Poly Phenylene Oxide (PPO)

In 1965, A. Hay of General Electric produced polyphenylene oxide by the copper catalyzed oxidation of 2, 6 xylenol [(CH3)2 C6H3 OH)].

This is an aromatic polyester in which benzene rings is linked at the 1 and 4 position via. Oxygen atom.

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Monomer Ingredients for PPO

This polymer is made from 2,6 dimethyl phenol

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Chemistry of Preparation of PPO

Poly-(phenylene oxide) is known as poly (2,6-dimethyl-p-phenylene ether).

The most successful method of preparation involves oxidative coupling of 2, 6 dimethyl phenol.

The reaction is carried out at 28-46°C by bubbling oxygen through a solution of the phenol in the presence of a copper (I) salt-amine complex for about 7 minutes.

The reaction mixture is added to methanol filtered and washed with methanol to give a colourless polymer.

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Chemistry of Preparation of PPO

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Relations of Structure and Properties of PPO

The rigid structure of the polymer molecules leads to a material of a high Tg of 208°C.

There is a also a secondary transition at 116°C and the small molecular motions that this facilitates at room temperature give the polymer in the mass a reasonable degree of toughness.

When polymerized the polymer is crystalline but has a surprisingly low reported melting point (Tm) 257°C.

The ratio of Tg & Tm of 0.91 (in terms of K) is uniquely high. Because of the small differences in Tg and Tm there is little time for crystallization to occur on cooling from the melt and processed polymer is usually amorphous.

However if molecular movements are facilitated by raising the

temperature or by the presence of solvent crystallization can occur. CORPORATE TRAINING AND PLANNING

Relations of Structure and Properties of PPO

The polymer is dissolved by halogenated and aromatic hydrocarbons

of similar solubility parameter. Stress cracking can occur with some

liquids. Being only lightly polar and well below the Tg at common ambient

temperature the polymer is an excellent electrical insulator even at high

frequencies. The polymer exhibit very good hydrolytic stability. One particular feature of PPO is its exceptional dimensional stability

amongst the so-called engineering plastics. It has a low co-efficient of thermal expansion, low molding shrinkage

and low water absorption thus enabling molding to close tolerances. It is more or less self-extinguishing polymer with a good chemical

resistance properties..

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Characteristics of PPO (For Identification)

It is semi-crystalline and having melting point of 257°C Characterized by good dimensional stability and excellent

resistance to hydrolysis and very good dielectric properties

over a wide range of temperature Its short term and long term service temperatures are 100

and 80°C It is characterized by orange yellow flame with black smoke

and self extinguishing character It melts but chars It smells phenolic (ink smell) while it is burnt.

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Characteristics of PPO

Possesses high melting point and glass transition temperature Low co-efficient of thermal expansion Continuos use temperature upto 100°C Excellent electrical properties Low loss factor Dissipation factor is quite low Very good dimensional stability High heat distortion temperature (179°C) Low moulding shrinkage Low warpage Good impact resistance Low water absorption Soluble only in halogenated and aromatic hydrocarbons Excellent flame retardancy Outstanding hydrolytic stabilityCORPORATE TRAINING AND PLANNING

Properties of PPO

Properties Units ValuesSpecific gravity ---- 1.5 – 1.10Tensile strength MPa 41-110Tensile modulus MPa 234-276Flexural modulus Mpa 221-276Elongation at break % 2-3 Impact strength izod, Notched, J/m 107-537Hardness R 115-120Deflection temperature under load 0C 82-149(1.82 Mpa)Vicat softening point °C 250-310Coefficient of linear expansion mm/mm/0C 6-14 x 10-5

Water absorption, 24hrs % 0.06-0.12Dielectric strength KV/mm 15.7-27-6Dielectric constant 10-6 Hz 2.7-2.9 Power factor 0.0001-0.0025Glass transition temperature °C 100-150

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Properties of PPO

Electrical Properties

The electrical and dielectric properties of noryl are very good and almost independent of frequency and temperature.

Chemical Properties

PPO. mod. is resistance to dilute acids strong alkalines, solutions, alcohols, detergents, fats and oils depending on the additives.

It is not resistant to concentrated acids, ketones, chlorinated hydrocarbons, aromatics they swell in many aliphatics.

PPO mod. Is susceptible to stress cracking because of the styrene content.

