Graphene‐based polymer composites with ultra‐high in‐plane thermal conductivity: A comparison study between optothermal Raman spectroscopy and laser flash method

Abstract

We developed a simple solution mixing and molding process for the incorporation of graphene nano‐flakes (GNFs) in polymer films. Poly(vinylidene fluoride‐co‐hexafluoropropylene) (PVDF‐HFP) and poly(ethylene‐co‐methacrylic acid) (PEMAA) were used for preparation of the samples. The orientation and stacking of GNFs were confirmed using a scanning electron microscope. The thermal conductivity values for these composites were obtained using (1) laser flash method (commercially available) and (2) an optothermal Raman (OTR) technique (homemade device). The former measures the thermal diffusivity (α) and one needs to measure the density (ρ) and the heat capacity (Cp) of the composites in order to measure the in‐plane thermal conductivity (κ = α.ρ.Cp), while the latter measures the in‐plane thermal conductivity directly from the relation between the excitation power and the position of the Raman resonance. The data obtained from Raman spectroscopy were analyzed, assuming heat propagation in three and two dimensions. The Raman results obtained based on the two‐dimensional model were very close to the results obtained using the laser flash method with less than 10% difference. The OTRspectroscopy was found to be a promising technique for measuring the in‐plane thermal conductivity of carbon‐based polymer composites. PVDF‐HFP and PEMAA composite films with very high in‐plane thermal conductivity (25 W m−1 K−1) were obtained through the incorporation of GNFs (20 wt % concentration). Considering a very low thermal conductivity of these polymers (<0.2 W m−1 K−1), this corresponds to a large enhancement of roughly 12 400%. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48927.

The effect of graphene flake size on the properties of graphene‐based polymer composite films

“…G1-based polymer composites showed the highest value for the in-plane thermal conductivity as shown in Figure 5, which was also reported in our previous papers. 27,30 An ultra-high value of~26 W/m/K was achieved, which again is the highest measured values for in-plane thermal conductivity for PVDF composites. For the same graphene wt%, the in-plane thermal conductivity value was lower for G2 and G3, respectively indicating that the average flake size also has a direct effect on the in-plane thermal conductivity values of the composites.…”

“…This technique was explained and used by the authors in a previous study and it was explained in detail in the supporting information (SI). 27 An 850-mm focal length spectrometer with 2400 groves/mm holographic grating was used in the measurements to obtain precise relation between the laser power and Raman shift. Elemental analysis for the graphene type was performed using FlashEA 1112 from ThermoFisher Scientific.…”

Enhancement of thermal, morphological, and mechanical properties of compatibilized based onPA6‐enriched graphene oxide/EPDM‐g‐MA/CR: Graphene oxide andEPDM‐g‐MAcompatibilizer role

“…Polyamide 6 (PA6) with the trade name of Ultramid® B3S, with density of 1.13 g/cm 3 and a melting point of 220 C from BASF (Germany), and chloroprene rubber (CR) with the trade name of Bayprene 226 with a density of 1.23 g/cm 3 and Mooney viscosity of 73 ± 2 was provided by the LANXESS (Germany). EPDM-grafted maleic anhydride (Royaltuf 465A), with a specification: Mooney viscosity of 58 ± 2, propylene/ethylene ratio of 45/55 and MA content of 1% as a compatibilizer was supplied by Uni, Louisiana.…”

“…Graphene‐based nanocomposites have received much attention in various fields due to their high specific surface area, good compatibility, low mass density, delicate flexibility as well as the excellent synergistic effect of graphene with other materials. Numerous studies have attempted to develop new and improved graphene‐based polymer composites 1–3 . However, the dispersion behavior of graphene in the polymer matrix and the interfacial bonding between graphene and polymers still limits the better performances and broader applications of the prepared graphene‐polymer nanocomposites.…”

“…Numerous studies have attempted to develop new and improved graphene-based polymer composites. [1][2][3] However, the dispersion behavior of graphene in the polymer matrix and the interfacial bonding between graphene and polymers still limits the better performances and broader applications of the prepared graphene-polymer nanocomposites. A particular branch of graphene research deals with graphene oxide (GO).…”