Ash characteristics in controlled diode laser pyrolysis of chlorinated rubber

This paper describes the effects of 60 W High Power Diode Laser (HPDL) beam s on the removal of chlorinated rubber (CR) paint fi om concrete surfaces a nd the ash particles generated from this process. The physical characterist ics, including shape and size distribution of the removed and collected air borne CR particles, down to a size of around 1 mu m in diameter, were deter mined using optical microscopy and image analysis. The shape of the particl es observed was highly irregular, displaying no symmetry. The size distribu tion of the collected particles was found to range between 1-2000 mu m, wit h the maximum concentration being found between 29 and 60 mu m. The chemica l characteristics of the CR ash particles were investigated by means of ESE M and EDX techniques. From a comparative analysis, it was found that the co ncentration of chlorine within the CR material was significantly reduced af ter HPDL treatment. This, together with DTA/TGA results indicated a combust ive degradation of the CR polymer through the interaction with the process gas, oxygen, and the laser irradiation. Also, a strong correlation between laser power and average particle sizes has been found, with higher powers g enerally producing larger particle sizes, opposite effects have been found by changing the oxygen flow rare, with higher oxygen flow producing, on ave rage, smaller particles. An interpreation of the combustion process, as wel l as a brief discussion on operational safety and environmental impact of t he products is attempted. (C) 2000 Elsevier Science Ltd. All rights reserve d.