Basic properties and uses of 14 engineering plastics

1, polyamide PA

Basic nature

Specific gravity: PA6-1.14g/cm3, PA66-1.15g/cm3, PA1010-1.05g/cm3

Molding shrinkage: PA6-0.8-2.5%, PA66-1.5-2.2%

Molding temperature: 220-300 ° C

Drying conditions: 100-110 ° C, 12 hours

Material performance

Tough, wear-resistant, oil-resistant, water-resistant, anti-enzytic, but absorbent. Nylon 6 has good elasticity, high impact strength and high water absorption; nylon 66 has better performance than nylon 6, high strength and good wear resistance; nylon 610 is similar to nylon 66, but has low water absorption and low rigidity; nylon 1010 is translucent and has low water absorption. Good cold resistance.

Molding characteristics

1. The melting point of the crystal material is relatively high, the melting temperature range is narrow, and the thermal stability is poor. When the material temperature exceeds 300 degrees and the residence time exceeds 30 minutes, it decomposes. It is easier to absorb moisture and needs to be dried. The water content should not exceed 0.3%;

2, good liquidity, easy to overflow. It is advisable to use a nozzle when self-locking and should be heated;

3. The molding shrinkage range and shrinkage rate are large, the directionality is obvious, and shrinkage and deformation are easy to occur;

4. The mold temperature is selected according to the wall thickness of the plastic part in the range of 20-90 degrees. The injection pressure is selected according to the type of the injection machine, the material temperature, the shape of the plastic part, the mold casting system, and the molding cycle is selected according to the wall thickness of the plastic part. When the viscosity of the resin is small, the injection and cooling time should be long, and white oil is used as a release agent;

5. The form and size of the mold casting system, increasing the size of the runner and gate can reduce shrinkage.

Scope of application

Production of general mechanical parts, wear-resistant parts, transmission parts, as well as chemicals, electrical appliances, meters, etc.

2, polycarbonate PC

Basic nature

Specific gravity: 1.18-1.20g/cm3

Mold shrinkage: 0.5-0.8%

Molding temperature: 230-320 ° C

Drying conditions: 110-120 ° C, 8 hours

Material properties:

High impact strength, good dimensional stability, colorless and transparent, good coloring, good electrical insulation, corrosion resistance and wear resistance, but poor self-lubrication, stress cracking tendency, high temperature easy hydrolysis, poor compatibility with other resins .

Molding characteristics

1. Amorphous material, good thermal stability, wide forming temperature range and poor fluidity. Low moisture absorption, but sensitive to water, must be dried. The molding shrinkage rate is small, and it is prone to melt cracking and stress concentration. Therefore, the molding conditions should be strictly controlled, and the plastic parts must be annealed;

2. The melting temperature is high and the viscosity is high. For plastic parts larger than 200g, a heated extension nozzle should be used;

3, the cooling rate is fast, the mold casting system is based on the principle of coarse and short, it is better to set up a cold well, the gate should be large, and the mold should be heated;

4, the material temperature is too low will cause lack of material, plastic parts are dull, the material temperature is too high and easy to overflow, plastic parts foaming. When the mold temperature is low, the shrinkage rate, elongation, impact strength are high, and the bending, compressive and tensile strengths are low. When the mold temperature exceeds 120 degrees, the plastic parts are cooled slowly, and the mold is easily deformed.

Scope of application

Make small parts, insulated transparent parts and impact resistant parts.

3. POM POM

Basic nature

Specific gravity: 1.41-1.43g/cm3

Molding shrinkage: 1.2-3.0%

Molding temperature: 170-200 ° C

Drying conditions: 80-90 ° C, 2 hours

Material performance

Good comprehensive performance, high strength, high stiffness, good wear resistance, low water absorption, good dimensional stability, but poor thermal stability, easy to burn, easy to age in the atmosphere.

Molding characteristics

1. Crystallized material, narrow melting range, fast melting and solidification, and crystallization occurs when the material temperature is slightly lower than the melting temperature. Medium mobility. Low moisture absorption, no drying treatment;

2. The friction coefficient is low, the elasticity is good, and the surface of the plastic part is prone to wrinkle pattern surface defects;

3, very easy to decompose, the decomposition temperature is 240 degrees. Irritating and corrosive gases occur during decomposition. Therefore, the mold steel should be made of corrosion-resistant materials.

