Spray-tester

It is also possible to test the resistance to humidity by submitting bonded samples to an accelerated weathering tester such as the QUV spray tester, which combines water spray and condensation plus UV light to simulate sun rays. We will study this in the Weathering section hereunder. 

A direct comparison of the results obtained by the simplified shear cell methodology and the Flowfactor Tester of Jenike and associates is difficult since the experimental procedures differ. Figures 10 and 11 show the yield loci obtained using both methods. For free flowing spray-dried lactose the yield loci are very similar (Fig. 10) and nearly linear, as is generally observed [45]. Bigger... 

Figure 4 Schematic production sequence for the manufacture of metered-dose inhalers by pressure filling (1) suspension mixing vessel (2) can cleaner (3) can crimper and filler (4) check weigher (5) can coder and heat tester (6) priming and spray testing (7) labeler (8) feeds for tested cans and actuators. (Courtesy of Ellis Horwood Publishers, Ref. 10.)...

Figure 2. Effect of mild abrasion from a Brush Pilling Tester on new cotton fibers treated with a) distilled water, b) magnesium bicarbonate, c) Wei T o 12 spray and d) Wei T o 2 solution.

EXPLOSION and FIRE CONCERNS noneombustible liquid NFPA rating Health 2, Flammability 0, Reactivity 0 no flash point in conventional closed tester reacts violently with barium, beryllium, lithium, dinitrogen tetraoxide, and sodium hydroxide decomposes in a fire to hydrogen chloride and phosgene use water spray, fog or suitable agent for firefighting purposes. 

Another technique is that of spraying or overlaying colonies with a suspension of bacteria that require for growth a compound which is the end product of the pathway one desires to derepress. Constitutive mutants often overproduce the end product, excrete it, and cross-feed such tester cultures (O Donovan and Gerhart, 1968). 

Trigger spray products use a different protocol in the United States, where the product is sprayed directly onto the test surface according to anticipated label instructions. Therefore, the tester must stipulate how much product is sprayed and how far the product is held from the surface when sprayed, as this can influence how much of the cleaner reaches the surface. As new product forms develop, like disinfectant wipes, this requires new EPA methods modifications of the germicidal spray test for wipes-type products are now being seen in some of the literature [107,108]. 

Testers may be tempted to force quicker corrosion testing by increasing the amount of chemical stress. Steel that corrodes in a 0.05% sodium chloride (NaCl) solution will corrode even more quickly in 5% NaCl solution the same is true for zinc-coated steel. The problem is that the amount of acceleration is different for the two metals. An increase in NaCl content has a much more marked effect for zinc-coated substrates than for carbon steel substrates. Strom and Strom [1] have demonstrated this effect in a test of weakly accelerated outdoor exposure of painted zinc-coated and carbon steel samples. In this weakly accelerated test, commonly known as the Volvo Scab test, samples are exposed outdoors and sprayed twice a week with a salt solution. Table 7.1 gives the results after 1 year of this test, using different levels of NaCl for the twice-weekly spray. 

Because materials experience such long wet times outdoors, the typical fluorescent UV weathering tester condensation cycle is at least four hours. Furthermore, the condensation is conducted at an elevated temperature (typically 50°C), which greatly accelerates the moisture attack. The fluorescent UV weathering tester s long, hot condensation cycle reproduces the outdoor moisture phenomenon far better than other methods such as water spray, immersion, or high humidity. 

In addition to the standard condensation mechanism, the fluorescent UV weathering tester can also be fitted with a water spray system to simulate other damaging end-use conditions, such as thermal shock or mechanical erosion. TTie user can program the UV to produce cycles of wetness alternating with UV, a situation that is identical to natural weathering. 

Most xenon arc testers simulate the effects of moisture through water spray and/or humidity control systems. The limitation of water spray is that when relatively cold water is sprayed onto a relatively hot test specimen, the specimen cools down. This may slow down the degradation. However water spray is very useful for simulating thermal shock and erosion. In a xenon arc, highly purified water is necessary to prevent water spotting. Because humidity can affect the degradation type and rate of certain indoor products, such as many textiles and inks, control of relative humidity is recommended in many test specifications. Modern xenon test chambers are available with relative humidity control. 

Rotating-drum testers have a spray bar and nozzles which spray the specimens with water as they rotate past it. Specimens are wetted for approximately three seconds out of each one minute revolution. Because of the vertical position of the specimens, the water quickly mns off the surface. Between these wettings, it is possible for specimens to dray off as they rotate away from the spray. 

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