Exposure cabinets

The entire x-ray exposure cabinet including it s extension into the lower electrical cabinet is shielded with a minimum of one-inch of steel clad, lead plate with fiilly welded (fused lead) joints. The safety interlock switch on the cam-lock inter-face ... 

An industrial standard method has been developed to test the lightfastness of polymers in accelerated test equipment [103]. The apparatus consists of a quartz-xenon tube with a special optical filter between the light source and the specimen to produce light that resembles window glass-filtered daylight [104], Samples are mounted at a specific distance from the arc and are supported on a frame which revolves around the arc 1 to 5 times per minute for uniform exposure. A blower unit in the base provides a flow of air which makes it possible to maintain a black panel temperature of 45°C, measured by a black panel thermometer which is positioned at level with the samples. A black panel unit consists of a bimetallic thermometer mounted on a steel frame. Both faces of the frame plate and also the stem of the thermometer are coated with a heat-resistant glossy black enamel. The relative humidity level in the exposure cabinet is closely controlled. 

Habib and Asker (68) showed that metronidazole solutions decompose more under artificial sunlight [from two 40 W fluorescent sunlamps and fluorescent radiation (from cool white tubes)] in a Atlas HPUV Actinic Exposure Cabinet, than under UV-A radiation, as shown in Table 4. 

Nylon fabric was also exposed in darkness to the same temperature, humidity and acid conditions described above. The fabrics were placed in an Atlas Gas Exposure Cabinet model GE-IRC. Filtered air was allowed to flow through the cabinet. For each treatment, fabrics were exposed to light and darkness simultaneously to insure equal amounts of exposure. Following exposure, all fabrics were rinsed in distilled water, neutralized in 1.0% sodium carbonate, rinsed again in distilled water and air dried. The fabrics were then stored at 21 + 1 C and 65 + 1% R.H. for at least 24 hours. 

Design and validation characteristics of environmental chambers for photostability testing have been described in the literature (e.g., Boxhammer, 1998). Bench top light exposure cabinets (Atlas Company), which are widely used by many pharmaceutical and cosmetic companies (Thoma and Kiibler, 1994), may serve as an example for the high equipment technology available today. These units complete a range of equipment with filtered xenon arc radiation and contain most of the features previously mentioned. The focal points are ... 

The standardized tests use special apparatuses called exposure cabinets for exposure to salt mist, heat and moisture. Normative documents contain special sections specif 4ng the form, size and quantity of metal samples along with their preparation procedure for the tests. Preparation of the samples... 

Accelerated UV tests provide an alternative and generally much more rapid means of measuring the effects of light on polymers under consistent and reproducible conditions. The UV light is generally provided by xenon arc lamps and some modern UV exposure cabinet provide a very rapid assessment of polymeric materials (Figure 3.4) and correlate well with environmental exposure. Any element of the environment can be incorporated into a weatherometer . For example, relative humidity may be varied and an alternating water spray can be incorporated to simulate rain. As has already been noted this surface treatment may... 

The main purpose of cabinet tests is to accelerate material degradation simulating a long service and allowing to preview the corrosion occurring during in-service exposure. Cabinet tests are a useful indication of possible corrosion performance in natural environments and, in many cases, can be used to provide a relative comparison of material performance. 

Exposme of coated specimens to effects of UV radiation experienced in outdoor sunlight conditions which may be combined with other exposures such as moisture and erosion. Exposure cabinets use carbon arc (ASTM D 822), xenon lamp (ASTM G 26) or fluorescent lamp (ASTM G 53). 

Process 2 post-etch-pnnch The difference in this sequence is the order in which the laminate material is punched (tooled). The innerlayer detail is resist-coated and placed in the exposure cabinet. The artwork layers have already been pre-aligned as the top and bottom... 

The cabinet system includes full radiation safety in the form of dual, forced breaking door interlocks so that there can be no risk of exposure outside the cabinet. Equally the system is equipped with emergency stops and red lights indicating when X-rays are on, in accordance with the international regulations. 

The CASS Test. In the copper-accelerated acetic acid salt spray (CASS) test (42), the positioning of the test surface is restricted to 15 2°, and the salt fog corrosivity is increased by increasing temperature and acidity, pH about 3.2, along with the addition of cupric chloride dihydrate. The CASS test is used extensively by the U.S. automobile industry for decorative nickel—chromium deposits, but is not common for other deposits or industries. Exposure cycle requirements are usually 22 hours, rarely more than 44 hours. Another corrosion test, now decreasing in use, for decorative nickel—chromium finishes is the Corrodkote test (43). This test utilizes a specific corrosive paste combined with a warm humidity cabinet test. Test cycles are usually 20 hours. 

Fig. 4.17 Samples of high-purity AZ31 (upper photographs) and ZW3 (lower photographs) magnesium-base alloys, fitted with mild-steel nuts and bolts and exposed to a variety of corrosion conditions, (a) 4-S hours immersion in 37 salt soln., (b) 180 days immersion in distilled water, (c) 4 days immersion in borehole water, (d) 180 days in humidity cabinet sea-water spray and (e) 180 days atmospheric exposure...

Special cabinets are used for salt mist exposure in which a fine mist of a sodium chloride solution is produced at specified conditions. Change in mass or any physical property can be measured. This type of exposure has its origins in the determination of corrosion resistance rather than changes in bulk properties. 

Less than 1 pphm (parts per hundred million) of ozone in the atmosphere can severely attack non-resistant rubbers. However, there is far less, if any, problem with plastics and tests are rarely made. If required, the methods standardised for rubbers in ISO 1431 [24] could be used, which involve exposure in a special cabinet with controlled levels of ozone. 

Temperature and humidity is controlled to minimize evaporation of reagents and to keep performance of electronic equipment optimal. Ventilation is adequate for the removal of noxious fumes and odors. Formaldehyde and xylene vapor concentrations must be below maximum permissible levels. For formaldehyde, this level is 0.75 ppm for an 8-h time-weighted average, or 2.0 ppm for a 15-min short-term exposure. For xylene, the level is 100 ppm for an 8-h time-weighted average and 200 ppm for a 15-min short-term exposure. The monitoring of the work area and employees can be performed on a yearly basis. Chemical and biological safety cabinets are checked for proper airflow on a yearly basis. 

The relative aggressiveness of the environments proved to be consistent for all substrates, with the room temperature control the least hostile (virtually no loss of adhesion), and the cycle tests the most aggressive (up to 100% loss of adhesion within 60 days). Humidity cabinet exposure and 60°C water immersion yielded very similar values. As a result, for reasons of clarity, only water immersion data is actually presented here. Joint strength data obtained from either the Ford APG or Fisher Body Cycle Tests were identical, and were therefore also represented by one set of data points. The relative aggressiveness of the host environments toward... 

Caution UV radiation is harmful to eyes and skin the reaction vessel may be wrapped with aluminum foil or the reaction conducted in a closed photochemical reaction cabinet to prevent exposure to the harmful UV rays. 

Provision is made in ISO 4665 for exposure of strained test pieces so that, in addition to the effect of light and temperature (and perhaps rain), the effect of ozone can be investigated. The procedures are the same as in ISO 1431 for exposure in an ozone cabinet. 

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