Scope of application

Make wear-reducing parts, transmission parts, and parts such as chemicals and instruments.

4. Polyphenylene ether PPO

Basic nature

Specific gravity: 1.07g/cm3

Mold shrinkage: 0.3-0.8%

Molding temperature: 260-290 ° C

Drying conditions: 130 ° C, 4 hours

Material performance

1, as white particles. Good comprehensive performance, can be used in 120 degree steam, good electrical insulation, low water absorption, but there is a tendency to stress cracking. Modified polyphenylene ether can eliminate stress cracking;

2. Excellent electrical insulation and water resistance, good dimensional stability. Its dielectric properties rank first in plastics;

3. MPPO is a modified material prepared by blending PPO and HIPS. Currently, the materials on the market are such materials;

4, has a higher heat resistance, glass transition temperature of 211 degrees, melting point of 268 degrees, heating to 330 degrees has a tendency to decompose, the higher the PPO content, the better the heat resistance, the heat distortion temperature can reach 190 degrees;

5, good flame retardancy, self-interest, and moderate flammability after mixing with HIPS. Lightweight, non-toxic for the food and pharmaceutical industries. Poor light resistance, it will change color when used in the sun for a long time;

6, can be blended with ABS, HDPE, PPS, PA, HIPS, glass fiber, etc.

Molding characteristics

1. Non-crystalline material, low moisture absorption;

2, poor fluidity, similar to Newtonian fluid, viscosity is sensitive to temperature, the thickness of the product is generally above 0.8mm. It is easily decomposed and generates corrosive gases during decomposition. The molding temperature should be strictly controlled, the mold should be heated, and the casting system should have a small resistance to the flow;

3, the water absorption rate of polyphenylene ether is very low 0.06%, but a small amount of water will cause the surface of the product to appear silvery and other non-smooth phenomenon, it is best to dry, the temperature can not be 150 degrees higher, otherwise the color will change;

4. The molding temperature of polyphenylene ether is 280-330 degrees, and the molding temperature of modified polyphenylene ether is 260-285 degrees.

Scope of application

Production of heat-resistant parts, insulation parts, wear-reducing parts, transmission parts, medical and electronic parts; gears, blades, valves and other parts that can be used at higher temperatures, can be used instead of stainless steel; can be made of screws, fastened Parts and connectors; electrical parts for motors, rotors, housings, transformers.

5, thermoplastic polyester

Polyethylene terephthalate PET

Basic nature

In the past, it was mostly used as fiber, that is, polyester fiber, and it is now rapidly developing in engineering plastics and packaging plastics. Depending on the application, PET can be classified into fiber grade, film grade, blow molding grade and reinforcement.

Material performance

1. It is a colorless transparent or milky white translucent solid;

2, has a high tensile strength, stiffness and hardness, but has a certain flexibility, good wear resistance, creep resistance, and can maintain these good mechanical properties in a wide temperature range;

3. Excellent electrical insulation;

4, has excellent weather resistance, after six years of outdoor exposure, its mechanical properties can still maintain the initial 80%;

5, resistant to weak acid, good chemical stability to organic solvents and oils.

Scope of application

1. Making a film, a photosensitive film, such as a film film base, a photographic film film;

2. As a package for food, medicine, textiles, precision instruments, electrical components, etc., the hollow container made of high strength, good transparency, non-toxic and tasteless, is a widely used plastic packaging material for carbonated beverages, beer, edible oil, etc.; material;

3, used to make a variety of electrical insulation materials, such as wires, switches, electrical enclosures.

Polybutylene terephthalate PBT

Basic nature

PBT used as engineering plastics has two kinds of unmodified and modified. The unmodified grade has high molding shrinkage and mechanical properties are inferior to other engineering plastics, so it is rarely used alone. Nearly 80% of PBT is modified.

Material performance

1. It is a milky white crystalline solid, tasteless, odorless, non-toxic, and the surface of the product is shiny. The flexibility is better than PET, and the melting temperature and rigidity are relatively small;

2. It has excellent electrical insulation. It can be maintained even in humid and harsh environments;

3. Good weather resistance;

4, can resist the corrosion of general chemicals, such as weak acid.

