User:Moira M. Esson/Notebook/CHEM-581/2012/08/31: Difference between revisions

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==Viscosity of PVOH Stock Solutions==
==Viscosity of PVOH Stock Solutions==
'''General Procedure''':  
'''General Procedure''':  
#Using an Ostwald viscometer, time the rate at which H<sub>2</sub>O flows from the top most line to the bottom most line. Run at least three trials
#Using an ASTM kinematic viscometer, time the rate at which H<sub>2</sub>O flows from the top most line to the bottom most line. Run at least three trials
#*'''Note''':The amount of solution in the viscometer does not matter, but the viscometer can hold no more than 10mL
#*'''Note''':The amount of solution in the viscometer does not matter, but the viscometer can hold no more than 10mL
#Measure the temperature of the surroundings. Record the temperature
#Measure the temperature of the surroundings. Record the temperature
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  |}
  |}
* Average time = 276.45 s
* Average time = 276.45 s
==Preparation==
==Preparation==
*Prepared 500mL stock solution of PVOH (MW 130,000)in H<sub>2</sub>O
*Prepared 500mL stock solution of PVOH (MW 130,000)in H<sub>2</sub>O

Revision as of 18:29, 6 September 2012

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Objectives

  1. Make PVOH films by acid catalyzed dehydration in H2O.
  2. Make a 500mL stock solution for PVOH(MW 22,000) in H2O
  3. Create four dilute solutions for each MW PVOH(eight solutions in total), diluting by 0.75, 0.5, 0.25, and 0.125
  4. Test the viscosity of the four solutions

PVOH plus acid films

  1. The General Procedure for creating films(described on 08/29/2012) was followed except for the addition of 1-2 drops of acid before heating and stirring the solution
  • 0.5 g PVOH (MW 22,000) and 2 drops of 12 M HCl in 3 mL H2O
    • Actual mass PVOH = 0.5163 g
    • Note: After addition of the 12M HCl and heating for ~5 minutes, the gel formed a brown color
  • 1 g PVOH (MW 22,000) and 1 drop of 12 M H2SO4 in 6 mL H2O
    • Actual mass PVOH = 1.0204 g
      • Note: After heating the solution for ~5 minutes, the gel formed a brown tint
  • 1 g PVOH (MW 22,000) and 1 drop of 12 M H3PO4 in 6 mL H2O
    • Actual mass PVOH = 1.0040 g

Preparation of PVOH Stock Solutions

  1. In a clean 600mL beaker, place 200mL distilled H2O with a magnetic stirrer and heat until ~90°C
  2. Slowly add 5grams of PVOH (MW 22,000) over a 30 minute period. Continuously stirring. Stir slowly to avoid frothing of the gel. Heat and stir until polymer is completely dissolve
    • Note: The polymer is completely dissolved when the solution is clear(~1hr of heating)
  3. Let the solution cool to room temperature.
  4. Pour into a 500 mL volumetric flask and fill with H2O.
  5. Dilute the solution by pouring the following volumes into separate 50 mL volumetric flasks and then filling with H2O.
    • Concentration of original stock solution = 15.95 mM
    • Use 37.5 mL of 15.95 mM solution to dilute to 11.96 mM
    • Use 25 mL of 15.95 mM solution to dilute to 7.98 mM
    • Use 1.25 mL of 15.95 mM solution to dilute to 3.99 mM
    • Use 6.25 mL of 15.95 mM solution to dilute to 1.99 mM

Viscosity of PVOH Stock Solutions

General Procedure:

  1. Using an ASTM kinematic viscometer, time the rate at which H2O flows from the top most line to the bottom most line. Run at least three trials
    • Note:The amount of solution in the viscometer does not matter, but the viscometer can hold no more than 10mL
  2. Measure the temperature of the surroundings. Record the temperature
  3. Rinse the same viscometer with the lowest concentrated stock solution that needs to be tested
  4. Time the rate at which the lowest concentrated stock solution flows from the top most line to the bottom most line. Run at least three trials
  5. Repeat steps 2 and 3 for each of the stock solutions, ensuring to systematically increase the concentration of each stock solution tested

Viscosity Calculations

  • Viscosity of pure H2O at 26°C
Trial [ ] Time [s]
1 238.79
2 242.62
3 241.63
  • Average time = 241.01 s


  • Viscosity of 1.99 mM PVOH in H2O at 26°C
Trial [ ] Time [s]
1 279.37
2 281.97
3 283.12
  • Average time = 281.49 s


  • Viscosity of 3.99 mM PVOH in H2O at 26°C
Trial [ ] Time [s]
1 246.42
2 250.31
3 251.86
  • Average time = 249.53 s


  • Viscosity of 7.98 mM PVOH in H2O at 26°C
Trial [ ] Time [s]
1 273.99
2 276.73
3 278.63
  • Average time = 276.45 s

Preparation

  • Prepared 500mL stock solution of PVOH (MW 130,000)in H2O

Observations

  • PVOH (MW 130,000) film(prepared 08/29/12) when dried was very rigid and curled slightly
  • Preparation of 500mL stock solution of PVOH (MW 130,000)in H2O required more time(~2-2.5 hrs). Complete dissolution of the polymer required extra time and more vigorous stirring
    • When dissolving the PVOH (MW 130,000) a large gel-like sphere formed in the center of the solution



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