Injection Molding Data – 20 Plastic Properties（Middle）

PA6 polyamide 6 or nylon 6

Typical application range: It is widely used in structural components due to its good mechanical strength and stiffness. It has good wear resistance and is also used to manufacture bearings.

Injection mold process conditions: drying treatment: since PA6 is easy to absorb moisture, special attention should be paid to drying before processing. If the material is supplied in waterproof packaging, the container shall be kept closed. If the humidity is greater than 0.2%, it is recommended to dry for 16 hours in hot air above 80C. If the material has been exposed to air for more than 8 hours, it is recommended to dry it under vacuum at 105C for more than 8 hours. Melting temperature: 230~280C, 250~280C for reinforced varieties. Mold temperature: 80~90C. Mold temperature significantly affects the crystallinity, which in turn affects the mechanical properties of plastic parts. The crystallinity is very important for structural parts, so it is recommended that the mold temperature be 80~90C. For thin-walled plastic parts with long process, it is also recommended to use higher mold temperature. Increasing the mold temperature can improve the strength and stiffness of the plastic parts, but reduce the toughness. If the wall thickness is greater than 3mm, it is recommended to use a low temperature mold of 20~40C. For glass reinforced materials, the mold temperature shall be greater than 80C. Injection pressure: generally between 750~1250bar (depending on material and product design). Injection speed: high speed (slightly lower for reinforced materials).

Runner and gate: Since the setting time of PA6 is very short, the gate position is very important. The hole diameter of the gate shall not be less than 0.5 * t (where t is the thickness of the plastic part). If hot runner is used, the gate size should be smaller than that of conventional runner, because hot runner can help prevent premature solidification of materials. If submerged gate is used, the minimum diameter of the gate shall be 0.75 mm.

Chemical and physical properties: The chemical and physical properties of PA6 are very similar to those of PA66. However, its melting point is low and the process temperature range is wide. Its impact resistance and solubility are better than PA66, but its moisture absorption is also stronger. Because many quality characteristics of plastic parts are affected by moisture absorption, this should be fully considered when using PA6 to design products. In order to improve the mechanical properties of PA6, various modifiers are often added. Glass is the most common additive. Sometimes synthetic rubber, such as EPDM and SBR, is added to improve impact resistance. For products without additives, the shrinkage of PA6 is between 1% and 1.5%. Adding glass fiber additive can reduce the shrinkage to 0.3%~0.5% (but it is slightly higher in the direction perpendicular to the flow). Shrinkage rate of forming assembly is mainly affected by crystallinity and moisture absorption of materials. The actual shrinkage is also a function of the plastic part design, wall thickness and other process parameters.

Typical application range of PA66 polyamide 66 or nylon 66: Compared with PA6, PA66 is more widely used in the automotive industry, instrument housings and other products requiring impact resistance and high strength.

Injection mold process conditions: drying treatment: if the material is sealed before processing, then there is no need to dry. However, if the storage container is opened, it is recommended to dry it in hot air at 85C. If the humidity is greater than 0.2%, vacuum drying at 105C for 12 hours is also required. Melting temperature: 260~290C. The product of glass additive is 275~280C. The melting temperature shall not be higher than 300C. Mold temperature: 80C is recommended. The mold temperature will affect the crystallinity, which will affect the physical properties of the product. For thin-walled plastic parts, if the mold temperature is lower than 40C, the crystallinity of the plastic parts will change with time. In order to maintain the geometric stability of the plastic parts, annealing treatment is required. Injection pressure: usually 750~1250bar, depending on material and product design. Injection speed: high speed (lower for reinforced materials). Runner and gate: Since the setting time of PA66 is very short, the gate position is very important. The hole diameter of the gate shall not be less than 0.5 * t (where t is the thickness of the plastic part). If hot runner is used, the gate size should be smaller than that of conventional runner, because hot runner can help prevent premature solidification of materials. If submerged gate is used, the minimum diameter of the gate shall be 0.75 mm.

