Twenty-one properties of plastics, this time I sorted them all out

1. ABS plastic

English name: Acrylonitrile Butadiene Styrene
Specific gravity: 1.05 g/cm3 Molding shrinkage: 0.4-0.7% Molding temperature: 200-240℃ Drying conditions: 80-90℃ for 2 hours

Material properties	1. Good overall performance, high impact strength, chemical stability, and good electrical properties. 2. Good fusion with 372 plexiglass, made of two-color plastic parts, surface can be chrome-plated and painted. 3. There are high impact resistance, high heat resistance, flame retardant, reinforced, transparent and other grades. 4. Fluidity is slightly worse than HIPS, better than PMMA, PC, etc., and flexibility is good.	It is suitable for making general mechanical parts, anti-friction and wear-resistant parts, transmission parts and telecommunications parts.
Formability	1. Amorphous materials, with medium fluidity and high moisture absorption, must be fully dried. Plastic parts that require a glossy surface must be preheated and dried at 80-90 degrees for a long time for 3 hours. 2. It is advisable to take high material temperature and high mold temperature, but it is easy to decompose if material temperature is too high (decomposition temperature is >270 degrees). For plastic parts with high precision, mold temperature should be 50-60 degrees. For thermoplastic parts, mold temperature should be 60-80 degrees. 3. To solve water-entrapment pattern, it is necessary to improve fluidity of material, adopt methods such as high material temperature, high mold temperature, or change water level. 4. If heat-resistant or flame-retardant materials are formed, plastic decomposition products will remain on the surface of mold after 3-7 days of production, causing surface of mold to shine. Mold needs to be cleaned in time, and an exhaust position needs to be added on the surface of mold.

2. PS plastic

English name: Polystyrene
Specific gravity: 1.05g/cm3 Molding shrinkage: 0.6-0.8% Molding temperature: 170-250℃ Drying conditions: ---

Material properties	Excellent electrical insulation (especially high-frequency insulation), colorless and transparent, second only to organic glass in light transmittance, coloring, water resistance, and good chemical stability. Strength is average, but quality is brittle, and it is prone to stress brittle cracks. Resistant to benzene, gasoline and other organic solvents.	Suitable for making insulating transparent parts, decorative parts and chemical instruments, optical instruments and other parts.
Formability	1. Amorphous material has low moisture absorption, does not need to be fully dried, and is not easy to decompose, but has a large thermal expansion coefficient and is prone to internal stress. It has good fluidity and can be molded with a screw or plunger injection machine. 2. It is suitable to use high material temperature, high mold temperature, low injection pressure, prolonging injection time is beneficial to reduce internal stress, prevent shrinkage cavity and deformation. 3. Various types of gates can be used, and gate is connected with plastic part by an arc to avoid damage to plastic part when gate is removed. Demoulding slope is large, and ejection is uniform. Wall thickness of plastic part is uniform, and it is best not to have inserts. If there is an insert, it should be preheated.

3. PMMA plastic (plexiglass)

English name: Polymethyl Methacrylate
Specific gravity: 1.18 g/cm3 Molding shrinkage: 0.5-0.7% Molding temperature: 160-230℃ Drying conditions: 70-90℃ for 4 hours

Material properties	Excellent transparency, high strength, certain heat and cold resistance, corrosion resistance, good insulation, comprehensive performance exceeds polystyrene, but brittle, easy to melt in organic solvents, such as light-transmitting materials, its surface hardness Slightly lower, easy to rub flowers.	It is suitable for making transparent insulating parts and parts with general strength.
Formability	1. Amorphous materials, high moisture absorption, need to be dry, not easy to decompose, medium fluidity, prone to poor filling, mold sticking, shrinkage, weld marks, etc. 2. It is suitable for high-pressure injection. Under the condition of no defects, high material temperature and high mold temperature are used to increase fluidity, reduce internal stress, improve transparency and strength. Surface of mold gating system should be smooth and clean, with a large demoulding slope. Ejection is uniform. At the same time, an exhaust port is provided to prevent foaming.

