Evaluation Techniques and Equipment

A number of lightfastness and weatherability test methods have in several countries been developed into industrial standards. 

Attempts have been made to replace the Blue or Wool Scale by physical devices that measure the radiation of the light source. To determine the radiation of a given light source, the irradiance (in W/m2) is multiplied by the exposure time (in s). The equipment necessary to carry out such measurements is commercially available. Measurement in the UV region would be desirable. It has recently become possible to purchase an instrument which can measure spectrum-related irradiance in the important UV range. 

Very light and weather resistant systems require very long outdoor exposure times. In order to accelerate the testing of pigmented systems, test methods have been developed which simulate outdoor conditions. The evaluation of such a test is not only conveniently accelerated, but the resulting data are easy to reproduce and independent of location, climate, date, and time. 

the compulsory requirement for automotive coatings of a two-year Florida exposure can be reduced to a period of less than 6 months. This is advantageous for the developmental process. 

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. 

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Evaluation techniques and equipment are as varied as the individual catalytic processes themselves. The long term goal of catalyst evaluation is to reduce the size of the testing equipment consistent with reliable and accurate data as it relates to the commercial process. Invariably, the farther removed in physical size the process simulation attains, the more likely that errors will be introduced which can affect data accuracy, accuracy being defined as commercial observations. In addition, smaller equipment size also places less demand on the physical integrity of a catalyst particle therefore, additional test methods have been developed to simulate these performance characteristics. Despite these very important limitations, laboratory reactors fully eight orders of magnitude (100 million times) smaller are routinely used in research laboratories by both catalyst manufacturers and petroleum refiners. 

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