Experiments to Experiments: Final Post

In long term experiments, sometimes it takes experiments to get to the start of new experiments. For my summer in lab, this was the case for much of the time. In my last blog post, I talked about the polymerizations of 11-aminoundecanoic acid. The sample of polymer with four regions pictured in that post has gone on to become a multi-month acid aging experiment. On the very last day of lab, one of my lab peers and I spent the afternoon preparing the acid solutions for this experiment. The samples of polymer will be aged in four different conditions — acetic acid, propionic acid, butyric acid and water, all in a 120C oven. To prepare the samples for aging in anaerobic conditions, argon was bubbled into the pressure tubes in which they aged for a minimum of 20 minutes.

This experiment will continue well into the school year to study the aging process of pure polyamide-11. The polymer used, an in-house polymerization, has no additives such as plasticizer.

It did, however, take experiments to get to the start of the experiment. Figuring out the best way to make the sample sheet of polymer without oxidation hit a few bumps in the road. Polymerizing together purchased, small beads of polymer from Sigma Aldrich was not successful — the polymer aged too quickly. The current experiment used a sample polymerized from monomer instead and its going to be an adventure to see where it goes.

I mentioned plasticizer a few lines up, and fortunately, there is great news on that front. I previously made a post about the Batch TGA process  — a long, taxing and nerve-wracking procedure that is however, time saving and rewarding. Because the Batch TGA method was used in Kranbuehl lab with little precedent, no statistical analysis of the accuracy of the method compared to the instrumental TGA from Thermal Advantage was had been made, until this summer. To performed this analysis, I selected a group of significant samples from a Batch TGA that I had previously run and took on the task of re-running them on the Thermal Advantage instrument. (A few re-re-runs were required as unexpected noise showed up on the instrument print out one day, resulting in unreliable data, but this was quickly fixed.)

After all the data from the Thermal Advantage Instrument was collected and set up to be compared to the Batch TGA, it became clear that some sort of test was going to be required. TGA runs have natural variance from one sample to another, even on the Thermal Advantage Instrument. At first, I tried an ANOVA1 test before realizing the test was not fit for the type of analysis. So, I went back into learning some MATLab and reviewing Statistics (which I had not taken since high school) and settled on a paired T-test. Typically, paired t-tests are used to examine before/after results but it was also applicable to compare the two methods.

The methods were compared for accuracy in both measuring water content and plasticizer content. A confidence interval of 95% was selected, meaning that if a the p-value came out over 0.05, the methods had no statistically significant differences! And they did both yield p-values about 0.05, which was wonderful news and allows the lab to continue using the Batch TGA as a time saving method.

As for personal successes this summer, there were many. I learned to use instruments that briefly had baffled me (such as my first time Differential Scanning Calorimeter runs, my new favorite instrument) and the MTS. This is all very exciting for me personally, as I am excited to teach new lab members the ropes that I spent the summer learning when research kicks up for the school year.