Determining the molecular effects of short wave UV light on bis-2-ethylhexyl phthalate (DEHP) plasticized poly(vinyl chloride) (PVC) is vital for both green chemistry and environmental purposes. The effects of energy-efficient light treatments for removing toxic plasticizer from plastic films and/or clear plastics after disposal were studied using a variety of analytical techniques including sum frequency generation vibrational spectroscopy and secondary ion mass spectrometry. The surface and bulk of pure PVC and 25 wt% DEHP-plasticized PVC were analyzed before and after a variety of short wave UV treatments from 30min to 8h in length. It was determined that 254 nm UV exposure at 53 W/m2 yielded products phthalic acid, mono-ethylhexyl phthalate and phenyl ring hydroxylated DEHP as well as smaller molecules in the bulk and surface after only 1h exposure time. For pure PVC after 1h exposure, only a minor amount of bulk and surface changes occurred; after 5h exposure increases in polymer conjugation from chlorine removal and dramatic surface CH group reordering were observed. When hydroxide radicals from 35 wt% H2O2 solution were added with the intention of increasing DEHP degradation rates, fewer bulk DEHP molecules were removed up to 8h due to competing radical-polymer reactions. Our results indicate a simple exposure to short wave UV is more effective at eliminating bulk DEHP while H2O2/UV combination should be used only if accelerated PVC degradation is desired.

Molecular changes of phthalate-plasticized poly(vinyl chloride) from short wave UV treatments

248th National Meeting (2014)

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