The quantification of di-octyl terephthalate and calcium carbonate in polyvinyl chloride using Fourier transform-infrared and Raman spectroscopy

Irvin, KS, Potgieter, JH, Liauw, C, Sparkes, R and Potgieter-Vermaak, S (2022) The quantification of di-octyl terephthalate and calcium carbonate in polyvinyl chloride using Fourier transform-infrared and Raman spectroscopy. Journal of Applied Polymer Science, 139 (24). p. 52372. ISSN 0021-8995

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Abstract

The polyvinyl chloride (PVC) industry relies heavily on material property testing during the development of a product. Many of these testing procedures are outdated and time-consuming, resulting in high financial input. Non-destructive, fast, easy-to-use testing methods can significantly reduce the time required to quantify raw materials. We explored alternative analysis techniques, Fourier transform-infrared (FT-IR) and micro-Raman spectroscopy to quantify the main components within a plasticised PVC (pPVC) compound with dioctyl terephthalate (DOTP) plasticizer and calcium carbonate filler. This can reduce costs in the testing and development of new products up to 50%. We prepared 36 samples with varying proportions of DOTP and calcium carbonate and analyzed them using a Raman Microscope and FT-IR Spectrometer. We found a strong correlation (R2 = 0.923) between DOTP and FT-IR spectroscopy data, as well as a strong correlation (FT-IR R2 = 0.910; Raman R2 = 0.813) between the calcium carbonate and data obtained with both spectroscopies. We reported for the first-time correlations that could be used to determine the raw material levels within pPVC provided by both techniques. Five samples were then made and tested, showing some success in the quantification. This study provided a solid baseline for reducing the time taken to make a recommendation from >168 h to <1 h and therefore reducing the costs of product development by up to 50%.