Chemical and physical properties: PA66 has a high melting point in polyamide materials. It is a semi crystalline crystalline material. PA66 can also maintain strong strength and stiffness at higher temperatures. PA66 still has hygroscopicity after molding, and its degree mainly depends on the composition of the material, wall thickness and environmental conditions. In product design, the influence of moisture absorption on geometric stability must be considered. In order to improve the mechanical properties of PA66, various modifiers are often added. Glass is the most common additive. Sometimes synthetic rubber, such as

EPDM and SBR, is added to improve impact resistance. The viscosity of PA66 is low, so the liquidity is good (but not as good as PA6). This property can be used to process very thin components. Its viscosity is very sensitive to temperature changes. The shrinkage of PA66 is between 1% and 2%, and the addition of glass fiber additive can reduce the shrinkage to 0.2% and 1%. The shrinkage rate is different in the flow direction and the direction perpendicular to the flow direction. PA66 is resistant to many solvents, but weak to acids and other chlorinating agents.

Typical application scope of PBT: household appliances (food processing blades, vacuum cleaner elements, electric fans, hair dryer shells, coffee containers, etc.), electrical components (switches, motor housings, fuse boxes, computer keyboard keys, etc.), and automobile industry (radiator grilles, body panels, wheel covers, door and window components, etc.).

Injection mold process conditions: drying treatment: this material is easy to hydrolyze at high temperatures, so drying treatment before processing is very important. The recommended drying conditions in air are 120C, 6-8 hours, or 150C, 2-4 hours. The humidity must be less than 0.03%. If the moisture absorption dryer is used for drying, the recommended condition is 150C, 2.5 hours) Melting temperature: 225~275C, recommended temperature: 250C. Mold temperature: 40~60C for unreinforced materials. The cooling channel of the mold should be well designed to reduce the bending of the plastic parts. The loss of heat must be fast and uniform. It is recommended that the diameter of the mold cooling channel be 12mm. Injection pressure: medium (up to 1500bar). Injection speed: The injection speed should be as fast as possible (because PBT solidifies quickly). Runner and gate: it is recommended to use circular runner to increase pressure transmission (empirical formula: runner diameter=plastic part thickness+1.5mm). Various types of gates can be used. Hot runner can also be used, but pay attention to prevent material leakage and degradation. The gate diameter should be 0.8~1.0 * t, where t is the thickness of the plastic part. For submerged gates, a minimum diameter of 0.75 mm is recommended.

Chemical and physical properties:

PBT is one of the toughest engineering thermoplastic materials. It is a semi crystalline material with excellent chemical stability, mechanical strength, electrical insulation characteristics and thermal stability. These materials have good stability in a wide range of environmental conditions. The moisture absorption property of PBT is very weak. The tensile strength of non reinforced PBT is 50MPa, and that of glass additive PBT is 170MPa. Excessive glass additives will cause the material to become brittle. PBT; Crystallization is rapid, which will lead to bending deformation due to uneven cooling. For materials with glass additives, the shrinkage in the flow direction can be reduced, but the shrinkage in the vertical direction of the flow direction is basically the same as that of ordinary materials. Generally, the shrinkage of materials is between 1.5% and 2.8%. The shrinkage of the material containing 30% glass additive is between 0.3% and 1.6%. The melting point (225% C) and high temperature deformation temperature are lower than PET materials. Vicat softening temperature is about 170C. The glass transition temperature is between 22C and 43C. Because of the high crystallization rate of PBT, its viscosity is very low, and the cycle time of plastic processing is generally low.

Typical application scope of PC polycarbonate: electrical and commercial equipment (computer components, connectors, etc.), appliances (food processing machines, refrigerator drawers, etc.), transportation industry (front and rear lights of vehicles, dashboard, etc.).

Injection mold process conditions: drying treatment: PC material has hygroscopicity, and drying before processing is very important. The recommended drying conditions are 100C to 200C for 3-4 hours. The humidity before processing must be less than 0.02%. Melting temperature: 260~340C. Mold temperature: 70~120C. Injection pressure: Use high injection pressure as much as possible. Injection speed: Use low speed injection for smaller gates and high speed injection for other types of gates.

Chemical and physical properties: PC is an amorphous engineering material, which has particularly good impact strength, thermal stability, glossiness, bacterial inhibition, flame retardancy and pollution resistance. The notch Izod impact strength of PC is very high, and the shrinkage is very low, generally 0.1%~0.2%. PC has good mechanical properties, but poor flow characteristics, so the injection process of this material is difficult. When selecting PC materials of what quality, the final expectation of the product should be taken as the benchmark. If high impact resistance is required for plastic parts, PC materials with low flow rate shall be used; On the contrary, PC materials with high flow rate can be used to optimize the injection process.