4. POM plastic

English name: Polyoxymethylene (Polyformaldehyde)
Specific gravity: 1.41-1.43 g/cm3 Molding shrinkage: 1.2-3.0% Molding temperature: 170-200℃ Drying conditions: 80-90℃ for 2 hours

Material properties	Good overall performance, high strength, high rigidity, good wear resistance, low water absorption, good dimensional stability, but poor thermal stability, easy to burn, and easy to age when exposed to sun in atmosphere.	Suitable for making anti-friction and wear-resistant parts, transmission parts, and chemical, instrument and other parts
Formability	1. Crystallization material, narrow melting range, fast melting and solidification, crystallization occurs when material temperature is slightly lower than melting temperature. Medium mobility. Hygroscopicity is small, without drying treatment. 2. Coefficient of friction is low, elasticity is good, and surface of plastic part is prone to surface defects such as wrinkles. 3. It is easy to decompose, and decomposition temperature is 240 degrees. When decomposed, irritating and corrosive gases will occur. Therefore, mold steel should be made of corrosion-resistant materials.

5. PP plastic

English name: Polypropylene
Specific gravity: 0.9-0.91 g/cm3 Molding shrinkage: 1.0-2.5% Molding temperature: 160-220℃ Drying conditions: ---

Material properties	Small density, strength, rigidity, hardness and heat resistance are all better than low-pressure polyethylene, and can be used at about 100 degrees. It has good electrical properties and high-frequency insulation and is not affected by humidity, but it becomes brittle at low temperatures, not resistant to molds and easy to age .	Suitable for making general mechanical parts, corrosion-resistant parts and insulating parts
Formability	1. Crystalline material, low hygroscopicity, prone to melt rupture, and easy to decompose when in contact with hot metal for a long time. 2. Fluidity is good, but shrinkage range and shrinkage value are large, shrinkage, dents, and deformation are prone to occur. 3. Cooling speed is fast, gating system and cooling system should dissipate heat slowly, and pay attention to controlling molding temperature. Directionality is obvious when material temperature is low. It is especially obvious at low temperature and high pressure. When mold temperature is lower than 50 degrees, plastic part is not smooth, it is easy to cause poor welding and marks. Above 90 degrees, it is easy to warp and deform. 4. Thickness of plastic wall must be uniform, avoid lack of glue, sharp corners, to prevent stress concentration.

6. PE plastic

English name: Polyethylene
Specific gravity: 0.94-0.96 g/cm3 Molding shrinkage: 1.5-3.6% Molding temperature: 140-220℃ Drying conditions: ---

Material properties	Corrosion resistance, excellent electrical insulation (especially high-frequency insulation), can be chlorinated, irradiated and modified, and can be reinforced with glass fibers. Low-pressure polyethylene has a high melting point, rigidity, hardness and strength, low water absorption. Excellent electrical properties and radiation resistance; high-pressure polyethylene has good softness, elongation, impact strength and permeability; ultra-high molecular weight polyethylene has high impact strength, fatigue resistance and wear resistance.	Low-pressure polyethylene is suitable for making corrosion-resistant parts and insulating parts; high-pressure polyethylene is suitable for making films, etc.; ultra-high molecular weight polyethylene is suitable for making shock absorption, wear-resistant and transmission parts.
Formability	1. Crystalline material, low moisture absorption, no need to fully dry, excellent fluidity, fluidity is sensitive to pressure, high-pressure injection is suitable for molding, material temperature is uniform, filling speed is fast, and pressure is sufficient. It is not suitable to use a direct gate to prevent uneven shrinkage and increased internal stress. Pay attention to location of gate to prevent shrinkage and deformation. 2. Shrinkage range and shrinkage value are large, directionality is obvious, it is easy to deform and warp. Cooling speed should be slow, mold should be equipped with a cold cavity and a cooling system. 3. Heating time should not be too long, otherwise it will decompose and burn. 4. When soft plastic parts have shallow side grooves, they can be forcibly demoulded. 5. Melt rupture may occur, and should not be in contact with organic solvents to prevent cracking.

7. PVC

English name: Poly(Vinyl Chloride)
Specific gravity: 1.38g/cm3 Molding shrinkage: 0.6-1.5% Molding temperature: 160-190℃ Drying conditions: ---

Material properties	Excellent mechanical properties, electrical properties, strong acid and alkali resistance, good chemical stability, but low softening point.	It is suitable for making thin plates, wire and cable insulation layers, seals, etc.
Formability	1. Amorphous material has low moisture absorption and poor fluidity. In order to improve fluidity and prevent air bubbles, plastic can be pre-dried. Mold gating system should be thick and short, gate section should be large, and there should be no dead angle. Mold must be cooled and surface should be chrome-plated. 2. It is very easy to decompose, and it is easier to decompose when it is in contact with steel and copper at a temperature of 200 degrees. When it decomposes, it will escape corrosion and irritating gas. Forming temperature range is small. 3. When nozzle of screw injection machine is used, aperture should be large to prevent material stagnation in dead corners. It is best not to have inserts, if there are inserts, it should be preheated.