Scope of application

1. Make various auto parts, such as door handles, bumpers, mirror housings, etc.

2, the production of electrical and electronic parts, such as connectors, sockets, plugs, fuse boxes, etc.;

3, the production of various electrical enclosures and components, such as telephones, indoor and outdoor lighting appliances, hair dryer components.

6, ultra high molecular weight polyethylene

Basic nature

The relative molecular mass is more than 1.5 million, and the comprehensive performance is a special engineering plastic that is not available in conventional molecular weight polyethylene. The molecular structure is identical to ordinary polyethylene, but the molecular weight is particularly high. In UHMWPE with a relative molecular mass of more than 1.5 million, there are also grades with a relative molecular mass of 2 million, 3 million, or even more than 5 million.

Material performance

1. The average molecular weight is about 350,000 to 8 million. Due to its high molecular weight, it has excellent resistance to impact, abrasion, self-lubrication and chemical corrosion.

2, excellent low temperature resistance, high impact strength at -40 ° C, even at -269 ° C;

3. It has electrical insulation, low water absorption and physiological inertia;

4. Excellent resistance to stress cracking, creep resistance and fatigue resistance.

Scope of application

Used in machinery, transportation, textile, paper, mining, agriculture, chemical and sports equipment, etc., which is the most widely used in large packaging containers and pipelines; it has also been used as a heart valve or orthopedic part due to its excellent physiological inertia. , artificial joints, etc. are used in clinical medicine.

7, thermoplastic

Polyacrylonitrile-butadiene-styrene ABS

Basic nature

Specific gravity: 1.05g/cm3

Molding shrinkage: 0.4-0.7%

Molding temperature: 200-240 ° C

Drying conditions: 80-90 ° C, 2 hours

Material performance

1. Good comprehensive performance, high impact strength, good chemical stability and electrical properties;

2, and 372 plexiglass has good weldability, can be made into two-color plastic parts, and can be chrome-plated and painted;

3, with high impact, high heat, flame retardant, enhanced, transparent and other levels;

4, the fluidity is a little worse than HIPS, better than PMMA, PC, etc., and good flexibility.

Molding characteristics

1. Amorphous material, medium fluidity, large moisture absorption, must be fully dried, plastic parts with surface requirements of gloss must be preheated and dried for 80-90 degrees for 3 hours;

2, should take high material temperature, high mold temperature, but the material temperature is too high and easy to decompose (decomposition temperature is >270 degrees), for high precision plastic parts, mold temperature should be 50-60 degrees, high gloss, resistance For thermoplastic parts, the mold temperature should be 60-80 degrees;

3, if you need to solve the water trap, you need to improve the fluidity of the material, take high material temperature, high mold temperature, or change the water level and other methods;

4. If the heat-resistant grade or flame-retardant grade material is formed, after 3-7 days of production, plastic decomposition products will remain on the surface of the mold, which will cause the surface of the mold to be bright. It is necessary to clean the mold in time, and the surface of the mold needs to increase the exhaust position.

Scope of application

Make general mechanical parts, wear-resistant parts, transmission parts and telecommunications parts.

8. Polyphenylene sulfide PPS

Basic nature

Specific gravity: 1.36g/cm3

Molding shrinkage: 0.7%

Molding temperature: 300-330 ° C

Material performance

1, electrical insulation (especially high-frequency insulation) is excellent, white, hard and brittle, falling on the ground with metal sound, light transmittance is second only to plexiglass, coloring water resistance, chemical stability. Has excellent flame retardancy and is non-combustible plastic;

2, the strength is general, the rigidity is very good, but the quality is brittle, easy to produce stress brittle fracture; not resistant to organic solvents such as benzene, gasoline; long-term use temperature up to 260 degrees, stable in 400 degrees of air or nitrogen. After being modified by adding glass fiber or other reinforcing materials, the impact strength can be greatly improved, heat resistance and other mechanical properties are also improved, the density is increased to 1.6-1.9 g/cm3, and the molding shrinkage is as small as 0.15-0.25. %.

