Enhancement Of Thermal Properties Research Articles

Layered double hydroxides bundled Agar-g-PAN/Ag nanocomposite films: A strategy to improve thermal, barrier and antibacterial properties

With an aim of designing a biodegradable packaging material with considerable stability, herein, layered double hydroxides (LDH) bundled agar grafted polyacrylonitrile nanocomposites (Agar-g-PAN/Ag/LDH) incorporated with silver nanoparticles (Ag Nps) have been synthesized using surfactant free in situ polymerization method. The LDH platelets form a laminating structure around the Agar-g-PAN copolymeric network while the Ag Nps are dispersed throughout the material. The prepared nanocomposite films exhibit high thermal stability because of the sandwiching of polymeric chains in between the LDH platelets which also evidences the improvement in fire retardancy. The comparative analysis of limiting oxygen indices of Agar-g-PAN/Ag/LDH nanocomposites with PAN and Agar-g-PAN clearly indicates the fire-repellent nature of the materials. Proper exfoliation and partial intercalation of the LDH platelets as well as presence of Ag Nps result in almost five-fold enhancement in oxygen barrier properties of Agar-g-PAN/Ag/LDH nanocomposite films as compared to the copolymeric matrix. The combination of LDH with Ag Nps shows a synergistic effect in improving the biodegradability and chemical resistance of the nanocomposite films. The antibacterial studies indicate remarkable antibacterial properties of the Agar-g-PAN/Ag/LDH nanocomposites which are more pronounced for gram negative bacterial strains. The synthesized nanocomposite films are biodegradable and chemically inert with enhancement in thermal, barrier and antibacterial properties, making them suitable candidates for packaging applications.

Copper foam reinforced polymer-based phase change material composites for more efficient thermal management of lithium-ion batteries

In this study, copper foam reinforced polymer-based composite phase change materials (CPCM) were prepared to solve the problems of low thermal conductivity, melting leakage, and poor mechanical strength in the realistic application of phase change materials. The CPCM consists of paraffin (PA) and styrene-ethylene-butylene-styrene (SEBS). Stability and mechanical tests were conducted and it was found that CPCM-90 (with a mass fraction of PA at 90 %) exhibited excellent leakage protection ability, shape stability, and bending resistance. The enthalpy of CPCM-90 is up to 168.11 J/g. After filling CPCM into copper foam (CF) with 98 % porosity, the thermal conductivity of the CF/CPCM-90 is improved up to 0.943 W/m·K, nearly 3 times higher than the thermal conductivity of CPCM-90. In addition, the reinforcement of copper foam allows CF/CPCM-90 before and after the phase transformation to withstand mechanical stress of 2 MPa and 0.7 MPa respectively with only 1 % strain. The CF/CPCM-90 also maintained its structural integrity during phase transformation, distinguishing it from CPCM, which commonly experiences cracking and deformation. Furthermore, CF/CPCM-90 maintains battery temperatures below 60 °C for 70 min at 7 W of heat generation and 34 min even at 13 W. Notably, at all heating powers, the duration below 60 °C of the CF/CPCM group is 3 times longer than in the copper foam group and 4 times longer than in the control group (no CF/CPCM-90 or CF). The CF/CPCM-90 shows very effective temperature control for LIBs and has great potential for realistic application regarding battery thermal management. Moreover, this paper provides ideas for further engineering applications of phase change materials in terms of synergistic enhancement of thermal conductivity, leakage prevention, and mechanical properties.

Innovative integration of pyrolyzed biomass into polyamide 11: Sustainable advancements through in situ polymerization for enhanced mechanical, thermal, and additive manufacturing properties

The incorporation of pyrolyzed biomass, i.e., biochar, in polymers can be viewed as a sustainable approach that reduces bio-waste in a smart way. Herein, various biochar concentrations were integrated into the biobased polyamide 11 (PA11) matrix via in situ polymerization. Scanning electron microscopy (SEM) micrographs demonstrated the homogeneous dispersion of up to 50 wt% biochar within the PA11 matrix, free from any phase separation, particle agglomeration, or crack formation. Consequently, there was a remarkable enhancement in mechanical and thermal properties. Notably, tensile strength and modulus increased by 35% and 72%, respectively, while the thermal decomposition process was significantly delayed with the incorporation of biochar particles. Furthermore, the viscoelastic performance of the PA11 matrix exhibited substantial improvement upon the addition of the filler particles. These impressive results verified the excellent interfacial compatibility achieved between the PA11 matrix and biochar, owing to the utilization of in situ polymerization. To demonstrate the potential application of these composites in additive manufacturing, a filament with a uniform diameter was fabricated from a composite comprising 50 wt% biochar. It was successfully employed in material extrusion to print a complex object. The resulting structure exhibited high shape fidelity, precise dimensions, and no noticeable defects. This groundbreaking strategy not only highlights the utilization of biochar as a sustainable filler but also underscores the efficacy of in situ polymerization in fabricating high-performance PA11/biochar composites for various demanding applications, including filament production for additive manufacturing.

Enhancement of tensile, thermal and barrier properties of polyphenylene sulfide/carboxylated graphene antibacterial nanocomposites

Enhancement of tensile, thermal and barrier properties of polyphenylene sulfide/carboxylated graphene antibacterial nanocomposites

Effects of cross-linking degree and steric hindrance on the thermal degradation behavior of novel hybrid zirconium-silicone resin

Although silicone resins are commonly seen as popular candidates for heat-resistant applications, the severe weight loss at the temperature from 400 to 800 °C remains a challenge. Herein, we reported a strategy to enhance the thermal resistance by introducing Zr into the main chain. Molecular simulation shows the Zr atoms led to the formation of high energy Zr–O bonds and increased the cross-linking degree which in turn suppressed the formation of cyclic oligomers, the results was further supported by TG-IR. The degradation activation energy was increased from 75.26 (ZAS0) to 88.67 kJ/mol (ZAS5) for the major degradation stage. The degradation kinetics study shows the degradation of ZAS5 followed the cylindrical symmetrical three-dimensional diffusion mechanism (n = 1.5). This work could provide a systemic experimental and theoretical foundation for thermal properties enhancement through metal atoms incorporation.

Crosslinking networks in epoxidized natural rubber/hemp hurd bio‐composites for the enhancement of thermal, mechanical, and water repellence properties

AbstractEpoxidized natural rubber (ENR) bio‐composites filled with hemp hurd were fabricated via reactive batch‐mixing and vulcanization. The effect of the ENR‐hemp hurd grafting, silane modification, sulfur vulcanization, and the built‐up crosslinking networks on the thermomechanical and physical properties were analyzed. It was observed that the reactive mixing of ENR and hemp hurd caused epoxy ring opening followed by ether bonding of ENR onto the hemp hurd. There was evidence showing that the hemp fillers were also involved in the sulfur vulcanization. The sulfur vulcanized ENR bio‐composites displayed a low swelling index, homogeneous filler dispersion, and superior thermomechanical properties. The vulcanized bio‐composites with silane‐modified hemp hurd showed slightly less grafting but substantially reduced water absorption. The hardness, tensile strength, and modulus of the optimized formulation displayed a 300%, 1030%, and 960% enhancement as compared to the ENR baseline, respectively.Highlights ENR bio‐composites with hemp hurd were fabricated. Crosslinking networks were built‐up within the ENR/hemp bio‐composites. SiHemp show similar reinforcement but more water repellence. The synthesized composites had enhanced thermal and mechanical properties.