8. PA plastic (nylon)

English name:Polyamide
Specific gravity: PA6-1.14 g/cubic centimeter PA66-1.15 g/cubic cm PA1010-1.05 g/cubic cm Molding shrinkage: PA6-0.8-2.5% PA66-1.5-2.2% Molding temperature: 220-300℃ Drying conditions: 100 -110℃ for 12 hours

Material properties	Tough, wear-resistant, oil-resistant, water-resistant, anti-enzyme bacteria, but water-absorbing. Nylon 6 has good elasticity, high impact strength and large 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 less water absorption and lower stiffness Nylon 1010 translucent, small water absorption, good cold resistance	Suitable for making general mechanical parts, anti-friction and wear-resistant parts, transmission parts, and chemical, electrical, instrument and other parts
Formability	1. Crystalline material, high melting point, narrow melting temperature range, poor thermal stability, material temperature exceeds 300 degrees, and residence time exceeds 30 minutes, it will decompose. It is easy to absorb moisture and needs to be dried, and water content should not exceed 0.3%. 2. Good fluidity, easy to overflow. Self-locking nozzles should be used and should be heated. 3. Molding shrinkage range and shrinkage rate are large, directionality is obvious, shrinkage cavity and deformation are prone to occur. 4. Mold temperature is selected in the range of 20-90 degrees according to wall thickness of plastic part, injection pressure is selected according to type of injection machine, material temperature, shape and size of plastic part, and mold gating system, molding cycle is selected according to wall thickness of plastic part. If viscosity of resin is small, time for injection and cooling should be longer, and white oil should be used as a release agent. 5. Form and size of mold gating system, increasing size of runner and gate can reduce shrinkage.

9. PC plastic

English name: Polycarbonate
Specific gravity: 1.18-1.20 g/cm3 Molding shrinkage: 0.5-0.8% Molding temperature: 230-320℃ Drying conditions: 110-120℃ for 8 hours

Material properties	High impact strength, good dimensional stability, colorless and transparent, good colorability, good electrical insulation, corrosion resistance, wear resistance, but poor self-lubrication, tendency to stress cracking, easy hydrolysis at high temperature, poor compatibility with other resins .	Suitable for making small instrument parts, insulating transparent parts and impact-resistant parts
Formability	1. Amorphous material, good thermal stability, wide molding temperature range, poor fluidity. Low moisture absorption, but sensitive to water, must be dried. Molding shrinkage rate is small, melting cracking and stress concentration are prone to occur, so molding conditions should be strictly controlled, and plastic parts must be annealed. 2. High melting temperature, high viscosity, plastic parts larger than 200g, it is advisable to use a heated extension nozzle. 3. Cooling speed is fast, gating system of mold should be thick and short. It is advisable to set up a cold well, gate should be large, and mold should be heated. 4. If material temperature is too low, it will cause material shortage, and plastic parts will be dull. If material temperature is too high, it will easily overflow and plastic parts will blister. When mold temperature is low, shrinkage rate, elongation rate and impact strength are high, but bending resistance, compression resistance and tensile strength are low. When mold temperature exceeds 120 degrees, cooling of plastic part is slow, and it is easy to deform and stick to mold.

10. PPO plastic (MPPO)

English name: poly(phenylene oxide)
Specific gravity: 1.07 g/cm3 Molding shrinkage: 0.3-0.8% Molding temperature: 260-290℃ Drying conditions: 130℃ for 4 hours

Material properties	1. It is white particles. Good overall performance, can be used in steam at 120 degrees, good electrical insulation, small water absorption, but tends to stress cracking. Modified polyphenylene ether eliminates stress cracking. 2. It has outstanding electrical insulation and water resistance, and good dimensional stability. Its dielectric properties rank first among plastics. 3. MPPO is a modified material made by blending PPO and HIPS, and materials currently on the market are all this kind of material. 4. It has high heat resistance, glass transition temperature is 211 degrees, melting point is 268 degrees, and it has a tendency to decompose when heated to 330 degrees. The higher content of PPO, the better heat resistance, and heat distortion temperature can reach 190 degrees. 5. Good flame retardancy, self-breathing, and moderate flammability after mixing with HIPS. Lightweight, non-toxic and can be used in food and pharmaceutical industries. Poor light resistance, it will change color when used in sun for a long time. 6. It can be blended and modified with ABS, HDPE, PPS, PA, HIPS, glass fiber, etc.	1. It is suitable for making heat-resistant parts, insulating parts, wear-reducing and wear-resistant parts, transmission parts, medical and electronic parts. 2. It can be used as gears, fan blades, valves and other parts used at higher temperatures, and can replace stainless steel. 3. It can make screws, fasteners and connectors. 4. Electrical parts of motors, rotors, casings, and transformers.
Formability	1. Non-crystalline material, low moisture absorption. 2. Poor fluidity, similar to Newtonian fluid, viscosity is sensitive to temperature, and thickness of product is generally above 0.8 mm. It is easily decomposed and produces corrosive gas when decomposed. Molding temperature should be strictly controlled, mold should be heated, and gating system should have small resistance to material flow. 3. Water absorption rate of polyphenylene ether is very low, about 0.06%, but a small amount of moisture will cause silver threads and other roughness on the surface of product. It is best to dry it, and temperature should not be higher than 150 degrees, otherwise color will change. 4. Molding temperature of polyphenylene ether is 280-330 degrees, and molding temperature of modified polyphenylene ether is 260-285 degrees.

11. PSU plastic

English name: Polysulfone
Specific gravity: 1.25-1.35 g/cm3 Molding shrinkage: 0.5-0.7% Molding temperature: 290-350℃ Drying conditions: 130-150℃ for 4 hours

Material performance/use	1. Polysulfone is an amber transparent solid material with high hardness and impact strength, non-toxic, good heat and cold resistance and aging resistance, and can be used for a long time at -100--175 degrees. It is resistant to corrosion of inorganic acid, alkali and salt, but not resistant to aromatic hydrocarbons and halogenated hydrocarbons. Polyarylsulfone has high hardness, radiation resistance, good heat resistance and cold resistance, and is self-absorbing, and can be used for a long time at -100-175 degrees. 2. Wear resistance of material can be greatly improved through glass fiber reinforced modification. 3. Polysulfone can be made into modified products of polysulfone with ABS, polyimide, polyether ether ketone and fluoroplastics, mainly to improve its impact strength and elongation, solvent resistance, environmental resistance, processing performance and electroplatability. Such as PSF/PBT, PSF/ABS, PSF+mineral powder.	1. It is suitable for making heat-resistant parts, insulating parts, wear-reducing and wear-resistant parts, instrumentation parts and medical equipment parts. Polyarylsulfone is suitable for making low-temperature working parts. 2. Polysulfone is commonly used in electronic and electrical industry to manufacture integrated circuit boards, coil tube frames, contactors, sleeve frames, capacitor films, and high-performance alkaline battery casings. 3. Polysulfone is used in microwave oven equipment, coffee heaters, humidifiers, hair dryers, cloth steamers, beverage and food dispensers, etc. in household appliances. It can also replace non-ferrous metals for precision structural parts such as clocks, copiers, and cameras. 4. Polysulfone has passed relevant specifications in the fields of medicine and food in United States, can replace stainless steel products. Due to characteristics of polysulfone resistance to steam, hydrolysis, non-toxicity, high temperature steam sterilization, high transparency, and good dimensional stability, it can be used as surgical tool trays, sprayers, fluid controllers, heart valves, pacemakers, gas masks, dental trays, etc.
Formability	1. Amorphous material, high moisture absorption, water absorption rate 0.2%-0.4%, must be fully dried before use, prevent re-absorption, to ensure that water content is below 0.1%. 2. Molding performance is similar to that of PC, but thermal stability is poor, and it begins to decompose at 360 degrees. 3. Poor fluidity, fast cooling, suitable for high temperature and high pressure molding. Mold should have sufficient strength and rigidity, set a cold slug well, runner should be short, and size of gate should be 1/2-1/3 of wall thickness of plastic part 4. In order to reduce internal stress of injection molded products, mold temperature should be controlled at 100-140 degrees. After molding, annealing treatment can be taken. Annealing treatment in glycerin bath, 160 degrees, 1-5 minutes; or take air bath, 160 degrees, 1-4 hours. Annealing time depends on size and wall thickness of article. 5. Polysulfone is close to a Newtonian body in a molten state, similar to polycarbonate, and its fluidity is sensitive to temperature. In the range of 310 degrees to 420 degrees, fluidity will double for every 30 degrees of temperature increase. Therefore, processing fluidity is mainly improved by increasing temperature during molding.

