
Disadvantages include high water absorption, poor dyeability, affecting dimensional stability and electrical properties. Fiber reinforcement can reduce water absorption, allowing it to operate under high temperature and high humidity conditions. Nylon has excellent compatibility with glass fiber (can be used for extended periods below 100℃), corrosion resistance, lightweight parts, and ease of molding. Main disadvantages of PA (polyvinyl chloride) include: high water absorption, strict injection molding requirements, poor dimensional stability, and hot products due to its high specific heat.
PA66 is PA series with the highest mechanical strength and widest application. Its high crystallinity results in high rigidity, hardness, and heat resistance. PA1010, first developed in China in 1958, is semi-transparent, has a low specific gravity, high elasticity and flexibility, lower water absorption than PA66, and reliable dimensional stability.
Nylon 66 has the highest hardness and rigidity among nylons, but the lowest toughness. Order of toughness for various nylons is: PA66 < PA66/6 < PA6 < PA610 < PA11 < PA12. Nylon has a ULS 44-2 flammability rating, an oxygen index of 24-28, and a decomposition temperature >299℃, with spontaneous combustion occurring at 449-499℃. Nylon has good melt flowability, allowing for product wall thicknesses as small as 1mm.
Main technical performance indicators and applications of PA are shown in Table 1.
Table 1: Main Technical Performance Indicators of Polyamide (Nylon)

2. Processing Characteristics of PA
2.1. PA is hygroscopic and must be thoroughly dried before processing. Moisture content should be controlled below 0.3%. Properly dried raw materials result in high-gloss finished products; otherwise, they are relatively rough. PA does not gradually soften with increasing temperature; instead, it softens within a narrow temperature range close to its melting point. Melting point is very distinct, and once temperature is reached, it will flow (unlike PS, PE, PP, etc.).
PA has a much lower viscosity than other thermoplastics, and its melting temperature range is narrow (only around 5℃). PA has good flowability, making it easy to fill molds and avoid burrs. "Drooling" is prone to occur at nozzle, requiring a larger suction area.
PA has a high melting point and a high solidification point. Molten material can solidify at any time within mold due to a drop in temperature below melting point, hindering completion of molding. Therefore, high-speed injection molding is necessary (especially for thin-walled or long-flow parts). Nylon molds require adequate venting.
PA has poor thermal stability in molten state and is easily degraded. Barrel temperature should not exceed 300℃, and heating time of molten material in barrel should not exceed 30 minutes. PA has high requirements for mold temperature; its crystallinity can be controlled by adjusting mold temperature to obtain desired properties.

 