Nanoadditives induced enhancement of thermal energy storage properties of molten salt: Insights from experiments and molecular dynamics simulations

Current concentrated solar power (CSP) plants use molten salts as heat storage and heat transfer medium. The thermal property enhancement of molten salts can increase the efficiency and lower the investment cost of CSP plants. In this study, the experiments and molecular dynamics (MD) simulations were employed to investigate the effect of doping Al2O3, SiO2 nanoparticles or multi-walled carbon nanotubes (MWCNTs) on the specific heat capacity (SHC) of ternary carbonate salt. The results show that the SHC of molten salt can be enhanced by adding nanoadditives. The addition of MWCNTs has the largest SHC enhancement in both solid and liquid states. Based on MD simulations, the radial distribution functions, number density distribution and vibrational density of states were further analyzed to reveal the effect of nanoadditive, base salt and interface thermal resistance between them on SHC at different temperatures. It is found that the nanoadditive agglomeration, the ion spacing of base salt, and the thermal resistance between base salt and nanoadditive is independent on temperature and cannot result in the enhanced SHC of liquid nanocomposites. Moreover, the thickness of interfacial layer changes with temperature. The thicker interfacial layer leads to the higher SHC of liquid nanocomposites. The interfacial layer also has a decisive influence on SHC of solid nanocomposites. The scanning electron microscopy images show that the layered, needle-like, and network-like interfacial layers are observed in Al2O3, SiO2 and MWCNT nanocomposites, respectively. The present findings are helpful to understand the mechanisms governing thermal energy storage, and provide guidelines for the performance optimization of molten salt based nanocomposites.

Enhancement of mechanical and thermal properties of poly methyl methacrylate composite bone cements with zinc oxide nanostructures modified carbon fibres additives

Acrylic bone cement, which primarily consists of polymethyl methacrylate (PMMA), is widely used in orthopaedics, dentistry, and particularly in joint arthroplasty surgery. However, bone cements (BCs) have several limitations, including low mechanical properties, bioactivity issues, and high heat generation during polymerization. In recent years, there has been significant interest in studying the development of mechanical, thermal, and antibacterial properties of bone cement. In this study, ZnO nanostructures modified CFs were added to PMMA BCs at concentrations ranging from 0.10 wt% to 1.00 wt%, and the mechanical and thermal properties of the novel PMMA composite BCs were investigated. The novel composite materials were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, and Fourier-transform infrared spectroscopy (FTIR). Mechanical tests including compression and 4-point bending were performed on the composite structures, along with thermogravimetric analysis (TGA). The results revealed that the composite cement containing 0.25 wt% ZnO/CFs reinforcement agent exhibited the best mechanical properties and thermal stability. The flexural strength of the 0.25 wt% ZnO/CFs reinforced PMMA composite BCs increased by 78.9%, while the compression strength increased by 277.4% compared to the control group.

An Atomistic Study of the Tensile Deformation of Carbon Nanotube-Polymethylmethacrylate Composites.

There has been growing interest in polymer/carbon nanotube (CNT) composites due to an exceptional enhancement in mechanical, structural, thermal, and electronic properties resulting from a small percentage of CNTs. However, the performance of these composites is influenced by the type of polymer used. PMMA is a polymer of particular interest among many other polymers because of its biomaterial applications due to its biocompatibility, non-toxicity, and non-biodegradability. In this research, we utilized a reactive force field to conduct molecular dynamics simulations to investigate changes in the mechanical properties of single-walled carbon nanotube (SWCNT)-reinforced Poly (methyl methacrylate) (PMMA) matrix composites. To explore the potential of SWCNT-reinforced PMMA composites in these applications, we conducted simulations with varying CNT diameters (0.542-1.08 nm), CNT volume fractions (8.1-16.5%), and temperatures (100 K-700 K). We also analyzed the dependence of Young's modulus and interaction energy with different CNT diameters, along with changes in fracture toughness with varying temperatures. Our findings suggest that incorporating a small amount of SWCNT into the PMMA polymer matrix could significantly enhance the mechanical properties of the resulting composite. It is also found that the double-walled carbon nanotube has roughly twice the tensile strength of SWCNT, while maintaining the same simulation cell dimensions.