12. PTFE plastic (F4)

English name: Polytetrafluoroethylene
Specific gravity: 2.1-2.2 g/cm3 Molding shrinkage: 3.1-7.7% Molding temperature: 330-380℃ Drying conditions: ---

Material properties	1. Long-term use temperature -200--260 degrees, excellent chemical corrosion resistance, corrosion resistance to all chemicals, lowest friction coefficient among plastics, and good electrical properties, its electrical insulation is not affected by temperature It is known as "King of Plastics". 2. It is transparent or translucent, the higher crystallinity, the worse transparency. Raw materials are mostly powdery resins or concentrated dispersions, which are thermoplastic polymers with extremely high molecular weight and high crystallinity.	Suitable for making corrosion-resistant parts, wear-reducing and wear-resistant parts, seals, insulating parts and medical device parts
Formability	1. Crystallization material, low moisture absorption. 2. Poor fluidity, easy to decompose, and produce corrosive gas when decomposed. Molding temperature should be strictly controlled, mold should be heated, and gating system should have small resistance to material flow. 3. Powdered resin is often formed by powder powder metallurgy method, using sintering method. Sintering temperature is 360-380 degrees, and should not exceed 475 degrees. Emulsion resin is usually processed by cold extrusion and sintering process, which can form an anti-corrosion layer on the surface of article. If transparency and toughness of product are required, rapid cooling should be adopted. Extrusion molding can also be adopted, tubes, rods, and profiles can be extruded. 4. Melt viscosity of PTFE is very high, and viscosity of bulk decreases with increase of shear stress, showing characteristics of its non-Newtonian fluid. 5. Secondary processing can be hot-compressed, welded, bonded, reinforced, mechanically processed, etc. to make final product.

13, ASA plastic

English name: Acrylonitrile Styrene acrylate copolymer
Specific gravity: 1.05 g/cm3 Molding shrinkage: 0.4-0.7% Molding temperature: 170-230℃ Drying conditions: 80-90℃ for 2 hours

Material properties	ASA polymers are amorphous materials that can be processed by extrusion and injection molding into products that are extremely resistant to weathering influences. Mechanical properties of terpolymer ASA are generally similar to ABS resin, difference is that performance of ASA is much less affected by outdoor climate than ABS resin.	Suitable for making general construction fields, outdoor furniture, and car exterior mirror housings
Formability	1. Amorphous materials, with medium fluidity and high moisture absorption, must be fully dried. Plastic parts that require a glossy surface must be preheated and dried at 80-90 degrees for a long time for 3 hours. 2. It is advisable to take high material temperature and high mold temperature, but it is easy to decompose if material temperature is too high (decomposition temperature is > 250 degrees). For plastic parts with high precision, mold temperature should be 50-60 degrees, which is good for gloss and heat resistance. For plastic parts, mold temperature should be 60-80 degrees. 3. Grades of ASA basic resin sold in the market are: Luran S brand (BASF Plastic Materials Company); Gelog brand (General Plastics Company); Centrex brand (Monsanto Company).

14. PPS plastic

English name:Phenylene sulfide
Specific gravity: 1.36g/cubic centimeter Molding shrinkage: 0.7% Molding temperature: 300-330℃ Drying conditions: ---

Material properties	1. Excellent electrical insulation (especially high-frequency insulation), white hard and brittle, metal sound when dropped on the ground, light transmittance second only to organic glass, coloring, water resistance, and good chemical stability. It has excellent flame retardancy and is a non-combustible plastic. 2. Average strength, good rigidity, but brittle, prone to stress brittle cracking, not resistant to benzene, gasoline and other organic solvents. Long-term use temperature can reach 260 degrees, and it remains stable in 400 degrees of air or nitrogen. After modification by adding glass fiber or other reinforcing materials, impact strength can be greatly improved, heat resistance and other mechanical properties are also improved, density is increased to 1.6-1.9, and molding shrinkage is as small as 0.15-0.25%.	It is suitable for making heat-resistant parts, insulating parts, chemical instruments, optical instruments and other parts.
Formability	1. Amorphous material, low moisture absorption, but should be dried and formed. 2. Fluidity is between ABS and PC, with fast solidification, small shrinkage, and easy decomposition. Higher injection pressure and injection speed are selected. Mold temperature is 100-150 degrees. Taper of main channel should be large and the flow channel should be short.

