Opacity Measurements

The opacity for cellulose-starch composite films was measiued by using a JENWAY 6405 UV-VIS spectrophotometer and defined as the area under the absorbance spectrum between 400 and 800 nm according to the ASTM D 1003-00 method (ASTM D 

1003-00 Standard Test Method for Haze and Luminous Transmittance of Transparent Plastics). The film samples were cut into a rectangular piece (1x2.5 cm), fixed on the inner side of a 1cm of spectrophotometer cell and the absorbance spectrum recorded. The film opacity measurements were repeated three times. 

Composite sample comprising lignocellulosic filler-beech wood sawdust, namely AAMSt/St/BWS, is more less transparent comparatively with sample comprising beech cellulose. Film sample based only the plasticized starch matrix with chemically modified starch microparticles in composition maintains relative transparency. 

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Source sampling of particulates requites isokinetic removal of a composite sample from the stack or vent effluent to determine representative emission rates. Samples are coUected either extractively or using an in-stack filter EPA Method 5 is representative of extractive sampling, EPA Method 17 of in-stack filtration. Other means of source sampling have been used, but they have been largely supplanted by EPA methods. Continuous in-stack monitors of opacity utilize attenuation of radiation across the effluent. Opacity measurements are affected by the particle size, shape, size distribution, refractive index, and the wavelength of the radiation (25,26). 

Baghouses are preferred over venturi scrubbers for controlling particulate matter emissions from loading and pushing operations because of the higher removal efficiencies. ESPs are effective for final tar removal from coke oven gas. Stack air emissions should be monitored continuously for particulate matter. Alternatively, opacity measurements of stack gases can suffice. Fugitive emissions should be monitored annually for VOCs. 

PVC and EVA form incompatible polymer blends as indicated from permeability and opacity measurements. 

Rowe RC. Quantitative opacity measurements on tablet film coatings containing titanium dioxide. Int J Pharmaceut 1984 22 17-23. 

An interesting example of the application of the concept of steric stabilization is the interpretation of the optical performance of alkyd paints pigmented with TiOi by Franklin et al -. Having established from electrophoresis and opacity measurements that the electric charge on the particles is not the controlling factor in flocculation, a study was made of the adsorption characteristics of the resin using pigments coated with different levels of silica/ alumina such that the surfaces created varied from predominantly silica to mostly alumina. 

Conditions Letdown ratio, 50 1 Battenfeld press, 85 tons Barrel temperature, 230-250 °C. Testing Color data generated from 7.5 cm diameter injection-molded disks and opacity measured on nominal 0.575 mm thick press-outs from the letdowns. 

Let me speak first of the dust. The first precaution was to stop the fan and close the valve placed before it when, accidentally, the opacity measuring device shows abnormally high values for the dust content after the electrostatic precipitator. The second precaution was to stop also when the return temperature of the secondary circuit gets above 60 deg.C. 

In general, the terms clarity, haze, turbidity, transparency and so on are habitually used interchangeably, and sometimes without distinction, to describe the optical properties of a prodnct. However, it is important to realise that these various terms and measures are different and can, on some occasions, point in opposite directions. This chapter is focnsed primarily on the opacity measurement as a proxy for optical properties. Furthermore, since haze and clarity are generally observed to be inversely dependent, i.e., high haze yields low (poor) clarity and vice versa, these two terms are used interchangeably. 

This explains why brightness and opacity measurements are usually part of a color measurement. 

Air Permeability. Air permeabiUty is an important parameter for certain fabric end uses, eg, parachute fabrics, boat sails, warm clothing, rainwear, and industrial air filters. Air permeabiUty of a fabric is related to its cover, or opacity. Both of these properties are related to the amount of space between yams (or fibers in the case of nonwovens). The most common method for specifying air permeabiUty of a fabric involves measuring the air flow per unit area at a constant pressure differential between the two surfaces of the fabric. This method, suitable for measuring permeabiUty of woven, knitted, and nonwoven fabrics, is described in ASTM D737. Units for air permeabiUty measured by this method are generally abbreviated as CFM, or cubic feet per square foot per minute. 

Limits on emissions are both subjective and objective. Subjective limits are based on the visual appearance or smell of an emission. Objective limits are based on physical or chemical measurement of the emission. The most common form of subjective limit is that which regulates the optical density of a stack plume, measured by comparison with a Ringelmann chart (Fig. 25-1). This form of chart has been in use for over 90 years and is widely accepted for grading the blackness of black or gray smoke emissions. Within the past four decades, it has been used as the basis for "equivalent opacity" regulations for grading the optical density of emissions of colors other than black or gray. 

Opacity The degree to which a plume of exhaust gases obscures the view of an observer, measured in terms of percentage obscuration, with 100% meaning that the plume completely obscures the line of sight through the plume. 

Because of the subtle effects on the loading wave profile, many of the melting studies have utilized physical property measurements such as resistivity or optical opacity. Perhaps more direct are the release-wave speed... 

Opacity or transparency is important when the amount of light to be transmitted is a consideration. These properties are usually measured as haze and luminous transmittance. As reviewed haze is defined as the percentage of transmitted light through a test specimen that is scattered more than 2.5° from the incident beam. Luminous transmittance is the ratio of transmitted light to incident light. Table 5-7 provides the optical and various other properties of different transparent plastics. 

Recorders measure steam flow, air flow, FW flow, drum water level, steam temperatures, flue gas temperatures, flue gas analysis and smoke opacity. 

Crisp, S., Abel, G. Wilson, A. D. (1979). The quantitative measurement of the opacity of aesthetic dental materials. Journal of Dental Research, 58, 1585-96. 

Little information is available on other tests of strength. Isolated measurements give a flexural strength of 24-5 MPa (0ilo, 1988) and a tensile strength of 13-6 MPa (Kent Wilson, 1971). These values lie within the range of those recorded for glass polyalkenoate cement. Translucency is easily achieved as values for the inverse property of opacity show (Table 6.10). 

Evaluation of these optical properties may be done by simple observation this approach is useful clinically (Knibbs, Plant Pearson, 1986), since acceptability of the colour match to the surrounding tooth material can be readily seen without the need for instrumental measurement. On the other hand, for quantitative evaluation of optical properties, some kind of instrumental measurement is necessary, and the property usually evaluated is opacity. 

The main technique that has been used for the measurement of opacity has been to prepare a standard disc of AB cement 1-0 mm thick and aged for 24 hours at 37 °C. This disc, contained in a small trough of water to prevent desiccation, is placed in a reflectometer on a black background. It is then illuminated with diffuse light and the amount of light reflected from it, is measured. The disc is then placed on a white background of 70% reflectivity, and the new amount of reflected light, measured. The contrast ratio 7 o/ o is defined as the Cp., opacity (Crisp et al., 1979). 

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