Thermal Conductivity Of Natural Rubber Research Articles

Co-modified h-BN was used to improve the mechanical properties and thermal conductivity of natural rubber

With the rapid development of electronic devices and rubber tires, the industry has put forward new requirements for the heat dissipation of rubber components. With excellent thermal conductivity, oxidation resistance, and thermal stability, hexagonal boron nitride (h-BN) is often added to plastics or rubber as a thermally conductive filler, but is less effective when used directly. In this study, h-BN-K was prepared by direct modification of the mixed solution of KH-550, and KH-570, while h-BN-PK was prepared by co-modification of dopamine, KH-550, and KH-570. Two modified h-BN were added to natural rubber (NR) to improve the vulcanization properties, mechanical properties, and thermal conductivity. It was found that the tensile strength and thermal conductivity of 20 wt% h-BN-PK/NR composites were 30.6 MPa and 0.335 W/mK, which were 39.1% and 110.7% higher compared to pure NR (22.0 MPa and 0.159 W/mK), respectively. In addition, the addition of h-BN improved the thermal stability performance of NR to some extent. In conclusion, the h-BN-PK/NR composites provide a certain reference for the use of thermally conductive NR and suggest new ideas for heat dissipation of electronic devices.

Improving the thermal conductivity of natural rubber by constructing three-dimensional thermal conductivity networks and chemically bonded filler-matrix interaction

It has become the mainstream way to take advantage of the new carbon materials to modify polymer matrix to prepare thermal interface materials (TIMs) with excellent comprehensive properties for the modern electronic packaging materials. Yet, how to make full use of the properties of new carbon materials is still facing the severe challenges. Herein, thiol-functionalized carbon nanotubes/natural rubber (CNTs-SH/NR) TIMs with three-dimensional networks (3D) and covalently bonded filler/matrix interactions were fabricated through the surface chemical treatment as well as ice-templated approach. The results proved that CNTs-SH/NR TIMs could achieve a high through-plane thermal conductivity of 1.22 W m −1 K −1 with CNTs-SH content was 25 wt%. Simultaneously, it showed sensitive heat response capacity. The improvement of filler/matrix interface and 3D networks were of great importance in abating the total thermal resistance. Moreover, the method provide a novel route to design high-performance thermal conductive TIMs and apply for the thermal management of electronics. • CNTs fillers with dual functions of thermal conductivity and enhancement are prepared by chemical etching and surface modification. • The covalent bonding between CNTs and NR is helpful to further improve the thermal conductivity of NR TIMs. • A thermal conductivity of 1.22 W m -1 K -1 is achieved for NR based TIMs.

Natural rubber nanocomposites: effect of carbon black/multi-walled carbon nanotubes hybrid fillers on the mechanical properties and thermal conductivity

ABSTRACT This work presents the effect of carbon black (CB)/multiwall carbon nanotubes (MWCNT) hybrid filler system on the mechanical properties and thermal conductivity of natural rubber (NR) based nanocomposites. A 30 phr (parts per hundred of rubber) of CB nanocomposite was used as a reference for which various amounts (0.5, 1, 2 and 5 phr) of MWCNT were incorporated as a CB replacement. Scanning electron microscopy (SEM) was used to investigate the state of dispersion of the CB/MWCNT fillers inside the NR matrix, while dynamic mechanical analysis (DMA) was performed to characterize their storage and loss moduli, Payne effect and loss factor (tan δ). The scorch time (t10) and optimum curing time (t90) gradually increased with increasing MWCNT content due to the shape difference between CB and MWCNT, as well as the adsorption of curatives onto the MWCNT. Finally, due to the intrinsic properties of MWCNT and its synergy with CB, substantial improvements in thermal conductivity and mechanical properties were achieved by the substitution of 5 phr CB with MWCNT. For example, a thermal conductivity of 0.602 W/m.K was achieved, which corresponds to a 80% increase compared to the reference sample. Furthermore, a 72% and 54% increase of the modulus at 100% and 300% strain (M100 and M300) was respectively achieved, while the elongation at break decreased by only 20%.

