2.3. Material Characterization

Viscosity measurements were performed in a MCR 301 rheometer (Anton Paar GmbH, Graz, Austria). Steady state shear rate sweeps were performed using a 25 mm plate–plate geometry in an interval of 1–1000 s⁻¹. At least 3 independent samples were measured. Results were averaged and standard deviations were presented as error bars. X-ray diffraction (XRD) of the samples was measured using a Bruker D8 ADVANCE (Breika, MA, USA) using a Cu Kα radiation source operated at a voltage of 40 kV with a scanning range of 5–80 deg. Raman spectroscopy experiments were performed in an alpha300 system (WITec, Ulm, Germany) coupled to an optical microscope equipped with a piezo scanner (P-500, Physik Instrumente, Hamburg, Germany) and a Nikon 50x objective (NA = 0.6). A linearly polarized laser (λ = 785 nm) was focused onto the sample with a polarization angle of 0° and no analyzer in the light path. The Raman scattered light was detected on a thermoelectrically cooled CCD detector (DU401A-BV, Andor, Belfast, UK) with an integration time of 5 s. Analysis was performed with WiTec Project FOUR 4.1. Single spectra were taken in at least 3 different regions of the samples and results were averaged. Differential scanning calorimetry (DSC) experiments were performed in a Q20 (TA Instruments, New Castle, DE, USA). Temperature sweeps were performed from room temperature (25 °C) to 250 °C at a rate of 10 °C/min to evaluate the residual cure of the resins. A subsequent cooling and heating sweep at 10 °C/min was performed to confirm all the resin was cured in the first sweep. Thermograms were analyzed using the TA Universal Analysis software. Tensile testing of samples was performed in a universal testing machine (Shimadzu, Japan) at a constant speed of 1 mm/min according to ASTM D638. At least 5 specimens were tested and the Young’s modulus, tensile strength and elongation at break values were dissected for each one of the measured specimens. Young’s modulus was determined as the slope between 0.05% and 1.0% strain in the stress–strain plots. Tensile strength was obtained as the maximum stress value in the curve. Elongation at break was obtained as the strain value in the rupture point (maximum value in the X axis). Results were averaged and standard deviations were presented as error bars. Electrical conductivity was measured according to ASTM D257 in a Keithley 6517B electrometer (Keithley, Cleveland, OH, USA) applying a voltage of 500 V. At least 3 samples were measured and results were averaged with standard deviations presented as error bars. Sheet resistance was calculated as the bulk resistivity divided by the thickness of the sample. UV–Vis spectra were recorded in a Varian Cary 50 Conc spectrophotometer. Surface analysis was performed using a scanning electron microscope (SEM) FEI-Quanta 200 3D (Thermo Fisher, Waltham, MA, USA). Samples were coated prior to scanning with a layer of Au in a SCD 004 Sputter Coater (BAL-TEC, Balzers, Lichtenstein).