I. PS (Polystyrene)
PS is an amorphous polymer with good fluidity and low water absorption (less than 00.2%) and is a transparent plastic that is easy to mold and process. Its products have a light transmission rate of 88-92%, strong coloring power, and high hardness.
How, PS products are brittle, easy to produce internal stress cracking, heat resistance is poor (60-80 ℃), non-toxic, specific gravity of about 1.04g \ cm3 (slightly greater than water).
Molding shrinkage (its value is generally 0.004-0.007 in/in), transparent PS – the name indicates only the transparency of the resin, not crystallinity. Chemical and physical properties: Most commercial PS is a transparent, non-crystalline material.
PS has very good geometric stability, thermal stability, optical transmission properties, electrical insulation properties, and a very slight tendency to absorb moisture.
It is resistant to water, and dilutes inorganic acids, but can be corroded by strong oxidizing acids such as concentrated sulfuric acid, and can swell and deform in some organic solvents).
Process characteristics of PS
PS melting point of 166 ℃, the processing temperature is generally appropriate at 185-215 ℃, melting temperature is 180 ~ 280 ℃, for flame retardant materials its upper limit of 250 the ℃, decomposition temperature of about 290 ℃, so its processing temperature range is wide.
Mold temperature is 40~50℃, injection pressure: is 200~600bar, and injection speed is recommended to use fast injection speed, runners and gates can use all conventional types of gates.
PS materials usually do not need to be dried before processing, unless they are stored improperly. If drying is required, the recommended drying conditions are 80C and 2 to 3 hours.
Because of the low specific heat of PS, its production of some mold heat dissipation that can be quickly cold condensation curing, its cooling rate than the general raw materials is faster, the opening time can be earlier.
Its plasticization time and cooling time are shorter, the molding cycle time will be reduced some; PS products with the increase in injection mold temperature and better luster.
Typical application areas
Packaging products (containers, hoods, bottles), disposable medical supplies, toys, cups, knives, tape shafts, storm windows, and many foam products – egg crates.
Meat and poultry packaging trays, bottle labels and foamed PS cushioning materials, product packaging, housewares (cutlery, trays, etc.), electrical (clear containers, light scatterers, insulating films, etc.)
2. HIPS (modified polystyrene)
HIPS for PS-modified materials, molecules containing 5-15% rubber composition, its toughness than PS increased by about four times, impact strength greatly improved (high-impact polystyrene).
There have been flame retardant grades, stress cracking resistance grades, high gloss grades, very high impact strength grades, glass fiber reinforced grade, and low residual volatile classification. Other important properties of standard HIPS: bending strength 13.8 to 55.1 MPa.
Tensile strength 13.8-41.4MPa; elongation at break 15-75%; density 1.035-1.04 g/ml; it has the advantages of PS with molding process, and strong coloring power. hips products are opaque. hips low water absorption, processing without pre-drying.
Process characteristics of HIPS
Because the HIPS molecule contains 5-15% rubber, to a certain extent affects its fluidity, injection pressure and molding temperature should be higher. The cooling rate is slower than that of PS, so sufficient holding pressure, holding time and cooling interval are required.
The injection molding cycle will be a little longer than PS, the processing temperature is generally 190-240 ℃ appropriate. HIPS resin absorbs moisture slowly, so generally does not need to dry.
Sometimes too much moisture is absorbed from the surface of the material, which affects the appearance of the final product.
There is a special problem with the “white edge” in HIPS parts, which can be improved by increasing the mold temperature and clamping force, reducing the pressure and time of holding pressure, etc. The water trap in the product will be more obvious.
Typical application areas
The main application areas are packaging and disposables, instrumentation, household appliances, toys, recreational products, and the construction industry.
Flame retardant (UL V-0 and UL 5-V), impact-resistant polystyrene has been produced and is widely used in TV housings, commercial machinery, and electrical products.
3. SA (SAN-styrene-acrylate copolymer/Powerful adhesive)
Properties of SA
Chemical and physical properties: SA is a hard and transparent material, which is not easy to produce internal stress cracking. It has high transparency, and its softening temperature and impact strength are higher than PS.
The styrene component makes SA hard, transparent, and easy to process; the acrylonitrile component makes SA chemically and thermally stable; SA has a strong ability to withstand load, chemical reaction resistance, heat deformation resistance, and geometric stability.
The Vicat softening temperature of SA is about 110℃. The deflection temperature under load is about 100C, and the shrinkage rate of SA is about 0.3~0.7%.
Process characteristics of SA
The processing temperature of SA is generally 200-250℃. The material is easy to absorb moisture and needs to be dried for more than one hour before processing, its liquidity is a little worse than PS, so the injection pressure is also slightly higher (injection pressure: 350~1300bar), and injection speed: high-speed injection is recommended.
Mold temperature control is better at 45-75℃. Drying treatment: If the storage is not proper, SA has some moisture absorption characteristics.
The recommended drying condition is 80℃, 2~4 hours. Melting temperature: 200~270℃. If processing thick-walled products, the melting temperature below the lower limit can be used. For reinforced materials, the injection mold temperature should not exceed 60°C.
The cooling system must be well designed because the mold temperature will directly affect the appearance, shrinkage, and bending of the product. Runners and gates: All conventional gates can be used. Gates must be properly sized to avoid streaks, burnt spots, and voids.