Enhanced thermal conductivity of natural rubber based thermal interfacial materials by constructing covalent bonds and three-dimensional networks

With the rapid development of electronic integration technology, the timely and efficient heat dissipation capacity has become increasingly important to ensure reliability and lifetime of electronics. Thermal interface materials (TIMs) were considered as the best candidate to tackle this issue. In this work, the three-dimensional structures with covalent bond connections of boron nitride/natural rubber (BN/NR) thermal interface composites were successfully prepared and its possessed an ameliorated through-plane thermal conductivity of 0.79 W m−1 K−1 when BN content were 25 wt%. The results demonstrated that three-dimensional network structures and chemical interactions between BN and NR had a significant contribution in reducing interfacial thermal resistance. Meanwhile, the sensitive thermal response, satisfactory electrical insulation and good mechanical properties made its own high probability for the TIMs applications. Importantly, this tactics created a new means to construct elastomer-based thermal management materials and applied for the electronic packing materials.

Regenerative cooling using elastocaloric rubber: Analytical model and experiments

Caloric materials exhibit significant entropy variations when applying appropriate excitation, pushing forward the development of solid-state cooling systems. Their development includes materials' properties optimization, with a focus on their adiabatic temperature change when driven at their limit. In order to sustain the device development, an analytical model for regenerative cooling systems is presented in this work. It consists of a caloric material driven cyclically so that it exhibits harmonic temperature variations, whereas an oscillating fluid layer is exchanging heat with the caloric material, leading to a net heat flux along one given direction. The heat transfer equation was solved analytically for harmonic excitations along the direction perpendicular to caloric material layers separated by fluid layers. In the second step, the problem was solved along an axis parallel to the layers. In order to validate the model, an experimental proof of concept was developed based on a natural rubber tube inside which water flows harmonically. The comparison between the model and experiment is given, while the model highlights the importance of the thermal boundary layer and how the geometry of the device easily compensates for the low thermal conductivity of natural rubber.

Fabrication of natural rubber dielectric elastomers with enhanced thermal conductivity via dopamine chemistry

Abstract Herein, boron nitride (BN) is modified by bio-inspired dopamine chemistry to increase thermal conductivity of natural rubber (NR) dielectric elastomer. With in situ self-polymerization of dopamine, poly(dopamine) (PDA) is coated on the BN platelets surface. After PDA modification, the BN platelets are homogeneously dispersed in polymeric matrix, resulted in enhanced mechanical properties, thermal conductivity and dielectric properties. The NR composites acquire the maximum thermal conductivity coefficient (0.46 W/mK), which is approximately 460% of pure NR without thermal conductive filler (0.10 W/mK). Moreover, the NR composites exhibit high dielectric strength and large energy density due to the PDA modification on BN platelets.

Effect of networked hybridized nanoparticle reinforcement on the thermal conductivity and mechanical properties of natural rubber composites.

Thermal conductivity of natural rubber (NR) was enhanced by incorporating novel conductive hybrid nanofillers, namely polyaniline grafted carbon black (PANI/CB) nanoparticles and carbon black nanoparticles linked with carbon microfiber (CF/CB) composites. The PANI/CB hybrid fillers were synthesized using an in situ method, where aniline monomers were initially adsorbed onto carbon black spherical domains and, afterwards, it was polymerized in the presence of an oxidizer. Final rubber composites were prepared through melt mixing, where PANI/CB and CF/CB filler loading was kept at 40 parts per hundred of rubber (phr). The thermal conductivity values of the rubber composites with CF/CB (20 : 20) and PANI/CB (20 : 20) yield were 0.45 W m−1 K−1 and 0.31 W m−1 K−1, respectively and the thermal conductivity improved significantly compared to the control (0.25 W m−1 K−1) sample. The higher thermal conductivity values of CF/CB and PANI/CB incorporated composites suggest that the generated networked structure of CF and PANI nanofibers with CB nanoparticles has immensely contributed to enhancing the heat dissipation compared to that of the neat CB rubber composite. Scanning electron micrographs (SEM) confirmed the attachment of the synthesized PANI onto the spherical CB nanoparticles and interconnected morphology of CF/CB and PANI/CB hybrid fillers. The synthesized PANI/CB hybrid filler was further characterized using Fourier-transform infrared (FTIR) spectroscopy to evaluate the chemical properties. Furthermore, thermogravimetric analysis revealed the higher thermal stability of CF/CB (20 : 20) and PANI/CB (20 : 20) composites compared to the control. Moreover, the addition of CF/CB (20 : 20) and PANI/CB (20 : 20) improved the mechanical properties such as ultimate tensile strength, modulus at break, resilience and abrasion resistance significantly and well above the minimum required standard mechanical parameters in the tyre industry. These reinforced composites show great potential to be used as heat dissipating rubber composites in the tyre industry.

