Effect of dry heat treatment between room temperature and 160 degrees C on surgical masks

The Covid-19 crisis has led to a high demand and use of surgical masks worldwide, causing risks of shortages and pollution. Therefore, decontamination of surgical masks could be an opportunity to reduce these risks. In our study, we applied dry heat to the masks for 15 min at different temperatures and studied the consequences of heat on surface chemistry and fiber morphology. We focus here on the effects of dry heat treatment on the masks and not on the verification of mask disinfection, which has been thoroughly studied in existing literature. The masks that were heated to 70 degrees C, 100 degrees C, 130 degrees C, 140 degrees C, 150 degrees C did not show significant changes at the nanometric scale and the standard deviation of the surface temperature of the worn masks is similar to that of the unheated control mask. However we show a slight heating altered the hydrophobicity of the surface, and induced a significative modification of the wetting angle of water droplets. The mask heated to 157 degrees C has a higher surface temperature standard deviation and fused fibers are observed by scanning electron microscopy. The mask heated to 160 degrees C melted and then hardened as it cooled making it completely unusable.