# Formation of Conductive Networks in Polysulfone Filled with Graphite-Derived Materials
## 2 Materials and Methods
### Characterization  
Bulk and tapped densities were measured using an Autotap Quantachrome Instruments analyzer in accordance with the ISO 787-11 standard [36].  
To assess the porosity of composite materials, density measurements were carried out using hydrostatic weighing and a gas pycnometer, and based on data on its composition, the maximum possible theoretical density of the material was calculated.  
The measurement of helium pycnometric density was carried out using an automatic true density analyzer Densi 100.  
The composites' density was measured using hydrostatic weighing in distilled water and ethyl alcohol according to ISO 1183-1: 2019 [37] (Plastics--Methods for determining the density of non-cellular plastics). For these measurements, AND GR 202 analytical balance (AND, Tokyo, Japan) equipped with a hydrostatic weighing AD-1653 was utilized.  
The microstructure of the obtained samples was studied on the obtained in liquid nitrogen thin sections and chips using Hitachi TM-1000 and TESCAN VEGA COMPACT scanning electron microscopes.  
Zwick/Roell Z020 universal tensile testing machine (Zwick GmbH & Co., Ulm, Germany) using a MultiXtens high-precision strain measurement system was used to realize three-point bending tests. Before testing, all the samples were conditioned under a standard 23/50 atmosphere for 88 h. Tests were carried out in accordance with ISO 291: 2008 [38] (Plastics--Standard atmospheres for conditioning and testing). The total number of specimens tested at one point in mechanical tests was seven or more.  
The thermal conductivity of the samples was calculated based on the results of experimental measurements of thermal diffusivity, determination of density by hydrostatic weighing, and calculation of heat capacity using the rule of mixtures.  
Thermal conductivity was calculated using the formula:  
\[\lambda(t)=a(t)\cdot d_{k}\cdot C_{p}(t)\]  
where \(\lambda(t)\) is thermal conductivity coefficient at temperature \(t\), W/m\(\cdot\)K, \(a(t)\) is thermal diffusivity at certain temperature \(t\), mm\({}^{2}\)/s, \(d_{k}\) is the density of material, g/cm\({}^{3}\), and \(C_{p}(t)\) is specific heat capacity, J/(g\(\cdot\)K).  
NETZSCH LFA447 NanoFlash instrument (Selb, Germany) was used to measure thermal diffusivity. Investigation was carried out in the temperature range of 25 to 300 \({}^{\circ}\)C. Cylindrical samples with a diameter of 12.7 mm and a thickness of 1.5 mm and square samples measuring 8 \(\times\) 8 mm, thickness 1.5 mm were used in these experiments. Measurements were realized in accordance with ASTM E1461-07 [39] (Standard Test Method for Thermal Diffusivity by Flash).  
The thermal diffusivity of the samples was measured in two directions: in the direction of pressing and perpendicular to the direction of pressing of the workpieces as shown in Figure 1.  
The specific heat capacity \(C_{p}\) of composite materials in the temperature range from 25 to 150 \({}^{\circ}\)C was calculated using the rule of mixtures.  
\[C_{p-comp}=C_{p-n}W_{n}+C_{p-r}(1-W_{n})\]  
where \(C_{p-comp}\) is the heat capacity of the composite (J/K), \(C_{p-n}\) is the heat capacity of the first component (J/K), and \(W_{n}\) is the first component mass fraction (wt. %). The raw materials' heat capacities were studied using a NETZSCH DSC 204 Phoenix F1 differential scanning calorimeter (Selb, Germany). Investigations were carried out following ISO 11357-4:2021. Plastics. Differential scanning calorimetry (DSC). Part 4: Determination of specific heat capacity [40], sapphire was used as a standard sample. Samples with a diameter of 5 mm and a mass of 24-25 mg were used and the experiments were carried out in a protective argon atmosphere.  
The determination of volumetric resistivity at a temperature of 23 \({}^{\circ}\)C was carried out by the four-probe method using a potentiostat-galvanostat brand P-20X.