Optimal mold temperature for PA is 50-90℃. Processing temperature for PA1010 is 220-240℃, and for PA66, it is 270-290℃. PA products sometimes require annealing or conditioning depending on quality requirements.
2.2. PA12: Before processing, humidity of polyamide 12 or nylon 12 should be below 0.1%. If material is stored exposed to air, it is recommended to dry it in hot air at 85℃ for 4-5 hours. If material is stored in a sealed container, it can be used directly after 3 hours of temperature equilibration. Melting temperature is 240-300℃; for materials with ordinary properties, it should not exceed 310℃, and for materials with flame-retardant properties, it should not exceed 270℃.
Mold Temperature: 30-40℃ for unreinforced materials, 80-90℃ for thin-walled or large-area components, and 90-100℃ for reinforced materials. Increasing temperature will increase crystallinity of material. Precise control of mold temperature is crucial for PA12. Injection Pressure: Up to 1000 bar (low holding pressure and high melt temperature are recommended). Injection Speed: High speed (better for materials with glass additives).
Runners and Gates: For unreinforced materials, due to their lower viscosity, runner diameter should be around 30 mm. For reinforced materials, a large runner diameter of 5-8 mm is required. All runner shapes should be circular. Gate should be as short as possible.
Various types of gates can be used. Avoid using small gates for large parts to prevent excessive pressure or shrinkage. Gate thickness should ideally be equal to part thickness. If using a submarine gate, a minimum diameter of 0.8 mm is recommended. Hot runner molds are effective, but require precise temperature control to prevent material leakage or solidification at nozzle. If using a hot runner, gate size should be smaller than that of a cold runner.
2.3. PA6 Polyamide 6 or Nylon 6: Because PA6 readily absorbs moisture, special care must be taken with drying before processing. If material is supplied in waterproof packaging, container should be kept sealed. If humidity is greater than 0.2%, drying in hot air above 80℃ for 16 hours is recommended. If material has been exposed to air for more than 8 hours, vacuum drying at 105℃ for at least 8 hours is recommended.
Melting temperature: 230~280℃, 250~280℃ for reinforced varieties. Mold temperature: 80~90℃. Mold temperature significantly affects crystallinity, which in turn affects mechanical properties of molded part. Crystallinity is important for structural components, therefore a mold temperature of 80~90℃ is recommended.
For thin-walled parts with long flow paths, higher mold temperatures are also recommended. Increasing mold temperature can improve strength and rigidity of molded part, but it reduces toughness. If wall thickness is greater than 3mm, a low-temperature mold of 20~40℃ is recommended. For glass-reinforced materials, mold temperature should be greater than 80℃. Injection pressure: Generally between 750~1250 bar (depending on material and product design).
Injection speed: High speed (slightly lower for reinforced materials). Runners and gates: Due to the very short solidification time of PA6, gate location is very important. Gate diameter should not be less than 0.5*t (where t is thickness of molded part). If using a hot runner system, gate size should be smaller than with a conventional runner system, as hot runner helps prevent premature solidification of material. If using a submarine gate, minimum gate diameter should be 0.75 mm.
2.4. PA66 Polyamide 66 or Nylon 66: If material is sealed before processing, drying is not necessary. However, if storage container has been opened, drying in hot air at 85℃ is recommended. If humidity is greater than 0.2%, vacuum drying at 105℃ for 12 hours is also required.
Melting temperature: 260~290℃. For products with glass additives, 275~280℃. Melting temperature should not exceed 300℃. Mold temperature: 80℃ is recommended. Mold temperature will affect crystallinity, which in turn affects physical properties of product.
For thin-walled parts, if a mold temperature below 40℃ is used, crystallinity of part will change over time. To maintain geometric stability of part, annealing is required. Injection pressure: Typically 750~1250 bar, depending on material and product design. Injection speed: High speed (slightly lower for reinforced materials).
Runners and gates: Due to short solidification time of PA66, gate location is crucial. Gate diameter should not be less than 0.5*t (where t is thickness of plastic part). If using a hot runner, gate size should be smaller than with a conventional runner, as hot runner helps prevent premature solidification. If using a submarine gate, minimum gate diameter should be 0.75 mm.
3. Typical applications:
3.1. PA12 (Polyamide 12 or Nylon 12): Water meters and other commercial equipment, cable sleeves, mechanical cams, sliding mechanisms, and bearings, etc.
3.2. PA6 (Polyamide 6 or Nylon 6): Widely used in structural components due to its excellent mechanical strength and rigidity. Also used in bearing manufacturing due to its excellent wear resistance.
3.3. PA66 (Polyamide 66 or Nylon 66) Applications: Compared to PA6, PA66 is more widely used in automotive industry, instrument housings, other products requiring impact resistance and high strength.

1. POM Properties: POM is a crystalline plastic with excellent rigidity, commonly known as "polyamide 66". POM is a tough and elastic material that retains excellent creep resistance, geometric stability, and impact resistance even at low temperatures. It possesses excellent fatigue resistance, creep resistance, abrasion resistance, and heat resistance.
POM is not easily hygroscopic, has a specific gravity of 1.42 g/cm³, and a shrinkage rate of 2.1% (POM's high crystallinity results in a relatively high shrinkage rate, reaching 2%~3.5%, which is significant; different reinforcing materials have different shrinkage rates). Dimensional control is difficult, and heat distortion temperature is 172℃. POM exists in both homopolymer and copolymer forms.
Homopolymer materials have excellent tensile strength and fatigue strength, but are not easy to process. Copolymer materials exhibit excellent thermal and chemical stability, are easy to process. Both homopolymers and copolymers are crystalline, do not readily absorb moisture.
2. Processing Characteristics of POM POM does not require drying before processing, but preheating (around 100℃) during processing is beneficial for product dimensional stability. POM has a narrow processing temperature range (195-215℃). Prolonged residence time in barrel or temperatures exceeding 220℃ will cause decomposition (homogeneities: 190-230℃; copolymers: 190-210℃). Screw speed should not be too high, and residual weight should be low.
POM products have significant shrinkage (higher mold temperatures can be used to reduce post-molding shrinkage), making them prone to shrinkage or deformation. POM has a high specific heat, requiring high mold temperatures (80-105℃). Products are very hot after demolding; care must be taken to prevent burns. Injection pressure should be 700-1200 bar. POM is best processed under medium pressure, medium speed, and high mold temperature conditions.
Runners and gates can be of any type. If using a tunnel gate, a shorter type is preferred. Hot runners are recommended for homopolymer materials. For copolymer materials, both internal and external hot runners can be used.
3. Typical Applications: POM has a very low coefficient of friction and excellent geometric stability, making it particularly suitable for gears and bearings. Due to its high-temperature resistance, it is also used in piping components (pipe valves, pump housings), lawn equipment, etc.

