Use of Infrared Spectroscopy and Near Infrared Hyperspectral Images to Evaluate Effects of Different Chemical Agents on PET Bottle Surface

Abstract

PET-poly (ethylene terephthalate)-bottle surfaces were exposed to chemical agents and evaluated with middle infrared spectroscopy (MIR) and near infrared hyperspectral imaging (HSI-NIR). Images (928-2.524 nm) were acquired at different times from bottle surfaces exposed to alkaline, acidic and ethanolic media. Savitzky-Golay smoothing (2 nd order polynomial and 5-point window) combined with Standard Normal Variate (SNV) was used for pre-processing data. Scores from principal component analysis (PCA) on images showed discrimination of PET according to exposure time, particularly when employing NaOH. After the first two hours of chemical exposure, significant contribution of the (-CO + OH) combination band indicated formation of glycol ethylene on the PET surface, which was confirmed from PCA loading plots. MIR reflectance spectra ranged from 4.000 to 650 cm-1. Changes in spectral intensities could be associated with depolymerization of PET when exposed to NaOH. These were confirmed with PCA and attributed to the carboxylate group of terephthalate.

Construction Strategy for Flexible and Breathable SiO2/Al/NFs/PET Composite Fabrics with Dual Shielding against Microwave and Infrared–Thermal Radiations for Wearable Protective Clothing

“…In addition, there is a significant decrease in reflectivity and transparency and an increase in absorption in the long-wave NIR range (1100–2500 nm), particularly in the bands at 1624 nm, 2094 nm, 2217 nm, 2299 nm, and 2408 nm. This significant NIR absorption may be attributed to the first and second overtones of the stretching corresponding to hydrogen-containing groups (C–H groups sin aromatics molecules, -CH 2 groups, –O–H groups) and oxygen-containing groups (–C=O, –C–O, –COO), as well as aromatic and methylene-based combination bands in the PET backbone [ 30 ]. Compared to the PET fabric, the NFs/PET fabric exhibits significantly increased reflectance (66–69%) and absorbance (30–32%) in the visible and short-wave NIR light regions, making it almost opaque.…”

“…Polymers 2024,16, x FOR PEER REVIEW 9 of 20 Al20min/NFs/PET (S4) and SiO2/Al/NFs/PET (S4-1 to S4-3) composite fabrics drastically decreases to about 20-30% in the visible band, while the absorbance is enhanced to 70-80% and the transmittance is close to zero. This may be due to the micro/nano-scale roughness imparted to the fiber surface by the Al nanoparticles and SiO2 nanoparticles, which leads to the strong scattering and destructive interference of visible light[30]. Meanwhile, the reflectance of the Al/NFs/PET (S4) and SiO2/Al/NFs/PET (S4-1 to S4-3) composite fabrics rises from 23% to 70% with an increasing wavelength in the near-infrared region, while the absorbance reduces from 76% to 30%.…”