Typical application areas
Electrical (sockets, housings, etc.), daily goods (kitchen appliances, refrigerator units, TV bases, cassette boxes, etc.), automotive industry (headlight boxes, reflectors, dashboards, etc.), household goods (tableware, food knives, etc.), chemical packaging safety glass, water filter housings, and faucet twists.
Medical products (syringes, blood suction tubes, kidney permeation folding devices, and reactors). Packaging materials (cosmetic cases, lipstick sleeves, mascara cap bottles, hoods, cap sprays, and nozzles, etc.), special products (disposable lighter casings, brush substrates and stiff bristles, fishing tackle, dentures, toothbrush handles, pen sticks, musical instrument mouthpieces, and directional monofilament), etc.
Performance of ABS
ABS is synthesized by three chemical monomers: acrylonitrile, butadiene, and styrene. (Each monomer has different characteristics: acrylonitrile has high strength, thermal stability, and chemical stability; butadiene has the toughness and impact resistance; styrene has easy processing, high gloss, and high strength.
The polymerization of the three monomers produces a terpolymer with two phases, a continuous phase of styrene-acrylonitrile and a dispersed phase of polybutadiene rubber.) Morphologically, ABS is a non-crystalline material with high mechanical strength and good “tough, tough, steel” properties.
ABS is an amorphous polymer, a general-purpose engineering plastic with a wide variety of uses, also known as “general-purpose plastics” (MBS is called transparent ABS), ABS is easy to absorb moisture, the specific gravity of 1.05g/cm3 (slightly heavier than water), low shrinkage (0.60%), dimensional stability, and easy to mold and process.
The properties of ABS depend mainly on the ratio of the three monomers and the molecular structure in the two phases. This allows for great flexibility in product design and has resulted in hundreds of different qualities of ABS materials on the market.
These different qualities offer different properties, such as medium to high impact resistance, low to high glglossigh-temperature twist properties, etc. ABS materials offer superb processability, appearance, low creep and excellent dimensional stability, and high impact strength.
ABS is a light yellow granular or beaded opaque resin, non-toxic, odorless, low water absorption, with good overall physical and mechanical properties, such as excellent electrical properties, wear resistance, dimensional stability, chemical resistance, and surface gloss, and easy-to-process molding. The disadvantages are weather resistance, poor heat resistance, and flammability.
Process characteristics of ABS
ABS is hygroscopic and moisture-sensitive, so it must be dried and preheated (at least 2 hours at 80~90C) before molding and processing, and the moisture content must be controlled to less than 0.03%.
The melt viscosity of ABS resin is less sensitive to temperature (unlike other amorphous resins), and the injection temperature of ABS is slightly higher than that of PS, but it cannot be used to increase its viscosity by blindly increasing the temperature. The general processing temperature is 190-235℃.
The melt viscosity of ABS is medium, higher than PS, HIPS, and AS, and needs to use a higher injection pressure (500 ~ 1000bar) beer.
ABS material is better used the medium to high-speed injection speed beer. (Unless the shape is complex, thin-walled parts need to use a higher injection speed), the product’s water mouth positions are easy to produce for airlines.
ABS molding temperature is high, the mold temperature is generally adjusted at 25-70 ℃. When producing larger products, the temperature of the fixed mold (front mold) is generally slightly higher than that of the moving mold (back mold) by about 5℃. (The temperature of the mold will affect the finish of the plastic parts, and a lower temperature will lead to a lower finish)
ABS should not stay in the high-temperature barrel for too long (should be less than 30 minutes), otherwise it is easy to decompose and yellow.
Typical application range
Automobiles (instrument panels, tool hatches, wheel covers, reflector boxes, etc.), refrigerators, large strength tools (hair dryers, blenders, food processors, lawn mowers, etc.), telephone housings, typewriter keyboards, recreational vehicles such as golf trolleys and jet sled vehicles, etc.
Performance of BS
BS is butadiene – styrene copolymer, it has certain toughness and elasticity, low hardness (softer), and good transparency. the specific gravity of BS material is 1.01f\cm3 (similar to water). The material is easy to color, has good fluidity, and is easy to mold and process.
Process characteristics of BS
The processing temperature range of BS is generally 190-225℃, and the mold temperature is better at 30-50℃. The material should be dried before processing, because of its good fluidity, and the injection pressure and injection speed can be lower.
6. PMMA (acrylic)
PMMA is an amorphous polymer, commonly known as organic glass. With excellent transparency, good heat resistance (heat deflection temperature of 98 ℃), with good impact resistance characteristics, its products have medium mechanical strength, low surface hardness, and easy to be scratched by hard objects and leave traces, compared with PS, not easy to the brittle, specific gravity of 1.18g/cm3.
PMMA has excellent optical properties and resistance to weathering characteristics. PMMA products have very low birefringence, especially suitable for making video discs, etc. PMMA has room temperature creep characteristics. The increase in load and time can lead to a stress-cracking phenomenon.
Process characteristics of PMMA
PMMA processing requirements are more stringent, it is sensitive to water and temperature, to be fully dried before processing (recommended drying conditions for 90 ℃, 2 ~ 4 hours), its melt viscosity is large, and needs to be higher (225-245 ℃) and pressure molding, mold temperature at 65-80 ℃ is better. PMMA stability is not good, subject to high temperatures or in the higher temperature for too long will cause degradation.
The screw speed should not be too large (about 60% can be), thicker PMMA parts are easy to appear as “cavity”, and need to take a large gate, “low material temperature, high mold temperature, slow” injection method to process.