1. PC Performance: Polycarbonate is a thermoplastic resin containing —[O-R-O-CO]— linkages in its molecular chain. Based on different ester groups in its molecular structure, it can be classified into aliphatic, alicyclic, and aliphatic-aromatic types. Among these, aromatic polycarbonates are of practical value, with bisphenol A type polycarbonate being the most important, typically with a molecular weight of 30,000-100,000.
PC (polycarbonate) is an amorphous, odorless, non-toxic, highly transparent colorless or slightly yellow thermoplastic engineering plastic with excellent physical and mechanical properties, especially outstanding impact resistance, high tensile strength, flexural strength, and compressive strength; it also has good toughness, good heat and weather resistance, is easy to color, and has low water absorption.
PC has a heat distortion temperature of 135-143℃, low creep, and dimensional stability; it possesses good heat and low-temperature resistance, exhibiting stable mechanical properties, dimensional stability, electrical properties, flame retardancy over a wide temperature range, and can be used long-term at -60~120℃; it has no obvious melting point, melting at 220-230℃; due to high rigidity of its molecular chains, resin melt viscosity is high; it has low water absorption and low shrinkage (generally 0.1%~0.2%), high dimensional accuracy, good dimensional stability, and low film permeability; it is a self-extinguishing material; it is light-stable but not resistant to ultraviolet light, and has good weather resistance;

 

It is oil-resistant and acid-resistant, but not resistant to strong alkalis, oxidizing acids, amines, and ketones. It is soluble in chlorinated hydrocarbons and aromatic solvents, possessing antibacterial properties, flame retardant properties, anti-fouling properties. However, long-term immersion in water can easily cause hydrolysis and cracking. Its disadvantages include poor fatigue strength, susceptibility to stress cracking, poor solvent resistance, poor flowability, and poor abrasion resistance. PC can be injection molded, extruded, compressed, blow molded, thermoformed, printed, bonded, coated, and machined, with injection molding being the most important processing method.
2. Processing Characteristics of PC: PC material is sensitive to temperature; its melt viscosity decreases significantly with increasing temperature, and its flow rate increases. It is not sensitive to pressure. To improve its flowability, heating is necessary. PC material must be thoroughly dried before processing (around 120℃ for 3-4 hours), and moisture content should be controlled below 0.02%. Trace amounts of moisture at high temperatures will cause finished product to have a cloudy color, silver streaks, and bubbles. PC has considerable forced elastic deformation capacity at room temperature and high impact toughness, therefore it can be cold-formed through cold pressing, cold drawing, and cold rolling.
PC material is best molded under conditions of high material temperature, high mold temperature, and high pressure at low speed. Low-speed injection is used for smaller gates, while high-speed injection is used for other types of gates. A mold temperature of around 80-110℃ is preferable, and a molding temperature of 280-320℃ is ideal. PC products are prone to surface defects such as air bubbles and air streaks at the sprue, and have high internal residual stress, making them susceptible to cracking.
Therefore, molding and processing requirements for PC material are relatively high. PC material has a low shrinkage rate (0.5%) and minimal dimensional changes. Internal stress in PC extrusion products can be eliminated through annealing. For extrusion, molecular weight of PC should be greater than 30,000, a gradually increasing compression screw with a length-to-diameter ratio of 1:18~24 and a compression ratio of 1:2.5 should be used. High-quality, high-transparency bottles can be produced using extrusion blow molding, injection-blow molding, and injection-stretch-blow molding.
3. Typical Applications: Three main application areas of PC are glass assembly, automotive industry, electronics and electrical appliance industry. Other applications include industrial machinery parts, optical discs, consumer electronics, office equipment such as computers, medical and healthcare products, films, leisure and protective equipment, etc.

1. EVA Properties: EVA is an amorphous plastic, non-toxic, with a specific gravity of 0.95 g/cm³ (lighter than water). Its products have poor surface gloss, good elasticity, are relatively soft and lightweight, have low mechanical strength, good flowability, are easy to process and mold. It has a relatively large shrinkage rate (2%). EVA can be used as a carrier for color masterbatches.
2. EVA Processing Characteristics: EVA has a low molding processing temperature (160-200℃) with a wide range. Its mold temperature is low (20-45℃). Material must be dried before processing (drying temperature 65℃). During EVA processing, mold temperature and material temperature should not be too high, otherwise surface will be relatively rough (not smooth). EVA products tend to stick to front mold; therefore, it's best to design cold slug well at main runner with a pull-tab design. They decompose easily at temperatures exceeding 250℃. EVA is best processed using "low temperature, medium pressure, and medium speed" conditions.

