Objectives
- Make PVOH films by acid catalyzed dehydration in H2O.
- Make a 500mL stock solution for PVOH(MW 22,000) in H2O
- Create four dilute solutions for each MW PVOH(eight solutions in total), diluting by 0.75, 0.5, 0.25, and 0.125
- Test the viscosity of the four solutions
PVOH plus acid films
- 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
- In a clean 600mL beaker, place 200mL distilled H2O with a magnetic stirrer and heat until ~90°C
- 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)
- Let the solution cool to room temperature.
- Pour into a 500 mL volumetric flask and fill with H2O.
- 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:
- 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
- Measure the temperature of the surroundings. Record the temperature
- Rinse the same viscometer with the lowest concentrated stock solution that needs to be tested
- 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
- 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
|
- Viscosity of 1.99 mM PVOH in H2O at 26°C
Trial [ ]
|
Time [s]
|
1 |
279.37
|
2 |
281.97
|
3 |
283.12
|
- Viscosity of 3.99 mM PVOH in H2O at 26°C
Trial [ ]
|
Time [s]
|
1 |
246.42
|
2 |
250.31
|
3 |
251.86
|
- Viscosity of 7.98 mM PVOH in H2O at 26°C
Trial [ ]
|
Time [s]
|
1 |
273.99
|
2 |
276.73
|
3 |
278.63
|
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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