The importance of particle size to spray hazard analysis composition has a marginally lower average transmission than the 70% ethanol: 30% propellant mixture. This suggests that a greater volume of propellant will produce an aerosol cloud with a higher concentration of droplets. When the particle size of the plume is analyzed, it becomes apparent that the particle size distributions produced with the propellants differ considerably. Figure 6 shows that a higher ethanol volume results in a consistently larger size distribution than the 30% ethanol formulation. Figure 6 shows that a higher propellant volume results in a significantly smaller particle size distribution and, particularly, an increase in the percentage volume smaller than 10μm, which could represent an increased inhalation risk. The effects of using different valves were then investigated. In these tests, droplet size was found to change depending on the valve used, with the standard valve producing, on average, larger particles. However this change is relatively small. Conversely, when the transmission is investigated, it is revealed that the vapor tap has a much higher average transmission, corresponding to a lower concentration of droplets and a drier spray (Figure 7). By monitoring the production of the spray plume in real time, laser diffraction allows developers to investigate droplet size in detail at the point of expulsion. This helps with understanding the mechanisms of aerosolization and how to control it to ensure safe delivery. In summation Regulations such as REACH are designed to actively stimulate the chemicals market within the EU. In return, however, they require manufacturers to fully understand the nature of their products. For sprays and aerosols, measuring particle size is an important part of this process. Several particle sizing techniques that work on very different principles can be employed for the analysis of sprays. Today, the need to produce the most detailed data models available to support REACH product registration has led to the inclusion of new analytical techniques, such as real time laser diffraction alongside traditional aerodynamic measurements, to comprehensively understand spray behavior. These bring detailed information to developers, helping to support the introduction of products that combine high performance with safety. Spray Figures 4a and 4b: Particle/droplet size distribution during start-up and spray stabilization. Distribution is noticeably narrower following stabilization. Figure 4a: Figure 4b: Figure 5: Transmission (%) profiles for samples with different propellant mixtures over time. Average transmissions are shown to be relatively similar, although the sample containing greater volume of propellant produces an aerosol cloud with a noticeably higher concentration of droplets. 44 Spray May 2014
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