1. PVC Properties: PVC is an amorphous plastic with poor thermal stability and is easily decomposed by heat (improper melting temperature parameters will lead to material decomposition). PVC is difficult to burn (good flame retardancy), has high viscosity, poor flowability, high strength, good weather resistance, and excellent geometric stability. Stabilizers, lubricants, processing aids, colorants, impact modifiers, and other additives are often added to PVC materials in practical applications.
There are many types of PVC, including soft, semi-rigid, and rigid PVC. Its density is 1.1-1.3 g/cm³ (heavier than water), with a high shrinkage rate (1.5-2.5%) and a relatively low shrinkage rate, typically 0.2-0.6%. PVC products have poor surface gloss (although a transparent rigid PVC developed in the US recently rivals PC). PVC is highly resistant to oxidizing agents, reducing agents, and strong acids. However, it can be corroded by concentrated oxidizing acids such as concentrated sulfuric acid and concentrated nitric acid, and is not suitable for contact with aromatic hydrocarbons or chlorinated hydrocarbons.
2. Processing characteristics of PVC: Narrower processing temperature range than conventional PVC (160-185℃), more difficult processing, higher process requirements, and generally no drying required during processing (if drying is necessary, it should be done at 60-70℃). Lower mold temperature (20-50℃).
PVC processing is prone to air bubbles and black streaks, so strict control of processing temperature (185~205℃) is essential. Injection pressure can reach up to 1500 bar, and holding pressure up to 1000 bar. To avoid material degradation, a suitable injection speed should be used, screw speed should be low (below 50%), residual volume should be small, and back pressure should not be too high.
Good mold venting is crucial. PVC material should not remain in high-temperature barrel for more than 15 minutes. For PVC, a large injection volume is recommended, and molding under "medium pressure, slow speed, and low temperature" conditions is preferable. PVC products are prone to sticking to front mold; mold opening speed (first stage) should not be too fast. A pull-tab type gate at cold slug well in runner is recommended. Before stopping injection molding of PVC, barrel should be cleaned with PS sprue material (or PE material) to prevent PVC decomposition and generation of high hydration (Hd), which corrodes screw and barrel inner wall. All conventional gates can be used.
For machining smaller parts, it is best to use a pin gate or submarine gate; for thicker parts, a fan gate is preferable. Minimum diameter of a pin gate or submarine gate should be 1mm; thickness of a fan gate should not be less than 1mm.
3. Typical Applications: Water supply pipes, household pipes, building wall panels, commercial machine housings, electronic product packaging, medical devices, food packaging, etc.

1. Properties of PPO: Polyphenylene oxide is poly2,6-dimethyl-1,4-phenylene ether, also known as polyphenylene oxide, or simply Polyphenylene oxide (PPO). Modified polyphenylene oxide is polyphenylene oxide modified with polystyrene or other polymers, abbreviated as MPPO.
PPO (NORLY) is an engineering plastic with excellent overall performance. It has higher hardness than PA, POM, and PC, high mechanical strength, good rigidity, good heat resistance (heat distortion temperature 126℃), high dimensional stability (shrinkage rate 0.6%), and low water absorption (less than 0.1%). Its disadvantages include instability under ultraviolet light, high price, and low usage.
PPO is non-toxic, transparent, and has a low relative density. It possesses excellent mechanical strength, resistance to stress relaxation, creep resistance, heat resistance, water resistance, and water vapor resistance. It has good electrical properties over a wide temperature and frequency range, is non-hydrolyzable, has low molding shrinkage, is flame-retardant and self-extinguishing, but has poor resistance to inorganic acids, alkalis, aromatic hydrocarbons, halogenated hydrocarbons, and oils. It is prone to swelling or stress cracking. Its main drawback is poor melt flowability, making processing and molding difficult. In practical applications, most PPO is MPPO (PPO blends or alloys). Modifying PPO with PS can significantly improve processing performance, stress cracking resistance, and impact resistance, while reducing costs, although heat resistance and gloss are slightly reduced. Modified polymers include PS (including HIPS), PA, PTFE, PBT, PPS, and various elastomers, polysiloxanes, PS-modified PPO paraffin wax. MPPO is the largest product category and the most widely used general-purpose engineering plastic alloy. Major MPPO varieties include PPO/PS, PPO/PA/elastomer, and PPO/PBT elastomer alloys.
2. Processing characteristics of PPO: PPO has high melt viscosity, poor flowability, and requires demanding processing conditions. Before processing, it needs to be dried at 100-120℃ for 1-2 hours. Molding temperature is 270-320℃, and mold temperature should ideally be controlled at 75-95℃. It requires molding under conditions of "high temperature, high pressure, and high speed." During injection molding process, jetting patterns (snake-like patterns) are easily generated in front of sprue; a larger sprue channel is preferable.
For standard molded parts, minimum thickness ranges from 0.060 to 0.125 inches, while for structural foam parts, minimum thickness ranges from 0.125 to 0.250 inches. Their flammability ranges from UL94 HB to V-O.