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Properties of PPO

Weathering Resistance

Weathering resistance of PPO mod. is less than that of the unmodified material but still relatively high.

The long-term heat resistance in air and water in the presence of oxygen is inferior to that of polyacetals .

Flammability

Flame retardant grades are self-extinguishing and non-dripping.

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Properties of PPO

Toxicity

Correspondingly marked grades are non-toxic Grades incorporating demolding aids, UV stabilizer and glass fiber reinforcements are permitted.

Restrictions apply only to colored grades (cadmium pigments).

Suitable non-toxic pigments are carbon black,Ti02,ultramarine blue and iron oxide.that of polyacetals

Flammability

Flame retardant grades are self-extinguishing and non-dripping.

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Additives of PPO

1. Flame retardants

2. Glass fibers

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Grades of PPO

They are available in the following grades.

Glass reinforced

Foam grade

Plating grade

High modulus grade

Blow moulding grade

Injection moulding grade

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Processing considerations of PPO

Typical cylinder temperatures are about 280-300°C and mold temperatures 100 – 120°C.

If overheated, the material oxidizes resulting in poor finish and streakiness. Because of this it is advisable to purge machines before they are cooled down after molding.

The melt of PPO are almost Newtonian viscosity being almost independent of shear rate.

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Processing considerations of PPO

Due to their extremely low moisture absorption PPO resin can be molded without the need of drying.

Surface defect in case of due to the trapped moisture, can be avoided by proper drying.

Drying temperature vary with the resin grades. Temperature of 110°C for 2 hours are recommended for drying.

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Processing considerations of PPO

They can be processed by the following processing techniques.

Extrusion

Foam moulding

Thermoforming

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Surface Finishing of PPO

Screen printing and hot embossing are common.

Alkyd, acrylic and epoxide based lacquers are used for coating. Vacuum metallizing is used for metal finishes.

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Machineability of PPO

Joining Welding Surface temperature of 260 to 2900C are selected for heated tool welding. Friction welding takes place at speeds of 1200 rpm and contact pressure of 20 N mm-2. Ultrasonic and resistance wire welding are also used.

Bonding PPO can be bonded using solvents such as dichloroethylene, toluene, chloroform or 950, dichloroethylene with 5% carbontetrachloride .High tensile and shear strength are achieved with rubber, epoxide, resin, silicon, cyanoacrylate and PU adhesives.

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Applications of PPO

Automotive

Electricals/Electronics

Miscellaneous

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Applications of PPO

Automotive:

Instrument panels, steering column, cladding, central consoles, loud speaker housings ventilator grills, nozzles, parcel shelves, radiator tanks, cable connectors, bulb sockets, air inlet and outlet grills and outer mirror housings.

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Applications of PPO

Electricals/Electronics:Television tuner strips, microwave insulation component,

transformer housings. Computer terminals, printers, modems, typewriter bases, video games, copier, capacitor casings, outlet boxes, coil bobbins, smoke detectors, intrusion alarm, motor covers and switches.

Capacitor casing

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Applications of PPO

Miscellaneous:Water pumps, water meters, sprinkler systems, hot water

tank, washing machine parts, welder’s protective visors, tennis racquets, textile components and valves for drink vending machines.

Welder’s protective visor Washing machine parts

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Applications of PPO

Kettle

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Polyphenylene oxide is completely miscible with polystyrene in all proportions. The glass transition temperature of these blends change smoothly with composition.

These blends with 25-60% (weight) of PPO, designed for injection or blow moulding, extrusion calendering, thermoforming and reinforced with 0-30 weight percentage glass fiber.

They have good processability, toughness, flame retardance, dimensional stability, resistance to hot water, economy, HDT (95-150°C), low density and moisture absorption.

Blends of PPO

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PPO / Nylons

These are blends (compatibilized) with 40-60 weight percentage of nylon.

PPO provide excellent heat resistance, toughness and nylon (crystalline) resists oils, gasoline and solvent, PPO / Nylons alloys have a lower density, higher toughness and show less tool/machine wearcompared to machine filled Nylon.

Polyamide grades are used for automotive body panels which require paint oven temperature upto 175°C.

PPO/Nylon grades are used in fluid handling applications which require chemical resistance, dimensional stability and heat resistance

Blends of PPO

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List of Manufacturers/Suppliers of PPO

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