Polyphenylene ether is also one of the five general engineering plastics will be one of it has a rigid, high heat resistance, flame retardant, high strength, excellent electrical properties, etc. In addition, PPO also has wear-resistant, non-toxic, Advantages PPO dielectric constant and dielectric loss in engineering plastics is one of the smallest species, almost no temperature, humidity.
Commonly used by the 2, 6-dimethylphenol synthetic polyphenylene ether, has excellent overall performance, the biggest feature is the long-term load, with excellent dimensional stability and outstanding electrical insulation, the use of a wide temperature range , Can be long-term use in the range of -127 ~ 121 ℃. Has outstanding water resistance, steam resistance, products have higher tensile strength, impact strength and creep resistance. In addition, there are better wear resistance And electrical properties.
1, PPO processing
Polyphenylene ether processing to injection molding, extrusion, molding based, but also foaming, blowing plastic, glass fiber reinforced, electroplating, vacuum coating, printing, machining and welding. PPO back to the material can be reused, the general re-use 3 Times, its performance is not significantly reduced.PPO poor melt flow, processing difficult, most of the practical application of modified PPO. The following describes the PPO injection molding process.
PPO pretreatment
PPO is a non-crystalline polymer, water absorption is very low, but the water will make the product surface silver, bubbles and other defects, for which raw materials can be placed in an oven 80 ~ 100 ℃, dried 1-2h after use.
Injection molding machine selection
The PPO melt should be used screw molding machine molding, the nozzle is straight through the better, the aperture of 3-6mm. The mainstream of the mold should adopt a larger taper or pull the hook, runner to stubby as well.
Injection temperature
Polyphenylene ether molding temperature is 280-330 degrees, the molding temperature of the modified polyphenylene ether is 260-285 degrees. PPO plastic raw material injection molding process Melt temperature: 270-290 ℃.
PPO has a high heat resistance, thermal decomposition temperature of 350 ℃, no obvious thermal degradation within 300 ℃ .In general, the barrel temperature is controlled at 260 ~ 290 ℃, the nozzle temperature is lower than the barrel temperature of about 10 ℃.
Due to the high viscosity of the PPO melt, high mold temperature should be used in the injection molding.Usually, the mold temperature is controlled at 100-150 ° C. When the mold temperature is lower than 100 ° C., the thin plastic parts are prone to underfill and delamination; While above 150 ℃, prone to bubbles, silver, warping and other defects.
Injection pressure
PPO melt viscosity, injection molding, should take high-pressure, high-speed injection, packing and cooling time can not be too long.Improve the injection pressure, is conducive to the filling of the melt, the general injection pressure control in the 100-140MPa, Paul Pressure control at 40-80MPa. According to the specific circumstances to make adjustments.
Injection speed
Products with long runners require rapid injections, but in this case ensure adequate breathability of the membrane.
2, PPO blend modification
The performance of polyphenylene ether is very good, but solvent resistance is poor, the product prone to stress cracking, notched impact strength is low, expensive raw materials, fatal weakness is its melt viscosity is very large, poor mobility, and softening temperature above 300 ℃, However, the high temperature processing at 330 ℃ is prone to degradation, resulting in the difficulty of processing and energy consumption.In order to overcome these shortcomings, new properties are given to PPO, and a variety of modification methods are carried out.
Blending Modification of PPO and PS
PPO and PS are amorphous polymers, compatibility is very good, by mixing PS, can reduce processing costs, greatly improving the processing of PPO formability, but a slight decrease in heat resistance.This is the first generation of polyphenylene ether Alloy, PPO has been widely used, in order to improve the performance of these alloys, people have been doing a variety of improvements.
Blending Modification of PPO and PA
The blending of the two not only improves the processability and solvent resistance of PPO, but also improves the heat resistance and dimensional stability of PA, so as to realize the complementary advantages. However, the compatibility of the two is poor and completely incompatible System, the phase separation of the blended alloy is serious, resulting in the brittleness of the alloy.The researchers made a great deal of research on the compatibilization, toughening and strengthening of the PPO / PA alloy, and have made a lot of research achievements and made the PPO / PA alloy Be widely used.
Blending Modification of PPO and PBT
The blend of the two materials effectively solves the problem of large water absorption of the PPO / PA alloy, but both systems also need compatibilizing agent for compatibilization.The toughness and strength of the PPO / PBT alloy can not meet the needs of various applications Requirements, and PPO / PA blend system also need to be toughened, enhanced.
Blending Modification of PPO and PPS
In recent years, some electronic and electrical components in the surface assembly process, steam welding and VPS solder is becoming the mainstream, it is required to use the resin should also be resistant to high temperatures above 260 ℃, and pure PPO glass transition temperature of only 210 ℃ , Can not meet such a high heat requirements, it developed a high heat-resistant PPO / PPS alloy, but both also need compatibilization.
PPO and PTFE blend modified
Both blend materials, both PPO heat resistance, mechanical properties, dimensional stability and PTFE wear resistance, lubricity, water absorption, high precision products to meet the close to the physical properties of metal parts and bearing performance The overall performance requirements.
Blending Modification of PPO and SBS
PPO and SBS has a good compatibility, PPO / SBS alloy PPO improves the flexibility and impact properties, with low water absorption, toughness, high heat distortion temperature and dimensional accuracy characteristics, mainly for the electrical industry and cars Industrial and other fields.
3, PPO applications
Electronic and electrical
Electrical and electronic industry is widely used in the manufacture of connectors, coil bobbins, mechanical parts cover, switch relays, tuning equipment, large electronic displays, variable capacitors, battery accessories, microphones and other components.
auto industry
Suitable for instrument panels, window frames, shock absorbers, pump filters, radiator grille, speaker grilles, consoles, fuse boxes, relay boxes, connectors, wheel covers and so on.
Household appliances
For TV, computers, video cameras, video tapes, tape recorders, air conditioners, warmers, rice cookers and other spare parts. For copiers, computer systems, printers, fax machines and other external components and components.
industrial machinery
Suitable for the production of heat-resistant parts, insulating parts, wear-resistant wear-resistant parts, transmission parts; production of gears, blades, valves and other parts used at higher temperatures can be used instead of stainless steel; also can produce screws, fasteners and connections Pieces.