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.
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 [%]
|
2.0256 |
4.9902 |
7.0158 |
500 |
6.38E-4 |
1.40 |
|
- Serial Dilution of PVOH Stock Solution
Dilution
|
'M1</sub'[mol/L]
|
'V1</sub' [mL]
|
'M</sub'[mol/L]
|
'V1</sub' [mL]
|
1 |
6.38E-4 |
6.25 |
7.98E-5 |
50 |
|
2 |
6.38E-4 |
12.5 |
1.59E-4 |
50 |
|
3 |
6.38E-4 |
25 |
3.19E-4 |
50 |
|
4 |
6.38E-4 |
35.5 |
4.78E-4 |
50 |
|
Viscosity of PVOH (MW 22000) Stock Solution
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 actual amount of solution in the viscometer does not matter, but the viscometer can hold no more than 10mL. Approximately 10mL should be used
- Measure the temperature of the surroundings. Record the temperature
- 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
- Wash the viscometer at least two times then discard the solution
- Pour approximately 10mL of the solution into the viscometer
- Draw the solution up past the lower bulb of the viscometer using a pipette pump
- 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
- Stop the stop watch once the bottom of the meniscus passes the lower mark on the viscometer
- 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]
|
1 |
238.79
|
2 |
242.62
|
3 |
241.63
|
- Viscosity of 7.98E-5M PVOH in H2O at 26°C
Trial [ ]
|
Time [s]
|
1 |
279.37
|
2 |
281.97
|
3 |
283.12
|
- Viscosity of 1.59E-4 M PVOH in H2O at 26°C
Trial [ ]
|
Time [s]
|
1 |
246.42
|
2 |
250.31
|
3 |
251.86
|
- Viscosity of 3.19E-4 M 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
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
|