Weathering artificial methods

The standard aging tests also encompass weathering test methods, both under natural and artificial exposure. Such tests possess the advantage of not being as restrictive as the above mentioned ones, thus allowing testing of a wider range of polymers and polymer based materials under their conditions [32]. 

An appraisal of artificial weathering methods was given in a report by Hoey and Hipwood who described the effectiveness of various weatherometer tests such as are described in BS 3900 Part F3 and ASTM 42 1964 (now ASTM G23 1989). Although these tests simulate atmospheric exposure it is not possible to obtain a direct correlation owing to variation in outdoor exposure conditions from place to place, but they serve a very useful purpose in providing a preliminary sorting of paints that can then be tested in the field. 

Specification for electroplated coatings of 65/35 tin/nickel alloy Method for the evaluation of results of accelerated corrosion tests on metallic coatings Methods of test for paints Cross-cut test Pull-off test for adhesion Resistance to artificial weathering (enclosed carbon arc) and Addendum No. 1 Resistance to continuous salt spray Notes for guidance on the conduct of natural weathering test... 

Studies are currently being conducted on smoke development and heat release rate from treated and untreated wood and wood products (52,56). An evaluation of the available treatment systems for wood shingles and shakes was completed using artificial weathering (11). A further development from this work was a new ASTM Standard Method D2898 (67,68) for testing durability of fire-retardant treatment of wood. 

The artificial induction of noble rot would greatly facilitate making botrytized sweet wine, extending their production to countries where conditions are unfavorable for the natural development of noble rot. Experiments have long been performed to this end. In the earliest work, Nelson and Amerine (1956) unsuccessfully tried to induce its development in the vineyard by inoculation. The necessary moisture condition after inoculation was impossible to reproduce under field conditions. In addition, the method creates the risk that other fungi (Penicillium, Aspergillus, Rhizopus), yeasts and, acetic acid bacteria could develop if unfavorable weather conditions arose (Dittrich, 1977). 

Resistance to light is determined for pigments dispersed in the material in which they to be used. Two methods of exposure are used under glass outdoors or in an artificial weathering unit equipped with a xenon arc as a source of radiation. The result of exposure is compared with a standard exposed to the same conditions. The evaluation is based on the color differences between the exposed and shadowed parts of the specimens. 

ASTM E1428 (a.l6) test method showing effect of OIT and DCOIT in a PVC formulation (containing a filler) against StreptoverticiIlium reticulum at a dose of 1000 ppm and following artificial weathering by QUV up to 500 hours... 

Method resp. set of exposure conditions A (artificial weathering) B (daylight behind window glass) 1 to 3... 

However, outdoor weathering tests are not quite reproducible due to the instability of the climate. Moreover, they are invariably slow, longer and longer exposure periods being required for the evaluation of new polymers with improved stability. This gradual increase in exposure time and a tendency towards more standardized methods has led industries to develop more powerful light sources and artificial weathering devices. 

Schaefer (1966) reported the activation of large numbers of ice nuclei on the addition of trace levels of iodine vapor to car exhaust (containing lead oxide nanoparticles) at temperatures from —3 to —20°C in the laboratory. The formation of lead iodide was concluded to have a seeding effect similar to that of silver iodide particles (Vonnegut, 1947), which had been used in an attempt to artificially modify cloud properties and enhance precipitation. Consequendy this method was proposed as a means to remove harmful aerosol formed in polluted urban areas, and also in artificial weather modification. However, the development of unleaded fuels, for which no similar ice nucleating ability was shown to occur in the presence of iodine (Hogan, 1967), provided a better long-term solution to this problem. 

Test method for low-temperature flexibility of latex sealing compounds after artificial weathering. 

Plastics- Instrumental determination of radiant exposure in weathering tests—General guidance and basic test method, Paints and varnishes—Artificial weathering and exposure to artificial radiation—Exposure to filtered xenon-arc radiation. 

After the pure loading tests artificial weathering tests are also required. In these weather exposure tests strips taken in the warp and weft directions are subjected to a standard climate. The exposure time is normally 1000 hours. After this time the strengths are determined. A time acceleration factor of 10 can be achieved. In other words, after 1000 hours of artificial weathering the strength loss after 10,000 hours can be determined. Alongside this are also calculation methods for the determination of the loss of... 

Various tests and analytical methods are used for the characterisation and evaluation of the properties of vegetable oil-based polymer composites. Mechanical tests for properties such as tensile, flexural, compressive, impact, hardness and wear are carried out by a universal testing machine (UTM), and by equipment for testing impact, hardness, abrasion loss, and so on. Weather and chemical resistance tests are performed in UV/ozone, an artificial environmental chamber and in different chemical media. Water uptake and biodegradability tests are carried out by standard ASTM methods. Biodegradability and biocompatibility may be studied by the same procedure as described in Chapter 2. However, in practice only a few such studies have been performed for vegetable oil-based composites. 

Using various model dispersions, acrylic/styrene and pure acrylic copolymer dispersion binders for masonry paints were investigated by studying the way in which chemically different monomers affected the film properties and those of formulated paints. The test methods used were for water resistance, water vapour transmission, tensile properties, colour variation, UV transmittance, UV stability, artificial weathering and weathering-induced chalking. 12 refs. 

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