15. ETFE plastic

English name: Polytetrafluoroethylene
Specific gravity: 1.7g/cubic centimeter Molding shrinkage: 3.1-7.7% Molding temperature: 300-330℃ Drying conditions: ---

Material properties	1. Long-term use temperature -80--220 degrees, excellent chemical corrosion resistance, corrosion resistance to all chemicals, lowest friction coefficient among plastics, and good electrical properties, its electrical insulation is not affected by temperature It is known as "King of Plastics". 2. Its chemical resistance is similar to that of polytetrafluoroethylene and better than that of vinylidene fluoride. 3. Its creep resistance and compressive strength are better than PTFE, its tensile strength is high, and its elongation can reach 100-300%. Good dielectric properties and excellent radiation resistance.	1. It is suitable for making corrosion-resistant parts, wear-reducing and wear-resistant parts, sealing parts, insulating parts and medical equipment parts. 2. Wire and cable insulation, anti-corrosion equipment, sealing materials, pump valve bushings, and chemical containers.
Formability	1. Crystallization material, low moisture absorption. It can be processed into products by the usual thermoplastic processing methods. 2. Poor fluidity, easy to decompose, and produce corrosive gas when decomposed. Molding temperature should be strictly controlled not to exceed 350 degrees, mold should be heated to 100-150 degrees, resistance of gating system to material flow should be small. It can form thin-walled simple products with a thickness of 0.7-0.8 mm. 3. Transparent pellets, injection molding, extrusion molding. Molding temperature is 300-330 degrees, and above 350 degrees is likely to cause discoloration or bubbles. High-speed and low-pressure molding is suitable, and it will be difficult to demould.

16. PFA plastic

English name: Polytetrafluoroethylene
Specific gravity: 2.13-2.167 g/cm3 Molding shrinkage: 3.1-7.7% Molding temperature: 350-400℃ Drying conditions: ---

Material properties	1. It is a copolymer of a small amount of perfluoropropyl perfluorovinyl ether and polytetrafluoroethylene. Melt adhesion is enhanced, melt viscosity is reduced, and performance is unchanged compared with PTFE. This kind of resin can be directly processed into products by ordinary thermoplastic molding methods. 2. Long-term use temperature -80--260 degrees, excellent chemical corrosion resistance, corrosion resistance to all chemicals, lowest friction coefficient among plastics, and good electrical properties, its electrical insulation is not affected by temperature It is known as "King of Plastics". 3. Its chemical resistance is similar to that of polytetrafluoroethylene and better than that of vinylidene fluoride. 3. Its creep resistance and compressive strength are better than PTFE, its tensile strength is high, and its elongation can reach 100-300%. Good dielectric properties and excellent radiation resistance. Flame retardancy up to V0 level.	1. It is suitable for making corrosion-resistant parts, wear-reducing and wear-resistant parts, sealing parts, insulating parts and medical equipment parts. 2. High-temperature wires, cable insulation, anti-corrosion equipment, sealing materials, pump valve bushings, and chemical containers.
Formability	1. Crystallization material, low moisture absorption. It can be processed into products by usual thermoplastic processing methods. 2. Poor fluidity, easy to decompose, and produce corrosive gas when decomposed. Molding temperature should be strictly controlled not to exceed 475 degrees, mold should be heated to 150-200 degrees, and resistance of pouring system to material flow should be small. 3. Translucent pellets, injection molding, extrusion molding. Molding temperature is 350-400 degrees, above 475 degrees is easy to cause discoloration or bubbles. And note that demoulding will be more difficult. 4. Because molten material has a corrosive effect on metal, mold needs to be electroplated with chrome for long-term production.

