Because of the rising need for injection molding goods in automobiles, construction, and other sectors, injection molding technology has also been developed and improved over the last many years. Injection molding is a technique of industrial product manufacturing modeling. Rubber injection molding and plastic injection molding are commonly utilized for items. Injection molding may also be separated into injection molding, molding, and die casting.
Plastic Injection Mold Material Guide – Advantages & Applications Of 20 Common In Injection Molding Materials
ABS (acrylonitrile butadiene styrene copolymer)
① Typical application range:
Automobile (instrument panel, tool compartment door, wheel cover, reflector box, etc.), refrigerator, high-strength tools (hair dryer, mixer, food processor, lawn mower, etc.), telephone shell, typewriter keyboard, entertainment vehicles such as golf cart and jet sledge, etc.
② Injection molding process conditions:
- Drying treatment: ABS material is hygroscopic and requires drying treatment before processing. It is recommended that the drying conditions be 80 ~ 90 ℃ for at least 2 hours. The material humidity shall be less than 0.1%.
- Melting temperature: 210 ~ 280 ℃; Recommended temperature: 245 ℃.
- Mold temperature: 25 ~ 70 ℃. (mold temperature will affect the finish of plastic parts, and lower temperature will lead to lower finish).
- Injection pressure: 500 ~ 1000bar.
- Injection speed: medium and high speed.
③ Chemical and physical properties:
ABS is synthesized from acrylonitrile, butadiene and styrene. Each monomer has different characteristics: acrylonitrile has high strength, thermal stability and chemical stability; Butadiene has toughness and impact resistance; Styrene has easy processing, high finish and high strength. In terms of morphology, ABS is an amorphous material. The polymerization of three monomers produces a terpolymer with two phases, one is the continuous phase of styrene-acrylonitrile and the other is the dispersed phase of polybutadiene rubber. The characteristics of ABS mainly depend on the ratio of three monomers and the molecular structure in the two phases. This can have great flexibility in product design, and thus produce hundreds of ABS materials of different quality in the market. These different quality materials provide different characteristics, such as medium to high impact resistance, low to a high finish and high-temperature distortion. ABS material has super workability, appearance characteristics, low creep, excellent dimensional stability, and high impact strength.
PA6 (polyamide 6 or nylon 6)
① Typical application range:
It is widely used in structural components because of its good mechanical strength and stiffness. Because of its good wear resistance, it is also used to manufacture bearings.
② Injection molding process conditions:
Drying treatment: because PA6 is easy to absorb water, special attention should be paid to the 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 in hot air above 80 ℃ for 16 hours. If the material has been exposed to air for more than 8 hours, vacuum drying at 105 ℃ for more than 8 hours is recommended.
Melting temperature: 230 ~ 280 ℃, 250 ~ 280 ℃ for reinforced varieties.
Mold temperature: 80 ~ 90 ℃. Mold temperature significantly affects the crystallinity, which in turn affects the mechanical properties of plastic parts. For structural parts, crystallinity is very important, so it is recommended that the mold temperature is 80 ~ 90 ℃. For thin-walled plastic parts with long process, it is also recommended to use higher die temperature. Increasing the mold temperature can improve the strength and stiffness of plastic parts (increase the crystallinity), but reduce the toughness. If the wall thickness is greater than 3mm, it is recommended to use a low-temperature mold at 20 ~ 40 ℃. For glass reinforced materials, the mold temperature shall be greater than 80 ℃.
Injection pressure: generally between 750 ~ 1250bar (depending on material and product design).
Injection speed: high speed (slightly lower for reinforced materials).
Runner and gate: because the solidification time of PA6 is very short, the position of gate is very important. The gate aperture shall not be less than 0.5 * t (where t is the thickness of plastic parts). If a hot runner is used, the gate size should be smaller than that of a conventional runner, because a hot runner can help prevent premature solidification of the material. If a submerged gate is used, the minimum diameter of the gate shall be 0.75mm.
③ Chemical and physical properties:
The chemical and physical properties of PA6 are 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%. The addition of glass fiber additives can reduce the shrinkage to 0.3% (but slightly higher in the direction perpendicular to the process). The shrinkage of molding assembly is mainly affected by the crystallinity and moisture absorption of the material. The actual shrinkage is also a function of plastic part design, wall thickness and other process parameters.
