In the engineering plastics will be divided into two categories of general engineering plastics and special engineering plastics
General engineering plastics, including polycarbonate (PC), polyamide (PA), polyacetal (POM), modified polyphenylene ether (denatured PPE), polyester (PETP, PBTP), polyarylate, PMMA English name: Polymethylethyl Methacrylate. Thermosetting plastics are unsaturated polyester, phenolic plastics, epoxy plastics and so on. Their basic characteristics are tensile strength of more than 50Mpa, tensile strength of 500kg/cm, impact resistance of more than 50J/m, bending elasticity of 24000kg/cm, load bending temperature of more than 100 ℃, hardness, aging excellent. Polypropylene can also be included in the scope of engineering plastics if it improves its hardness and cold resistance. Specialty engineering plastics and crosslinked non-crosslinked type of points. Crosslinking type are: polyamidobismaleamide, polytriazine, crosslinked polyimide, heat-resistant epoxy tree fingers. Non-crosslinking type are: polysulfone (PSU), polyethersulfone (PES), polyphenylene sulfide (PPS), polyimide (PI Polyimide), polyetherether ketone (PEEK) Polybismaleimide, Polysufone (PSF), BTResin, polyetheroylideneglycol PEI, liquid crystal polymers (LCP) and so on.
The chemical structure of each engineering plastic is different, so their drug resistance, friction characteristics, motor characteristics, etc. differ. The following is a brief description of the properties of engineering plastics;
PMMA Poly(methyl methacrylate)
English name: Polymethyl Methacrylate
Typical applications:
Automotive industry (signaling equipment, dashboards, etc.), pharmaceuticals (blood storage containers, etc.), industrial applications (video discs, light diffusers), consumer products, and other products. diffusers), consumer goods (beverage cups, stationery, etc.).
Injection molding process conditions:
Drying treatment: PMMA is hygroscopic so drying treatment before processing is necessary. Suggested drying conditions are 90℃, 2~4 hours.
Melting temperature: 240~270℃.
Mold temperature: 35~70℃.
Injection speed: medium
Chemical and physical properties:
PMMA has excellent optical properties and resistance to weather changes. White light penetration up to 92%.PMMA products have a very low birefringence, especially suitable for the production of video discs, etc.PMMA has room temperature creep characteristics. With the increase in load, time growth, can lead to stress cracking phenomenon. PMMA has good impact resistance characteristics.
POM Polyformaldehyde
English name: Polyoxymethylene (Polyformaldehyde)
Typical applications:
POM has a very low coefficient of friction and very good geometric stability, especially suitable for the production of gears and bearings. It is also used in piping devices (piping valves, pump housings), lawn equipment, etc., as it is also resistant to high temperatures.
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; 190~210℃ for *** polymer materials.
Mold temperature: 80~105℃. In order to reduce the shrinkage rate after molding can choose a higher mold temperature.
Injection pressure: 700~1200 bar
Injection speed: medium or high injection speed.
Runner and gate: any type of gate can be used. If a tunnel gate is used, a shorter type is preferred. For homopolymer materials it is recommended to use hot nozzle runners. For *** polymer materials both internal and external hot runners can be used.
Chemical and Physical Properties:
POM is a tough, resilient material with good creep resistance, geometric stability and impact resistance even at low temperatures.POM is available in both homopolymer and ****opolymer materials. Homopolymer materials have good ductile strength, fatigue strength, but not easy to process. *** polymer materials have good thermal stability, chemical stability and easy to process. Both homopolymer and *** polymer materials are crystalline and do not readily absorb moisture. the high degree of crystallinity of POM results in a fairly high shrinkage rate, which can be as high as 2% to 3.5%. There are different shrinkage rates for different reinforced materials.
PA plastic (nylon) (polyamide)
English name: Polyamide
Specific gravity: PA6-1.14 g/cm3, PA66-1.15 g/cm3, PA1010-1.05 g/cm3,
Molding shrinkage: PA6-0.8-2.5%, PA66-1.5-2.2%, PA66-1.5-2.2%. 1.5-2.2%
Molding temperature: 220-300 ℃
Drying conditions: 100-110 ℃ 12 hours
Material Properties: tough, wear-resistant, oil-resistant, water-resistant, anti-enzymatic bacterial, but water absorption; nylon 6 good elasticity, high impact strength, water absorption is larger; nylon 66 performance is better than nylon 6, high strength, wear resistance is good; nylon 610 Nylon 610 is similar to nylon 66, but with small water absorption and low stiffness; nylon 1010 is semi-transparent, with small water absorption and good cold resistance.