Chemical and physical properties: PC is an amorphous engineering material, which has particularly good impact strength, thermal stability, glossiness, bacterial inhibition, flame retardancy and pollution resistance. The notch Izod impact strength of PC is very high, and the shrinkage is very low, generally 0.1%~0.2%. PC has good mechanical properties, but poor flow characteristics, so the injection process of this material is difficult. When selecting PC materials of what quality, the final expectation of the product should be taken as the benchmark. If high impact resistance is required for plastic parts, PC materials with low flow rate shall be used; On the contrary, PC materials with high flow rate can be used to optimize the injection process.

Typical application scope of PET polyethylene terephthalate: automobile industry (structural components such as reflector box, electrical components such as headlight reflector, etc.), electrical components (motor housing, electrical connectors, relays, switches, microwave oven internal components). Industrial applications (pump housings, hand instruments, etc.).

Injection mold process conditions: drying treatment: drying treatment before processing is necessary, because PET has strong moisture absorption. The recommended drying condition is 120~165C, 4 hours of drying. The humidity shall be less than 0.02%. Melting temperature: 265~280C for unfilled type; For glass filling type: 275~290C. Mold temperature: 80~120C. Injection pressure: 300~1300bar. Injection speed: higher injection speed can be used without causing embrittlement. Runners and Gates: All generic types of gates can be used. The gate size shall be 50-100% of the thickness of the plastic part.

Chemical and physical properties: the glass transition temperature of PET is about 165C, and the crystallization temperature range of the material is 120~220C. PET has strong hygroscopicity at high temperature. For glass fiber reinforced PET materials, bending deformation is very easy to occur at high temperatures. The crystallization degree of the material can be improved by adding crystallization reinforcement agent. Transparent products processed with PET have glossiness and thermal distortion temperature. Special additives such as mica can be added to PET to minimize bending deformation. If a lower mold temperature is used, transparent products can also be obtained using unfilled PET materials

Typical application scope of PMMA polymethyl methacrylate: automobile industry (signal light equipment, instrument panel, etc.), pharmaceutical industry (blood storage container, etc.), industrial application (video disk, light scattering device), and consumer goods (beverage cup, stationery, etc.).

Injection mold process conditions: drying treatment: PMMA is hygroscopic, so drying treatment before processing is necessary. The recommended drying condition is 90C for 2-4 hours. Melting temperature: 240~270C. Mold temperature: 35~70C. Injection speed: medium

Chemical and physical properties: PMMA has excellent optical properties and weather resistance. The penetrability of white light is up to 92%. PMMA products have very low birefringence, especially suitable for making video discs. PMMA has room temperature creep characteristics. With the increase of load and time, stress cracking may occur. PMMA has good impact resistance. The shrinkage is about 0.5%.

Typical application range of POM polyoxymethylene: POM has very low friction coefficient and good geometric stability, especially suitable for making gears and bearings. Because of its high temperature resistance, it is also used for pipeline devices (valves, pump shells), lawn equipment, etc.

Injection mold process conditions: drying treatment: if the material is stored in a dry environment, drying treatment is usually not required. Melting temperature: 190~230C for homopolymer material; The copolymer material is 190~210C. Mold temperature: 80~105C. In order to reduce the shrinkage after molding, higher mold temperature can be selected. Injection pressure: 700~1200bar Injection speed: medium or high injection speed. Runners and Gates: Any type of gate can be used. If a tunnel gate is used, a shorter type is preferred. Hot nozzle runner is recommended for homopolymer materials. For copolymer materials, either internal hot runner or external hot runner can be used.

Chemical and physical properties: POM is a tough and elastic material, which has good creep resistance, geometric stability and impact resistance even at low temperatures. POM has both homopolymer and copolymer materials. Homopolymer materials have good ductility and fatigue strength, but are not easy to process. Copolymer materials have good thermal stability, chemical stability and are easy to process. Both homopolymer materials and copolymer materials are crystalline materials and not easy to absorb water. The high crystallinity of POM results in a very high shrinkage, which can be as high as 2%~3.5%. There are different shrinkage rates for different reinforced materials.

Typical application scope of PP polypropylene: automobile industry (PP containing metal additives is mainly used: mudguard, vent pipe, fan, etc.), apparatus (dishwasher door liner, dryer vent pipe, washer frame and cover, refrigerator door liner, etc.), and daily consumer goods (lawn and garden equipment such as lawn mower and sprinkler, etc.).