- PA12 (polyamide 12 or nylon 12)
① Typical application range:
Water meters and other commercial equipment, cable sleeves, mechanical cams, sliding mechanisms, bearings, etc.
② Injection molding process conditions:
Drying: the humidity shall be below 0.1% before processing. If the material is stored exposed to air, it is recommended to dry in hot air at 85 ℃ for 4 ~ 5 hours. If the material is stored in a closed container, it can be used directly after 3 hours of temperature balance.
Melting temperature: 240 ~ 300 ℃; It shall not exceed 310 ℃ for ordinary materials and 270 ℃ for materials with flame retardant characteristics.
Mold temperature: 30 ~ 40 ℃ for unreinforced materials, 80 ~ 90 ℃ for thin-wall or large-area elements, and 90 ~ 100 ℃ for reinforced materials. Increasing the temperature will increase the crystallinity of the material. Accurate control of mold temperature is very important for PA12.
Injection pressure: up to 1000 bar (low holding pressure and high melting temperature are recommended).
Injection speed: high speed (better for materials with glass additives).
Runner and gate: for materials without additives, the runner diameter should be about 30mm due to the low viscosity of the material. For reinforced materials, a large runner diameter of 5 ~ 8mm is required. The runner shape shall be all circular. The injection port shall be as short as possible. Multiple forms of gates can be used. Do not use small gate for large plastic parts, which is to avoid excessive pressure or excessive shrinkage of plastic parts. The gate thickness should preferably be equal to the thickness of the plastic part. If a submerged gate is used, a minimum diameter of 0.8mm is recommended. Hot runner mold is very effective, but it requires accurate temperature control to prevent material leakage or solidification at the nozzle. If a hot runner is used, the gate size should be smaller than the cold runner.
③ Chemical and physical properties:
PA12 is a linear, semi crystalline crystalline thermoplastic material from butadiene. Its properties are similar to those of PA11, but its crystal structure is different. PA12 is a good electrical insulator and, like other polyamides, will not affect the insulation performance due to humidity. It has good impact resistance and mechanochemical stability. PA12 has many improved varieties in plasticizing and reinforcing properties. Compared with PA6 and PA66, these materials have a lower melting points and density and very high moisture regain. PA12 has no resistance to strong oxidizing acids. The viscosity of PA12 mainly depends on humidity, temperature and storage time. It has good liquidity. The shrinkage is between 0.5% and 2%, which mainly depends on the material type, wall thickness, and other process conditions.
- PA66 (polyamide 66 or nylon 66)
① Typical application range:
Compared with PA6, PA66 is more widely used in the automotive industry, instrument shell,s and other products requiring impact resistance and high strength.
② Injection molding process conditions:
Drying: if the material is sealed before processing, it is not necessary to dry. However, if the storage container is opened, it is recommended to dry in hot air at 85 ℃. If the humidity is greater than 0.2%, vacuum drying at 105 ℃ for 12 hours is also required.
Melting temperature: 260 ~ 290 ℃. The product temperature of glass additive is 275 ~ 280 ℃. Melting temperatures above 300 ° C shall be avoided.
Mold temperature: 80 ℃ 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 40 ℃, 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 (slightly lower for reinforced materials).
Runner and gate: because the solidification time of PA66 is very short, the position of gate is very important. The gate aperture shall not be less than 0.5 * t (where t is the thickness of plastic parts). 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 material. If a submerged gate is used, the minimum diameter of the gate shall be 0.75mm.
③ 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 temperature. PA66 is still hygroscopic 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. PA66 has low viscosity, so it has good fluidity (but not as good as PA6). This property can be used to process very thin components. Its viscosity is sensitive to temperature changes. The shrinkage of PA66 is between 1% ~ 2%, and the addition of glass fiber additive can reduce the shrinkage to 0.2% ~ 1%. The difference of shrinkage in the process direction and the direction perpendicular to the process direction is large. PA66 is resistant to many solvents, but weak to acids and other chlorinating agents.
- PBT (polybutylene terephthalate)
① Typical application range:
Household appliances (food processing blades, vacuum cleaner components, electric fans, hair dryer shells, coffee utensils, etc.), electrical components (switches, motor shells, fuse boxes, computer keyboard keys, etc.), automobile industry (radiator grid windows, body panels, wheel covers, door and window components, etc.).