Typical application range
Automotive industry (signal light equipment, instrument panel, etc.), pharmaceutical industry (blood storage containers, etc.), industrial applications (video discs, light scatterers), and consumer goods (beverage cups, stationery, etc.).
Performance of PE
PE is the largest producer of plastic, characterized by soft, non-toxic, cheap, easy processing, good chemical resistance, not easy to corrode, and printing difficulties.
It has many types, commonly used LDPE (low-density polyethylene) and HDPE (high-density polyethylene), translucent plastic, low strength, the specific gravity of 0.94g/cm3 (smaller than water); very low-density LLDPE resin (density below 0.910g/cc, LLDPE, and LDPE density are in 0.91-0.925 (between).
LDPE is softer, (commonly known as soft glue) HDPE is commonly known as hard soft glue, it is harder than LDPE, is a semi-crystalline material, after molding shrinkage is high, between 1.5% to 4% poor light transmission, crystallinity, it is easy to environmental stress cracking phenomenon.
The cracking phenomenon can be mitigated by using materials with very low flow characteristics to reduce internal stress. It is easily dissolved in hydrocarbon solvents when the temperature is higher than 60°C, but its resistance to dissolution is somewhat better than LDPE.
The high crystallinity of HDPE leads to its high density, tensile strength, high-temperature twist temperature, viscosity, and chemical stability. It has greater resistance to permeation than LDPE. the impact strength of PE-HD is lower. The properties are mainly controlled by density and molecular weight distribution.
The molecular weight distribution of HDPE suitable for injection molding is very narrow. For densities from 0.91 to 0.925g/cm3, we call it type I PE-HD; for densities from 0.926 to 0.94g/cm3, it is called type II HDPE; for densities from 0.94 to 0.965g/cm3, it is called type III HDPE.
The material has good flow characteristics with MFR between 0.1 and 28. The higher the molecular weight, the worse the flow characteristics of LDPE, but with better impact strength. HDPE is susceptible to environmental stress cracking.
HDPE is easily dissolved in hydrocarbon solvents when the temperature is above 60C, but its resistance to dissolution is better than LDPE.
LDPE is a semi-crystalline material and has a high shrinkage rate after injection molding, between 1.5% and 4%.
LLDPE’s (linear low-density polyethylene) higher resistance to elongation, penetration, impact, and tearing makes LLDPE suitable for use as a film.
Its excellent resistance to environmental stress cracking, low-temperature impact resistance, and warpage resistance make LLDPE attractive for pipe, sheet extrusion, and all molding applications. the latest application of LLDPE is as a ground film for landfill and waste liquid pond liners.
Process characteristics of PE
The most significant feature of PE parts is the molding shrinkage, easy to produce shrinkage and deformation. PE material has little water absorption and can be used without drying.
PE has a wide range of processing temperatures, not easy to decompose (decomposition temperature of 320 ℃), if the pressure is high, high density of the parts, and shrinkage is small. PE fluidity is medium, to strictly control the processing conditions and maintain a constant mold temperature (40-60 ℃).
The degree of crystallization of PE is related to the injection molding process conditions, it has a high cold solidification temperature, and low mold temperature, so the degree of crystallization is low. In the crystallization process, due to the anisotropy of shrinkage, resulting in internal stress concentration, PE parts are prone to deformation and cracking.
The product is put in a water bath of 80℃ hot water, which can make the pressure get some relaxation. During the molding process, the material temperature and mold temperature should be higher, the injection pressure should be lower under the premise of ensuring the quality of the parts, the cooling of the mold especially requires rapid and uniform, and the products are hotter when they are taken off the mold.
HDPE drying: if stored properly, no drying is needed. Melting temperature: 220~260C. For materials with larger molecules, it is recommended that the melting temperature range is between 200~250C.
Mold temperature: 50~95C. Higher mold temperature should be used for plastic parts with a wall thickness below 6mm, and lower mold temperature for plastic parts with a wall thickness above 6mm.
The cooling temperature of plastic parts should be uniform to minimize the difference in shrinkage. For optimal cycle time, the cooling cavity diameter should be not less than 8mm and the distance from the mold surface should be within 1.3d (where “d” is the diameter of the cooling cavity).
Injection pressure: 700~1050 bar. injection speed: high-speed injection is recommended. Runners and gates: The runner diameter should be between 4 and 7.5 mm and the runner length should be as short as possible. It is possible to use various types of gates and the gate length should not exceed 0.75mm, especially for hot runner molds.
LLDPE’s “softness on extension” is a disadvantage in the blown film process, as LLDPE blown film bubbles are not as stable as those of LDPE. Typical die gap dimensions for LDPE and LLDPE are 0.024-0.040 in and 0.060-0.10 in, respectively.
Typical Application Areas
LLDPE has penetrated most traditional markets for polyethylene, including film, molding, tubing, and wire and cable. Impermeable floor membranes are a newly developed LLDPE market. Mulch film, a large extruded sheet, is used as a waste landfill and waste pond liner to prevent leakage or contamination of surrounding areas.
Examples include the production of bags, garbage bags, stretch wraps, industrial liners, towel liners, and shopping bags, all of which take advantage of the improved strength and toughness of this resin.
Clear films, such as bread bags, have been dominated by LDPE because it has better turbidity. However, blends of LLDPE with LDPE will improve strength. resistance to penetration and stiffness of LDPE film without significantly affecting the transparency of the film.
HDPE applications: refrigerator containers, storage containers, household kitchenware, sealing caps, etc.
