Published: Jan 2012
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DYNAMIC MECHANICAL AND TENSILE PROPERTIES are determined in all branches of materials science. There is a large body of published structure/property information that can be integrated with coatings research and development. By using structure/property information, coatings chemists can design and optimize chemical structures of the binder components of coatings. Purposeful and enlightened formulation with well-designed components makes it possible to obtain desirable coatings performance in many cases. Determination of dynamic mechanical and tensile properties requires the use of free films. This requirement is a serious limitation because many, if not most, of the performance properties of coatings are influenced by coating-substrate interactions. Therefore, tests of coatings intact on their end-use substrates must be thoughtfully coupled with free film determinations. The practical utility of basic methods described in this section is greatly enhanced when results are interpreted in relation to results of adhesion, abrasion, hardness, flexibility, toughness, and internal stress tests as described elsewhere in the manual. Dynamic mechanical analysis (DMA) and stress-strain analysis (SSA) of tensile properties are complementary methods in several ways. DMA involves very small strains, whereas SSA involves the maximum strain that the sample can withstand. Since the small strains used in DMA usually do not exceed the tensile strength or yield strength of the sample, the method is nondestructive. This feature facilitates property determination over a wide temperature range on a single sample, that is, DMA is often used as a temperature-scanning method. In contrast, SSA data are usually obtained at a single temperature, preferably on an instrument located in a controlled temperature and humidity room. Since the sample is broken in each test, it is very arduous to carry out SSA over a wide temperature range, and SSA is not amenable to temperature scanning.
Hill, Loren W.