Process induced alignment of carbon nanotube decreases longitudinal thermal conductivity of Al2O3 based porous composites

Alumina (Al₂O₃) based porous composites, reinforced with zirconia (ZrO₂), 3 and 8 mol% Y₂O₃ stabilized ZrO₂ (YSZ) and 4 wt% carbon nanotube (CNT) are processed via spark plasma sintering. The normalized linear shrinkage during sintering process of Al₂O₃-based composite shows minimum value (19.2–20.4%) for CNT reinforced composites at the temperature between 1650 °C and 575 °C. Further, the combined effect of porosity, phase-content and its crystallite size in sintered Al₂O₃-based porous composite have elicited lowest thermal conductivity of 1.2 Wm⁻¹K⁻¹ (Al₂O₃-8YSZ composite) at 900 °C. Despite high thermal conductivity of CNT (∼3000 Wm⁻¹K⁻¹), only a marginal thermal conductivity increase (∼1.4 times) to 7.3–13.4 Wm⁻¹K⁻¹ was observed for CNT reinforced composite along the longitudinal direction at 25 °C. The conventional models overestimated the thermal conductivity of CNT reinforced composites by up to ∼6.7 times, which include the crystallite size, porosity, and interfacial thermal resistance of Al₂O₃, YSZ and, CNT. But, incorporation of a new process induced CNT-alignment factor, the estimated thermal conductivity (of <6.6 Wm⁻¹K⁻¹) closely matched with the experimental values. Moreover, the high thermal conductivity (<76.1 Wm⁻¹K⁻¹) of the CNT reinforced porous composites along transverse direction confirms the process induced alignment of CNT in the spark plasma sintered composites.     

Micro‐contact reconstruction of adjacent carbon nanotubes in polymer matrix through annealing‐Induced relaxation of interfacial residual stress and strain

Thermoplastic polyurethane (TPU)/multi‐walled carbon nanotubes (CNT) nanocomposites were prepared by twin‐screw extrusion and micro injection molding. The electrical conductivity of micro injection molded polymer nanocomposites exhibits a low value and uneven distribution in the micromolded samples. Real‐time tracing of electrical conductivity was conducted to investigate the post thermal treatment on the electrical conductivity of microinjection molded composites. The results show that postmolding thermal treatment leads to a significant increase in the electrical conductivity by over three orders of magnitude for 5 wt % CNT‐filled TPU composites. In‐situ Transmission electron microscopy confirms the conductive CNT network does not change at the micron/sub‐micron scale during thermal treatment. TEM image analysis by a statistical method was used to determine the spatial distribution of CNT in the sample and showed that the average distance between adjacent CNT reduced slightly at the nanometer scale after postmolding thermal treatment. A new conductive mechanism is proposed to explain the enhancement of electrical conductivity after thermal treatment, i.e. micro‐contact reconstruction of adjacent CNT in the polymer matrix through annealing‐induced relaxation of interfacial residual stress and strain. Raman spectra and small angle X‐ray scattering curve of annealed samples provide supporting evidence for the proposed new conductive mechanism. The electron tunneling model was used to understand the effect of inter‐particle distance on the conductivity of polymer composites. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42416.     

Prediction of the effective thermal conductivity of carbon nanotube‐reinforced polymer systems

A study dealing with the effect of the carbon nanotubes (CNTs), at various weight fractions, on the effective thermal conductivity of a CNT‐reinforced polymer by associating it with the Kapitza resistance (R_Kap) phenomena is presented. The finite element method was utilized as a tool for the models' solution by using the principles of the representative volume element. An intermediate continuum layer between polymer matrix and CNTs was considered for the representation of the R_Kap phenomena. The influence of the intensity of R_Kap phenomena at various CNT contents was investigated through the parametric study of the R_Kap value and the thickness of the intermediate layer. The predicted results were compared against experimental measurements derived from an equivalent CNT–epoxy resin system. The discrepancy between calculated and measured values is diminished when the R_Kap phenomena are taken into account, thus confirming the existence of thermal resistance between the CNTs and the polymer matrix. The R_Kap rise as the % CNT weight content is increased. This behavior is correlated to the higher CNT agglomeration at higher CNT contents, which is proven by the scanning electron microscopy and thus providing a first indication of the effect of the CNT agglomeration on the effective thermal conductivity at various CNT contents. POLYM. COMPOS., 35:1997–2009, 2014. © 2014 Society of Plastics Engineers     

