The polymer type for each moldable plastic was determined by IR spectroscopy. Five plastics were identified as PCL based on spectral matching to reference spectra (Pearson's r >0.96) (Figures ). The remaining seven plastics had IR spectra that were inconsistent with PCL (Figure ) and instead matched reference spectra of thermoplastic polyurethane (TPU) (Pearson's r >0.95) (Figures ). For example, the IR spectra of these samples had a weak NH stretching vibration at ~3350 cm -1 , a shouldering amide I band at ~1685 cm -1 , an amide II band at ~1530 cm -1 , and C-O and C-O-C vibrations at ~1310 cm -1 and ~1260 cm -1 , respectively, peaks characteristic of polyurethanes. The carbon, hydrogen, and nitrogen content of selected plastics provided additional support to the TPU identification. Those identified as TPU by IR spectroscopy contained bulk nitrogen and had ratios of H/C less than expected for PCL (Table ).