 

3. Typical Applications: PPO and MPPO can be processed using various methods such as injection molding, extrusion, blow molding, compression molding, foaming, electroplating, vacuum coating, and printing. Due to their high melt viscosity, processing temperatures are relatively high.
PPO and MPPO are mainly used in electronics, automobiles, home appliances, office equipment, and industrial machinery, utilizing MPPO's heat resistance, impact resistance, dimensional stability, scratch resistance, and peeling resistance. Their paintability and electrical properties make them suitable for automotive dashboards, radiator grilles, speaker grilles, consoles, fuse boxes, relay boxes, connectors, and wheel covers. In electronics industry, they are widely used to manufacture connectors, coil winding spools, switches, relays, tuning equipment, large electronic displays, variable capacitors, battery components, microphones, and other parts.
In home appliances, they are used for components in televisions, cameras, videotapes, tape recorders, air conditioners, heaters, rice cookers, etc. They can also be used for external parts and components in copiers, computer systems, printers, fax machines, etc. Additionally, they can be used for camera housings and components, water pumps, blowers, silent gears, pipes, valve bodies, surgical instruments, sterilizers, and other medical device components.
Large-scale blow molding is suitable for producing large automotive parts such as spoilers and bumpers. Low-foaming molding is suitable for manufacturing large products with high rigidity, dimensional stability, excellent sound absorption, and complex internal structures, such as various machine housings, bases, and internal supports. It offers high design freedom and lightweight products.

1. PBT Properties: PBT is one of the toughest engineering thermoplastics. It is a semi-crystalline material with excellent chemical stability, mechanical strength, electrical insulation properties, and thermal stability. These materials exhibit good stability under a wide range of environmental conditions. PBT has very low moisture absorption. Unreinforced PBT has a tensile strength of 50 MPa, while glass-added PBT has a tensile strength of 170 MPa. Excessive glass additives will cause material to become brittle.
PBT crystallizes very rapidly, which can lead to bending deformation due to uneven cooling. For materials with glass additives, shrinkage rate in flow direction can be reduced, but shrinkage rate perpendicular to flow direction is essentially same as that of ordinary materials.
Shrinkage rate of general PBT materials is between 1.5% and 2.8%. Materials containing 30% glass additives shrink between 0.3% and 1.6%. Melting point (225℃) and high-temperature distortion temperature are lower than PET materials. Vicat softening temperature is approximately 170℃. Glass transition temperature is between 22℃ and 43℃.
Due to PBT's high crystallization rate, its viscosity is very low, and cycle time for processing molded parts is generally also low.
2. PBT Processing Characteristics: Drying Treatment: This material is easily hydrolyzed at high temperatures, so pre-processing drying is crucial. Recommended air drying conditions are 120℃ for 6-8 hours, or 150℃ for 2-4 hours.
Humidity must be less than 0.03%. If using a desiccant dryer, recommended conditions are 150℃ for 2.5 hours. Processing temperature is 225-275℃, with 250℃ recommended. For unreinforced materials, mold temperature should be 40-60℃. Mold's cooling channels should be well-designed to minimize part warping. Heat dissipation must be rapid and uniform.
A 12mm diameter cooling channel is recommended. Use moderate injection pressure (up to 1500 bar) and the fastest possible injection speed (as PBT solidifies quickly). Runners and gates: Circular runners are recommended to increase pressure transmission (empirical formula: runner diameter = part thickness + 1.5mm).
Various types of gates can be used. Hot runners can also be used, but care must be taken to prevent material leakage and degradation. Gate diameter should be between 0.8 and 1.0 * t, where t is part thickness. For submarine gates, a minimum diameter of 0.75mm is recommended.
3. Typical applications: Household appliances (food processing blades, vacuum cleaner components, electric fans, hair dryer housings, coffee makers, etc.), electrical components (switches, motor housings, fuse boxes, computer keyboard keys, etc.), automotive industry (radiator grilles, body panels, wheel covers, door and window components, etc.).