User:Elizabeth Ghias/Notebook/Experimental Chemistry/2012/09/07

Objective

To conduct Differential Scanning Calorimetry, to complete the cross-linking reactions conducted last week, and to finish evaporating water from the two films made on Wednesday.

Description

Differential Scanning Calorimetry

1. The masses of three DSC pans and lids were measured.
2. 3 ± 0.3 mg of film (Films 1, 3, and 5 were used, see below) were added to each pan.
3. Each pan and lid were placed into the press.
4. The three samples were placed into the DSC in spaces 6,7, and 8.
5. The DSC was run for the each of the three trials with the following program:
   1. Equilibrate (20.00°C)
   2. Ramp (20°C/min to 240°C/min)
   3. Ramp (20°C/min to 20°C/min)
   4. Isothermal (5 minutes)
   5. Repeat steps 2 to 4

Crosslinking Reactions

0.2 g of Films 2,4,5,6, and 7 (See below for list of films) were placed into an oven set to 90°C for 90 minutes.

Evaporation of Films made on 9/5

• The films made on Wednesday were placed on a hot plate to allow excess water left in the films to evaporate.
  • One film contained 0.5014 g PVA (MW = 22,000) in 5 mL water, with 0.0554 g succinic acid and 3 drops of phosphoric acid
  • The other film consisted of 0.5067 g PVA (MW = 22,000) in 5 mL water, with 0.0562 g maleic acid and 3 drops of phosphoric acid

List of Films

• Film 1 = 0.5110 g PVA (MW = 22,000) in 3 mL H₂O, no acid
• Film 2 = 1.0084 g PVA (MW = 22,000) in 6 mL H₂O, no acid
• Film 3 = 0.5078 g PVA (MW = 22,000) in 3 mL H₂O, with 3 drops of HCl
• Film 4 = 1.0044 g PVA (MW = 22,000) in 6 mL H₂O, with 3 drops of HCl
• Film 5 = 0.5066 g PVA (MW = 22,000) in 3 mL H₂O, with 0.05 g succinic acid and 3 drops of HCl
• Film 6 = 0.50 g PVA (MW = 22,000) in 3 mL H₂O, with 0.05 g Maleic acid and 3 drops of HCl
• Film 7 = 1.0010 g PVA (MW = 22,000) in 6 mL H₂O, with 3 drops of phosphoric acid
• Film 8 = 0.5053 g PVA (MW = 22,000) in 3 mL H₂O, with 3 drops of phosphoric acid

Data

Differential Scanning Calorimetry

Trial 1 (Film 1) - mass of pan and lid = 0.05002 g, mass of pan and lid with material = 0.05285 g

Trial 2 (Film 3) - mass of pan and lid = 0.04993 g, mass of pan and lid with material = 0.05317 g

Trial 3 (Film 5) - mass of pan and lid = 0.04880 g, mass of pan and lid with material = 0.05132 g

Crosslinking Reactions

After 90 minutes in the oven:

• Film 2 - color remained the same, film became harder/more brittle
• Film 4 - color changed from clear to black/red depending on the thickness of the film. Thicker portions of the film were darker than thinner parts, which appeared red. The black parts of the film were very hard, while the thinner parts of the film were more flexible.
• Film 5 - color changed from clear to black, film became harder/more brittle
• Film 6 - color changed from clear to black, film became harder/more brittle
• Film 7 - Film remained the same

Notes

• The color change from clear to black is the result of the crosslinking that occurred in the presence of the acid.
• Film 7 remained the same because a weak acid was added, not a strong acid.
• The hot plate used to evaporate the excess water from the films made on Wednesday was too hot and thus, bubbling was observed in the films. We will remake the films on Monday.