Particulates from PTFE degradation in terrestrial and microgravity

It has recently been discovered that the ultrafine particles generated during polymer thermodegradation are a major health hazard, owing to their unique pathway of processing in the lung. This hazard in manned spacecraft is poorly understood because the particulate products of polymer thermodegradation are generated under low gravity conditions. Particulates generated from the degradation of polytetrafluoroethylene (PTFE), insulation coating for 20 AWG copper wire (representative of spacecraft application) under intense current overload, were studied in terrestrial gravity and microgravity. Microgravity tests were done in a 1.2-s drop tower at the Colorado School of Mines. Thermophoretic sampling was used for particulate collection. Transmission electron microscopy (TEM) was used to examine the smoke particulates. The pigmentation of PTFE insulation seems to have an overwhelming effect on size, shape and morphology of the particulate. Nanometer-sized particles were found in all cases, but their extent of aggregation and size distribution were dependent on both PTFE pigmentation and gravity; higher aggregation occurred in low gravity. Four different color insulations (viz. white, black, red and yellow) were studied.