Ftir spectrometer

Infrared absorption spectra of calcium carbonate, modified calcium carbonate particles and stearic acid were obtained using the potassium bromide technique (KBr) with an FTIR spectrometer at the absorbance mode from 4000 to 400 cm⁻¹ with automatic signal gain (32 scans) at a resolution of 4 cm⁻¹ (PIKE technologies, Bruker, France). A KBr pellet was used as a background.
ATR-FTIR spectra of the papers were recorded on the same FTIR device using same parameters and a Gladi Atrvertex 70 module. Baseline of spectra was adjusted with the same correction (polynomial with 1 iteration and 6 points at 3800, 2280, 1900, 1262, 800 and 411 cm⁻¹) and were normalized to the C-H deformation of anomeric bond at 895 cm⁻¹, not affected by coating modification.

The mechanical stability of the composite materials was characterized by using a MARK-10 ESM303 Tension/Compression Test Stand, in conjunction with a Perkin Elmer FTIR Spectrometer outfitted with a Pike Technologies Mid-Infrared Integrating Sphere. First, the samples’ total infrared reflectance and transmittance were measured at uniaxial strains of 0%, 30%, and 50%, as described above. Next, the samples were cycled 1000 times between applied strains of 0% and 50%. In turn, the samples’ total infrared reflectance and transmittance were again measured at uniaxial strains of 0%, 30%, and 50%, as described above. The experiments were performed for at least four different samples, with similar results obtained in each instance.

We used a PerkinElmer FT-IR Spectrometer (PIKE Technologies GladiATR) from the Department of Polymers and Materials at the Universidad de Sonora. Previous studies characterizing biophysical properties of cuticular lipids in insects have used FT-IR analysis [17 (link)]. It has been reported that the spectra display a small peak in the 2800–3000 cm⁻¹ range, which corresponds to the absorption range of hydrocarbon groups like methylene (-CH2-) and methyl (-CH3). These groups are characteristic of elytral waxes.
For the chemical composition analysis, we used three samples: the most hydrophobic sample (individual 5 KB, CA: 104°), the most hydrophilic sample (individual 1, HMO, CA: 52°) and an intermediate sample (individual 9 from KB), with a contact angle (CA) of 75°. Measurements were performed in the spectral range of 400–4000 cm⁻¹, using a total of 16 scans per sample.