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LAB 46 - syikin - Experiment 46 Viscosity of High Polymer...

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Experiment 46 : Viscosity of High Polymer Solutions Abstract The determination of intrinsic viscosity and several other quantities in this experiment is done by measuring the time required for a given volume of liquid to flow through a capillary tube of Ubbelohde-type viscometer. From this experiment, it was found that the intrinsic viscosity of polyethylene glycol was 55 ± 5 mL/g. From the result of the intrinsic viscosity, the polymer’s molecular weight was found out to be 36000 ± 16000 g/mol. Assuming that the polymer forms a sphere, the radius was calculated to be ( 29 m 9 10 5 6 - ± . Then, by assuming that the polymer has carbon-carbon backbone with tetrahedral angles, the calculated radius is ( 29 m 10 10 4 . 1 0 . 128 - ± . Alternatively, by assuming that the polymer segments pack together, the radius was found out to be ( 29 m 9 10 3 . 0 3 . 2 - ± . Finally, the length of the molecule was calculated to be ( 29 m 7 10 4 . 1 0 . 3 - ± . Introduction The experiment utilizes the use of Ubbelohde-type viscometer which employs capillary flow method to find the intrinsic viscosity of polyethylene glycol. The experiment was done by measuring the flow time of different concentrations of the polymer. Then, graphs of - 1 1 o c η η and o c η η ln 1 versus concentration was plotted and the average of the intercepts gives the intrinsic viscosity. From the intrinsic viscosity,
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other measurements such as molecular weight, radius and the length of the polymer were obtained. Data and Calculation Solvent (ml) 10 10 20 30 40 65 90 Polymer (ml) 0 10 10 10 10 10 10 Total (ml) 10 20 30 40 50 75 100 Run 1 (sec) 70.00 201.54 145.30 122.16 109.25 97.00 89.63 Run 2 69.81 201.66 145.47 123.28 109.32 96.85 89.63 Run 3 67.84 201.66 145.50 122.16 109.06 96.91 89.75 Run 4 70.03 202.63 145.12 122.25 109.90 96.91 89.44 Run 5 67.53 202.38 145.54 122.00 109.46 97.06 90.65 Run 6 67.69 201.82 146.01 121.69 109.60 96.68 89.35 Run 7 67.63 201.97 145.05 120.75 109.30 96.19 89.49 Run 8 67.59 - - - - - - Run 9 67.84 - - - - - - Run 10 67.40 - - - - - - Average 68.3360 201.9514 145.4271 122.0414 109.4129 96.8000 89.7057 Std. Dev. 1.1206 0.4084 0.3195 0.7526 0.2729 0.2946 0.4376 Table 1. Flow time of pure solvent and dilute polyethylene glycol solution in Ubbelohde- type viscometer. Sample calculation of concentration : 10ml solvent and 10ml polymer solution V V V c c ion Concentrat + = = 0 0 0 where ( 29 mL g mL mL mL mL g c 02500 . 0 10 10 10 05000 . 0 = + × = ( 29 ( 29 o o o o o o o o o o o o c V V V V V V V c V V c V V V V c c + + + - + + + = 2 2 ( 29 ( 29 mL mL mL mL mL g mL mL mL g mL mL ml mL mL g c 02 . 0 10 10 10 05000 . 0 10 10 05000 . 0 02 . 0 10 10 10 05000 . 0 2 2 × + × - + + × + × = o c = initial concentration of stock polymer o V = initial volume of stock polymer V = 10 mL of solvent
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mL g mL mL mL mL 00056 . 0 00006 . 0 10 10 10 = × + + So, for 10mL solvent and 10mL polymer solution, concentration = 0.0250 ± 0.0006 mL g Note : 10mL pipet tolerance = ± 0.02 mL Sample calculation of density : 10ml solvent and 10ml polymer solution The experiment assumes that density is a linear function of concentration. Therefore two points below are plotted on density versus concentration graph and the equation of the line was used to calculate the densities.
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