Abstract: Polymers have become unavoidable in daily life. Manufacturers attempt to make durable components. Despite significant progress, failures routinely occur.
Service Related: Thermometers used in a hospital environment exhibited yellowish discoloration. Alcohol and phenol type disinfectants caused the discoloration. A clear polycarbonate window was attacked chemically by the disinfectants.
Improper Material: Improperly functioning controllers with built-in airflow sensors failed at Santoprene seals. Santoprene is a mixture of EPDM with some polypropylene (PP). Maximum controller rating was 150°F. Elevated temperature exposure revealed leaching of EPDM from seals at ~120°F. A higher cured grade of Santoprene was recommended.
Inferior Material: Cracked plastic water supply fittings intended to be polyphenyl sulfone (PPSU) failed via environmental stress cracking (ESC). Silicone and carboxylic ester were identified as the ESC agents. Failed parts were a blend of PPSU and polysulfone (PSU). Generally PPSU is more resistant to environmental agents than PSU.
Authors: Fahmida Hossain and Veda-Anne Ulčickas
Keywords: Santoprene Seals, Leaching, Environmental Stress Cracking