8. PP (polypropylene)
Performance of PP
PP is a crystalline polymer. PP is the lightest of the commonly used plastics, with a density of only 0.91g/cm3 (smaller than water). PP has good resistance to stress cracking and high bending fatigue life, commonly known as “hundredfold rubber”. PP’s comprehensive performance is better than PE material.
The disadvantages of PP: are low dimensional accuracy, insufficient rigidity, poor weather resistance, easy to produce “copper damage”, it has the phenomenon of post-shrinkage, after demolding, easy to age, brittle, and easy to deform.
PP has been the main raw material for the manufacture of fibers, because of its coloring ability, wear resistance, chemical resistance, and favorable economic conditions.
PP is a semi-crystalline material. It is stiffer and has a higher melting point than PE. Since homopolymer-type PP is very brittle at temperatures above 0°C, many commercial PP materials are irregular copolymers with 1-4% ethylene or higher ratios of ethylene content in pincushion copolymers. The strength of PP increases with the increase of ethylene content.
The Vicat softening temperature of PP is 150°C. Due to its high crystallinity, this material has good surface stiffness and scratch resistance.
PP does not suffer from environmental stress cracking. Usually, PP is modified by adding glass fiber, metal additives, or thermoplastic rubber. the flow rate MFR of PP ranges from 1 to 40.
Low MFR PP materials have better impact resistance properties but lower ductility strength. For the same MFR, the strength of the copolymer type is higher than that of the 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 HDPE and other materials. The addition of a 30% glass additive can reduce the shrinkage to 0.7%.
Both homopolymer-type and copolymer-type PP materials have excellent resistance to moisture absorption, acid and alkali corrosion, and solubility. However, it has no resistance to aromatic hydrocarbon (such as benzene) solvents, chlorinated hydrocarbon (carbon tetrachloride) solvents, etc. PP also does not have oxidation resistance even at high temperatures like PE.
Process characteristics of PP
PP has good fluidity at melt temperature and good molding performance. PP has two characteristics in processing.
One: the viscosity of PP melt decreases significantly with the increase of shear speed (less affected by temperature).
The second: the molecular orientation degree is high and presents a large shrinkage rate. the processing temperature of PP is 220~275℃, note that it is better not to exceed about 275℃, it has good thermal stability (decomposition temperature is 310℃), but at high temperatures (270-300℃), there is the possibility of degradation when staying in the barrel for a long time.
Because the viscosity of PP decreases significantly with the increase of shear speed, so increasing the injection pressure and injection speed will improve its fluidity and shrinkage deformation and depression.
Mold temperature (40~80℃), 50℃ is recommended. The degree of crystallization is mainly determined by the mold temperature, and it is advisable to control within the range of 30-50℃. the PP melt can cross the very narrow mold gap and appear phi.
PP in the melting process, to absorb a lot of melting heat (specific heat is larger), the product out of the mold is hotter. PP material processing does not need to dry, PP shrinkage and crystallinity are lower than PE.
Injection speed usually uses a high-speed injection to minimize internal pressure. If defects appear on the surface of the product, then low-speed injection at higher temperatures should be used. Injection pressure: Up to 1800 bar.
Runners and gates: For cold runners, typical runner diameters range from 4 to 7 mm, and it is recommended to use injection ports and runners with a round body. All types of gates can be used.
Typical gate diameters range from 1 to 1.5 mm, but gates as small as 0.7 mm can be used. For edge gates, the minimum gate depth should be half the wall thickness; the minimum gate width should be at least twice the wall thickness, and PP materials are perfectly suited for hot runner systems.
PP has been the main raw material for manufacturing fibers due to its coloring ability, resistance to abrasion, chemical resistance, and favorable economic conditions.
Typical application areas
Automotive industry (mainly PP with metal additives: fenders, vent pipes, fans, etc.), apparatus (dishwasher door liners, dryer vent pipes, washing machine frames, and covers, refrigerator door liners, etc.), consumer goods (lawn and garden equipment such as lawn mowers and water sprinklers, etc.).
Injection molded products are the second largest market for PP homopolymers, including containers, sealers, automotive applications, housewares, toys, and many other consumer and industrial end uses.
9. PA (nylon)
Performance of PA
PA is also a crystalline plastic (nylon for tough angular translucent or milky white crystalline resin), as engineering plastics nylon molecular weight is generally 15-30,000, many varieties, commonly used in the injection molding process nylon 6, nylon 66, nylon 1010, nylon 610, etc.
Nylon has toughness, wear resistance, and self-lubricating, its advantages are mainly organic mechanical strength, good toughness, fatigue resistance, smooth surface, high softening point, heat resistance, low coefficient of friction, wear resistance, self-lubricating, shock absorption and silencing, oil resistance, weak acid resistance, alkali resistance, and general solvent, good electrical insulation, self-extinguishing, non-toxic, odorless, good weather resistance.
The disadvantage is large water absorption, and poor dyeieffectfect the dimensional stability and electrical properties, fiber reinforcement can reduce the wateabsorptioon so that it can work at high temperatures and high humidity.
Nylon and glass fiber affinity is very good (100 ℃ can be used for a long time), corrosion resistance, light weight of that and s, and easy molding. pa disadvantages are mainly: easy to absorb water, injection molding technology requirements are more stringent, poor dimensional stability, because of its specific heat, the product is hot.