Molding properties:
1. Crystalline material, high melting point, melting temperature range is narrow, thermal stability is poor, the material temperature exceeds 300 degrees, retention time of more than 30min is decomposed. Easily hygroscopic, need to dry, water content shall not exceed 0.3%.
2. Good fluidity, easy to overflow. Suitable for self-locking nozzle, and should be heated.
3. Molding shrinkage range and shrinkage rate is large, the direction of the obvious, easy to occur shrinkage, deformation, etc..
4. Mold temperature according to the wall thickness of the plastic parts in the range of 20-90 degrees selected, injection pressure according to the type of injection machine, material temperature, shape and size of the plastic parts, mold pouring system selected, molding cycle according to the wall thickness of the plastic parts selected. When the viscosity of the resin is small, the injection and cooling time should be longer, and white oil should be used as the mold release agent.
5. The form and size of the mold casting system, increase the size of the runner and gate can reduce shrinkage.
Applications:
Suitable for the production of general mechanical parts, wear parts, transmission parts, as well as chemical, electrical, instrumentation and other parts
PC Polycarbonate
English name: Polycarbonate
Typical applications:
Electrical and commercial equipment (computer components, connectors, etc.), appliances (food processing machines, refrigerator drawers, etc.). processors, refrigerator drawers, etc.), and the transportation industry
(front and rear lights, instrument panels, etc.).
Injection molding process conditions:
Drying treatment: PC material is hygroscopic, drying before processing is very important. Suggested drying conditions are 100℃ to 200℃ 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.
Chemical and Physical Properties:
PC is a non-crystalline engineering material with exceptionally good impact strength, thermal stability, gloss, bacterial inhibition, flame retardancy, and resistance to contamination.PC has a very high notched Izod impact stregth and very low shrinkage, typically 0.1% to 0.2%. ~PC has very good mechanical properties, but poor flow characteristics, so the injection molding process of this material is more difficult. The quality of the PC material to be used is based on the final expectations of the product. If the part requires high impact resistance, then use a PC material with a low flow rate; conversely, a PC material with a high flow rate can be used to optimize the injection molding process.
PETG Glycol-modified PET; Copolyesters
Typical applications:
Pharmaceutical equipment (test tubes, reagent bottles, etc.), toys, monitors, light source housings, protective masks, refrigerator freshness trays, and more.
Injection mold process conditions:
Drying treatment: drying treatment before processing is necessary. Humidity must be less than 0.04%. Suggested drying conditions are 65C, 4 hours, and be careful not to exceed 66C.
Melting temperature: 220~290C.
Mold temperature: 10~30C, 15C is recommended.
Injection pressure: 300~1300bar.
Injection speed: higher injection speeds can be used if they don't lead to embrittlement. speed.
Chemical and Physical Properties:
PETG is a transparent, amorphous material. The glass transition temperature is 88 C. The allowable range of injection molding process conditions for PETG is somewhat wider than for PET, and it has the combined properties of transparency, high strength, and high capriciousness.
PAR or PAT polyarylate or polyarylate
Specific gravity:1.2-1.26g/cm3
Molding shrinkage:0.8%
Molding temperature:300-350C
Drying conditions:100-120C-5hours
Material properties:
1, Transparent amorphous thermoplastic engineering plastics, with excellent heat resistance, flame retardancy and non-toxicity. It can be directly processed into products by ordinary thermoplastic molding methods.
2, has excellent thermal properties, in the 1.86MPA load, its heat distortion temperature up to 175 degrees, decomposition temperature of 443 degrees. Its various mechanical properties are less affected by temperature.
Molding properties:
1. With the increase of wall thickness of the product, molding shrinkage increases.
2. Moisture absorption is small, about 0.1-0.3%, but injection molding trace moisture will cause polyarylate decomposition. Therefore, the material must be dried before molding. Make its water content less than 0.02%.
Use:
1, suitable for the production of heat-resistant, flame-resistant and high dimensional stability of electrical parts. Connector, coil holder, relay shell.
2, lighting parts. Can be made into transparent lampshade, illuminator, automobile reflector.
3, the definition of polyarylate is a bivalent phenol and aromatic acid reaction generated by the aromatic condensation polymers, the following collation of A bisphenol and terephthalic acid, isophthalic acid mixed with benzene dicarboxylic acid generated by the non-crystalline polyarylate.