A method to improve the barrier performance of flexible riser internal pressure sheath—Heat transfer experiment and simulation

A considerable amount of acidic gas penetrates into the annulus between the internal pressure sheath and the outer protective sheath during the service of flexible risers, which will inevitably lead to corrosion of the metal functional layer. Many researchers have modified nanocomposites from the mass transfer perspective to reduce the materials' permeability coefficient. While permeation is an integrated process of heat and mass transfer process, heat distribution directly impacts gas permeation. Herein, the thermal conductivity of flexible riser liner materials is predicted for the first time by a combination of molecular dynamics and experiments, and then the radial temperature distribution under different seawater temperatures and internal fluid temperatures is investigated by finite element analysis. Finally, the effect of temperature distribution on the permeation coefficient was analyzed. The results demonstrate that the thermal conductivity can be predicted by molecular dynamics simulation, and the thermal conductivity of (polyvinylidene difluoride) PVDF/TiO₂ decreases, while the thermal conductivity of PVDF/carbon nanotube (CNT) increases compared with pure PVDF. The temperature distribution of the internal pressure sheath material decreases when condensate water is present. As the fluid temperature rises from 30 to 110°C, the maximum increase ratio in the permeability of PVDF/CNT over PVDF increased from 3.6% to 14.8%, and the maximum decrease ratio of PVDF/TiO₂ permeability coefficient compared with PVDF is from 1.2% to 4.6%. The results present a new idea to improve the barrier properties of materials by decreasing thermal conductivity.     

Thermal transport phenomena and limitations in heterogeneous polymer composites containing carbon nanotubes and inorganic nanoparticles

An Off-Lattice Monte Carlo model was developed to investigate effective thermal conductivities (K_eff) and thermal transport limitations of polymer composites containing carbon nanotubes (CNTs) and inorganic nanoparticles. The simulation results agree with experimental data for poly(ether ether ketone) (PEEK) with inclusions of CNTs and tungsten disulfide (WS₂) nanoparticles. The developed model can predict the thermal conductivities of multiphase composite systems more accurately than previous models by taking into account interfacial thermal resistance (R_bd) between the nanofillers and the polymer matrix, and the nanofiller orientation and morphology. The effects of (i) R_bd of CNT–PEEK and WS₂–PEEK (0.0232–115.8 × 10⁻⁸ m²K/W), (ii) CNT concentration (0.1–0.5 wt%), (iii) CNT morphology (aspect ratio of 50–450, and diameter of 2–8 nm), and (iv) CNT orientation (parallel, random and perpendicular to the heat flux) on K_eff of a multi-phase composite are quantified. The simulation results show that K_eff of multiphase composites increases when the CNT concentration increases, and when the R_bd of CNT–PEEK and WS₂–PEEK interfaces decrease. The thermal conductivity of composites with CNTs parallel to the heat flux can be enhanced ∼2.7 times relative to that of composites with randomly-dispersed CNTs. CNTs with larger aspect ratio and smaller diameter can significantly improve the thermal conductivity of a multiphase polymer composite.     

Improved dispersion of carbon nanotubes in poly(vinylidene fluoride) composites by hybrids with core–shell structure

Core–shell structure hybrids of carbon nanotubes (CNTs)/BaTiO₃ (H‐CNT‐BT) and commercial multi‐wall CNTs are respectively incorporated into poly(vinylidene fluoride) (PVDF) for preparing the composites near the percolation thresholds. A comprehensive investigation for CNT's dispersion and composite's conductivity is conducted between H‐CNT‐BT/PVDF and CNT/PVDF at different depths vertical to the injection's direction. Gradual increases of the conductivity in two composites are observed from the out‐layer to the core part which infers an inhomogeneous CNT's dispersion in the interior of composites due to their migration under flow during the injection. However, the use of H‐CNT‐BT fillers with core–shell structure enables to reduce this inhomogeneous dispersion in the composite. Furthermore, the conductive network of CNTs in H‐CNT‐BT/PVDF is less sensitive to the thermal treatment than the one in CNT/PVDF composite, which infers the core–shell structure of hybrids can ameliorate the sensitivity of the conductive network. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45693.     