PA66 is the highest mechanical strength of the PA series, the most widely used species. Its crystallinity is high, so its rigidity, and redness, and heat resistance are high. PA1010 is our first in 1958, translucent, has a small specific gravity, elasticity, and flexibility, has hater absorption than Poland and has reliable dimensional stability.
Nylon in nylon 66 has the highest hardness and rigidity, but the worst toughness. Various nylons are ordered by toughness: PA66 ＜PA66/6＜PA6＜PA610＜PA11＜PA12
The combustibility of nylon is ULS44-2 level, oxygen index is 24-28, the decomposition temperature of nylon > 299 ℃, in 449 ~ 499 ℃ will occur spontaneous combustion. The melt flow of nylon is good, so the wall thickness of the product can be as small as 1mm.
The process characteristics of PA
PA is easy to absorb moisture, must be fully dried before processing, and the water content should be controlled at 0.3% or less. The raw material is well dried, and the product is a high gloss, otherwise, it is rough, PA does not gradually soften with the increase in heat temperature, but in a narrow temperature range near the melting point, the melting point is obvious, once the temperature reaches the flow (different from PS, PE, PP and other materials).
The viscosity of PA is much lower than other thermoplastics, and its melting temperature range is narrow (only about 5 ℃). PA has a high melting point and a high freezing point, so the molten material can be solidified at any time in the mold because the temperature drops below the melting point, which prevents the completion of mold filling. Therefore, high-speed injection must be used, (especially for thin-walled or long process parts). Nylon mold to have more adequate exhaust measures.
PA in the molten state, thermal stability is poor and easy to degrade. Barrel temperature should not exceed 300and ℃, molten material in the barrel heating time should not exceed 30 minutes Kushi, PA mold temperature requirements are high, the use of high and low mold temperature to control its crystallinity, to obtain the desired performance.
PA material mold temperature at 50-90 ℃ is better, PA1010 processing temperature at 220-240 ℃ is appropriate, PA66 processing temperature of 270-290 ℃. PA products sometimes need to be “annealed” or “moisture treatment” according to quality requirements. PA products sometimes need to be “annealed” or “moisture treatment” according to quality requirements.
PA12 polyamide 12 or nylon 12 should be kept below 0.1% humidity before processing. If the material is stored exposed to air, it is recommended that it be dried in hot air at 85C for 4 to 5 hours.
If the material is stored in an airtight container, it can be used directly after 3 hours of temperature equilibration. Melting temperature is 240~300C; do not exceed 310C for common characteristics materials and 270C for materials with flame retardant characteristics.
Mold temperature: 30~40C for unreinforced materials, 80~90C for thin wall or large area components, and 90~100C for reinforced materials. increasing the temperature will increase the crystallinity of the material.
Precise control of mold temperature is important for PA12. Injection pressure: up to 1000bar (low holding pressure and high melting temperature are recommended). Injection speed: high speed (better for materials with glass additives).
Runners and gates: For materials without additives, the runner diameter should be around 30mm due to the low viscosity of the material. For reinforced materials, a large runner diameter of 5~8mm is required.
The runner shape should be all round. The injection port should be as short as possible. Various types of gates can be used. Do not use small gates for large parts to avoid excessive pressure or shrinkage on the part.
It is better to have a gate thickness equal to the thickness of the part. If a submerged gate is used, a minimum diameter of 0.8 mm is recommended. hot runner molds are effective, but require very precise temperature control to prevent material leakage or solidification at the nozzle. If a hot runner is used, the gate size should be smaller than a cold runner.
PA6 Polyamide 6 or Nylon 6: Since PA6 absorbs moisture easily, special attention should be paid to drying before processing. If the material is supplied in a waterproof package, the container should be kept airtight.
If the humidity is greater than 0.2%, drying in hot air at 80C or higher for 16 hours is recommended. If the material has been exposed to air for more than 8 hours, vacuum drying at 105C for more than 8 hours is recommended. Melting temperature: 230~280C, for reinforced varieties 250~280C.
Mold temperature: 80~90C. Mold temperature significantly affects the crystallinity, which in turn affects the mechanical properties of the molded part. For structural parts, crystallinity is important, so a mold temperature of 80~90C is recommended, and a higher mold temperature is also recommended for thin-long-flowing flow plastic parts. Increasing the mold temperature increases the strength and stiffness of the part, but decreases its 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 mold temperature should be greater than 80 C. Injection pressure: generally between 750~1250 bar (depending on the material and product design).
Injection speed: High speed (to be slightly reduced for reinforced materials). Runners and gates: Since the solidification time of PA6 is very short, the location of the gate is very important.
The gate aperture should not be less than 0.5*t (where t is the thickness of the molded part). If using a hot runner, the gate size should be smaller than using a conventional runner, because the hot runner can help stop the material from solidifying too early. If a submerged gate is used, the minimum diameter of the gate should be 0.75mm.
PA66 Polyamide 66 or Nylon 66 If the material is sealed before processing, then drying is not necessary. However, if the storage container is opened, then it is recommended to dry the process 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 to 290 C. For products with glass additives, 275 to 280 C. Melting temperatures above 300 C should be avoided. mold temperature: 80 C is recommended. mold temperature will affect the degree of crystallinity, which will affect the physical properties of the product.
For thin-walled plastic parts, if a mold temperature below 40C is used, the crystallinity of the part will change over time, and annealing is required to maintain the geometric stability of the part.
Injection pressure: typically 750 to 1250 bar, depending the on material and product design. Injection speed: High speed (should be slightly lower for reinforced materials).
Runners and gates: Due to the short solidification time of PA66, the location of the gate is very important. The gate aperture should not be less than 0.5*t (where t is the thickness of the plastic part).
If using a hot runner, the gate size should be smaller than using a conventional runner, because the hot runner can help stop the material from solidifying prematurely. If a submerged gate is used, the minimum diameter of the gate should be 0.75mm.
Typical application areas
PA12 Polyamide 12 or Nylon 12 is used in applications such as water meters and other commercial equipment, cable sleeves, mechanical cams, sliding mechanisms, and bearings.
PA6 Polyamide 6 or nylon 6 application range: Widely used for structural components due to good mechanical strength and stiffness. It is also used in the manufacture of bearings due to its excellent wear resistance.
PA66 Polyamide 66 or nylon 66 application range: compared with PA6, PA66 is more widely used in the automotive industry, instrument housing, and other products that require impact resistance and high strength requirements.
POM is a crystalline plastic, its steel is very good, commonly known as “race steel”. POM is a tough and flexible material, even at low temperatures still has good creep resistance, geometric stability, and impact resistance, it has fatigue resistance, creeps resistancewearsar resistance, heat resistance, and other excellent performance.
POM is not easy to absorb moisture, a specific gravity of 1.42g/a cm3, shrinkage rate of 2.1% (POM’s high degree of crystallization leads to it having a fairly high shrinkage rate which e, can be as high as 2% to 3.5%, larger, for a variety of different enhanced materials have different shrinkage rates), size is difficult to control, heat deflection temperature of 172 ℃.
POM both homopolymer materials and copolymer materials. Homopolymer materials have good ductility strength, and fatigue strength, but not easy to process. Copolymer materials have very good thermal stability, chemical stable quality, and easy processing. Both homopolymer and copolymer materials are crystalline and do not absorb moisture easily.
POM process characteristics
POM can be processed without drying, preferably in the process of preheating (about 100 ℃), the stability of the product size is good. POM processing temperature range is very narrow (195-215 ℃), a little longer in the barrel or the temperature exceeds 220 ℃ will decompose (homopolymer materials for 190-230 ℃; copolymer materials for 190-210 ℃). The screw speed should not be handed hand, tand htheamount of residue should be small
POM pproduct’sshrinkage is large (to reduce the shrinkage rate after molding can choose a higher mold temperature), and easy to pproduceduce shrinkage or deformation. pom specific heat, high mold temperature (80-105 ℃), the product is hot after demolding, need to prevent burns fingers. Injection pressure 700~1200bar.
POM should be processed under medium pressure, medium speed, and high mold temperature. Any type of gate can be used for runners and gates. If a tunnel-shaped gate is used, a shorter type is preferred. For homopolymer materials, hot nozzle runners are recommended. For copolymer materials, both internal and external hot runners can be used.
Typical Application Areas
POM has a very low coefficient of friction and good geometrical stability, making it particularly suitable for making gears and bearings. Because it also has high-temperature resistance, it is also used for piping devices (piping valves, pump housings), lawn equipment, etc.
11. PC (bulletproof rubber)
Polycarbonate is a thermoplastic resin containing -[O-R-O-CO]-link in the molecular hair chain, according to the molecular structure with different ester groups can be divided into an aliphatic spin, alicyclic, aliphatic-aromatic type, which has practical value is aromatic polycarbonate, and bisphenol A polycarbonate is the most important, the molecular weight is usually 3-100,000. 100,000.
PC is an amorphous, odorless, non-toxic, highly transparent colorless or slightly yellow thermoplastic engineering plastic, with excellent physical and mechanical properties, especially excellent impact resistance, tensile strength, bending strength, high compression strength; good toughness, good heat and weather resistance, easy coloring, low water absorption rate.
PC heat deflection temperature of 135-143 ℃, small creep, size stability; good heat resistance and low-temperature resistance, stable mechanical properties in a wide temperature range, dimensional stability, electrical properties, and flame retardancy, can be used in -60 ~ 120 ℃ for a long time;
No obvious melting point, in 220-230 ℃ is a molten state; due to the rigidity of the molecular chain, the resin melt viscosity is large. Small water absorption, small shrinkage (generally 0.1%~0.2%), high dimensional accuracy, good dimensional stability, small film permeability; self-extinguishing material.
Stable to light, but not resistant to ultraviolet light, good weather resistance; oil resistance, acid resistance, not resistant to strong alkalis, oxidizing acids and amines, ketones, soluble in chlorinated hydrocarbons and aromatic solvents, inhibition of bacterial properties, flame retardant properties, and anti-pollution properties, easy to cause hydrolysis and cracking in water for a long time.
The disadvantage is easy to produce stress cracking due to poor fatigue strength, poor solvent resistance, poor fluidity, poor and wear resistance. pc can be injection molding, extrusion, Molding, blow molding thermoforming, printing, bonding, coating, and machining, the most important processing method is injection molding.
Process characteristics of PC
PC material is more sensitive to temperature, its melt viscosity decreases significantly with the increase in temperature, the flow is accelerated, not sensitive to pressure, to improve its fluidity, to take the approach of temperature rise.
Pc material should be fully dried before processing (about 120 ℃, 3 ~ 4 hours), and the moisture should be controlled within 0.02%, trace moisture in high-temperature cure processing will make the products produce white cloudy color, silver, and bubbles, PC at room temperature have as considerable ability to force high elastic deformation.
