Noryl is a blend of polyphenylene oxide (PPO) and polystyrene (PS) that was developed by General Electric Plastics in 1966 (now owned by SABIC). It is a rare example of a homogeneous mixture of the two polymers. Most polymers are incompatible with one another, so tend to produce separate phases when mixed. The compatibility of the two polymers in Noryl is caused by the presence of a benzene ring in the repeat units of both chains.
The addition of polystyrene to PPO increases the glass transition temperature above 100 °C, owing to the high Tg of PPO, so Noryl is stable in boiling water. The precise value of the transition depends on the exact composition of the grade being used. There is a smooth linear relation between weight content of polystyrene and the Tg of the blend. Noryl has good electrical resistance, so is widely used for switch boxes. However, product design is important in maximising the strength of the product, especially in eliminating sharp corners and other stress concentrations. Injection moulding must ensure that mouldings are stress-free.Like most other amorphous thermoplastics, Noryl is sensitive to environmental stress cracking when in contact with many organic liquids. Compounds such as gasoline, kerosine and methylene chloride may initiate brittle cracks which lead to product failure.
Noryl has numerous applications in electronics, electrical equipment, coating, machinery, etc. Noryl has possible applications in the production of hydrogen, where it could serve as cost-effective electrodes in an electrolyzer, replacing expensive rare elements. It is highly resistant against the alkaline potassium hydroxide. For conductivity the plastic is sprayed with a nickel-based catalyst. Noryl is being investigated as a possible replacement for polycarbonate used in the manufacturing of Blu-ray Discs. It is also used in certain construction products.