Quantitative Analyze of Fourier Transform Infrared Spectroscopy (FTIR) of Poly (Lactic Acid) after UV/Ozone Irradiation

Poly (lactic acid) (PLA) is a bio-degradable thermoplastic polymer with helix polymer chains that derived from renewable plant sources, such as corn , rice, wheat and sweet potato. PLA converts in human body to CO2 and H2O via metabolic reactions. In this study, the Fourier transform infrared Spectroscopy technique was used to investigate the chemical structure of PLA. First, the standard FTIR of PLA was examined; it was then compared to the FTIR spectrum of UV/Ozone irradiated fibers under different conditions. FTIR Quantitative Analyze method was used to investigate the type and amount of chemical changes in the fiber structure. For this purpose, the area of the modified peaks was measured, and the peak related to the Carbon―Hydrogen bond in the range of 2979-3528 cm was selected as the reference peak. Then by dividing the area of other peaks to the area of the reference peak and normalizing the spectra, the chemical changes in fiber structure were assessed. The results show that with UV/Ozone irradiation under different conditions, the number of Carbon―Carbon and Carbon―Hydrogen bonds do not change; However, the number of oxygen-containing functional groups (Carboxyl, Carbonyl and Hydroxyl) increases significantly. This indicates the oxidation process of the fibers. On the other hand, with pre-impregnating of fibers in different solutions and then UV/Ozone irradiation, oxidation is achieved with greater intensity and speed; so that some polar groups are removed from the ends of polymer chains.