Evaluation of Some Beneficial Environmental Impacts and Enhanced Thermal Properties Resulting from Waste Plastic Integration into Concrete

Evaluation of Some Beneficial Environmental Impacts and Enhanced Thermal Properties Resulting from Waste Plastic Integration into Concrete

Enabling superior thermo-mechanical performance of hydrated salt-based phase change energy storage cementitious composite using graphene oxide reinforced micro-interface

Thermal energy storage cementitious composites (TESCCs) with encapsulated phase change materials (PCMs) were promising candidates for thermal comfort and energy saving in solar passive buildings. However, serious deterioration of mechanical properties and low heat transfer efficiency had hindered their application. In this study, a high-strength encapsulated PCM with a simple production process was developed by encapsulating eutectic hydrated salt PCM within UV-curable polyurethane acrelate resin, and the presented encapsulated PCM (UPE) was used to partially replace sand in cement mortar to prepare TESCC/UPE. Moreover, graphene oxide (GO) modification was conducted to form GO-TESCC/UPE, synergistically enhancing the mechanical strength and heat transfer efficiency. The compressive strength, microstructure and thermal conductivity of TESCCs were studied. Surface heat storage coefficient was presented to further assess the heat transfer and heat storage capacity of TESCCs. Moreover, GO-TESCC/UPE containing 20 vol% encapsulated PCM exhibited 28-day compressive strength of 35.3 MPa, with a 25% improvement over TESCC/UPE. The thermal conductivity and surface heat storage coefficient were also optimized by GO modification. The enhancement of thermal and mechanical properties can be attributed to the fact that GO-TESCC/UPE had a denser interface transition zone (ITZ) and lower harmful porosity due to the excellent compatibility between cement matrix and UPE. In addition, a simplified meso-mechanical model demonstrated that a denser ITZ can mitigate the stress concentration inside the matrix, thus enhancing mechanical properties of TESCCs. This study confirmed the effectiveness of reinforcing ITZ to enhance the thermo-mechanical properties of heat storage cementitious materials.

Magnesium phosphate cement incorporating sheep wool fibre for thermal insulation applications

The increasing use of synthetic fibres in clothing and the high quality of sheep wool fibre (SWF) from the Australian and New Zealand market leads to a decline in the interest in SWFs produced in European countries, considering them as waste that could be valorised within the framework of a circular economy. The use of natural fibre in cement-based composites presents the main issue of durability due to the alkaline pH media of conventional cement. The use of a low-pH cement could improve the viability of combining natural fibres in this low-pH cement as matrix for developing composites. One of these low-pH cements is magnesium phosphate cement (MPC). As a ceramic material the MPC presents high thermal conductivity (∼1 W m−1 K−1) to be used as isolating material. The present work combines MPC formulated with an industrial by-product (low-grade magnesium oxide; LG-MgO) and Spanish SWF, to develop new sustainable cement-based materials (Sust-MPC-SWF) for thermal building insulation applications. The physical, thermal, and mechanical properties of Sust-MPC-SWF were evaluated to determine the optimal formulation through a design of experiments (DoE). Thirteen formulations designed by DoE were conducted with different sheep wool fibre/cement (SWF/C) and sheep wool fibre/extra water (SWF/EW) ratios. A statistical model was obtained and the optimal formulation (SWF/C = 0.36 and SWF/EW = 0.25) was validated. The increase in SWF content led to an enhancement of thermal and acoustic insulation properties of Sust-MPC-SWF, with similar results to other building materials commercialized with these features.

