ReviewForExam1

ReviewForExam1 - Review for Exam 1 MatSE 448 ChE 442...

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Review for Exam 1 MatSE 448 / ChE 442 Wednesday, Feb. 9 (in class) 12:20 - 1:20 Bring : Pen or pencil, calculator and one 8.5” x 11” paper with anything you want to write on one side Review : Homeworks, Quizzes, Notes
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Quiz 1 1. What is a thermoplastic elastomer? What are two types of thermoreversible junctions used in thermoplastic elastomers? Do both types create recyclable elastomers? Thermoplastic elastomers have reversible ‘crosslinks’ formed on cooling when the A blocks of an A-B-A triblock copolymer either crystallize or vitrify (form a glass) While the B blocks are soft and rubbery (with T g far below room temperature). Both crystalline and glassy junctions melt on heating, allowing recycling. 2. You obtain two samples of monodisperse polystyrene, A (molar mass = 100 kg mol -1 ) and B (molar mass = 500 kg mol -1 ). If equal weights of A and B are blended together, calculate the weight-average molecular weight of the mixture. Some of these equations may be useful. ii i n nM w M nn   32 2 z wM M  0.5 100 kg/mol 0.5 500 kg/mol 300 kg/mol 1 i w i i M w 2 w i M w
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Quiz 2 1. Isotactic polypropylene is semicrystalline at room temperature with T g = -20 o C and T m = 170 o C. Atactic polyvinylacetate is a glassy polymer at room temperature with T g = 35 o C and will not crystallize at any temperature, owing to its tacticity. For linear samples of isotactic polypropylene and atactic polyvinylacetate with similar molecular weights, which polymer has higher viscosity at 180 o C and why? Above T m , polypropylene has no knowledge of the crystalline state. Polyvinylacetate is closer to T g so it has higher viscosity. 2. Calculate the number-average degree of polymerization for linear BPA- polycarbonate with the structure below, if the number-average molecular weight is 67 kg/mol. 67000 g/mol 264 254 g/mol n n mon M N M       16 12 g/mol 3 16 g/mol 14 1 g/mol 254 g/mol mon M 
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Quiz 3 1. What are the low shear rate limiting value of viscosity and the high shear rate limiting value of viscosity for the following simple models? Power Law Model Ellis Model Carreau Model Carreau-Yasuda Model 2. What is the effect of a uniform isotropic pressure on a. melt density at a fixed temperature? density increases slightly (liquids have small compressibility) b. zero shear rate melt viscosity at a fixed temperature? viscosity increases slightly (liquids have small compressibility) c. Couette flow of the polymer very little effect, apart from slightly larger viscosity and density That is why we can remove the P from the stress tensor! 1 n ij m  1 0 1/2 1 ij         (1 ) / 2 2 0 1 n ij    ) / 0 1 na a ij  Power Law index n < 1 means polymer melts shear thin not thicken! 0
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ReviewForExam1 - Review for Exam 1 MatSE 448 ChE 442...

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