PTFE4775_Practiceproblems_Exam3

# PTFE4775_Practiceproblems_Exam3 - 1) True/False. When a...

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True/False. When a crosslinked rubber is stretched, its entropy increases and therefore it feels warm to the touch. True/False. In terms of probing the storage modulus of a polymer melt, heating up the melt has the same effect as lowering the deformation rate. True/False. Elastic deformation is the deformation of crosslinked thermosets whereas plastic deformation is the deformation of uncrosslinked thermoplastics. 2) For a polymer PX, the melt viscosity o = 10 5 Poise at 150 o C, and o = 10 2 Poise at 200 o C. What is the glass transition temperature of the polymer? 3) The following data are available for a polymer PZ: Melt viscosity at 100 . 0 o C for a sample with molecular weight of 5 kg / mol = 12,770 Poise. Melt viscosity at 125 . 0 o C for a sample with molecular weight of 20 kg / mol = 1,600 Poise. T g of PZ with molecular weight of 5 kg/mol = 60.0 o C. From these data, estimate th e e ntangl e m e nt mol ec ular w e ight of the polymer PZ. 4) For the model above, all the springs have the same constant E. Write the relationship between overall stress and overall strain in terms of E, e.g. = 3E  5) a) A constant strain = 10% is suddenly applied to a polymer PX, which we want to model using the above. The resulting initial stress is 20 kPa. This value then drops to 16 kPa in 51 seconds. What are the values for the parameters E and ? b) A mass of 0.25 kg is attached / hanging on a sample of PX (same polymer as in part a). The original dimensions of the piece are 1 m (length) × 1 cm × 1 cm. If the Poisson’s ratio of the polymer is 0.5, estimate the dimensions of the piece at 50 seconds. 1

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## This note was uploaded on 09/09/2011 for the course PTFE 4775 taught by Professor Unknown during the Fall '10 term at Georgia Institute of Technology.

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PTFE4775_Practiceproblems_Exam3 - 1) True/False. When a...

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