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

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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 from the prepared PVOH(MW 22,000) stock solution, diluting by 0.75, 0.5, 0.25, and 0.125
  4. Measure the viscosity of PVOH (MW 22,000) at the diluted concentrations and the stock solution

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.

Stock Solution Calculations

  • Stock Solution Preparation for PVOH (MW 22000)
Initial Mass [g] Additional Mass [g] Total Mass [g] Stock Volume [mL] Concentration [M] Weight percent [%]
2.02564.99027.01585006.38E-41.40
  • Serial Dilution of PVOH Stock Solution
Dilution 'M1'[mol/L] 'V1' [mL] 'M2'[mol/L] 'V2' [mL]
16.38E-46.257.98E-550
26.38E-412.51.59E-450
36.38E-425 3.19E-450
46.38E-435.54.78E-450

Viscosity of PVOH (MW 22000) Stock Solution

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 actual amount of solution in the viscometer does not matter, but the viscometer can hold no more than 10mL. Approximately 10mL should be used
  2. Measure the temperature of the surroundings. Record the temperature
  3. Wash the viscometer with the solution that needs to be tested. Wash by drawing the solution into the viscometer with a pipette pump past the top of the lower bulb and then allowing the solution to drain
  4. Wash the viscometer at least two times then discard the solution
  5. Pour approximately 10mL of the solution into the viscometer
  6. Draw the solution up past the lower bulb of the viscometer using a pipette pump
  7. Remove the pipette pump and let the solution drain from the viscometer. Once the bottom of the meniscus passes the first mark on the viscometer, start a stopwatch
  8. Stop the stop watch once the bottom of the meniscus passes the lower mark on the viscometer
  9. Repeat steps 6 through 8 at least two more times to obtain an average time in seconds for the solution to move between the two marks.
  • Note: Solutions should be run through the viscometer with increasing concentration(i.e. The lowest concentrated stock solution should be used first)


Viscosity Calculations

  • Viscosity of pure H2O at 26°C
Trial [ ] Time [s]
1238.79
2242.62
3241.63
  • Average time = 241.01 s


  • Viscosity of 7.98E-5M PVOH in H2O at 26°C
Trial [ ] Time [s]
1279.37
2281.97
3283.12
  • Average time = 281.49 s


  • Viscosity of 1.59E-4 M PVOH in H2O at 26°C
Trial [ ] Time [s]
1246.42
2250.31
3251.86
  • Average time = 249.53 s


  • Viscosity of 3.19E-4 M PVOH in H2O at 26°C
Trial [ ] Time [s]
1273.99
2276.73
3278.63
  • 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

Notes

  • An additional 2-3mL H2O was added to each solution to aid in the complete dissolution of the PVOH
  • Heat was reduced halfway through dissolving the PVOH because the solutions began to boil too rapidly
  • When pouring the ~0.5g PVOH (MW 22000) with HCl there was a small loss of sample when pouring the solution into a Teflon dish
  • Between the sample run of 7.97E-5 M PVOH solution and the sample run of 1.59E-4M PVOH solution, the viscometer was not washed


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