Polyphenylene ether (PPO), also known as polyphenylene ether in Chinese, is one of the world's top five general engineering plastics. It has the advantages of high rigidity, high heat resistance, flame retardant, high strength and excellent electrical properties. In addition, PPO also has the advantages of wear-resistant, non-toxic and pollution-resistant. PPO's dielectric constant and dielectric loss in the engineering plastics is one of the smallest varieties, almost independent of temperature, humidity. Can be used in the field of low, medium and high frequency electric field (the smaller the dielectric constant, the better the insulation) PPO's load deflection temperature up to 190 ℃ or more, the deformation temperature -170 ℃. (PPO or PPE) also known as polyphenylene oxide, chemical name is poly 2,6-dimethyl-1,4-phenylene ether. It is a linear polymer made of 2,6-dimethylphenol through oxygen and oxidative condensation reaction under the action of catalyst.

It is usually in the form of an earthy yellow powder. Commonly used polyphenylene ether synthesized from 2,6-dimethylphenol, has excellent comprehensive performance, the most important feature is that under long-term load, has excellent dimensional stability and outstanding electrical insulation, the use of a wide range of temperatures, can be used for a long time in the range of -127 ~ 121 ℃. With excellent water resistance, steam resistance, products with high tensile strength and impact strength, creep resistance is also good. In addition, it has good abrasion resistance and electrical properties.

Physical properties
1、White granule. Comprehensive performance is good, can be used in 120 ℃ 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 rank first among plastics.

3, MPPO for PPO and HIPS co-mingled modified materials, the current market materials are such materials.

4, has a high heat resistance, glass transition temperature of 211 ℃, melting point of 268 ℃, heated to 330 ℃ tendency to decomposition, the higher the content of PPO the better its heat resistance, heat distortion temperature of up to 190 ℃.

5, good flame retardancy, self-extinguishing, and HIPS mixed with medium flammability. Lightweight, non-toxic can be used in the food and drug industry. Poor rotational light resistance, long time in the sun will change color.

6, can be mixed with ABS, HDPE, PPS, PA, HIPS, glass fiber and other modified processing.

Material properties
A, PPO plastic material is non-toxic, transparent, low relative density, has excellent mechanical strength, stress relaxation resistance, creep resistance, heat resistance, water resistance, water vapor resistance, dimensional stability.

B, in a wide range of temperatures, frequency changes in the electrical properties, not hydrolyzed, small molding shrinkage, flame retardant and self-extinguishing, inorganic acids, alkalis, aromatic hydrocarbons, halogenated hydrocarbons, oils and other poor performance, easy to dissolve or stress cracking.

C, it has the advantages of high rigidity, high heat resistance, flame retardant, high strength and excellent electrical properties.

D, polyphenylene ether also has the advantages of wear-resistant, non-toxic, pollution-resistant.

E, PPO plastic raw materials dielectric constant and dielectric loss in engineering plastics is one of the smallest varieties, almost independent of temperature, humidity, can be used in the field of low, medium and high frequency electric field.

F, PPO's load deflection temperature up to 190 ℃ or more, embrittlement temperature of -170 ℃.

G, the main drawback is the poor melt fluidity, processing and molding difficulties.

Molding performance
1. Non-crystalline material, small moisture absorption.

2. Poor fluidity, similar to the Newtonian fluid, viscosity is more 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, the water absorption of polyphenylene ether is very low 0.06% or so, but trace amounts of water will lead to the surface of the product silver wire and other non-smooth phenomena, it is best to make dry treatment, the temperature should not be higher than 150 ℃, otherwise the color will change.

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

Application fields
1、It is suitable for making heat-resistant parts, insulating parts, wear-resistant parts, transmission parts, medical and electronic parts.

2、It can be used as gears, air blades, valves and other parts at higher temperatures, and can be used instead of stainless steel.

3、Can make screws, fasteners and connectors.

4、Electrical parts of motor, rotor, casing and transformer.

5, PPO and MPPO are mainly used in electronic and electrical appliances, automobiles, household appliances, office equipment and industrial machinery, etc., utilizing MPPO heat resistance, impact resistance, dimensional stability, scuffing resistance, peeling resistance.

6, Paintability and electrical properties, used to make automobile instrument panels, radiator grills, speaker grills, consoles, fuse boxes, relay boxes, connectors, wheel covers.

7, electronic and electrical industries are widely used in the manufacture of connectors, coil winding spools, mechanical parts shroud, switch relays, tuning equipment, large electronic displays, variable capacitors, battery accessories, microphones and other parts.

8, household appliances used in televisions, cameras, video tapes, tape recorders, air conditioners, heaters, rice cookers and other parts. Can be used as copy machines, computer systems, printers, fax machines and other external components and components.

9, in addition to cameras, timers, pumps, blower shells and parts, silent gears, pipes, valves, surgical instruments, sterilizers and other medical equipment parts.