PC material should be molded under high material temperature, high mold tempera,pure and high pressure, and slow speed injection for small gates and a high-speed injection for other types of gates.
The mold temperature should be controlled around 80-110℃, and the molding temperature should be 280-320℃. PC products are easy to have air flowers on the surface, airlines at the water spout, and large internal residual stress, which is easy to crack.
Therefore, PC material molding processing requirements are high. PC material shrinkage rate is low (0.5%), but the size change is not. PC material beer out of the product can be used to anneal the method to eliminate its internal stress.
Extrusion PC molecular weight should be greater than 30,000, to use gradual compression screw, length-diameter ratio 1:18 ~24, compression ratio 1:2.5, can use extrusion blow molding, injection – blow, injection – pull – blow piece molding high quality, high transparent bottle.
Typical application areas
PC’s three major application areas are the glass assembly industry, automotive industry, and eelectronics, and lectrical industry, followed by industrial machinery parts, CD-ROM, civil clothing, computers and other office equipment, medical and health care, film, le, insure and protective equipment, etc.
12. EVA (rubber adhesive)
EVA is an amorphous plastic, non-toxic, specific gravity of 0.95g/cm3 (lighter than water), its products have poor surface gloss, good elasticity, soft and light, low mechanical strength, good fluidity, easy to process molding. Shrinkage is large (2%), and EVA can be used as a carrier for color masterbatch.
EVA process characteristics
EVA molding processing temperature is low (160-200 ℃), a wide range of low mold temperature (20-45 ℃), the material should be dried before processing (drying temperature of 65 ℃). EVA processing mold temperature, material temperature is not easy too high, otherwise, the surface is relatively rough (not smooth).
EVA products are easy to stick before the mold, and the water mouth of the mainstream cold material cavity makes a better pull button type. EVA should be used in “low temperature, medium pressure, medium speed” process conditions for processing products.
13. PVC (polyvinyl chloride)
Performance of PVC
PVC is an amorphous plastic with poor thermal stability andis susceptible to thermal decomposition (improper melting temperature parameters will lead to the problem of material decomposition.)
PVC is difficult to burn (good flame retardancy), has hhighviscosity, poor fluidity, high strength, resistance to weathering cha,nges, and excellent geometric stability. PVC materials are often added to stabilizers, lubricants, auxiliary process agents, colorants, impact agents and other additives in actual use.
There are many types of PVC, divided into t, semi,-hard and hard PVC, with the density of 1.1-1.3g/cm3 (heavier than water), large shrinkage (1.5-2.5%), shrinkage is quite low, generally 0.2-0.6%, PVC products with poor surface gloss, (the United States recently studied a transparent hard PVC comparable to PC).
PVC is resistant to oxidizers, reducing agents and strong acids. It is very resistant to oxidizing agents, reducing agents, and strong acids. However, it can be corroded by concentrated oxidizing acids such as concentrated sulfuric acid and nitric acid and is not suitable for contact with aromatic hydrocarbons and chlorinated hydrocarbons.
Process characteristics of PVC
Narrower processing temperature range than PVC (160-185 ℃), more difficult processing, and high process requirements, processing can generally be done without drying (if you need to dry, at 60-70 ℃).
Mold temperature is lower (20-50 ℃). PVC processing is easy to produce airlines, black lines, etc., must be strictly controlled processing temperature (processing temperature 185-205 ℃), injection pressure can be as large as 1500 bar, holding pressure can be as large as 1000 bar, in order to avoid material degradation.
Generally need to use a fairly low injection speed, screw speed should be lower (less than 50%), the residual amount should be less, back pressure The back pressure should not be too high. Mold exhaust should be good.
PVC material should not stay in the high-temperature barrel for more than 15 minutes. It is better to use large water products to feed PVC, and adopt “medium pressure, slow speed, low temperature” conditions to form and process.
PVC products are easy to stick to the front mold, so the opening speed (the first section) should not be too fast, and the water spout should be made into a pull-button type at the cold cavity of the runner. All conventional gates can be used
For small parts, it is better to use pin-point gates or submerged gates; for thick parts, it is better to use fan gates. The minimum diameter of the pin-tip gate or submerged gate should be 1mm; the thickness of the fan gate should not be less than 1mm.
Typical application areas
Water supply pipeline, household pipeline, housing wall panel, commercial machine shell, electronic product packaging, medical equipment, food packaging, etc.
14. PPO (polyphenylene ether)
Performance of PPO
Polyphenylene ether is poly 2,6-dimethyl-1,4-phenylene ether, also known as polyphenylene propylene oxide, the English name Polyphenyleneoxiole (PPO for short), modified polyphenylene ether is modified with polystyrene or other polymers of polyphenylene ether, referred to as MPPO.
PPO (NORLY) is a comprehensive performance of excellent engineering plastics, hardness than PA, POM, and PC, high mechanical strength, good rigidity, good heat resistance (heat deflection temperature of 126 ℃), high dimensional stability (shrinkage of 0.6%), low water absorption (less than 0.1%).
The disadvantages are unstable to ultraviolet light, high price, and low dosage. PPO is non-toxic, and transparent, has small relative density, excellent mechanical strength, stress relaxation resistance, creep resistance, heat resistance, water resistance, and water vapor resistance.
In a wide range of temperatures, frequency change electrical properties, not hydrolysis, molding shrinkage is small, non-combustible self-extinguish resistance to inorganic acids, alkalis, aromatic hydrocarbons, halogenated hydrocarbons, oils, and other poor performance, easy to swell or stress cracking.