② Injection molding process conditions:
Drying treatment: this material is easy to hydrolyze at high temperature, so drying treatment before processing is very important. The recommended drying condition in air is 120 ℃ for 6 ~ 8 hours, or 150 ℃ for 2 ~ 4 hours. Humidity must be less than 0.03%. If drying with a moisture absorption dryer, the recommended condition is 150 ℃ for 2.5 hours.
Melting temperature: 225 ~ 275 ℃, recommended temperature: 250 ℃.
Mold temperature: 40 ~ 60 ℃ for unreinforced materials. The cooling cavity of the die should be well designed to reduce the bending of plastic parts. Heat must be lost quickly and evenly. It is recommended that the diameter of die cooling cavity is 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: Circular runner is recommended 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 between 0.8 ~ 1.0 * t, where t is the thickness of plastic parts. In the case of submerged gates, a minimum diameter of 0.75mm is recommended.
③ Chemical and physical properties:
PBT is one of the toughest engineering thermoplastic materials. It is a semi crystalline material with very good chemical stability, mechanical strength, electrical insulation characteristics and thermal stability. These materials have good stability under a wide range of environmental conditions. PBT has weak hygroscopic properties. 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 crystallizes rapidly, which will lead to bending deformation due to uneven cooling. For materials with glass additives, the shrinkage in the process direction can be reduced, but the shrinkage in the vertical direction of the process is basically no different from that of ordinary materials. The shrinkage of general materials is between 1.5% ~ 2.8%. The shrinkage of the material containing 30% glass additive is between 0.3% ~ 1.6%. The melting point (225 ℃) and high temperature deformation temperature are lower than those of pet. Vicat softening temperature is about 170 ℃. The glass transition temperature is between 22 ℃ and 43 ℃. Due to the high crystallization rate of PBT, its viscosity is very low, and the cycle time of plastic parts processing is generally low.
- PC (polycarbonate)
① Typical application range:
Electrical and commercial equipment (computer components, connectors, etc.), appliances (food processing machines, refrigerator drawers, etc.), transportation industry
(front and rear lights, instrument panel, etc. of the vehicle).
② Injection molding process conditions:
Drying treatment: PC material is hygroscopic, and drying before processing is very important. The recommended drying conditions are 100 ℃ to 120 ℃ for 3 ~ 4 hours. The humidity before processing must be less than 0.02%.
Melting temperature: 260 ~ 340 ℃.
Mold temperature: 70 ~ 120 ℃.
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.
③ Chemical and physical properties:
PC is an amorphous engineering material, which has particularly good impact strength, thermal stability, gloss, bacterial inhibition, flame retardant and pollution resistance. The notched Izod impact length of PC is very high (the crown of impact), and the shrinkage is very low, generally 0.1% ~ 0.2%. PC has good mechanical properties, but poor flow characteristics, so the injection molding process of this material is difficult. When selecting PC materials of what quality, the final expectation of the product shall be taken as the benchmark. If plastic parts require high impact resistance, PC materials with low flow rate shall be used; Conversely, PC materials with high flow rate can be used, which can optimize the injection molding process.
- PC / ABS (polycarbonate and acrylonitrile butadiene styrene copolymer and mixture)
① Typical application range:
Shells of computers and business machines, electrical equipment, lawn and gardening machines, auto parts (dashboard, interior decoration and wheel covers).
② Injection molding process conditions:
Drying treatment: drying treatment before processing is necessary. The humidity shall be less than 0.04%, and the recommended drying condition is 90 ~ 110 ℃ for 2 ~ 4 hours.
Melting temperature: 230 ~ 300 ℃.
Mold temperature: 50 ~ 100 ℃.
Injection pressure: depends on the plastic part.
Injection speed: as high as possible.
③ Chemical and physical properties:
PC / ABS has the comprehensive characteristics of PC and ABS. For example, the easy processing characteristics of ABS and the excellent mechanical characteristics and thermal stability of PC. The ratio of them will affect the thermal stability of PC / ABS materials. PC / ABS also shows excellent flow characteristics.
- PC / PBT (mixture of polycarbonate and polybutylene terephthalate)
① Typical application range:
Gearbox, automobile bumper and products requiring chemical reaction resistance, corrosion resistance, thermal stability, impact resistance and geometric stability.
② Injection molding process conditions:
Drying: it is recommended to dry at 110 ~ 135 ℃ for about 4 hours.
Melting temperature: 235 ~ 300 ℃.
Mold temperature: 37 ~ 93 ℃.
