Fig. 2

Raman spectra (a–c) and correlation values (d–f) of the samples as indicated. All spectra intensities are off-set for presentation. The ABS spectrum is presented in a as reference to compare with different paints including #1-#5, according to the characteristic peaks marked with dashed lines, where the circulated areas suggest the presence of TiO₂. Sample #1 is centrifuged and separated to get layers that yield spectra in b. The middle layer is further analysed in c with the possible assignments as the references. In d–f, the spectra of paint sample #1 and its middle layer (Middle-2) are correlated with 10 common plastics including PS, PET, PE, PVC, PP, PA, PMMA, PC, PUR, and ABS, before (d, f) and after (e) removing the signal in the low wavenumber range [< 800 cm⁻¹, circulated in a] that is dominated by TiO₂