Uatr two spectrometer

Fourier transform infrared (FTIR) spectroscopy measurements were done in a Perkin Elmer UATR TWO spectrometer (PerkinElmer limited, Seer Greeb, UK), employing a resolution of 4 cm⁻¹. Measurements were carried out in attenuated total reflectance modes (with ATR accessory) from 400 to 4000 cm⁻¹, performing 16 scans per sample over the surface in a dried state.
Raman spectra were taken in a Renishaw InVia Reflex Raman system (Renishaw plc, Old Town, Wotton-under-Edge, UK). It was used by employing a grating spectrometer with a Peltier-cooled charge-coupled device (CCD) detector, coupled to a confocal microscope. All spectra were processed using Renishaw WiRE 3.3 software. The scans were obtained from the surface of the samples and the depth profiles were carried out positioning the laser each 2 μm.

The apparent density ( ${\rho }_{app}$ ) of the ground WB fibers was measured by reading the volume occupied by 2.1 g of WB fibers in a 50 mL graduated cylinder. The real particle density ( ${\rho }_{real}$ ) was calculated the same way, with the only difference that WB fibers were pressed by a 73 g weight made of steel. The moisture content of WB fibers was determined by oven-drying 500 g of a sample until it reached a constant weight. The morphological shape of the WB fibers was evaluated by taking images with an optical microscope (SOM Wild M3 Heerbrugg), while the chemical composition was evaluated through infrared spectroscopy in ATR configuration using a Perkin-Elmer UATR Two spectrometer. The reported spectrum was the average of 16 scans with 4 cm⁻¹ resolution in the 4000–400 cm⁻¹ range. Finally, the thermal stability of dried WB fibers was investigated through thermogravimetric analysis (TGA; Perkin-Elmer TGA4000) equipped with an infrared detector (Perkin-Elmer Spectrum One) in order to simultaneously evaluate the structure of the degradation products. TGA tests were also conducted under isothermal conditions (200 °C) for 10 min to evaluate the maximum processing residence time within the internal mixer.