In terms of applications, there is a tendency for automotive and mechanical uses to increase, while electrical uses are declining slightly. In the automobile, there are automobile lamp lenses such as the lens in the steering lamp, the diffuser lens in the rear lamp, the lens in the indoor lamp, the electronic products such as the reflector of the rotary lamp, the FL fuse, and the body of the searchlight, the lens, and the indicator gauge of the hydraulic rangefinder, and so on, and in the electricity, there are the switches, the relays, and the cover of the LED reflector in the electric apparatus, and in the OA affairs machine, there are the cylinder clamp of the FDD, the wheel housing of the CFD, the slide of the facsimile machine, and so on. For OA equipment, there are FDD cartridges, CFD wheel housings, fax machine slides, etc. In machinery-related applications, it is used in clocks and watches, AV machine gears, pumps, and bearing retainers. In the medical field, they are used for eye-dotting containers and examination drug containers. In the medical field, it is used for eye-dotting containers and inspection medicine containers, etc. In addition, it is used for heat-resistant beverage bottles that utilize multi-layer and insertion methods. The bottom of golf clubs is also a new application.
It has a glass transition temperature of 193 degrees Celsius, which is higher than that of polycarbonate. Because it is non-crystalline, it is in a glassy state in the practical temperature range. Also in terms of dynamic loss, at -60 degrees C can be considered another sharp peak, so the cold resistance is also very good.
UL temperature parameters are 140°C for electrical properties and 130°C for mechanical properties.
Because it is a non-crystalline plastic, it is susceptible to attack by aromatics, esters, aqueous chlorinated carbon, etc. It is also resistant to low concentration acids. It is resistant to low concentration of acids.
Because it is a polyester, it is subject to hydrolysis.
Transparency is excellent, with a light transmission rate of 87% at a thickness of 2mm, the same level as that of polycarbonate. Ultraviolet rays below 350m u can hardly pass through 0.1mm thickness. On the other hand, the transmittance rate for UV rays below 400m u is nearly 90%. The UV resistance is superior to that of polycarbonate.
Good weather resistance.
With a wide range of elasticity recovery and good recovery from deformation.
Limited oxygen index about 37%
Polyphenylene ether resin PPO
English name; Polyphenylene oxide-usually modified
Physical properties
Specific gravity:1.07g/cm3 Molding shrinkage:0.3-0.8% Molding temperature:260- 290℃ Drying condition:130℃. 290℃ Drying condition:130℃ 4 hours
Material properties
1. It is white granule. Good comprehensive performance, can be used in 120 degrees steam, good electrical insulation, small water absorption, but there is a tendency to stress cracking. Modified polyphenylene ether can eliminate stress cracking.
2, has outstanding electrical insulation and excellent water resistance, good dimensional stability. Its dielectric properties of plastics in the first place.
3, MPPO for PPO and HIPS **** mixing of modified materials, currently on the market are such materials.
4, high heat resistance, glass transition temperature of 211 degrees, melting point of 268 degrees, heated to 330 degrees has a tendency to decompose, the higher the content of PPO the better its heat resistance, heat distortion temperature of up to 190 degrees.
5, good flame retardant, self-interested, and HIPS mixed with medium flammability. Lightweight, non-toxic can be used in the food and drug industry. Poor spin resistance, long time use in the sun will change color.
6, can be mixed with ABS, HDPE, PPS, PA, HIPS, fiberglass and other **** modified processing.
Applications
1, suitable for making heat-resistant parts, insulating parts, wear-reducing parts, transmission parts, medical and electronic parts.
2, can be used for higher temperature gears, air blades, valves and other parts, can be used instead of stainless steel.
3, can make screws, fasteners and connectors.
4, motor, rotor, casing, transformer electrical parts.
Molding properties
1.Non-crystalline material, small moisture absorption.
2. Poor fluidity, similar to the Newtonian fluid, viscosity is sensitive to temperature, the thickness of the product is generally more than 0.8 mm. Very easy to decompose, decomposition of corrosive gases. It is desirable to strictly control the molding temperature, the mold should be heated, the pouring system should be small resistance to material flow.
3, polyphenylene ether water absorption is very low 0.06% or so, but a trace of moisture will lead to the surface of the product silver and other non-smooth phenomena, it is best to make the drying process, the temperature should not be higher than 150 degrees, otherwise the color will change.
