Weathering test

Coatings that are exposed to weathering undergo aging. Aging is defined as the sum of all irreversible chemical and physical processes that occur in the coating over the course of time. Aging is mainly caused by radiation, temperature, and moisture (rain and atmospheric humidity). 

Commercial test institutes in Florida are often commissioned to carry out natural weathering tests. The weather conditions in Florida are preferred because the same aging phenomena occur as in other locations but more quickly. Exposure time can be reduced by a factor of two to four when compared with other locations. The test 

In laboratories, coatings are artificially weathered in specially designed apparatus to simulate or measure the aging processes that occur during natural weathering. Artificial weathering involves a smaller number of parameters than natural weathering but can be controlled more uniformly and allows accelerated test conditions [9.49]-[9.51]. 

ASTM D 822 describes a standard procedure for operating light- and water-exposure apparatus (carbon-arc type) for testing coatings. ASTM G53 and DIN 53384 describe similar standard procedures for the light exposure or light and water exposure (fluorescent UV type) of nonmetallic materials [9.54]. 

Dieter Stoye, Werner Freitag copyright WILEY-VCH Vcrlag GmbH. 

---

The commercial polymers are mechanically similar to PTFE but with a somewhat greater impact strength. They also have the same excellent electrical insulation properties and chemical inertness. Weathering tests in Florida showed no change in properties after four years. The material also shows exceptional non-adhesiveness. The coefficient of friction of the resin is low but somewhat higher than that of PTFE. Films up to 0.010 in thick show good transparency. 

Nagaska el ai., Weathering Test on Zinc, Aluminium and Zinc-Aluminium Alloy Sprayed Coating for 5000 Days, Proc. lOth Int. Thermal Spray. Corf., DVS, Diisseldorf, Poster report (1983)... 

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... 

Test method for iron chip corrosion test for water soluble metalworking fluids Test method for accelerated weathering test conditions and procedures for bituminous materials (xenon-arc method)... 

Notes for guidance on the conduct of natural weathering tests... 

AB-type polycondensations, 330 AB-type polymers, 135 Accelerated weathering tests, 245 Acceptor-catalytic polyesterification, 75 4-Acetoxy benzoic acid, poly esterification of, 74... 

Weathering tests, 245 Wholly aromatic liquid crystalline polyesters, degradation of, 38 Wholly aromatic polyamides, 136-137, 139 synthesis of, 184-189 Wholly aromatic polyesters, 25-26, 32 copolymerization and, 35 synthesis of, 71-72... 

When a tracer is considered, it is important to evaluate its performance with respect to these criteria, especially stability during exposure and storage/analysis. Normal practice involves conducting weathering tests where field collectors are treated with known amounts of the tracer and an assessment is made of weathering, extraction and storage stability under conditions pertaining to the intended use. The characteristics of the tracer allow it to be applied uniformly over the application area. Typically, application monitors are used to verify both the application rate and the uniformity of the application. 

An aspect of particular interest is the performance of hindered amines in protective coatings such as lacquers. Weathering tests in our application laboratories have shown that a tetramethylpiperidine derivative (HALS 1) has in fact a very good protective effect. 

Decomposition of Peroxides by Various Stabilizers. The efficiency of tert-butyl hydroperoxide decomposition in tert-butyl alcohol by various additives was determined (Table 9). Under the conditions of these experiments, the phenolic antioxidants and dilauryl thiodipropionate had little or, often, no effect on the hydroperoxide decomposition. The three zinc salts effectively inhibited peroxide decomposition. This effect might briefly inhibit the onset of substrate oxidation under weathering-test conditions, but the peroxide would decompose whenever its concentration reached a sufficient level to permit significant light... 

Accelerated solvent extraction (ASE), capillary chromatography sample preparation, 4 609, 610 Accelerated temperature, humidity, and bias (THB) tests, 10 9 Accelerated weathering tests, 19 584 Acceleration, exponents of dimensions in absolute, gravitational, and engineering systems, <5 584t Accelerators, 9 554-555 10 411, 713 22 61 23 861-862 for cement, 5 485... 

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

Flowever, omitting to take account of the temperature of products used or stored in sunlight when selecting materials can lead to unexpected rates of deterioration or failure. Conversely, the temperatures reached during weathering tests, both natural and accelerated, need to be considered when assessing the results. 

A summary of important considerations in natural weathering tests can be given as ... 

ISO 9370, Plastics - Instrumental determination of radiant exposure in weathering tests - General guidance and basic test method, 1997. 

The general requirements for accelerated weathering apparatus are given in ISO 4892-1 [29], whilst ISO 4892 Parts 2-4 [26-28] deal more specifically with xenon arcs, fluorescent tubes and carbon arcs respectively. ISO 4892 refers to ISO 9370 [30] (Instrumental determination of radiant exposure in weathering tests), and CIE publication 85 (Solar spectral irradiance) [31]. 

The determination of tensile stress-strain properties is conducted in accordance with ISO 527 [4] and the values that can be obtained are illustrated in Figure 7.1. For weathering tests where cabinet space is restricted some workers have used a tensile impact dumbbell from ISO 8256 [5] with a square central section which allows test pieces to be exposed edge on. The considerable disadvantage is that modulus cannot be measured as there is no parallel gauge length. 

The fundamentals of weathering tests are outlined in Section 6.8. This section will provide some examples concerning the problems of correlation of accelerated and natural weathering. 

After weathering test bars (3 mm thick) for one year in a sunny climate, the retention of properties is, for example ... 

---