Polyphenylene ether is abbreviated as PPO , which is non-toxic, wear-resistant, heat-resistant, flame-retardant, high-strength and excellent in electrical properties. The dielectric constant and dielectric loss of PPO are among the smallest varieties in engineering plastics, and are hardly affected by temperature and humidity. Let's take a look at the PPO:
1, PPO processing
PPO processing is mainly based on injection molding, extrusion molding, molding, foaming, blow molding, glass fiber reinforced, electroplating, vacuum coating, printing, machining and welding. The recycled material of the PPO can be reused, and is generally reused three times, and its performance is not significantly reduced. PPO has poor melt flowability and is difficult to process, and most of the practical applications are modified PPO. The following describes the injection molding process of PPO.
PPO pretreatment
PPO is a non-crystalline polymer, the water absorption rate is very low, but the moisture will cause defects such as silver wire and bubbles on the surface of the product. For this reason, the raw material can be placed in an oven at 80~100 ° C and dried for 1-2 hours.
Injection molding machine selection
The PPO melt should be formed by a screw type injection molding machine, and the nozzle is preferably a straight-through type with a pore diameter of 3-6 mm. The main channel of the mold should adopt a larger taper or a pull hook, and the runner should be short and thick.
Injection temperature
The molding temperature of the polyphenylene ether is 280-330 degrees, and the molding temperature of the modified polyphenylene ether is 260-285 degrees. PPO plastic raw material injection molding process melt temperature: 270-290 ° C.
PPO has high heat resistance, thermal decomposition temperature of 350 ° C, no significant thermal degradation within 300 ° C. Usually, the barrel temperature is controlled at 260~290 °C, and the nozzle temperature is lower than the barrel temperature by about 10 °C.
Due to the high viscosity of the PPO melt, higher mold temperatures should be used during injection molding. Usually, the mold temperature is controlled at 100 to 150 °C. When the mold temperature is lower than 100 °C, the thin-walled plastic parts are prone to insufficient filling and delamination; when it is higher than 150 °C, bubbles, silver, warp and other defects are likely to occur.
Injection pressure
The viscosity of the PPO melt is large. When injection molding, high pressure and high speed injection should be adopted, and the pressure holding and cooling time should not be too long. Increasing the injection pressure is conducive to the filling of the melt. The general injection pressure is controlled at 100-140 MPa, and the pressure holding pressure is controlled at 40-80 MPa. Make adjustments based on specific conditions.
Injection speed
Articles with long runners require rapid injection, but in this case ensure that the membrane is sufficiently ventilated.
2. Blending modification of PPO
The performance of polyphenylene ether is very good, but the solvent resistance is poor, the product is prone to stress cracking, the notched impact strength is low, the raw material price is expensive, and the fatal weakness is that the melt viscosity is large, the fluidity is poor, and the softening temperature is above 300 ° C. The high temperature processing at 330 °C is prone to degradation, resulting in difficult processing and excessive energy consumption. In order to overcome these shortcomings, various new modifications have been made to the PPO.
Blending modification of PPO and PS
Both PPO and PS are amorphous polymers, and the compatibility is very good. By mixing with PS, the processing cost can be reduced, and the processing formability of PPO is greatly improved, but the heat resistance is slightly lowered. This is the first generation of polyphenylene ether alloy, which makes PPO widely used. In order to improve the performance of such alloys, people have been making various improvements.
Blending modification of PPO and PA
The blending of the two not only improves the processing performance and solvent resistance of the PPO, but also improves the heat resistance and dimensional stability of the PA, thereby achieving complementary advantages. However, the compatibility between the two is very poor, and it is a completely incompatible system. The phase separation of the blended alloy is severe, resulting in brittle alloy. Researchers have done a lot of research on the compatibilization, toughening and strengthening of PPO/PA alloys, and have achieved a lot of research results, and made PPO/PA alloys widely used.
Blending modification of PPO and PPS
In recent years, in the surface assembly process of some electronic and electrical components, soldering and VPS are becoming the mainstream of soldering. Therefore, the resin required to be used is also resistant to temperatures above 260 °C, while the glass transition temperature of pure PPO is only about 210 °C. It is impossible to meet such high heat resistance requirements, so a highly heat-resistant PPO/PPS alloy has been developed. But the two also need to increase capacity.
Blending modification of PPO and PBT
The blending materials of the two effectively solve the problem of large water absorption of the PPO/PA alloy. However, the two systems also need to add compatibilizer for capacity expansion. The toughness and strength of PPO/PBT alloys cannot meet various application requirements, and similar to PPO/PA blends, toughening and strengthening are required.
Blending modification of PPO and PTFE
The blended materials of both have the heat resistance, mechanical properties, dimensional stability of PPO and the wear resistance, lubricating property, low water absorption and high precision of PTFE. It can meet the comprehensive performance requirements of physical properties and bearing performance close to metal structural parts.
Blending modification of PPO and SBS
PPO has good compatibility with SBS. PPO/SBS alloy improves the flexural and impact properties of PPO. It has the characteristics of low water absorption, good toughness, high heat distortion temperature and high dimensional accuracy. It is mainly used in electrical industry and automobile. Industry and other fields.
3. Application of PPO
Household appliances
Used in TV sets, rice cookers, computers, cameras, tape recorders, air conditioners and heaters. Can be used as copiers, computer systems, printers, fax machines and other exterior parts and components.
Electronic and electrical
The electrical and electronic industry is widely used in the manufacture of connectors, coil bobbins, mechanical component shields, switch relays, tuning equipment, large electronic displays, variable capacitors and microphones.
auto industry
Suitable for instrument panel, window frame, shock absorber, pump filter, radiator grid, speaker grille, console, fuse box, relay box, connector and wheel cover.
industrial machinery
Suitable for making heat-resistant parts, insulating parts, wear-reducing parts, transmission parts; making gears, blades, valves and other parts used at higher temperatures, can be used instead of stainless steel; can also make screws, fasteners and connections Pieces.
Diamond Sintered Grinding Wheel
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