Analysis of adipate ester contents in poly(vinyl chloride) plastics by means of FT-Raman spectroscopy

Abstract

Fourier transform (FT-) Raman spectroscopy excited with a 1064 nm laser can be used to determine the content of plasticizers in commercial flexible poly vinyl chloride (PVC) products. Our previous study [T. Nørbygaard, R.W. Berg, Analysis of phthalate ester content in PVC plastics by means of FT-Raman Spectroscopy, Appl. Spectrosc. 58 (4) (2004) 410–413]—on detection of the presence of phthalate esters in PVC by FT-Raman spectroscopy—is here extended to the similar case of adipate esters (AEs) in samples of soft poly vinyl chloride plastics. Spectra of a range of adipate ester plasticizers (11 AEs) in pure form are reported. We studied if qualitative and quantitative determination of the adipate ester content would be possible based on the use of proper reference samples. It was found that AEs as a group cannot be definitively identified by their characteristic Raman bands because other aliphatic dicarboxylic esters have very similar bands. This limits the detection as to what kind of ester and how much is present in a sample. An essential finding was however that one can use the absence of any Raman band in the 1020–1060 cm −1 range of the adipate esters, as a means to verify that a given soft PVC plastics sample does not contain significant amounts of phthalate esters because these plasticizers do have strong bands at around 1060 cm −1. Furthermore it must be remembered that bands may occur at around 1040 cm −1 in a PVC sample for other reasons than phthalate ester content.