③ Chemical and physical properties:
PC / PBT has the comprehensive characteristics of PC and PBT, such as high toughness and geometric stability of PC, chemical stability, thermal stability and lubrication characteristics of PBT.
- PE-HD (high density polyethylene)
① Typical application range:
Refrigerator containers, storage containers, household kitchenware, sealing covers, etc.
② Injection molding process conditions:
Drying: if stored properly, drying is not required.
Melting temperature: 220 ~ 260 ℃. For materials with large molecules, it is recommended that the melting temperature range is 200 ~ 250 ℃.
Mold temperature: 50 ~ 95 ℃. Higher mold temperature shall be used for plastic parts with wall thickness less than 6mm, and lower mold temperature shall be used for plastic parts with wall thickness more than 6mm. The cooling temperature of plastic parts shall be uniform to reduce the difference in shrinkage. For the optimal processing cycle time, the diameter of the cooling cavity should not be less than 8mm, and the distance from the die surface should be within 1.3d (here “d” is the diameter of the cooling cavity).
Injection pressure: 700 ~ 1050bar.
Injection speed: high speed injection is recommended.
Runner and gate: the runner diameter shall be between 4 and 7.5mm, and the runner length shall be as short as possible. Various types of gates can be used, and the gate length shall not exceed 0.75mm. It is especially suitable for using hot runner mold.
③ Chemical and physical properties:
The high crystallinity of PE-HD leads to its high density, tensile strength, high temperature distortion temperature, viscosity and chemical stability. PE-HD has stronger impermeability than PE-LD. PE-HD has low impact strength. The characteristics of ph-hd are mainly controlled by density and molecular weight distribution. The molecular weight distribution of PE-HD suitable for injection mold is very narrow. For the density of 0.91 ~ 0.925g/cm3, we call it the first type PE-HD; For the density of 0.926 ~ 0.94g/cm3, it is called the second type PE-HD; For the density of 0.94 ~ 0.965g/cm3, it is called the third type PE-HD. The material has good flow characteristics with MFR between 0.1 and 28. The higher the molecular weight, the worse the flow characteristics of ph-ld, but it has better impact strength. PE-LD is a semi crystalline material with high shrinkage after molding, ranging from 1.5% to 4%. PE-HD is prone to environmental stress cracking. Cracking can be reduced by using materials with very low flow characteristics to reduce internal stress. When the temperature is higher than 60 ℃, PE-HD is easy to dissolve in hydrocarbon solvents, but its solubility resistance is better than PE-LD.
- PE-LD (low density polyethylene)
① Typical application range:
Bowl, cabinet, pipe coupling
② Injection molding process conditions:
Drying: generally not required
Melting temperature: 180 ~ 280 ℃
Mold temperature: 20 ~ 40 ℃. In order to achieve uniform cooling and economical heat removal, it is recommended that the diameter of the cooling cavity should be at least 8mm, and the distance from the cooling cavity to the mold surface should not exceed 1.5 times the diameter of the cooling cavity.
Injection pressure: up to 1500bar.
Holding pressure: up to 750bar.
Injection speed: fast injection speed is recommended.
Runner and gate: various types of runners and gates can be used. PE-LD is especially suitable for hot runner molds.
③ Chemical and physical properties:
The density of commercial PE-LD material is 0.91 ~ 0.94 g / cm3. PE-LD has permeability to gas and steam. PE-LD has a high coefficient of thermal expansion and is not suitable for processing products used for a long time. If the density of PE-LD is between 0.91 and 0.925 g / cm3, the shrinkage is between 2% and 5%; If the density is between 0.926 and 0.94 g / cm3, the shrinkage is between 1.5% and 4%. At present, the actual shrinkage also depends on the injection molding process parameters. PE-LD can resist a variety of solvents at room temperature, but aromatic and chlorinated hydrocarbon solvents can expand it. Similar to PE-HD, PE-LD is prone to environmental stress cracking.
- Pei (polyether)
① Typical application range:
Automotive industry (engine accessories such as temperature sensor, fuel and air processor), electrical and electronic equipment (electrical coupling, printed circuit board, chip shell, explosion-proof box, etc.), product packaging, aircraft internal equipment, pharmaceutical industry (surgical instruments, tool shell, non implantable instruments).
② Injection molding process conditions:
Drying treatment: Pei has hygroscopic properties and can lead to material degradation. The required humidity value shall be less than 0.02%. The recommended drying condition is 150 ℃ for 4 hours.
