t4f06 - Q1 The viscosity of a glassy material has decreased...

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Q1 The viscosity of a glassy material has decreased by a factor of 2 when the temperature is increased from 150 o C to 200 o C. Answer the following questions. 1. Glass working temperature is based on a. increasing the viscosity b. reducing the viscosity c. keeping the modulus remain constant 2. The viscous behavior of a material is a. thermally activated b. not thermally activated c. same as elastic behavior 3. The activation energy for viscous flow for the above glass in terms of the Boltzmann’s constant k is a. 5252.2 k b. 2773.0 k c. 1252.4 k 4. Ratio of the value of viscosity at 100 o C compared to that at 150 o C is a. 2.44 b. 0.82 c. 0.41 5. The unit of viscosity is a. pascals b. pascals/second c. pascals.second 6. The behavior of viscous materials is given by the applied stress proportional to a. strain b. strain rate c. inverse strain rate Q2. A polyethylene sample was subjected at room temperature (27 o C) to a tensile stress of 50 Psi and the stress is reduced to 25 Psi after 5 minutes when the cross- heads are held without movement. Answer the following questions. 7.Stress relaxation of the polymer is a result of a. elastic stretching of polymer chains b. thermally activated sliding of polymer molecules c. workhardening of polymers 8. The relaxation time of the above polymer at room temperature is a. 7.21 minutes b. 2.0 minutes c. 5.0 minutes 9. The load after 30 minutes at room temperature will be a. 72.2 Psi b. 3.2 Psi c. 0.78 Psi 10 What period of time (in minutes) is required before the stress falls to 10 Psi at room temperature a. 60 b. 11.6 c. 0.5 1
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11. If the load reached 10 Psi in 5 minutes, the relaxation time (minutes) of the polymer at 100 o C for the initially applied of 50 Psi is a. 7.21 b. 3.1 c. 1.6 12. The activation energy for stress relaxation in units of the Boltzmann’s constant (k) is a. 2580k b. 1293k c. 645 k Q3. Molecular weight of Na 2 O is 62 and that of SiO 2 is 60. If 42.86 gms of SiO 2 and 17.73 gms of Na 2 O are mixed and heated together, answer the following questions. 13. The number of gm.molecules of SiO
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This note was uploaded on 03/20/2008 for the course MSE 200 taught by Professor Wholedepartment during the Fall '08 term at N.C. State.

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t4f06 - Q1 The viscosity of a glassy material has decreased...

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