To crosslink the films prepared last class, to test the effects of using a lower molecular weight PVOH on the film, and to prepare a 0.2 M NaOH solution for use next class.
- Determined the concentration of HCl needed, by determining the amount of H+ in the H2SO4 used in previous crosslinking.
- 20ml of 100% H2So4 in 1 L of H20 was used, assuming complete dissociation
- 20ml* 1.84g/ml ÷ 98.079g/mol = 0.375moles of H2SO4 ÷ 1 Liter= 0.369 Molar H2SO4
- 0.369mols of H2SO4/L * 2mols HCl/1mol of H2SO4 = 0.7M HCl → 6ml of 12 M HCl
- Heat up a solution of 94 mL water and 6 mL 12 M HCl to 70°C
- Place the film in the solution and heat for 1 hour.
- Prepare a solution of bicarbonate (1.68 g in 100 mL).
- At the end of one hour, remove the films from the HCl, rinse with water, then place in the sodium bicarbonate solution for 15 minutes.
- Then remove the films from the bicarbonate solution and place in water.
- Leave the films in water until Friday.
Preparation of Lower Weight PVOH Films
- Measured out 6 1 g samples of PVOH (MW = 22,000)
- Prepared a solution of 0.22 g phenol in 10 mL water.
- Dissolved the PVOH samples in 30 mL water (in 100 mL beakers)
- Once the PVOH had dissolved, the corresponding amounts of phenol solution were added (1% film = 1 mL, 0.1% = 0.1 mL, 0.01% = 0.01 mL, 8.5% = 8.5 mL)
- 1 mL glutaraldehyde was added to each film
- The solution was allowed to stir and then was poured into an plastic dish and allowed to evaporate until Friday.
NaOH Calculations and Preparation
- need to prepare 50 mL of a 0.2 NaOH solution from a 0.5 N NaOH soln.
(0.5 moles/L)(X) = (0.2 moles/L)(0.05 L) → X = 0.02 L = 20 mL
- Measure out 20 mL 0.50 NaOH
- Add to 30 mL water
- Save for use on Friday.
No data was collected today.
Description of Films Prepared Last Class
- 1% film prepared in Erlenmeyer flask looked the best, was uniform, etc.
- 0.1% and 9% films were not uniform, had lumps of PVOH
- The poor quality of the films was attributed to the high molecular weight of the PVOH.