Injection mold process conditions: drying treatment: drying treatment is not required if storage is appropriate. Melting temperature: 220~275C, do not exceed 275C. Mold temperature: 40~80C, 50C is recommended. The degree of crystallization is mainly determined by the mold temperature. Injection pressure: up to 1800bar. Injection speed: Generally, high speed injection can minimize the internal pressure. If defects appear on the surface of the product, low-speed injection molding at a higher temperature should be used. Runners and gates: For cold runners, typical runner diameters range from 4 to 7 mm. It is recommended to use round injection ports and flow channels. All types of gates can be used. Typical gate diameters range from 1 to 1.5mm, but gates as small as 0.7mm can also be used. For edge gates, the minimum gate depth shall be half of the wall thickness; The minimum gate width shall be at least twice the wall thickness. PP material can completely use hot runner system.

Chemical and physical properties: PP is a semi crystalline material. It is harder than PE and has a higher melting point. Since homopolymer type PP is very brittle when the temperature is higher than 0C, many commercial PP materials are irregular copolymers with 1~4% ethylene added or clamped copolymers with higher ethylene content. Copolymer type PP materials have lower thermal distortion temperature (100C), low transparency, low gloss and low rigidity, but have stronger impact strength. The strength of PP increases with the increase of ethylene content. Vicat softening temperature of PP is 150C. Because of its high crystallinity, this material has good surface stiffness and scratch resistance. PP has no environmental stress cracking problem. Generally, PP is modified by adding glass fiber, metal additives or thermoplastic rubber. The flow rate MFR of PP ranges from 1 to 40. PP with low MFR has better impact resistance but lower ductility. For the same MFR materials, the strength of copolymer type is higher than that of homopolymer type. Due to crystallization, the shrinkage of PP is quite high, generally 1.8~2.5%. And the directional uniformity of shrinkage is much better than that of PE-HD and other materials. The shrinkage can be reduced to 0.7% by adding 30% glass additive. Both homopolymer and copolymer PP materials have excellent moisture absorption resistance, acid and alkali corrosion resistance, and solubility resistance. However, it has no resistance to aromatic hydrocarbon (such as benzene) solvents, chlorinated hydrocarbon (carbon tetrachloride) solvents, etc. PP does not have the same oxidation resistance as PE at high temperatures.

Typical application scope of PPE: electrical equipment such as dishwasher and washing machine for court use, such as controller shell and optical fiber connector.

Process conditions of injection mold: drying treatment: it is recommended to dry for 2-4 hours at 100C before processing. Melting temperature: 240~320C. Mold temperature: 60~105C. Injection pressure: 600~1500bar. Runners and Gates: All types of gates can be used. It is particularly suitable for the use of handle gates and sector gates.

Chemical and physical properties: Generally, commercially available PPE or PPO materials are mixed with other thermoplastic materials such as PS, PA, etc. These mixtures are still commonly referred to as PPE or PPO. Mixed PPE or PPO has much better processing characteristics than pure materials. The change in properties depends on the ratio of mixtures such as PPO and PS. The mixed material mixed with PA 66 has stronger chemical stability at high temperature. The hygroscopicity of this material is very small, and its products have excellent geometric stability. The material mixed with PS is amorphous, while the material mixed with PA is crystalline. The shrinkage can be reduced to 0.2% by adding glass fiber additive. This material also has excellent electrical insulation properties and low thermal expansion coefficient. Its viscosity depends on the ratio of mixture in the material, and the increase of PPO ratio will lead to the increase of viscosity

Typical application scope of PS polystyrene: product packaging household utensils, trays, electrical (transparent containers, light scattering devices, insulating films, etc.).

Injection mold process conditions: drying treatment: drying treatment is usually not required unless improper storage. If drying is required, it is recommended that the drying condition be 80C for 2-3 hours. Melting temperature: 180~280C. For flame retardant materials, the upper limit is 250C. Mold temperature: 40~50C. Injection pressure: 200~600bar. Injection speed: fast injection speed is recommended. Runners and Gates: All generic types of gates can be used.

Chemical and physical properties: Most commercial PS are transparent, amorphous materials. PS has very good geometric stability, thermal stability, optical transmission characteristics, electrical insulation characteristics and very small moisture absorption tendency. It can resist water and diluted inorganic acid, but can be corroded by strong oxidizing acid such as concentrated sulfuric acid, and can expand and deform in some organic solvents. The typical shrinkage is 0.4~0.7%.