exam 1 spring _09

# exam 1 spring _09 - EMA 3066 Exam 1 Name First Last I have...

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Unformatted text preview: EMA 3066, Exam 1 January 29, 2009 Name:______________________________ First Last I have neither given nor received help on this exam.___________________ Signature 1. Nylon 66 and PET have roughly the same glass transition temperature, while the polymer shown below has a much lower glass transition. Explain how the structure of each of these polymers causes the Tg’s to behave in this way. O ( O ( CH2 ) O 6 C O ( CH2 ) 4 C ) EMA 3066, Exam 1 January 29, 2009 2. Calculate Mn, Mw, and PDI for the following sample of PVC: mol% of chains 45.0 25.0 30.0 DP 1500 3500 4000 EMA 3066, Exam 1 January 29, 2009 3. The graph below shows a plot of reduced viscosity versus concentration for a sample of polystyrene measured in toluene at 25º C. From this data determine the molecular weight. The Mark-Houwink-Sakurada constants are K = 7.5x10-5 dL/g and a = 0.75 inherent viscosity (dL/g) 2.5 2 1.5 1 0 0.05 0.1 0.15 0.2 concentration (g/dL) 0.25 0.3 0.35 EMA 3066, Exam 1 January 29, 2009 4. a. Polystyrene with Mv of 350,000 g/mol is placed into cyclohexane at 34.5˚ C. These are theta conditions for PS. Under these conditions, the Mark-Houwink-Sakurada constants are K = 8.46x10-4 dL/g and a = 0.50. Calculate: i. The unperturbed end-to-end distance, assuming a freely jointed chain. Note: The length of a C-C bond is 1.54 Å. ii. The real end-to-end distance under these conditions. iii. The characteristic ratio of PS. b. Using the Mark-Houwink-Sakurada constants given in problem 3, calculate the chain expansion factor for PS in toluene at 25˚ C. EMA 3066, Exam 1 January 29, 2009 5. Calculate the solubility parameters for each of the following polymers using the parameters of Hoy, and identify a good solvent for each. A table with solvent solubility parameters is provided at the end of the exam. a. Nylon 6, = 1.15 g/cm3 b. polystyrene, = 1.1 g/cm3 EMA 3066, Exam 1 January 29, 2009 6. Based on the lattice theory of mixing, how do you expect the entropy of mixing of a polymer and a solvent to vary with molecular weight of the polymer? Explain your answer. EMA 3066, Exam 1 January 29, 2009 EMA 3066 Exam 1 Equation Sheet Mn NiMi Ni N i M i2 w i M i Mw NiMi w i PDI Mw Mn RT lim M n c 0 c r = / s = t / ts sp = (-s) / s = r –1 red = sp / c inh = (ln r) / c lim red lim inh c 0 c 0 red k ' 2 c inh k" 2 c KM a v a vol%crystallinity s x100 c a a wt %crystallinity c s x100 s c a /2 〈〉 〈〉 〈〉 / 〈〉 ∑ = 2.1x1021 dL/mol-cm3 R = 8.31 J/mol-K EMA 3066, Exam 1 January 29, 2009 EMA 3066, Exam 1 January 29, 2009 ...
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