Natural Rubber-Whisker Alumina Fiber Composite Materials for Mechanical and Thermal Insulation Applications

Alumina fiber is a ceramic material used as a dispersed phase or filler to reinforce the mechanical and improve thermal properties of natural rubber via vulcanization process at curing temperature 150°C. The amount of alumina fiber added in natural rubber was varied from 0 to 50 phr on 100 phr of natural rubber in a sulfur curing system. Adding 10 phr alumina fiber affects to obtain the best natural rubber composite samples having good mechanical and thermal properties. Tensile strength, elongation at break, Young’s modulus and thermal conductivity of adding 10 phr whisker alumina fiber encoded NR-Al-10 are equal to 14.38±1.95 MPa, 1038.4±41.45%, 545.63±25.67 MPa and 0.2376±0.0003 W/m.K, respectively, better than those of pure natural rubber compounds without adding alumina fiber. Tensile strength, elongation at break, Young’s modulus and thermal conductivity of natural rubber without adding alumina fiber are equal to 14.06±6.03 MPa, 949.41±52.15%, 496.32±8.54 MPa and 0.2500±0.0003 W/m.K, respectively.

Thermal Conductivity of Natural Rubber Using Molecular Dynamics Simulation.

Thermal conductivity of natural rubber has been studied by classic molecular dynamics simulations. These simulations are performed on natural rubber models using the adaptive intermolecular reactive empirical bond order (AIREBO) and the Green-Kubo molecular dynamics (MD) simulations. Thermal conductivity results are found to be very sensitive to the time step used in the simulations. For a time step of 0.1 fs, the converged thermal conductivity is 0.35 W/mK. Additionally the anisotropic thermal conductivity of a specially-modeled natural rubber model with straight molecular chains was studied and values of thermal conductivity parallel to the molecular chains was found to be 1.71 W/mK and the anisotropy, 2Kz/(Kx + Ky), was 2.67.

Contribution of Carbon Black to Thermal Conductivity of Natural Rubber

Eight kinds of carbon black filled natural rubber composites were prepared, and thermal conductivity was studied. Acetylene black contributes much to the thermal conductivity of rubber, and tiny loading results in considerable improvement. The conductive carbon black 40B2 is advantageous for the improvement in thermal conductivity of rubber when its loading reaches middle level, and at its middle level, also tiny loading results in much improvement. Most kinds of carbon black for rubber application filled rubber composites have good properties except for N134 and N660, especially the poor contribution of N660. Additionally, in the case of carbon black filled rubber composites, addition of filler may not necessarily benefit the thermal conductivity when filler loading is not much.

Thermal Conductivity of Soft Vulcanized Natural Rubber, Selected Values

Abstract Literature on thermal conductivity of natural rubber has been critically evaluated. Best values of thermal conductivity as a function of temperature were selected, and are presented in both graphical and tabular form. An attempt was made to consult all work that could significantly affect the choice of best values. Relevant references in the papers themselves were followed up until a substantially “closed system” had been generated, as shown by the fact that no new references were being turned up.