Exterior application tests

It has been shown that an accelerated test method (the automatic boil test—ASTM D-3434) is convenient for evaluating adhesive performance and for predicting durability for exterior applications. Samples are subjected to 800 cycles, which corresponds to approximately 16 years of exterior exposure for a good wood adhesive. Figure 6 compares the perform-... 

A major application of data base in our laboratories is in the tracking of coatings test exposure data. The two types of exposure records currently implemented are for exterior hardboard siding coatings, and for coil coatings. While these two classes of substrates and the coatings used for them are quite different, the basic structure of the data and reporting requirements are not. 

The enhancement of vertical condensers remains an area of high interest due to potential large-scale power and process industry applications, for example, desalination, reboilers, and OTEC power plants. Tubes with exterior longitudinal fins or flutes, spiral flutes, and flutes on both the interior and exterior (doubly fluted) have been developed and tested. The common objectives are to use the Gregorig effect to create thin-film condensation at the tips of the flutes and to drain effectively. 

The silicone polymer backbone is composed of Si-O-Si bonds. This bond is very strong and stable with a bond energy of 87 Kcal/ mole. The polymer can tolerate 250°C to 300°C without decomposing.— The fully compounded silicone sealant, when cured to a rubber, can withstand 200°C for sustained periods of time with no special additives and even higher temperatures with polymer modifications and/or heat stability additives.— The Sl-O-Si molecular structure is also transparent to U.V., so silicone sealants are virtually unaffected by weather. Samples of silicone sealants used in exterior construction applications have been tested after 20 years of actual performance. These samples exhibited essentially no change in physical properties or adhesion during that time period. 

Another chemical treatment that has resurged recently due to improvements made in its formulation is the hydroxymethylated resorcinol (HMR). HMR has been used successfully with several timbers and adhesives, to promote the exterior durability of their bonded joints [65, 71]. Consequently, this technique seems ready for industrial application, at least for the species and adhesives tested. Nevertheless, studies to clarify some aspects of its action mechanism are still needed [20]. 

The method is also applicable to foams having a higher-density exterior (solid skin) on one or both sides. In the former case, the specimen is tested with the skin facing down. 

TGSting. No test is available that reliably predicts the exterior durability of coatings, partly due to the wide variety of environments and application conditions (see Weathering). The limitations of accelerated tests, the need for data based on actual field experience, and methods of building a database are described in Reference 23. Use of reliability theory using statistical distribution functions of material, process, and exposure parameters for predicting exterior durability of automotive coatings has been recommended (46). Reference 55 reviews various test methods. 

Exterior testing for certain applications of plastics should be conducted to support microbiological results obtained in initial petri dish screening of biocides. This testing can be summarized as follows ... 

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