Chemical analyses of glycol-modified copolyester surface abrasion: Beyond the scratches from a mechanochemistry perspective

The observations reported in this study provide unequivocal evidence that polymer surface abrasion is a mechanochemical process that, upon more in-depth understanding, could be used to improve polymer durability and reduce environmental impact. • We report on the abrasion behavior of three chemically-related glycol-modified thermoplastic polymers, one of which is a potential replacement for polycarbonate as a tough, transparent packaging material. • The chemical properties of the polymer surfaces before and after mechanical abrasion have been interrogated by two different surface-sensitive spectroscopic techniques, namely, FTIR-ATR and XPS. • Differences in the chemical properties of abraded polymer surfaces have been identified and quantified to yield the carboxyl index. • The carboxyl index has been measured as a function of cycle number, particle size of abrading material and polymer chemistry. • The results obtained here are compared to other polymer degradation processes to discern the extent of mechanistic similarity. • Our findings indicate that abrasion-induced chemical changes measured by spectroscopic methods provide a more robust measurement of abrasion since these tests are independent of the measurement conditions. Thermoplastic abrasion constitutes an important consideration for not only improving the application lifetime of polymeric materials but also reducing the volume and impact of solid waste. This study explores the abrasion characteristics of a series of glassy glycol-modified polyesters without focusing exclusively on mechanical properties. Here, we demonstrate how changes in chemical characteristics, which are discernible by surface-sensitive spectroscopic methods, can be used to monitor the abrasion process, elucidate molecular-level mechanisms and differentiate the three polyesters under investigation on the basis of their abrasion response. Moreover, we introduce the carboxyl index discerned from Fourier-transform infrared spectroscopy in attenuated total reflection mode and utilize this novel index, in conjunction with the carboxyl bond content ascertained from X-ray photoelectron spectroscopy, to quantitatively describe polyester surface degradation. Comparison of several surface-related degradation mechanisms upon appropriate data normalization to account for material-specific abrasion properties or other relevant exposure conditions yields surprisingly similar responses, implying that polymer abrasion is an example of a mechanochemical process wherein both mechanical degradation and distinct chemical changes influence the abrasion-driven evolution of surface properties.