The enhancement of mechanical, physical, and thermal properties of modified asphalt mixture with lignin from mahogany sawdust in the presence of diphenylmethane 4,4′-diisocyanate

The road infrastructure condition, which can be easily damaged by the occurrence of potholes due to the weak adhesion between asphalt and aggregate, disrupts economic activity and requires high maintenance costs. This problem needs to be overcome by adding adhesive to modify the asphalt. Lignin is a sustainable biopolymer that can serve as a natural asphalt binder. Lignin isolated from mahogany sawdust combined with diphenylmethane 4,4′-diisocyanate has never been used to modify asphalt mixtures. This modification can improve the properties of the asphalt mixture, which is very important in road pavement engineering. This study aims to modify asphalt mixtures with lignin isolated from mahogany sawdust combined with diphenylmethane 4,4′-diisocyanate and investigate their physical, mechanical, and thermal characteristics. The isolated lignin was prepared for a modified asphalt mixture by reacting with diphenylmethane 4,4-diisocyanate and adding asphalt. Next, the asphalt mixture was mixed with sand aggregate in an extruder at 150 °C. The results showed an improvement in mechanical, physical, and thermal properties. The optimum composition of asphalt and lignin was 60:40 with a compressive strength value of 3.107 MPa, a water absorption value of 0.246%, and a melting point of 238 °C. The Fourier-transform infrared spectroscopy (FT-IR) spectrum showed a small band at 1715 cm−1, indicating the CO carbonyl group of the NH–CO–O urethane bond. The morphology showed that the surface structure of the modified asphalt mixture becomes more homogeneous due to the interaction between asphalt and polyurethane, which is the result of the reaction of lignin isolate with diphenylmethane 4,4′-diisocyanate.

Effect of the concentration of carbon nanotubes (CNTs) on the rheological behavior in a lubricating oil of plant-derived lubricant

Nanofluids have attracted a lot of attention since their significant enhancement in thermal properties, however there are few reports on the study of the viscosity of nanofluids from an experimental point of view. In this work, the rheological behavior of functionalized multi-walled carbon nanotubes (F-MWCNTs) and coated with MoS2 (MWCNTs-MoS2) in a commercial palm oil as base fluid was evaluated. The purification and functionalization process of the MWCNTs was performed by acid leaching and investigated by FTIR, and stable nanofluids were prepared with MWCNTs concerning time. The rheological behavior of nanofluids with MWCNTs was performed as a function of temperature at different concentrations (0.1, 0.5 and 1% wt.). The effect of time, temperature, shear rate and shear stress versus shear rate were determined. The results indicate that the nanofluid behaves as a Newtonian fluid independently of the MWCNTs concentrations and temperatures evaluated. The viscosity index increases by 16% at a concentration of 1% wt. of F-MWCNTs and for nanofluids added with MWCNTs-MoS2 had significant effect on the effect of temperature.

Thermal, mechanical and dielectric property enhancement of benzoxazine-containing phthalonitrile resin: The effect of functional oligomeric polyphenyl ether

Two oligomeric polyphenyl ethers (PPE) with different functional groups (hydroxyl group and allyl group) were introduced into the benzoxazine-containing phthalonitrile resin, in order to improve the dielectric properties. The polymerization mechanism of the two systems was investigated in detail and the comprehensive properties were studied. It was found that both hydroxyl-terminated PPE (PH) and allyl-terminated PPE (PA) could effectively promote the curing of phthalonitrile resin, while the PH system showed higher activity. Nevertheless, PH could not polymerize and chemically bonded with the crosslinking network. While the allyl groups in PA, however, could self-polymerize or copolymerize with phthalonitrile resin and the thermal resistance and dimensional stability improved as a consequence. PA system shows better dielectric properties, due to the low polarity of functional groups. Poly(MBP-30PA) showed the lowest dielectric constant of 2.88 at 1 MHz. Additionally, the mechanical strength of the glass fiber reinforced composites was also improved. G(MBP-20PA) showed flexural strength of 561.8 MPa, 155.1 MPa higher than that of G(MBP).