17. PAR plastic (U plastic)

English name: polyarylate
Specific gravity: 1.2-1.26 g/cm3 Molding shrinkage: 0.8% Molding temperature: 300-350℃ Drying conditions: 100-120℃-5 hours

Material properties	1. It is a transparent amorphous thermoplastic engineering plastic with excellent heat resistance, flame retardancy and non-toxicity. It can be directly processed into products by ordinary thermoplastic molding methods. 2. It has excellent thermal properties. Under load of 1.86MPA, its heat distortion temperature is as high as 175 degrees, and its decomposition temperature is 443 degrees. Its various mechanical properties are less affected by temperature.	1. It is suitable for making electrical parts with heat resistance, flame resistance and high dimensional stability. Connectors, bobbins, relay housings. 2. Lighting parts. It can be made into transparent lampshades, illuminators, car reflectors, etc.
Formability	1. As wall thickness of product increases, molding shrinkage increases. 2. Hygroscopicity is small, about 0.1-0.3%, but a small amount of moisture will cause polyarylate to decompose during injection molding. Therefore, material must be dried before molding. Make its moisture content less than 0.02%.

18. Bakelite

English name: Phenol-Formaldehyde (PF)
Specific gravity: 1.5-2.0 g/cm3 Molding shrinkage: 0.5-1.0% Molding temperature: 150-170℃

Material properties	Bakelite is a hard and brittle thermosetting plastic, commonly known as bakelite. High mechanical strength, tough and wear-resistant, dimensional stability, corrosion resistance, excellent electrical insulation performance.	It is suitable for making insulating mechanism components of electrical appliances and instruments, and can be used under hot and humid conditions
Formability	1. Formability is good, but shrinkage and directionality are generally larger than that of amino plastics, and it contains moisture volatiles. It should be preheated before molding, and exhaust should be exhausted during molding process. If there is no preheating, mold temperature and molding pressure should be increased. 2. Mold temperature has a great influence on the fluidity. Generally, when it exceeds 160 degrees, fluidity will drop rapidly. 3. Hardening speed is generally slower than that of amino plastics, and heat released during hardening is large. Internal temperature of large thick-walled plastic parts is easy to be too high, and uneven hardening and overheating are prone to occur.

19. Amino plastics

English name:MF,UF
Specific gravity: 1.5g/cubic centimeter Molding shrinkage: 0.6-1.0% Molding temperature: 160-180℃

Material properties	Good arc resistance and electrical insulation, good water resistance and heat resistance, suitable for compression molding	Suitable for making arc-resistant electrical parts and explosion-proof electrical insulation parts
Formability	1. It has good fluidity and fast hardening speed, so preheating and molding temperature should be appropriate, speed of coating, mold clamping and pressurization should be fast. 2. Large molding shrinkage. 3. It contains a lot of volatile matter and is easy to absorb moisture and agglomerate. It should be preheated and dried during molding to prevent re-absorption of moisture. However, if it is too dry, fluidity will decrease. Moisture and decomposition products are present during molding, and there is acidity. Mold should be chrome-plated to prevent corrosion, and exhaust should be exhausted during molding. 4. Molding temperature has a great influence on quality of plastic parts. If temperature is too high, it will easily cause decomposition, discoloration, and uneven color of bubbles. When temperature is too low, fluidity will be poor and dull. 5. Material is fine, specific volume is large, and material is filled with a lot of air. When using a pre-pressed ingot to form a large plastic part, it is easy to produce ripples and flow lines, so it is generally not suitable for use.

20. Epoxy resin (EP)

English name: Epoxide Resin
Specific gravity: 1.9 g/cm3 Molding shrinkage: 0.5% Molding temperature: 140-170℃

Material properties	It has good mechanical properties, electrical insulation and chemical stability, and has strong adhesion to many materials, but its performance is affected by the type and content of fillers. Alicyclic cluster epoxy plastics have high heat resistance. Suitable for casting and low pressure extrusion molding.	It is suitable for potting and fixing of electrical, electronic components and coils, and can also be used for repairing.
Formability	1. Castable. Good fluidity, small hardening shrinkage, but poor thermal rigidity, not easy to demould. 2. Hardening speed is fast, and generally no exhaust is required during hardening, and pressure should be increased immediately after loading.

21. Silicone plastic (IS)

English name:Silicone
Specific gravity: 1.75-1.95 g/cm3 Molding shrinkage: 0.5% Molding temperature: 160-180℃

Material properties	High and low temperature resistance, good water resistance, good high frequency insulation, good radiation resistance and ozone resistance	Suitable for potting and fixing electrical, electronic components and coils
Formability	1. Good fluidity, slow hardening speed, high molding temperature is required during compression molding. 2. After compression molding, it must be cured at high temperature.

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