Abstract
Twin screw extrusion is the preferred process to commercially produce nanocomposites by compounding the nanoparticles and polymer melts. Polymer nanocomposites, which contain nanoparticles dispersed in a polymer matrix, provide improved properties at low filler loadings. Nanoalumina particles recently have been used as fillers to polymer matrix that contributed enhanced physical properties of nanocomposites. Recently, concerns had been expressed that airborne nanoparticles particularly of nanoalumina released during compounding might present serious contamination of the air in the workplace. Researchers with experience in environmental health and polymer manufacturing monitored the compounding process for a model nanoalumina-containing nanocomposite using a TSI Fast Mobility Particle Spectrometer (FMPS). FMPS measurements were taken at background locations, source locations, and operators’ breathing zones; in parallel to the FMPS real time measurement, airborne nanoparticles were collected using polycarbonate filters fitted with filmed grids driven by a personal air sampling pump. Filter samples were analyzed for particle morphology and elemental composition. It was found that the nanoparticle number concentration was elevated during processing. The released nanoparticles are a complex mixture of the individual nanoalumina particles, agglomerates of those particles, polymer fume particles, and perhaps others.
Highlights
Polymers are often reinforced using a silicates, and recently, silver and engineered nanoparticles such as carbon nanotubes
This long-term monitoring shows total number concentration measured from the beginning of warm up to the end of the operation; background concentrations were measured in the sequence shown in Fig. 2(a) while source and breathing zone concentrations were only measured during the feeding of 5% nanoalumina
During Phase II, the calibration period, the twin screw feeder of nanoalumina particles placed nearby the primary feeding port of extruder was calibrated for the feeding rate by loading nanoalumina particles into a cup
Summary
Polymers are often reinforced using a silicates (nanoclays), and recently, silver and engineered nanoparticles such as carbon nanotubes. A local exhaust system had been installed on the TSE to help control xxx contaminants given off by the process It consists of a 30 cm (12 in.) diameter round hood connected to a flexible duct, with an exhaust air flow of 100 m3/h (60 ft3/min). During these experiments, the hood was positioned 30 cm (12 in.) above the extruder to collect polymer fumes given off from the melted mixture of polymer and nanoalumina; it was not placed near the feeding port. Released nanoparticles during the feeding of nanoalumina particles into the TSE would agglomerate with each other and with other particles present in the air, resulting in the generation of more particles in the larger size range This mechanism could explain the larger particle median and mode measured after the feeding process. The concentration at the background accumulated throughout the continuous feeding of nanoalumina, so that the concentration was highest at the end of feeding and it took time to gradually purge the high particle concentration by the local exhaust ventilation
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