Melting temperature: 340 ~ 400 ℃ for common materials; The reinforcement type is 340 ~ 415 ℃.
Mold temperature: 107 ~ 175 ℃, the recommended mold temperature is 140 ℃.
Injection pressure: 700 ~ 1500bar.
Injection speed: use the highest possible injection speed.
③ Chemical and physical properties:
Pei has strong high temperature stability. Even if it is non reinforced Pei, it still has good toughness and strength. Therefore, the superior thermal stability of Pei can be used to make high temperature and heat-resistant devices. Pei also has good flame retardancy, chemical resistance and electrical insulation properties. The glass transition temperature is very high, up to 215 ℃. Pei also has low shrinkage and good isotropic mechanical properties.
- Pet (polyethylene terephthalate)
① Typical application range:
Automotive industry (structural devices such as reflector box, electrical components such as headlamp reflector, etc.), electrical components (motor shell, electrical coupling, relay, switch, internal devices of microwave oven, etc.). Industrial applications (pump housings, hand instruments, etc.).
② Injection molding process conditions:
Drying treatment: drying treatment before processing is necessary because pet has strong moisture absorption. The recommended drying condition is 120 ~ 165 ℃ for 4 hours. The required humidity shall be less than 0.02%.
Melting temperature: 265 ~ 280 ℃ for unfilled type; For glass filling type: 275 ~ 290 ℃.
Mold temperature: 80 ~ 120 ℃.
Injection pressure: 300 ~ 1300bar.
Injection speed: a higher injection speed can be used without embrittlement.
Runner and gate: all general types of gates can be used. The gate size shall be 50 ~ 100% of the thickness of the plastic part.
③ Chemical and physical properties:
The glass transition temperature of pet is about 165 ℃, and the crystallization temperature range is 120 ~ 220 ℃. Pet has strong hygroscopicity at high temperature. For Glass Fiber Reinforced PET materials, bending deformation is also very easy to occur at high temperature. The crystallization degree of the material can be improved by adding crystallization enhancer. Transparent products processed with pet have gloss and heat 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 by using unfilled PET materials.
- PETG (ethylene glycol modified polyethylene terephthalate)
① Typical application range:
Medical equipment (test tubes, reagent bottles, etc.), toys, displays, light source covers, protective masks, refrigerator fresh-keeping plates, etc.
② Injection molding process conditions:
Drying treatment: drying treatment before processing is necessary. The humidity must be less than 0.04%. The recommended drying condition is 65 ℃ for 4 hours, and the drying temperature shall not exceed 66 ℃.
Melting temperature: 220 ~ 290 ℃.
Mold temperature: 10 ~ 30 ℃, recommended 15 ℃.
Injection pressure: 300 ~ 1300bar.
Injection speed: a higher injection speed can be used without embrittlement.
③ Chemical and physical properties:
PETG is a transparent, amorphous material. The glass transition temperature is 88 ℃. The allowable range of injection molding process conditions of PETG is wider than that of pet, and has the comprehensive characteristics of transparency, high strength and high willfulness.
- PMMA (polymethylmethacrylate)
① Typical application range:
Automobile industry (signal light equipment, instrument panel, etc.), pharmaceutical industry (blood storage container, etc.), industrial application (video disc, light diffuser), daily consumer goods (beverage cup, stationery, etc.).
② Injection molding process conditions:
Drying treatment: PMMA is hygroscopic, so drying treatment before processing is necessary. The recommended drying conditions are 90 ℃ and 2 ~ 4 hours.
Melting temperature: 240 ~ 270 ℃.
Mold temperature: 35 ~ 70 ℃.
Injection speed: medium
③ Chemical and physical properties:
PMMA has excellent optical properties and weather resistance. The penetration of white light is as high as 92%. PMMA products have very low birefringence and are especially suitable for making video discs. PMMA has room temperature creep characteristics. With the increase of load and time, it can lead to stress cracking. PMMA has good impact resistance.
- POM (polyoxymethylene)
① Typical application range:
POM has low friction coefficient and good geometric stability, especially suitable for making gears and bearings. Because it also has high temperature resistance, it is also used in pipeline devices (pipeline valves, pump shells), lawn equipment, etc.
② Injection molding process conditions:
Drying treatment: if the material is stored in a dry environment, drying treatment is usually not required.
Melting temperature: 190 ~ 230 ℃ for homopolymer materials and 190 ~ 210 ℃ for copolymer materials.
