Oxidation is a way in which polymers degrade that causes changes in the polymers physical and chemical properties, and can ultimately cause problems in the plastic’s performance over time. Upon oxidation, some notable changes to the polyolefin backbone (i.e., carbon-carbon bonding) include the incorporation of oxygen into the backbone in the form of carbonyl (C=O), peroxide (O-O-R), and hydroxyl (-OH) groups. There are currently few methods to quantify the formations of these groups in polymer structures as few high-throughput analytical techniques exist for solid phase quantification. The purpose of this work is to quantify oxidation by creating polymer calibration curves using doped films that contain a model compound. Polymers that were studied include polyethylene (PE), poly(methyl methacrylate) (PMMA), and polystyrene (PS). To make calibrant samples, the different polymer matrices were doped with various known concentrations (0.1-2 wt%) of the dopant molecules. Common plastic additives, 2-hydroxy-4-octyloxybenzophenone and dibutyl sebacate, were used as dopant molecules as they contain moieties that relate to oxidation, namely carbonyl, ester, and hydroxyl groups. The two dopants caused chemical changes within the films and these changes were characterized using ATR-FTIR. Oxidation within the films was determined by normalizing the area of the carbonyl peaks (around 1720 cm<sup>-1</sup>) to that of a normalization peak that is unique to each of the polymers. Calibration curves were created by making films with different concentrations of the dopant molecules. The calibration curves were then applied to thermally aged samples in order to quantify the reaction rate and extent of oxidation occurring within the polymers. Quantification of these aged samples aids in the development of a predictive model for the degradation of plastics under various environmental conditions.

Method for quantifying the oxidation within polymers using ATR-FTIR

255th National Meeting (2018)

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