How To Learn and Have Fun with Poly(Vinyl Alcohol) and White Glue
V. de Zea Bermudez, P. Passos de Almeida, and J. Féria Seita Universidade de Trás-os-Montes e Alto Douro, Secção de Química, Quinta de Prados, Apartado 202, Vila Real Codex 5001, PORTUGAL
The general behavior of Newtonian, shear-thinning, shear-thickening, thixotropic, negative thixotropic, and viscoelastic fluids is characterized and briefly discussed in terms of existing theoretical models. Whenever possible, examples of these types of fluids taken from everyday life are given for better understanding. This theoretical introduction is the basis for same, simple, and inexpensive laboratory work employing no special glassware and generally done by pairs of students. The work involves the synthesis of two well-known viscoelastic materials displaying unique properties: poly(vinyl alcohol) (PVA) and white glue, a poly(vinyl acetate)-based emulsion. The students are asked to perform a series of representative mechanical tests on both gels and to describe their observations in full detail. In particular, they are expected to recognize and identify the origin of the intriguing behaviors found (elasticity, spinability, self-siphoning effect, die-swell effect, Weissenberg effect). The tests include the preparation of fibers by extrusion, introducing concepts such as water solubility, hydrogen bonding, and glass transition temperature. The long list of questions, which ideally should be answered at the end of the laboratory work, allows the students to apply the new concepts acquired.
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de Zea Bermudez, Verónica; de Almeida, P. Passos; Seita, J. Féria. J. Chem. Educ.1998 75 1410.
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