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# HW6f10 - molecular weight increases from 40,000 g/mol to...

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Homework #6 Due 10/19/10 1. On a graph, sketch stress vs. strain rate for a Newtonian fluid, a pseudoplastic fluid, and a dilatant fluid. 2. Consider a polymer that undergoes degradation (decrease in molecular weight due to breaking of covalent bonds) during flow. How will the viscosity change with time? How is this situation different from a thixotropic or rheopectic fluid? 3. Calculate the percent change in viscosity per degree change in temperature for polystyrene at 230˚ C. The activation energy for flow is 104 kJ/mol. 4. a. By how many times will viscosity increase for a polystyrene melt if the molecular weight increases from 10,000 g/mol to 20,000 g/mol? b. By how many times will viscosity increase for a polystyrene melt if the
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Unformatted text preview: molecular weight increases from 40,000 g/mol to 80,000 g/mol? 5. Production of a nylon fiber requires spinning the fiber at a speed of 200 m/minute. If fiber is extruded through a hole 1 mm in diameter and the length of the hole is 5 cm, what is the pressure drop required across that hole? The viscosity for nylon under the processing conditions is 1400 poise. 6. For each of the items below, choose the processing technique that would be used to make the item. a. tray for frozen food b. plastic measuring cup c. thread for sewing d. a turkey made from epoxy (Thanksgiving decoration) e. drinking straw...
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