Molding characteristics

1. Amorphous material, small moisture absorption, but should be formed after drying;

2. The fluidity is between ABS and PC. It has fast solidification, small shrinkage and easy decomposition. It uses high injection pressure and injection speed. The mold temperature is taken from 100 to 150 degrees. The main channel should be large and the flow path should be short.

Scope of application

Production of heat-resistant parts, insulation parts, chemical instruments, optical instruments and other parts. Such as: TV, high-voltage components on the computer, the outer casing, the starting coil of the motor, the blade, the brush bracket and the rotor insulation parts, relays, electric irons, F-class film. In the automotive sector, exhaust gas recirculation valves and pump impellers, bearings, and sensing components can be fabricated.

9, polysulfone PSF or PSU

Basic nature

Specific gravity: 1.25-1.35g/cm3

Molding shrinkage: 0.5-0.7%

Molding temperature: 290-350 ° C

Drying conditions: 130-150 ° C, hour

Material performance

1. Polysulfone is amber transparent solid material with high hardness and impact strength, non-toxic, heat-resistant, cold-resistant and aging-resistant. It can be used for a long time at -100--175 degrees. Corrosion resistant to inorganic acid and alkali salts, but not resistant to aromatic hydrocarbons and halogenation;

2, through the glass fiber reinforced modification can greatly improve the wear resistance of the material;

3, polysulfone and ABS, polyimide, polyetheretherketone and fluoroplastics can be made into polysulfone modified products, mainly to improve their impact strength and elongation, solvent resistance, environmental resistance, processing Performance and platability. Such as PSF / PBT, PSF / ABS, PSF + mineral powder.

Molding characteristics

1. Amorphous material, large moisture absorption, water absorption rate 0.2%-0.4%, must be fully dried before use, and prevent moisture absorption. Ensure that the water content is below 0.1%;

2, the molding performance is similar to PC, the thermal stability is poor, and decomposition begins at 360 degrees;

3, poor fluidity, fast cooling, should be formed with high temperature and high pressure. The mold should have sufficient strength and rigidity, set the cold well, the flow path should be short, and the gate size should be 1/2-1/3 of the wall thickness of the plastic part;

4. In order to reduce the internal stress generated by the injection molded product, the mold temperature should be controlled at 100-140 degrees. After molding, it can be annealed glycerin bath annealing treatment, 160 degrees, 1-5 minutes; or take an air bath 160 degrees, 1-4 hours. The annealing time depends on the size and wall thickness of the article;

5. Polysulfone is close to Newtonian in the molten state. Similar to polycarbonate, the fluidity is sensitive to temperature. In the range of 310-420 degrees, the fluidity increases by 1 time for every 30 degrees of temperature increase. Therefore, the molding fluidity is improved mainly by increasing the temperature during molding.

Scope of application

1. It is suitable for making heat-resistant parts, insulating parts, wear-reducing parts, instrument parts and medical equipment parts, and also suitable for making low-temperature working parts;

2. Polysulfone is commonly used in the electronic and electrical industry to manufacture integrated circuit boards, coil tubes, contactors, sleeves, capacitor films, and high-performance alkaline battery casings;

3. Polysulfone is used in household appliances for microwave oven equipment, coffee heaters, humidifiers, hair dryers, steam dryers, beverages and food dispensers. It can also be used as a substitute for non-ferrous metals for precision structural parts such as watches, copiers, cameras, etc.;

4, polysulfone has passed the relevant regulations in the US medicine and food fields, can replace stainless steel products, used as surgical tool trays, sprayers, fluid controllers, heart valves, pacemakers, gas masks, dental trays, etc.

10, fluoroplastic

Fluoroplastics are paraffinic polymers in which some or all of the hydrogen is replaced by fluorine. They are polytetrafluoroethylene (PTFE), perfluoroethylene propylene (FEP) copolymer, polyperfluoroalkoxy (PFA) resin, polytrifluorocarbon. Vinyl chloride (PCTFF), ethylene-trifluorovinyl chloride copolymer (ECTFE), ethylene tetrafluoroethylene (ETFE) copolymer, polyvinylidene fluoride (PVDF) and polyvinyl fluoride (PVF).

