tough ness (or ductihty or viscosity) test or sample. measure of ductihty (or tenacity or viscosity), -messer, m. (degree of) viscosity or ductility or tenacity, -mass, n. Zahigkeits-einheit, /, unit of viscosity (or tenacity or ductility), -grad, m. Extmsion rheometers have been appHed to other materials with some success with adhesives and coatings (10,161). When melt viscosities of a wide range of materials must be measured, rotational viscometers are preferable. These instmments are useful when large numbers of quahty control or other melt viscosity test measurements are needed for batches of a single material or similar materials. Ī number of instmments are based on the extmsion principle, including sHt flow and normal capidary flow (Table 6). A simple deterrnination of free formaldehyde may be used to foUow the first stage of the reaction, and the build-up of polymer in the reaction mixture may be followed by cloud-point dilution or viscosity tests. In order to inhibit crystallization of methylo1 melamines, the reaction is continued until about one-fourth of the reaction product has been converted to low molecular weight polymer. A melamine laminating resin used to saturate the print and overlay papers of a typical decorative laminate might contain two moles of formaldehyde for each mole of melamine.
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