Characterization and thermal degradation kinetics of poly(l‐lactide) nanocomposites with carbon nanotubes

The purpose of this research was to study the thermal degradation kinetics of nanocomposites of poly(l ‐lactide) (PLLA) with carbon nanotubes (CNT) in order to provide further insight into their thermal stability. Nanocomposites were prepared by solvent casting with 1, 3, and 5% by weight of pristine CNT (P‐CNT) or functionalized CNT (F‐CNT), and were characterized using infrared spectroscopy, transmission electron microscopy, differential scanning calorimetry, thermogravimetric analysis, and dynamic‐mechanical‐thermal analysis. The kinetic parameters of thermal decomposition were determined employing Coats‐Redfern method to calculate the reaction order and E₂ function model to calculate the activation energy (Ea). We found no major changes in PLLA glass transition temperatures due to CNT presence, but melt‐crystallization temperature increased slightly in some composites. In general, composites consisting of 3% or 5% of F‐CNT had superior thermal stability than did pure polymer or P‐CNT composites. This improved thermal stability was revealed by slightly higher degradation and onset temperatures, and Ea obtained from kinetic analysis. In addition, 3% or 5% of F‐CNT in PLLA composites slightly enhanced the storage modulus above the glass transition. Therefore, functionalization promoted, in some extent, better morphology and dispersion of CNT into the matrix, which was responsible for improved thermal stability and thermomechanical performance of composites at higher temperatures relative to pure polymer. POLYM. ENG. SCI., 55:710–718, 2015. © 2014 Society of Plastics Engineers     

Effect of carbon nanotube dispersion and network formation on thermal conductivity of thermoplastic polyurethane/carbon nanotube nanocomposites

Carbon nanotubes (CNTs) were dispersed without any solvent in poly(tetramethylene ether glycol), (PTMEG) well above its melting point by ultrasonication in the pulse mode and different times. The polyol/CNT suspensions were used to prepare in situ polymerized thermoplastic polyurethane TPU/CNT nanocomposites with the CNT concentration of ～ 0.05 vol%, much below the CNT geometrical percolation threshold calculated at 0.43 vol%. Results of rotational rheological measurements and ultraviolet–visible (UV‐Vis) spectroscopy analysis revealed improvement in the nanoscale CNT dispersion with sonication time. Moreover, the optical microscopic images and sedimentation behavior for these samples pointed out to the formation of segregated CNT networks with different microstructures at different sonication times. Through‐plane thermal conductivity measurements showed an increase in thermal conductivity of the in‐situ polymerized TPU/CNT nanocomposites from polyol/CNT suspensions with increasing sonication time followed by a decrease at long sonication times. Different models were used to evaluate the role of CNT dispersion state and created microstructure on thermal conductivity of nanocomposites. The formation of a segregated network at medium sonication times consisting of large CNT aggregates and small bundles increased the nanocomposite thermal conductivity up to 99.7%, while at longer sonication times, an increase in interfacial area with a corresponding increase in kapitza boundary resistance, effectively decreased the system thermal conductivity. POLYM. ENG. SCI., 56:394–407, 2016. © 2016 Society of Plastics Engineers     

Enhanced thermoelectric properties of CNT dispersed and Na-doped Bi2Ba2Co2Oy composites

The thermoelectric properties of Bi₂Ba₂Co₂O_y and Bi_1.975Na_0.025Ba₂Co₂O_y+x wt% carbon nanotubes (CNT; x=0.00, 0.05, 0.10, 0.15, 0.5, and 1.0) ceramic samples synthesised by the solid-state reaction method were investigated from 300K to 950K. Na doping with a small amount played an important role in reducing resistivity and slightly reduced the Seebeck coefficients and the thermal conductivity. The CNT dispersant increased resistivity, but the thermal conductivity was reduced remarkably. In particular, the Bi_1.975Na_0.025Ba₂Co₂O_y+1.0wt% CNT sample exhibited an ultralow thermal conductivity of 0.39 W K⁻¹ m⁻¹ at 923K. This was attributed to the point defects caused by Na doping and the interface scattering caused by the CNT dispersant. The combination of Na doping and CNT dispersion had better effects on thermoelectric properties. The Bi_1.975Na_0.025Ba₂Co₂O_y+0.5wt% CNT sample exhibited a better dimensionless figure of merit (ZT) value of 0.2 at 923K, which was improved by 78.2%, compared with the undoped Bi₂Ba₂Co₂O_y sample.     

