Oxidation Ratio
Ratio analysis of infrared absorption bands provides a quantitative value for the level of chemical degradation in synthetic polymers or paper coatings. The ft-ir carbonyl index tracks the growth of oxygenated groups as a material ages or undergoes exposure to ultraviolet radiation. Because the carbonyl group absorbs energy at a specific wavelength near 1715 reciprocal centimeters, its intensity relative to a stable reference peak shows the extent of polymer chain scission.
This calculation assists in determining the remaining service life of a laminate or a protective film.
Absorption Analysis
Technicians use fourier transform infrared spectroscopy to scan the surface of a substrate and identify the chemical bonds present. To calculate the ft-ir carbonyl index, the area of the carbonyl peak is divided by the area of a non-reactive peak such as the methylene group. This method eliminates errors caused by variations in sample thickness or light scattering.
It produces a dimensionless number that allows for direct comparison between different batches of the same material.
Polymer Stability
High values for this ratio suggest that the polymer has lost its original mechanical properties and may become brittle. While the ft-ir carbonyl index is a standard tool for polyethylene films, its application to cellulose-based substrates requires careful correction for the natural presence of wood-derived carbonyls. A sudden rise in this index often correlates with a drop in elongation at break.