4, polyphenylene ether molding temperature of 280-330 degrees, modified polyphenylene ether molding temperature of 260-285 degrees.
Cylinder temperature Feeding zone 40～60℃(50℃)
Zone 1 240～280℃(250℃)
Zone 2 280～300℃(280℃)
Zone 3 280～300℃(280℃)
Zone 4 280～300℃(280℃)
Zone 5 280～ 300℃ (280℃)
Nozzle 280～300℃ (280℃)
Melt temperature 270～290℃
Cylinder temperature 200℃
Mold temperature 80～120℃
Injection pressure 100～140MPa (1000～1400bar)
Pressure holding Pressure 40% to 60% of injection pressure
Back pressure 3 to 10MPa (30 to 100bar)
Injection speed Fast injection is required for products with long runners; however, in this case, make sure that the mold has sufficient aeration
Screw speed Medium screw speed, with a converted linear speed of 0.6m/s
Metering stroke Medium screw Rotation speed of the screw, converted line speed of 0.6m/s
Measuring stroke (0.5-3.5)D
Residue volume 3-6mm, depending on the measuring stroke and diameter of the screw
Pre-drying Drying at 110℃ for 2h
Recycling rate The material can be reproduced and processed as long as the return material does not undergo thermal degradation
Shrinkage rate 0.8%～1.5%
Shrinkage rate 0.8%～1.5%
Shrinkage rate 0.8%～1.5 1.5%
Gating system Spot or submerged gates for small products, otherwise straight or disk gates; hot runners can be used
Machine downtime Shut down the heating system; operate a few metering cycles at low screw back pressure and empty the barrel as if it were an extruder
Barrel equipment Standard screw, non-return ring, straight-through nozzle
PBT Polybutylene terephthalate
English name: Polybutylene terephthalate
Typical applications:
Household appliances (food processor blades, vacuum cleaner components, electric fans, hair dryer housings, coffee containers, etc.), electrical components (switches, motor housings, fuse boxes, computers, keyboard keys, etc.), automotive industry, and electrical appliances. Electrical components (switches, motor cases, fuse boxes, computer keyboard keys, etc.), automotive industry (radiator grills, body panels, wheel covers, door and window parts, etc.).
Injection mold process conditions:
Drying treatment: this material is easily hydrolyzed at high temperatures, so drying treatment before processing is very important. Suggested drying condition in air is 120℃ for 6~8 hours or 150℃ for 2~4 hours. The humidity must be less than 0.03%. If dried with a hygroscopic dryer, the recommended conditions are 150°C, 2.5 hours.
Melting temperature: 225~275°C, recommended temperature: 250°C .
Mold temperature: 40~60℃ for unreinforced material. The cooling cavity of the mold should be well designed to reduce the bending of the part. The heat dissipation must be fast and even. The recommended diameter of the mold cooling channel is 12mm.
Injection pressure: Medium (up to 1500 bar).
Injection speed: The fastest possible injection speed should be used (because PBT solidifies very quickly).
Runners and gates: It is recommended to use round runners to increase pressure transfer (empirical formula: runner diameter = part thickness + 1.5mm). 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 molded part. In case of submerged sprues, a minimum diameter of 0.75mm is recommended.
Chemical and Physical Properties:
PBT is one of the toughest engineered thermoplastics, which are semi-crystalline materials with very good chemical stability, mechanical strength, electrical insulation properties and thermal stability. These materials are well stabilized under a wide range of environmental conditions. PBT has weak hygroscopic properties. Non-reinforced PBT has a tensile strength of 50 MPa and glass additive type PBT has a tensile strength of 170 MPa. too much glass additive will cause the material to become brittle. the crystallization of PBT is very rapid, which leads to bending deformation due to uneven cooling. For materials with glass additive types, the shrinkage in the process direction can be reduced, but the shrinkage in the direction perpendicular to the process is basically indistinguishable from that of ordinary materials. The shrinkage rate of normal materials is between 1.5% and 2.8%. Materials containing 30% glass additives shrink between 0.3% and 1.6%. The melting point (225°C) and high-temperature deflection temperature are lower than those of PET materials. The Vicat softening temperature is about 170°C. The glass transition temperature (glass trasitio temperature) is between 22℃ and 43℃. Because of its high rate of crystallization, PBT has low viscosity and generally lower cycle times for plastic part processing.
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