Exposure Assessment of Particulate Matter from Abrasive Treatment of Carbon and Glass Fibre-Reinforced Epoxy-Composites - Two Case Studies

ABSTRACT

The use of composites is ever increasing due to their important structural and chemical features. The composite component production often involves high energy grinding and sanding processes to which emissions workers are potentially exposed. In this study we investigated the machining of carbon and glass fibre-reinforced epoxy composite materials at two facilities. We measured particle number concentrations and size distributions of the released material in near field and far field during sanding of glass- and carbon fibre-reinforced composites. We assessed the means of reducing exposure during the work by means of different working style, local exhaust ventilation, and enclosing the process area. Machining processes released particles primarily in < 100 nm size range. Without enclosure, process particle concentrations were 3.9 × 10⁴ cm^–3 in the near field and 1.3 × 10⁴ cm^–3 in the far field. Therefore workers in the same area may not be aware of being exposed to the process particles and the need of wearing protective outfits. Comparison of workers working style and effect on near field particle concentrations showed that a careless working style increased particle concentrations of 1.1% and 14.1% when comparing with a careful working style. Investigating the effect of the local exhaust ventilation showed that a maximum flow rate caused removal of close to 100% of particles from the working zone. A 28% reduction in the flow rate reduced particle removal efficiency more than 50%. With the enclosure around the process area, the process particle concentrations were 1.7 × 10⁶ cm^–3 in the near field, while the concentration in the far field was negligible. The enclosure used was shown to provide an average protection factor of more than 100.