Mechanical,dielectric, and thermal properties of fluorosilicone rubber composites filled with silica/multiwall carbon nanotube hybrid fillers

In this work, hybrid fillers consist of modified silica (SiO₂) and multiwalled carbon nanotube (MWCNT) were used to improve the mechanical, dielectric, and thermal properties of fluorosilicone (FSR) composites via a direct mechanical mixing method. With the increase of CNT loading in SiO₂/CNT hybrid loading ratio, the tensile properties, dielectric constant, electrical conductivity, and thermal properties all increase without a sharp sacrifice of flexibility. The dielectric constant of FSR-S15/C5 achieved 7,370 @1 kHz, which is about four orders of the FSR-S20, and the dielectric loss remains as low as 0.676 @1 kHz. Therefore, the linkage of SiO₂ and FSR chains not only enhances the interfacial interaction between the fillers and FSR matrix but also decreases the agglomeration of the fillers in matrix. What is more, modified SiO₂ and CNT were designed as the effective hybrid filler to improve the performance of the polymeric matrix through synergic effect.     

Mechanical and thermal enhancements of benzoxazine‐based GF composite laminated by in situ reaction with carboxyl functionalized CNTs

An easy and efficient approach by using carboxyl functionalized CNTs (CNT‐COOH) as nano reinforcement was reported to develop advanced thermosetting composite laminates. Benzoxazine containing cyano groups (BA‐ph) grafted with CNTs (CNT‐g‐BA‐ph), obtained from the in situ reaction of BA‐ph and CNT‐COOH, was used as polymer matrix and processed into glass fiber (GF)‐reinforced laminates through hot‐pressed technology. FTIR study confirmed that CNT‐COOH was bonded to BA‐ph matrices. The flexural strength and modulus increased from 450 MPa and 26.4 GPa in BA‐ph laminate to 650 MPa and 28.4 GPa in CNT‐g‐BA‐ph/GF composite, leading to 44 and 7.5% increase, respectively. The SEM image observation indicated that the CNT‐COOH was distributed homogeneously in the matrix, and thus significantly eliminated the resin‐rich regions and free volumes. Besides, the obtained composite laminates showed excellent thermal and thermal‐oxidative stabilities with the onset degradation temperature up to 624°C in N₂ and 522°C in air. This study demonstrated that CNT‐COOH grafted on thermosetting matrices through in situ reaction can lead to obvious mechanical and thermal increments, which provided a new and effective way to design and improve the properties of composite laminates. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Ultradrawing properties of ultrahigh‐ molecular‐weight polyethylene/carbon nanotube fibers prepared at various formation temperatures

The influence of formation temperature on the ultradrawing properties of ultrahigh‐molecular‐weight polyethylene/carbon nanotube (UHMWPE/CNT) fiber specimens is investigated. Gel solutions of UHMWPE/CNT with various CNT contents were gel‐spun at the optimum concentration and temperature but were cooled at varying formation temperatures in order to improve the ultradrawing and tensile properties of the UHMWPE/CNT composite fibers. The achievable draw ratio (D_ra) values of UHMWPE/CNT as‐prepared fibers reach a maximum when they are prepared with the optimum CNT content and formation temperature. The D_ra value of UHMWPE/CNT as‐prepared fibers produced using the optimum CNT content and formation temperature is about 33% higher than that of UHMWPE as‐prepared fibers produced using the optimum concentration and formation temperature. The percentage crystallinity (W_c) and melting temperature (T_m) of UHMWPE/CNT as‐prepared fiber specimens increase significantly as the formation temperature increases. In contrast, W_c increases but T_m decreases significantly as the CNT content increases. Dynamic mechanical analysis of UHMWPE and UHMWPE/CNT fiber specimens exhibits particularly high α‐transition and low β‐transition, wherein the peak temperatures of α‐transition and β‐transition increase dramatically as the formation temperature increases and/or CNT content decreases. In order to understand these interesting drawing, thermal and dynamic mechanical properties of the UHMWPE and UHMWPE/CNT as‐prepared fiber specimens, birefringence, morphological and tensile studies of as‐prepared and drawn fibers were carried out. Possible mechanisms accounting for these interesting properties are proposed. Copyright © 2010 Society of Chemical Industry     

Comparison of Two‐Phase Thermal Conductivity Models with Experiments on Dilute Ceramic Composites

