Method[edit | edit source]
Samples of Gaphchromic polymer were exposed to UV radiation via a solar simulator for six hours. During the six hours, one sample was taken every ten minutes. This allows us to see a continuous rate of change in the transparency of the polymer. The longer the exposure, the darker the polymer turned.
Sample size[edit | edit source]
The diameter of the solar simulator's concentrated light circle is 3.7 centimeters. So in order to get 36 samples, they must be very small. I cut strips of polymer to create 8 sections that were 2 millimeters wide and were cut 4 times per section totaling in 32 strips roughly 2 millimeters by 5-10 millimeters.
Then I cut two sections that were slightly larger at about 4 millimeters wide. These sections were cut in half which made up the remaining four strips for a total of 36 samples.
Loading the samples[edit | edit source]
The solar simulator's beam runs horizontally along the table, and does not point downwards. A circular jig was made using a RepRap 3-D printer that allowed the samples to be sandwiched in between a piece of cardboard, and the circular jig. The jig had tabs that allowed us to use black plastic paper clips and a test tube stand to mount the samples. This allowed the beam of light to shine accurately and completely onto the sample of Gaphchromic polymer, and made for easy retrieval of samples.
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Components of jig
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Assembled jig
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Jig with lamp turned off
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Jig with lamp on
UV Spectroscopy[edit | edit source]
Once three 6 hour trials had been completed, I ran the samples through an ultra violet spectroscopy unit. See the UV spectroscopy protocol page for instruction on how to operate the machine: [1]
Because the sample sizes were so small, (with some help) I set the wavelength to the green range, and found the slit where the light from the UV spectroscopy unit was hitting the cuvette and placed all of my samples within that range.
I ran all 108 samples through the UV spectroscopy unit and then the samples were exported to an Excel file.