The main drawback is the poor melt fluidity, processing, and molding difficulties, most of the practical applications for MPPO (PPO blends or alloys), such as those modified with PS PPO, can greatly improve processing performance, improve stress cracking resistance and impact resistance. Improve stress cracking resistance and impact performance, reduce costs, and only slightly reduce heat resistance and gloss.
Modified polymers are PS (including HIPS), PA, PTFE, PBT, PPS, and a variety of elastomers, polysiloxane-modified field PPO paraffin, the largest product, MPPO is the largest amount of general engineering plastics alloy species. The larger MPPO varieties are PPO / PS, PPPA/elastomeromer, and PPO / PBT elastomer alloy.
Process characteristics of PPO
PPO has high melt viscosity, poor flowability, and high processing conditions. Before processing, it needs to be dried at a temperature of 100-120℃ for 1-2 hours, the molding temperature is 270-320℃, and the mold temperature is controlled at 75-95℃ as appropriate.
This plastic beer plastic production process in front of the watewaterspoutsy to produproducest the flow pattern (snake pattern)and , the water spout flow channel to larger is better.
For standard molded products, the minimum thickness ranges from 0.060 to 0.125, inches, and for structural foam parts, the minimum thickness ranges from 0.125 to 0.250 inches, and the flammability ranges from UL94 HB to V-O.
Typical Application Range
PPO and MPPO can be processed by various methods such as injection molding, extrusion, blow molding, molding, foaming and plating, vacuum coating, printing press processing, etc. Due to the high viscosity of the melt, the processing temperature is high.
PPO and MPPO are mainly used in electronic appliances, automobiles, household appliances, office equipment, industrial machinery, etc.
Using MPPO heat resistance, impact resistance, dimensional stability, scuff resistance, feeling resistance; paintability, and electrical properties: are used to make automotive instrument panels, radiator grills, speaker grills, consoles, fuse boxes, relay boxes, connectors, wheel covers; widely used in the electronic and electrical industry Manufacturing connectors, coil winding spools, switches,s and relays, tuning equipment, large electronic displays, variable capacitors, battery accessories, microphones, and other parts.
Used in household appliances for TV sets, camerasvideotapeses, tape recorders, air conditioners, heaters, rice cookers, and other parts. It can be used as outer parts and components of copiers, computer systems, printers, fax machines, etc.
In addition, it can be made into the outer shell and parts of cameras, timers, pumps, blowers, silent gears, pipes, valve bodies, surgical instruments, sterilizers,s and other medical apparatus parts.
Large blow molding can be done for large automotive parts such as damper, bumper, and low foam molding suitable for making high rigidity, dimensional stability, excellent sound absorption, the complex internal structure of large products, such as a variety of machine shells, bases, internal brackets, freedom of design, lightweight products.
15. PBT Polybutylene terephthalate
Performance of PBT
PBT is one of the toughest engineering thermoplastic materials, it is a semi-crystalline material with very good chemical stability, mechanical strength, electrical insulation p r op,p arties, and thermal stability.
These materials have excellent stability over a wide range of environmental conditions, and PBT has very weak moisture absorption properties. The tensile strength of unreinforced PBTs is 50 MPa, and the tensile strength of glass additive PBTs is 170 MPa.
Excessive glass additives will cause the material to become brittle; PBTs crystallize very quickly, which will lead to bending deformation due to uneven cooling.
For materials with glass additive type, the shrinkage in the process direction can be reduced, but the shrinkage in the perpendicular direction to the process is no different from that of ordinary materials. The general material shrinkage rate is between 1.5% and 2.8%. Materials containing 30% glass additives shrink between 0.3% and 1.6%.
Melting point (225%℃) and high tempo high-temperature on temperature are lower than PET material. Vicat softening temperature is about 170℃. The glass transition temperature (glass trasitiotemperature) is between 22°C and 43°C.
Because of the high crystallization rate of PBT, it has a low viscosity and the cycle time for processing plastic parts is generally lower.
Process characteristics of PBT
Drying: This material hydrolyzes easily at high temperatures, so it is important to dry it before processing. The recommended drying condition in the air is 120C, 6-8 hours, or 150℃, 2-4 hours.
The humidity must be less than 0.03%. If using a hygroscopic dryer, the recommended drying condition is 150 ° C for 2.5 hours. The processing temperature is 225~275℃, and the recommended temperature is 250℃. For the unenhanced material mold temperature is 40~60℃.
The cooling cavity of the mold should be well designed to reduce the bending of the plastic parts. Heat must be lost quickly and evenly. It is recommended that the diameter of the mold cooling cavity is 12mm. The injection pressure is moderate (up to 1500bar maximum), and the injection rate should be as fast as possible (because PBT solidifies quickly).
Runners and gates: It is recommended to use circular runners to increase the pressure transfer (empirical formula: runner diameter = thickness of the part + 1.5 mm). Various types of gates can be used.
Hot runners can also be used, but care should be taken to prevent material leakage and degradation. The gate diameter should be between 0.8 and 1.0*t, where t is the thickness of the plastic part. In the case of submerged gates, a minimum diameter of 0.75 mm is recommended.
Typical application areas
Household appliances (food processing blades, vacuum cleaner components, electric fans, hair dryer shells, coffee utensils, etc.), electrical components (switches, motor housings, fuse boxes, computer keyboard keys, etc.), automotive industry (radiator grille windows, body panels, wheel covers, door and window components, etc.).