Thermal shock resistance of cubic 8 mol% yttria‐stabilized zirconia (YSZ) can be increased by the addition of dilute second phases. This study addresses how these dilute second phases affect the thermal conductivity for two‐phase ceramic composites of 8 mol% YSZ with 10–20 vol% alumina (Al₂O₃) or 10–20 vol% mullite (3Al₂O₃·2SiO₂). Thermal conductivity measurements from 310 K (37°C) to 475 K (202°C) were made using the 3ω method and compared with results from 3D analytical models and a 2D computational microstructure‐based model (Object‐Oriented Finite Element Analysis, OOF2). The linear Rule of Mixtures was the least accurate and significantly overestimated the measured thermal conductivity at low temperatures, with errors in some cases exceeding 100%. Calculations using the Bruggeman and OOF2 models were both much better, and the deviation of less than ±2.5% across all compositions and temperatures is within the range of experimental and modeling uncertainty. The Maxwell Garnett equation was a close third in accuracy (±8%). A sensitivity analysis for each model quantifies how small perturbations in the thermal conductivity of the dispersed second phase influence the effective thermal conductivity of the composite, and reveals that the linear Rule of Mixtures model is physically unrealistic and oversensitive to the thermal conductivity of the dispersed phase.     

Effects of carbon nanotubes and interphase properties on the interfacial conductivity and electrical conductivity of polymer nanocomposites

L_c is the minimum length of carbon nanotubes (CNTs) required for efficient transfer of filler conductivity to polymer matrix in polymer CNT nanocomposites (PCNTs). In this work, L_c is correlated with the dimensions of the CNTs and the interphase thickness. Subsequently, the interfacial conductivity as well as the effective length and concentration of CNTs are expressed by CNT and interphase properties. Moreover, a simple model for the tunneling conductivity of PCNTs is developed with these effective terms. The impacts of all parameters on L_c, the interfacial conductivity, the fraction of CNTs in the networks and the conductivity of the PCNT are explained and justified. In addition, the predictions of the percolation threshold and conductivity are compared with the experimental results of several samples. The desirable values of interfacial conductivity are achieved by thin, short and super‐conductive CNTs, high waviness and a thick interphase. However, thin and long CNTs, low waviness, a thick interphase, poor tunneling resistivity due to the polymer matrix and a short tunneling distance advantageously affect the conductivity of PCNTs, because they produce large conductive networks. The predictions also show good agreement with the experimental measurements of percolation threshold and conductivity, which confirms the developed equations. © 2020 Society of Chemical Industry     

Enhanced anti‐deliquescent property and ultralow thermal conductivity of magnetoplumbite‐type LnMeAl11O19 materials for thermal barrier coating

Magnetoplumbite‐type LaMgAl₁₁O₁₉ ceramic has been proposed as one of promising candidates for the next generation thermal barrier coatings (TBCs) due to its low thermal conductivity. However, LaMgAl₁₁O₁₉ shows poor water‐resistance with significant weight loss at elevated temperatures in water‐containing atmosphere. In this work, we revealed that the essential reason for the poor water‐resistance of magnetoplumbite‐type LaMgAl₁₁O₁₉ ceramic is Mg²⁺ migration from the intrinsic site under moisture environment. And then an effective approach was proposed to improve its anti‐deliquescent property by completely substituting divalent alkaline earth ions Mg²⁺ with Zn²⁺. Finally, a panoscopic strategy was proposed to further lower thermal conductivity through co‐substituting La and Zn sites in LaZnAl₁₁O₁₉ with trivalent and divalent transition metal ions. The mechanism for the lowered thermal conductivity is due to the panoscopic approach, which providing all‐scale hierarchical architectures of phonon scattering mechanisms. The excellent anti‐moisture performance and ultralow thermal conductivity endow the LaZnAl₁₁O₁₉ based ceramics as a kind of promising candidates for advanced thermal barrier coatings.     

Thermal Conductivity of Molten Li2O–B2O3 and K2O–B2O3 Systems

Using the transient hot‐wire method, the thermal conductivity properties of the molten Li₂O–B₂O₃ and K₂O–B₂O₃ systems were measured. The thermal conductivity increases with decreasing the temperature due to the borate structure change. In addition, calculations of the one‐dimensional Debye temperature and the phonon mean free paths as a function of temperature of the alkali borate systems were made. At a fixed temperature of 1273 K, the effect of the alkali oxide concentration on the thermal conductivity was evaluated. Within a range of 10–30 mol% Li₂O (or K₂O), a positive relationship between the thermal conductivity and 4‐coordinate boron was obtained. However, below 10 mol% Li₂O (or K₂O), the change in the intermediate‐range order of the borate structure had a more dominant effect on the thermal conductivity. Finally, the effect of cations on the thermal conductivity in the various molten R₂O–B₂O₃ (R=Li, Na and K) systems was considered. Depending on the type of cation, the change in the ionization potential had an effect on the thermal conductivity and also resulted in a change in the bond strength.     

