Particle concentrations during the manufacturing of biobased composite polyurethane foam panels

Exposure to filler powder particles was evaluated during the manufacturing of 12 biobased nano-enabled polyurethane (PU) foam panels in a research and development facility based on a novel pilot plant technology. Particle emissions were investigated in PU foam production at weighing filler powders (GasBeton®, diatomite, and functionalized silica), 2) loading the powders into a reactive chamber and mixing, 3) casting into a foaming mold, and 4) a subsequent foaming phase, where the exposure assessment was performed for the first three phases.

Particle concentrations were measured in the near-field (NF) and far-field (FF) using online aerosol particle monitors, and particles were sampled from workplace air for gravimetric analysis and image and elemental analysis. Operational conditions were registered, including air flow measurements.

Process times were in the order of 1 minute; despite the use of online instruments with time resolutions of 1 second (ELPI), it was not possible to distinguish concentrations between different powder weighing. Due to incomplete air mixing in the NF, it was not possible to assess particle loss rates. Thus, emissions could not be quantified. Process particle number and ≤ 10 μm and respirable mass concentrations were up to 31.2 #/cm ³ (pouring; average duration 1 minute; handling rate 700 g/min), 538 μg/m ³ and 140 μg/m ³ (weighing; average duration 2 minutes; handling rate 350 g/min), respectively. Maximum exposure potential was assessed for each task, assuming a continuous process. The maximum risk characterization factor was 0.4 for crystalline silica external exposure, which is considered adequately controlled. Electron microscopy analysis of particles sampled from the air confirmed the presence of filler particles, whereas ICP-OES analysis led to inconclusive results.

Powder filler exposure was adequately controlled during continuous and manual weighing, pouring, and casting processes when local exhaust ventilations are applied. Exposure risk to liquid components was not evaluated.

Particle emissions during the manufacturing of 12 biobased composite polyurethane foam panels were investigated in a research and development facility. Due to process times of 1 to 2 minutes and an uncontrolled measurement environment by the use of local exhaust ventilations (LEVs), it was not possible to calculate emission rates using mass balance principles. Exposure assessment to filler particles was based on Electrical Low Pressure Impactor (ELPI) measurements, and the presence of filler particles was confirmed by analyzing collected particles by electron microscope. Gravimetric sampling was used to confirm the consistency of the ELPI measurements. Particle dispersion in the working hall was measured using online monitors at relevant locations. Maximum exposure potential for continuous processes was found to be adequately controlled when LEVs were present.