From What are Pop Bottles Made?
We drink soda pop every day from plastic bottles, with little thought of from what the bottles are made. This is a fairly easy analysis. We dissolve a 5-10 mg piece in trifluoroacetic acid-d (TFA -d) and run an 1H spectrum.
The TFA peak is at 11.5ppm. We have two fairly sharp singlets, one at 8.2ppm and the other at 4.9ppm. They integrate 1:1. The 8.2ppm peak is characteristic of terephthalate, the later of a polyester. This indicates polyethylene terephathalate.