High Thermal Conductivity Polymer Composites Fabrication through Conventional and 3D Printing Processes: State‐of‐the‐Art and Future Trends

AbstractThe lifespan and the performance of flexible electronic devices and components are affected by the large accumulation of heat, and this problem must be addressed by thermally conductive polymer composite films. Therefore, the need for the development of high thermal conductivity nanocomposites has a strong role in various applications. In this article, the effect of different particle reinforcements such as single and hybrid form, coated and uncoated particles, and chemically treated particles on the thermal conductivity of various polymers are reviewed and the mechanism behind the improvement of the required properties are discussed. Furthermore, the role of manufacturing processes such as injection molding, compression molding, and 3D printing techniques in the production of high thermal conductivity polymer composites is detailed. Finally, the potential for future research is discussed, which can help researchers to work on the thermal properties enhancement for polymeric materials.

Marble waste reinforced composite with tunable physico-mechanical and thermal properties: micromechanical simulation assisted experimental investigation

ABSTRACT This paper investigates the development of waste marble dust-reinforced particulate composites through an integrated approach of investigation. Samples of marble-epoxy composites were prepared with systematic variations in filler content to achieve tunable mechanical, physical, and thermal properties. Increasing ceramic filler's loading level resulted in superior properties of composite samples, as demonstrated by macroscale characterization such as compressive and flexural strength. Microstructural characterizations such as Fourier transform infrared spectroscopy (FT-IR), Field emission scanning electron microscopy (FE-SEM), thermogravimetric analysis (TGA), and X-ray diffraction (XRD) analysis were used to better understand the results. FT-IR results indicate chemical linkages forming between the epoxy resin and marble dust in the composite, while FE-SEM images suggest strong interfacial bonding between filler and matrix. TGA analysis shows enhancement of thermal properties with increasing filler content, while XRD indicates enhancement of crystallinity. Micro-mechanical modeling using the representative volume element (RVE) approach was also carried out using a commercial simulation package, determining Young’s modulus and comparing it with experimental results.

Synthesis and characterization of a contorted hexabenzocoronene epoxy toward high thermal stability and thermal conductivity

AbstractA contorted hexabenzocorone (HBC) mesogen based epoxy was synthesized and characterized for high thermal stability and thermal conductivity. Since HBC has a nano‐graphene like structure, which would have strong pi–pi interactions, it was expected that HBC epoxy would have superior heat resistance and thermal conductivity. Based on this hypothesis, HBC containing four epoxy groups at edges was synthesized and confirmed by NMR and mass spectrum. HBC epoxy was cured with diaminophenolsulfone and their thermal stability and thermal conductivity were investigated. As expected, the decomposition of 5 wt% occurred at 323.44°C, and thermal conductivity was 0.32 W/mK where the general thermal conductivity of epoxy resins is around 0.2 W/mK. Such enhancement of thermal properties would be explained by the formation of pi–pi stacking of HBC mesogens.

Preparation of branched Al2O3 and its synergistic effect with carbon nanotubes on the enhancement of thermal conductive and electrical insulation properties of silicone rubber composites

Preparation of branched Al2O3 and its synergistic effect with carbon nanotubes on the enhancement of thermal conductive and electrical insulation properties of silicone rubber composites

Enhancement of thermal properties of Al/MoO3 thermite by electrostatic spraying

AbstractTo improve the thermal properties of thermite safely and stably, electrostatic spraying was used to prepare the Al/MoO3 thermite. The Al/MoO3 thermites were detected and characterized by scanning electron microscopy (SEM) and X‐ray diffraction (XRD), and thermal decomposition experiments were carried out by differential scanning calorimetry (DSC). The heat release of the Al/MoO3 thermite prepared by the electrostatic spray (1044 J g−1) is significantly higher than that of the thermite prepared by the ultrasonic (692 J g−1), which is due to more uniform dispersion between Al and MoO3. The initial reaction temperature and activation energy (Ea) of the former keep it steady. Electrostatic spray ensures the safety and stability of the Al/MoO3 thermite. This study provides a new idea for safely and stably improving the thermal properties of thermite by enhancing surface homogenization, which is of great significance for practical applications.