Analytical Validation
Attenuated total reflection Fourier transform infrared spectroscopy provides a quantitative chemical fingerprint of polymer coatings and paper additives by measuring the absorbance of infrared radiation at the surface interface. atr-ftir spectroscopy relies on the penetration of an evanescent wave into the specimen pressed against a high refractive index crystal. Incident radiation undergoes internal reflection, losing energy at specific wavelengths where the molecular bonds of the substrate absorb the light. This attenuation allows for the identification of chemical species within a depth of a few microns from the surface.
The technique requires minimal sample preparation because the infrared beam probes the material directly without needing transparent films or destructive digestion. A change in the refractive index of the crystal relative to the sample governs the depth of penetration, forcing operators to maintain consistent pressure to obtain reproducible spectral intensity.
Material Characterization
Infrared spectra confirm the composition of adhesives and sizing agents applied during paper converting. atr-ftir spectroscopy detects the presence of specific functional groups such as carbonyls or hydroxyls that signal the degree of cure in crosslinking resins. The signal strength relates to the concentration of these molecules within the sampling volume. Technicians compare observed peaks against reference databases to verify the identity of unknown contaminants or synthetic binders.
Variations in spectra provide evidence of batch inconsistencies or raw material substitution in laminates. Precise contact ensures that the signal reflects the chemistry of the bulk substrate rather than surface artifacts or debris.
Surface Integrity
Process control relies on this method to monitor the uniformity of barrier coatings on food grade packaging substrates. atr-ftir spectroscopy differentiates between high density polyethylene and polypropylene layers based on their distinct vibrational modes. The absence of expected signals indicates a breakdown in application coverage or film thinning on the production line. Defective surface treatment leads to poor bond strength in subsequent lamination stages.
Analysts detect chemical degradation caused by ultraviolet exposure or high heat by observing shifts in baseline transmission values. This diagnostic capacity maintains the required performance standards of the final product.