PTFE PTFE

Basic nature

Specific gravity: 2.1-2.2g/cm3

Mold shrinkage: 3.1-7.7%

Molding temperature: 330-380 ° C

Material performance

1. Long-term use temperature -200--260 degrees, excellent chemical resistance, corrosion resistance to all chemicals, friction coefficient is the lowest in plastic, good electrical properties, electrical insulation is not affected by temperature Influence, known as the "plastic king";

2. It is transparent or translucent. The higher the crystallinity, the worse the transparency. Most of the raw materials are powdery resins or concentrated dispersions, which have extremely high molecular weight and are high crystallinity thermoplastic polymers.

Molding characteristics

1. Crystallized material, low moisture absorption;

2. Poor fluidity, easy to decompose, and corrosive gas generated during decomposition. The molding temperature should be strictly controlled, the mold should be heated, and the casting system should have a small resistance to the flow;

3. Powdered resin is usually formed by powder powder metallurgy, using a sintering method. The sintering temperature is 360-380 degrees and cannot exceed 475 degrees. The emulsion resin is usually processed by a cold extrusion and re-sintering process to form an anti-corrosion layer on the surface of the article. If the product is required to have transparency and toughness, rapid cooling should be adopted. It can also be extruded to extrude tubes, rods and profiles;

4. The viscosity of PTFE melt is very high, and the viscosity of the volume decreases with the increase of shear stress, indicating the characteristics of non-Newtonian fluid;

5, secondary processing, hot pressing compounding, welding, bonding, reinforcement, machining, etc., in order to obtain the final product.

Scope of application

Produces corrosion-resistant parts, wear-resistant parts, seals, insulation and medical device parts.

PTFE-ethylene copolymer ETFE

Basic nature

Specific gravity: 1.7g/cm3

Mold shrinkage: 3.1-7.7%

Molding temperature: 300-330 ° C

Material performance

1, long-term use temperature -80--220 degrees, has excellent chemical resistance, corrosion resistance to all chemicals, friction coefficient is the lowest in plastic, and has good electrical properties, its electrical insulation is not affected by temperature Influence, known as the "plastic king";

2. Its chemical resistance is similar to that of PTFE, better than vinylidene fluoride;

3, its creep resistance and compressive strength are better than PTFE, high tensile strength, elongation of 100-300%, good dielectric properties, excellent radiation resistance.

Molding characteristics

1. Crystallized material, low moisture absorption. It can be processed into a product by a processing method which is usually obtained from a thermoplastic;

2. Poor fluidity, easy to decompose, and corrosive gas generated during decomposition. Strictly control the molding temperature not to exceed 350 degrees, the mold should be heated to 100

11, polyaryl ether ketone PEAK

Polyaryletherketone (PEAK) is a type of polymer in which a phenylene ring is linked by an ether bond and a carbonyl group. At present, there are mainly polyetheretherketone (PEEK), polyetherketone (PEK), polyetherketoneketone (PEKK), polyetheretherketoneketone (PEEKK) and polyetherketoneetherketoneketone (PEKEKK). In the polyaryl ether ketone series, the lower the ratio (E/K) of the ether bond to the ketone group in the molecular chain, the higher the melting point and the glass transition temperature. The ether bond in the molecular structure of the poly(aryl ether ketone) makes it flexible, so it can be processed by a processing method of a thermoplastic engineering plastic.

Material performance

1, with good high temperature performance, long-term use temperature above 240 ° C;

2, the mechanical performance is extremely high. Excellent chemical resistance, good radiation resistance, and can withstand 10 gamma gamma irradiation;

3, the combustion performance can reach the level of UL94V-0, and the amount of smoke is very low and non-toxic when burning, and the heat released during combustion is also very small, which is an important technical performance for the interior decoration parts of the aircraft;

4. It has good electrical performance in a wide working temperature and frequency range, and has low dielectric loss under high frequency. It is an excellent C-class electrical insulating material with high temperature resistance and high strength.

Scope of application

1. Most of the structural components used in the aerospace field with high technology or in the automotive industry, electrical and electronic industry and machinery industry with strict technical requirements;

2. Various connectors for flame and oil resistance on aircraft; radomes for weather resistance and creep resistance;

3. Used in the automotive industry and machinery industry for various components that can withstand dynamic loads, such as bearing retainers, gears, hot water pumps, turbine blades, wear-resistant seal rings, etc.