Carbon nanotubes improve the adhesion strength of a ceramic splat to the steel substrate

A scratch technique was used to measure the adhesion strength of plasma sprayed carbon nanotube (CNT) reinforced aluminum oxide (Al₂O₃) splat on the steel substrate. The effect of adding carbon nanotube on the adhesion strength of a single splat was studied by varying the CNT content as 0, 4 and 8 wt.% in the Al₂O₃ matrix. Higher lateral force was required by the nanoindenter tip to detach CNT reinforced Al₂O₃ splats as compared to Al₂O₃ splat. The adhesion strength increased significantly from 0.52 ± 0.05 MPa for Al₂O₃ splat to 4.21 ± 0.49 MPa for Al₂O₃-4 wt.% CNT splat and 7.36 ± 3.96 MPa for Al₂O₃-8 wt.% CNT splat. A high variation in the adhesion strength of Al₂O₃-8 wt.% CNT splat was due to varying degree of CNT dispersion in the matrix. A significant increase in the adhesion strength of Al₂O₃-CNT splat was attributed to its better mechanical interlocking with the substrate as a result of enhanced melting and spreading caused by the higher thermal conductivity of nanotubes. CNTs also form anchors between the splat and the substrate resulting in higher adhesion strength.     

Effect of Carbon Nanotubes and Carbon Nanotubes/Gold Nanoparticles Composite on the Photocatalytic Activity of TiO2 and TiO2‐SiO2

A carbon nanotube (CNT)/gold nanoparticle (NP) nanocomposite was synthesized by simultaneously reducing the Au ions and depositing Au NPs on the surface of a CNT. The functional groups were investigated with Fourier transform infrared spectra. From the Raman spectra, the D‐band and G‐band of the CNT were identified. The deposition of nanometer‐sized Au NPs on the CNT sites was observed by transmission electron microscopy. The photodegradation of methylene blue (MB) in aqueous solutions was studied using various photocatalysts, including TiO₂, TiO₂‐SiO₂, CNT/TiO₂, CNT/TiO₂‐SiO₂, Au/TiO₂, CNT‐Au/TiO₂, and CNT‐Au/TiO₂‐SiO₂ composites. CNT addition leads to a synergic effect, improving the photoactivity of the catalysts. A possible physically based mechanism was proposed involving the reduction of electron‐hole recombination and fast electron‐transfer possibility.     

Synergy effects in dielectric and thermal properties of layered ethylene vinyl acetate composites with carbon and Fe3O4 nanoparticles

Properties of layered composites with carbon nanotube (CNT), GnP, Fe₃O₄ nanoinclusions, and hybrid composites with these nanoinclusions were investigated in the wide frequency range (from 20 Hz to 2 THz). All investigated composites (except with single Fe₃O₄ inclusions) are above percolation threshold. The strong enhancement of microwave and terahertz radiation absorption is observed in hybrid composites in comparison with composites with single inclusions. The synergy effect is discussed in terms of the complex impedance and the distribution of relaxation times. At low temperatures (below 200 K), the electrical conductivity of all hybrid composites follows the tunneling law model and the lowest potential barrier was estimated for composites with CNT inclusions. The best thermal properties are observed for composites with CNT inclusions. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48814.     

Measuring and predicting in‐plane thermal conductivity of carbon‐filled nylon 6,6 polymer composites

In this study, two different carbons (synthetic graphite particles and carbon fiber) were added to nylon 6,6, and the resulting composites were tested for both the through‐plane thermal conductivity k_thru and the in‐plane thermal conductivity k_in, using the transient plane source method. The first goal of this work was to use a finite element model to develop a procedure to accurately measure the material properties using this relatively new analytical procedure. Reproducible data can be obtained for nylon 6,6 polymer composites, by choosing a power dissipation (an input parameter to the transient plane source method) corresponding to a sensor temperature increase of 2 K above the initial temperature after 5 s. The second goal of this work was to develop a simple empirical model for the in‐plane thermal conductivity, which is easily measured with the transient plane source method. The results show that the product of the through‐plane and in‐plane thermal conductivities is a linear function of the volume percent ϕ. As the through‐plane thermal conductivity of these composites is accurately predicted with a modified Nielsen model, this empirical relationship can be used to estimate in‐plane thermal conductivities for a range of applications. POLYM. COMPOS. 27:1–7, 2006. © 2005 Society of Plastics Engineers