Mold temperature: 80 ~ 105 ℃. In order to reduce the shrinkage after forming, a higher mold temperature can be selected.
Injection pressure: 700 ~ 1200bar
Injection speed: medium or high injection speed.
Runner and gate: any type of gate can be used. If a tunnel gate is used, it is better to use a shorter type. A hot nozzle runner is recommended for homopolymer materials. For copolymer materials, either an internal hot runner or an external hot runner can be used.
③ Chemical and physical properties:
POM is a tough and elastic material, which has good creep resistance, geometric stability and impact resistance even at low temperature. POM has both homopolymer and copolymer materials. Homopolymer materials have good tensile strength and fatigue resistance, but it is not easy to process. Copolymer materials have good thermal stability, chemical stability and are easy to process Both polymer materials and copolymer materials are crystalline materials and are not easy to absorb water. The high degree of crystallization of POM leads to its high shrinkage, which can be as high as 2% ~ 3.5%. There are different shrinkage rates for various reinforced materials.
- PP (polypropylene)
① Typical application range:
Automotive industry (mainly PP containing metal additives: fender, ventilation pipe, fan, etc.), equipment (dishwasher door gasket, dryer ventilation pipe, washing machine frame and cover, refrigerator door gasket, etc.), daily consumer goods (lawn and gardening equipment such as lawnmower and sprinkler, etc.).
② Injection molding process conditions:
Drying: if stored properly, drying is not required.
Melting temperature: 220 ~ 275 ℃. Be careful not to exceed 275 ℃.
Mold temperature: 40 ~ 80 ℃, 50 ℃ is recommended. The crystallization degree is mainly determined by the mold temperature.
Injection pressure: up to 1800bar.
Injection speed: generally, high-speed injection molding can minimize the internal pressure. If there are defects on the product surface, low-speed injection molding at higher temperature should be used.
Runner and gate: for cold runner, the typical runner diameter range is 4 ~ 7mm. It is recommended to use an injection gate and runner with a circular body. All types of gates can be used. The typical gate diameter range is 1 ~ 1.5mm, but Gates as small as 0.7mm can also be used. For edge gates, the minimum gate depth should be half of the wall thickness; the minimum gate width should be at least half of the wall thickness Twice the thickness. PP material can use hot runner system.
③ Chemical and physical properties:
PP is a semi crystalline material. It is harder than PE and has a higher melting point. Because homopolymer PP is very brittle when the temperature is higher than 0 ℃, many commercial PP materials are irregular copolymers with 1 ~ 4% ethylene or clamp copolymers with higher ethylene content. Copolymer PP materials have a lower heat distortion temperature (100 ℃) , low transparency, low gloss and low rigidity, but it has stronger impact strength. The strength of PP increases with the increase of ethylene content. The Vicat softening temperature of PP is 150 ℃. Due to its high crystallinity, this material has good surface stiffness and scratch resistance. PP does not have the problem of environmental stress cracking. Usually, glass fiber, metal additives or thermoplastic rubber are added PP is modified by glue method. The flow rate MFR of PP ranges from 1 to 40. PP materials with low MFR have better impact resistance but lower tensile strength. For materials with the same MFR, 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. Add 30% glass filler Adding agent can reduce the shrinkage to 0.7%. Homopolymer and copolymer PP materials have excellent moisture absorption resistance, acid-base corrosion resistance and solubility. However, it has no resistance to aromatic hydrocarbon (such as benzene) solvent and chlorinated hydrocarbon (carbon tetrachloride) solvent. PP also does not have oxidation resistance at high temperature like PE.
- PPE (polypropylene)
① Typical application range:
Household products (dishwasher, washing machine, etc.), electrical equipment such as controller shell, optical fiber coupler, etc.
② Injection molding process conditions:
Drying: it is recommended to dry at 100 ℃ for 2 ~ 4 hours before processing.
Melting temperature: 240 ~ 320 ℃.
Mold temperature: 60 ~ 105 ℃.
Injection pressure: 600 ~ 1500bar.
Runner and gate: all types of gates can be used. It is especially suitable for handle gates and fan gates.