4. In medical devices, PPEK manufactures heaters and pressure sensor housings in hemodialysis machines and dental instruments that require sterilization. PPEK can also replace human metals to make human bones. The potential application prospects are very attractive.

12. Polyarylate PAR

Basic nature

Specific gravity: 1.2-1.26g/cm3

Mold shrinkage: 0.8%

Molding temperature: 300-350 ° C

Drying conditions: 100 to 120 ° C, 5 hours

Material performance

1. It is a transparent amorphous thermoplastic engineering plastic with excellent heat resistance, flame retardancy and non-toxicity. It can be directly processed into articles by ordinary thermoplastic molding methods;

2, has excellent thermal performance, under the load of 1.86MPA, its heat distortion temperature is as high as 175 degrees, the decomposition temperature is 443 degrees. Its various mechanical properties are less affected by temperature.

Molding characteristics

1. As the wall thickness of the product increases, the molding shrinkage rate increases;

2, the hygroscopicity is small, about 0.1-0.3%, but a small amount of moisture during injection will cause the decomposition of polyarylamine. Therefore, the material must be dried before molding. Making the water content less than 0.02%;

Scope of application

1. It is suitable for making electrical parts with high heat resistance, flame resistance and high dimensional stability. Connector, coil former, relay housing;

2. Lighting parts. Can be made into a transparent lampshade, illuminator, car reflector and so on.

13, liquid crystal polymer LCP

Liquid crystal polymer refers to a polymer material capable of forming a liquid crystal state under certain conditions, referred to as LCP, and is one of the fastest growing new materials in recent years. It can be divided into two types: lyotropic (LLCP) and thermotropic (TLCP). The thermotropic liquid crystal refers to a liquid crystal state which can be exhibited in a molten state, and is mainly used as an engineering plastics application. According to the temperature resistance grade, it can be roughly classified into three types: super heat resistant type, medium heat resistant type, and low heat resistant type.

Material properties

1. LCP is a high-strength, high-modulus, creep-resistant, high-impact-resistant polymer material, and its mechanical properties are much higher than ordinary engineering materials;

2, outstanding wear resistance, high surface hardness, low wear. The molding shrinkage rate is extremely small, and the processing fluidity is excellent. High thermal stability and heat resistance. Excellent electrical insulation;

3, has excellent chemical stability, is also very stable to ultraviolet radiation. It has outstanding flame retardancy, generally can achieve UL94V-0 flame retardant level without adding flame retardant, and smoke is very low;

4. It also has excellent vibration absorption characteristics, which can be used as an audio component to reduce noise.

Scope of application

1. High-density connectors, coil holders, bobbins, sockets, etc.; speaker vibration board and earphone switch in audio-visual equipment; floppy disk, hard disk drive, copy parts, etc. in office equipment;

2, in the chemical industry, for a variety of devices and components. Such as distillation tower packing, valves, oil well equipment, etc.;

3. In the advanced science and technology fields such as aerospace, aviation and military industry, it has broad application prospects. If it is resistant to high temperature, flame retardant and low smoke, it can be used for various parts inside the aircraft;

4. It has unique advantages for medical devices. Because the surgical instruments of LCP materials are invasive, they will become the master of medical miniaturization technology;

5, LCP other applications in microwave oven stove containers, packaging materials, sports equipment.

14, polyimide PI

Polyimide, referred to as PI, is the earliest special engineering plastics with high temperature resistance and high strength. It plays an extremely important role in heat-resistant engineering plastics and is a general term for aromatic heterocyclic polymers containing an imide group in the molecular main chain. The products that have been industrially produced and scaled mainly include homo-phenylene polyimide, polyamideimide (PAI), polyetherimide (PEI), and bismaleimide (BMI).

Material performance

1. Excellent mechanical properties, high tensile strength, excellent creep resistance and wear resistance;

2, excellent heat resistance, long-term use temperature are above 200 °C. The low temperature resistance is also very prominent, and the mechanical strength can be maintained at a low temperature of -269 ° C;

3. It is a flame retardant polymer with low combustion smoke density and low toxic gas content;

4, excellent radiation resistance, corona resistance is superior to other engineering plastics.