Polyphenol oxidase (PPO) is a thermoplastic that only exists as part of blends with other materials, as it is very difficult to process in a pure form. PPO is most common in blends with HIPS, but is also combined with polyamide (PA) and polypropylene (PP).
PPO has excellent dielectric and mechanical properties, and high heat resistance. The different blends with PPO are used in e.g. in electronics and HVAC applications and the automotive industry. Common applications include pump housings, valves, automotive chassis details, and sockets.
● Low density
● Very low moisture absorption
● Very good dimensional stability
● Excellent hydrolytic resistance
● Resistance to chemicals, including weak acids, alkalis, and some aliphatic compounds
● Good mechanical properties over a wide temperature range
● Low warpage tendency at high temperatures
● PPE+PS has a glass-transition temperature of 140°C
Some less optimal properties:
● Low resistance to aromatic and halogenated hydrocarbons and strong acids