③ Chemical and physical properties:
Generally, commercially available PPE or PPO materials are generally mixed with other thermoplastic materials, such as PS, PA, etc. these mixed materials are generally still called PPE or PPO. Mixed PPE or PPO has much better processing properties than pure materials. The change of properties depends on the ratio of mixtures such as PPO and PS. the mixed materials mixed with PA 66 have 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 additives. This material also has excellent electrical insulation characteristics and low coefficient of thermal expansion. Its viscosity depends on the ratio of the mixture in the material and the viscosity of PPO An increase in the ratio will lead to an increase in viscosity.
- PS (polystyrene)
① Typical application range:
Product packaging, household goods (tableware, tray, etc.), electrical (transparent container, light source diffuser, insulating film, etc.).
② Injection molding process conditions:
Drying: drying is usually not required unless stored improperly. If drying is required, the recommended drying condition is 80 ℃ for 2 ~ 3 hours.
Melting temperature: 180 ~ 280 ℃. For flame retardant materials, the upper limit is 250 ℃.
Mold temperature: 40 ~ 50 ℃.
Injection pressure: 200 ~ 600bar.
Injection speed: fast injection speed is recommended.
Runner and gate: all general types of gates can be used.
③ 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 acids, but can be corroded by strong oxidizing acids such as concentrated sulfuric acid, and can expand and deform in some organic solvents. The typical shrinkage is between 0.4 and 0.7%.
- PVC (polyvinyl chloride)
① Typical application range:
Water supply pipeline, household pipeline, house wallboard, commercial machine shell, electronic product packaging, medical equipment, food packaging, etc.
② Injection molding process conditions:
Drying treatment: drying treatment is not usually required.
Melting temperature: 185 ~ 205 ℃
Mold temperature: 20 ~ 50 ℃
Injection pressure: up to 1500bar
Holding pressure: up to 1000bar
Injection speed: in order to avoid material degradation, it is generally necessary to use a very slow injection speed.
Runner and gate: all conventional gates can be used. If machining smaller parts, it is best to use needle tip gate or submerged gate; For thicker parts, it is best to use fan gates. The minimum diameter of needle tip gate or submerged gate shall be 1mm; The thickness of fan gate shall not be less than 1mm.
③ Chemical and physical properties:
Rigid PVC is one of the most widely used plastic materials. PVC material is an amorphous material. Stabilizers, lubricants, auxiliary processing agents, pigments, impact agents and other additives are often added to PVC materials in practical use. PVC material has non flammability, high strength, weather resistance and excellent geometric stability. PVC has strong resistance to oxidants, 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 and chlorinated hydrocarbons. The melting temperature of PVC during processing is a very important process parameter. If this parameter is improper, it will lead to the problem of material decomposition. The flow characteristics of PVC are quite poor, and its process range is very narrow. In particular, PVC materials with large molecular weight are more difficult to process (this material usually needs to add lubricant to improve flow characteristics), so PVC materials with small molecular weight are usually used. The shrinkage of PVC is quite low, generally 0.2 ~ 0.6%.
- SA (styrene acrylonitrile copolymer)
① Typical application range:
Electrical (socket, shell, etc.), daily commodities (kitchen appliances, refrigerator devices, TV base, cassette box, etc.), automobile industry (headlight box, reflective environment, instrument panel, etc.), household products (tableware, food knives, etc.), cosmetics packaging, etc.
② Injection molding process conditions:
Drying: SA has some hygroscopic properties if stored improperly. The recommended drying condition is 80 ℃ for 2 ~ 4 hours.
Melting temperature: 200 ~ 270 ℃. If thick wall products are processed, a melting temperature lower than the lower limit can be used.
Mold temperature: 40 ~ 80 ℃. For reinforced materials, the mold temperature shall not exceed 60 ℃. The cooling system must be well designed because the mold temperature will directly affect the appearance, shrinkage and bending of the product.
Injection pressure: 350 ~ 1300bar.
Injection speed: high speed injection is recommended.
Runner and gate: all conventional gates can be used. The gate size must be appropriate to avoid streaks, spots and voids.
③ Chemical and physical properties:
SA is a hard, transparent material. Styrene makes SA hard, transparent and easy to process; The composition of acrylonitrile makes SA chemically and thermally stable. SA has strong load bearing capacity, chemical reaction resistance, thermal deformation resistance and geometric stability. The addition of glass fiber additives to SA can increase the strength and thermal deformation resistance and reduce the coefficient of thermal expansion. The Vicat softening temperature of SA is about 110 ℃. The deflection deformation temperature under load is about 100 ℃. The shrinkage of SA is about 0.3 ~ 0.7%.
