Infrared Spectra of Polyvinyl Chloride

Abstract

Fig. 1 and 2 show infrared spectra of PVC measured by the single-reflection ATR method, in which a diamond was used for the prism. The results of Fig. 1 were obtained from measurement of hard PVC which contained almost no plasticizer or other additives, while the results shown in Fig. 2 were obtained from measurement of soft PVC containing di-2-ethyl hexyl phthalate as the plasticizer. In addition, Fig. 3 shows the results of measurement of the infrared spectrum of di-2-ethyl hexyl phthalate using the same method. Comparing the infrared spectra of Figures 1, 2, and 3, it is clear that the soft PVC measurement results are greatly different from the results of the hard PVC, but are quite similar to the results obtained from measurement of di-2-ethyl hexyl phthalate. This is because the infrared spectrum of the phthalic ester is stronger than that of PVC. In the measurement results of the soft PVC, the peaks in the vicinities of 1425 cm -1 , 959 cm -1 and 610 cm -1 are peaks originating from the PVC, but when other additives such as calcium carbonate and silicate salt are also included as additives, the peaks near 1425 cm -1 and 959 cm -1 are overlapped and are therefore difficult to confirm. Therefore, in many infrared spectra of soft PVC, verification of PVC is accomplished using the C – Cl stretching vibration near 610 cm -1 . However, depending on the detector and measurement method used, confirmation using the peak associated with the above C – Cl stretching vibration may not be possible due to the measurement wavenumber range being used. Even in that case, if the sample is soft PVC, it can be assumed to be such based on the similarity of the measurement results with that of phthalic ester. However, due to concern regarding the adverse health affects of some phthalic ester plasticizers, soft PVC containing plasticizers other than phthalic esters are appearing. An example of this is exemplified by the labeling of " Non-phthalic ester PVC " on toys and other articles.