Dsc 7 calorimeter

The glass transition temperature (T_g) and the crosslinking density (ν_e) were determined by dynamic mechanical analysis (DMA) in a TA Q800 viscoelastometer (New Castle, DE, USA) in single cantilever bending mode. A temperature range of −100 °C to 250 °C was used at a heating rate of 4 °C/min. The frequency and amplitude used were 1 Hz and 15 μm, respectively. Equation (1) was used to calculate the crosslinking density [63 (link)]: $${\nu }_e=\frac{E_r}{3R{T}_r},$$
where R is the ideal gas constant (8.314 J/mol·K), E_r is the storage modulus in the rubbery state, and T_r is the temperature at which E_r was taken (245 °C).
Differential scanning calorimetry (DSC) was performed in a Perkin Elmer DSC-7 calorimeter (Waltham, MA, USA) calibrated with an indium standard. The samples, which were taken from the cured specimens, were heated from 30 °C to 250 °C at 20 °C/min under a nitrogen atmosphere.

Differential scanning calorimetry measurements were carried out
using a Perkin-Elmer DSC7 calorimeter with an intracooler cooling
unit at −20 °C (ethylene glycol–water, 1:1, V/V,
cooling mixture). Measurements were carried out at different scanning
rates |β| = 2, 10, and 20 °C min^–1 under
a nitrogen gas flow of 20 mL min^–1. Samples with
approximate mass between 2 and 5 mg were placed in 10 or 50 μL
aluminum pans, with similar empty ones used as reference. Temperature
calibration was performed with high grade standards:^{26 (link),27 (link)} biphenyl (CRM LGC 2610, T_fus = (68.93
± 0.03) °C) and indium (Perkin-Elmer, x = 0.9999, T_fus = 156.6 °C). Indium
was also used for enthalpy calibration (Δ_fusH_m = 3286 ± 13 J mol^–1). Benzoic acid (CRM LGC 2606, T_fus =
(122.35 ± 0.02) °C) was used to check the calibration. Pyris
software version 3.50 was used for instrument control and result analysis.
The reported first-order phase transition temperatures correspond
to the onset of the peaks. The glass transition temperatures were
determined from the midpoints of the characteristic baseline step
changes.

A differential scanning calorimetry (DSC) analysis of printed PLA and NFRCs was performed using a DSC 7 calorimeter (Perkin-Elmer, Waltham, MA, USA) to study NFRCs’ melting behavior and crystallinity. Only the first heating was performed from room temperature to 220 °C at a heating rate of 5 °C/min under an inert nitrogen atmosphere. The cold crystallization temperature $T_{cc}$ and melting temperature $T_m$ were recorded during the first heating. The degree of crystallinity $X_c$ was calculated during the first heating to determine the effect of the printing process on the crystallinity of the printed PLA and NFRCs. A similar approach has been used previously, in which only the first heating curves were recorded to correlate the degree of crystallinity resulting from the 3D printing process with the mechanical properties without eliminating the thermal history [48 (link),49 (link)]. $X_c$ was calculated using the following equation: $$X_c=\frac{\Delta H_m-\Delta H_{cc}}{\Delta H_{mo}\times W_{PLA}}$$
where $\Delta H_m$ is the melting enthalpy, $\Delta H_{cc}$ is the cold crystallization enthalpy, $\Delta H_{mo}=93\mathrm{J}/\mathrm{g}$ is the melting enthalpy of 100% crystalline PLA [50 (link)], and W_PLA is the weight fraction of PLA in the sample.

The phase behavior was studied by dynamic mechanical analysis (DMA) using a TA Q800 viscoelastometer (New Castle, DE, USA) that provided the loss tangent (tanδ) against temperature. The scans were carried out in single cantilever bending mode at a constant heating rate of 4 °C/min and a frequency of 1 Hz, from −100 to 150 °C. The melting and crystallization behavior of the materials was studied by DSC using a Perkin–Elmer DSC-7 calorimeter (Waltham, MA, USA), which was calibrated using an indium standard as a reference. The samples were first heated from 30 to 300 °C at 20 °C/min and then cooled at the same rate. The melting and crystallization temperatures (T_m, T_c) were determined, respectively, from the maxima of the corresponding peaks during the heating and cooling scans, and the melting and crystallization enthalpies were determined from the areas of each of these peaks. The degree of crystallization of PA410 was calculated from the melting and cold crystallization enthalpies, taking the enthalpy of a 100% crystalline ( $\Delta {\mathrm{H}}_{\mathrm{f}}^{\infty }$ ) PA410 as 269 J/g [5 (link)].