HW8 - kg of MDPE. 2.) Lets get some practice explaining...

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Chem Engr 178: HW 8 Due Friday Nov 7 1.) A sample of polyethylene that is cooled so rapidly that it doesn't crystallize has a density of 865 kg/m 3 while if the polyethylene were completely crystalline, it would have a density of 1000 kg/m 3 and a specific enthalpy of melting of 294 J/g. You are given a polyethylene (designated MDPE) with unknown crystallinity and measure its density to be 930 kg/m 3 . Find the weight fraction crystallinity, the volume fraction crystallinity and the enthalpy of melting you would measure using differential scanning calorimetry for 1
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Unformatted text preview: kg of MDPE. 2.) Lets get some practice explaining concepts. Please make your answers concise: a) Why do polymers usually melt over a range of temperatures unlike low molecular weight materials which usually have a sharp melting point. b) Why do polymers crystallize in a chain folded fashion rather than the thermodynamically preferred extended chain form. 3.) Y&L Problem 3.12 4.) Y&L Problem 4.4...
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This note was uploaded on 12/09/2011 for the course CHEM ENG 178 taught by Professor Segalman during the Fall '08 term at University of California, Berkeley.

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