10, large-scale blow molding can be made of large automotive parts such as flow barrier, bumper, low-foam molding is suitable for the production of high rigidity, dimensional stability, excellent acoustic absorption, the internal structure of complex large-scale products, such as a variety of machine shells, bases, internal brackets, the design of a large degree of freedom, product lightweight.

Injection molding process
l) non-crystalline material, moisture absorption is small, PPO's water absorption is very low, but the moisture will make the surface of the product silver, bubbles and other defects, for this reason, the raw material can be placed in the 80 ~ 1OOC oven Shen, dry 1-2h after use.

2) PPO's molecular bond rigidity, high glass transition temperature, not easy to orientation, but forced orientation is difficult to relax. So the residual internal stress in the product is high, generally after treatment.

3) PPO is an amorphous material, in the molten state of the rheology is close to the Newtonian fluid, but with the increase in temperature deviates from the Newtonian fluid to a greater extent.

4) PPO melt viscosity, so the processing should increase the temperature, and increase the injection pressure to improve the mold filling capacity.

5)The return material of PPO can be reused, generally reused 3 times, there is no significant reduction in its performance.

6) The PPO melt should be molded using a screw injection molding machine, the nozzle adopts a straight-through type is preferred, the aperture diameter of 3-6mm.

7) in PPO injection molding, it is appropriate to take high-pressure, high-speed injection, holding pressure and cooling time can not be too long.

8) The main flow channel of the mold should adopt a larger taper or use the pulling hook, the sprue is good to be short and thick.

9) The gate should be direct, fan-shaped or flat, the diameter should be appropriately increased when using the needle gate, for long sprue can be used hot runner structure.

10) PPO molding shrinkage is small, generally 0.2% -0.7%, so the product dimensional stability is excellent.

11) poor fluidity, similar to Newtonian fluid, viscosity is sensitive to temperature, product thickness 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.

12)The water absorption of polyphenylene ether is very low 0.06% or so, but the trace moisture will lead to the surface of the product such as silver wire and other non-smooth phenomena, it is best to make the drying process, the temperature should not be higher than 150 ℃, otherwise the color will change.

13) Polyphenylene ether molding temperature of 280-330 ℃, modified polyphenylene ether molding temperature of 260-285 ℃. PPO plastic raw materials injection molding process melt temperature: 270-290 ℃

PPO modified
Unmodified polyphenylene ether (PPO) resin has good mechanical properties, electrical properties, heat resistance, flame retardancy and chemical stability, but it is poor solvent resistance, products are prone to stress cracking, notched impact strength is low, in addition to the existence of an Achilles' heel - high viscosity of the melt, processing and molding is extremely poor, pure PPO Pure PPO resin can not be injection molding methods, which greatly limits its application.

In order to overcome these shortcomings, or to give it new properties, people have carried out a variety of modifications to PPO. The methods are chemical (copolymerization, blocking, grafting and reticulation, etc.) and physical (blending, filling, reinforcing and microfoaming, etc.) modification of two.

Chemical modification mainly includes:
(1) Structural modification of PPO, such as bromination, phosphorylation, sulfonylation, carboxylation, etc. to improve the solubility and permeability of PPO for membrane materials, or to give PPO flame retardant properties for flame retardant materials;

(2) The main chain or end group of PPO reacts with small molecules with functional groups to give PPO a certain polarity and reactivity, which is used as a bulking agent for PPO alloys;

(3) PPO and other macromolecules or small molecules through block or graft copolymerization to obtain new materials or used as a bulking agent for PPO alloys;

The most active research in the physical modification of polyphenylene ether is the alloying of PPO, mainly including:
(1) Utilizing the compatibility of PPO with polystyrene (PS) in a wide range of compositions to prepare PPO/PS-type alloys, i.e., the first generation of PPO alloys, by blending with a variety of polymers with styrene units;

(2) High-performance PPO alloys, i.e., second-generation PPO alloys, are prepared by blending with other engineering plastics, such as polyamide (PA), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyphenylene sulfide (PPS).

In addition, the polyphenylene ether alloys can be categorized according to the compatibility between the components:
(1) Compatible systems, mainly PPO/PS;

(2) Non-compatible systems, including PPO/PA, PPO/PBT, PPO/PET, PPO/polytetrafluoroethylene (PTFE), PPO/polyolefin (PO), and so on;

(3) Partially compatible systems, including PPO/polycarbonate (PC), PPO/PPS, PPO/styrene-butadiene-styrene copolymer (SBS), PPO/acrylonitrile-butadiene-styrene copolymer (ABS), PPO/poly(methyl methacrylate) (PMMA), PPO/styrene-acrylonitrile copolymer (SAN) and so on.

Problems and solutions encountered in material injection molding
Because PPO materials are used less, I believe that PPS we all use more frequently, so for you to bring is PPS (polystyrene sulfide) injection molding problems: