3 064 Quiz 10 10 03 Sample questions 1 What is the glass transition temperature of a polymer be measured How can it What molecular characteristics determine its value Illustrate by giving the chemical structure and Tg for polyethylene polyvinyl chloride and polystyrene 2 What is the glass transition temperature of a polymer be measured How can it What molecular characteristics determine its value Illustrate by giving the chemical structure and Tg for polyethylene polypropylene and polystyrene 3 Draw the chemical formulas for polydimethyl siloxane polyethylene polypropylene polyvinyl chloride polymethyl methacrylate polystyrene polytetrafluoroethylene polycarbonate and polyethylene terephthalate 4 For each of the previous polymers give the approximate glass transition temperature the percent crystallinity and some principal market applications 5 Describe the role of polarity and topology on glass transition temperature 6 Draw plots of modulus versus temperature for various polymers amorphous crystalline crosslinked non crosslinked Explain why the plots have the shape they do 7 Why is Teflon so good as a non stick surface How do they get it to stick to the pan 8 Explain what a spherulite is and describe the effect of spherulite size on polymer mechanical properties 9 Explain how the molecular weight distribution of a polymer can be measured by size exclusion chromatography Sketch the form of the raw data obtained from this instrument and state how the number and weight average molecular weight can be obtained from the data 10 Explain the effect of molecular weight on tensile strength and viscosity Give an example of an application of an ultra high molecular weight polymer 11 Define the Hermann s orientation function and explain how it can be determined experimentally Derive its value for uniaxial transverse and random orientation 12 Outline some methods for obtaining ultra high orientation in polymers e g Kevlar Spectra 13 Define the following elastic constants Poisson s ratio tensile modulus and compliance and shear modulus and compliance Give approximate values for the Poisson s ratio and tensile modulus of both glassy and rubbery polymers 14 Why does rubber have to be crosslinked to be useful usually How is this done show the chemistry 15 Only cis 1 4 polymerization of butadiene produces a good elastomer What are some other possibilities and why do they not make good rubbers How do we get the form we want 16 Outline the concepts involved in the kinetic theory of rubber elasticity 17 Give the relation for strain energy in a rubber as a function of the extension ratios and from this develop equations governing the extension ratio and the applied load for uniaxial tension equal biaxial tension and unequal biaxial tension 18 Develop an expression for the radius of a spherical rubber balloon as a function of the internal pressure 19 Consider two spherical rubber balloons initially identical inflated to r 2 the other to r 3 One is What happens when the balloons are connected at their necks so that air can flow from one to the other Just a qualitative description based on the rubber elastic curve below 20 Give the relation for strain energy in a rubber as a function of the extension ratios and from this develop equations governing the extension ratio and the engineering stress for uniaxial tension 21 Draw plots of modulus versus temperature for various polymers amorphous crystalline crosslinked non crosslinked Explain why the plots have the shape they do For the three element springdashpot model below a Sketch the relaxation and compliance functions Grel t and Jcrp t conceptually without recourse to equations b Develop the differential equation for the model and solve it for relaxation Grel t c Derive or at least set up the expression for the complex modulus of the model 22 Explain the significance of the terms complex modulus storage modulus loss modulus 23 What is the rationale for claiming that the presence of a lowtemperature loss peak is a necessary and sufficient condition for good room temperature impact strength