Enhancement Of Thermal Properties Research Articles

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.

Effect of modified zinc oxide nanoparticles on enhancement of mechanical, thermal and antibacterial properties of disinfectant natural rubber latex foams

Natural rubber latex foams (NRLF) filled with unmodified zinc oxide (ZnO) and modified ZnO nanoparticles (ZnOnp) through the chemical coating on the calcium carbonate (CaCO3) are manufactured. This aimed to develop the mechanical, thermal, antibacterial properties of the NRLF for creating new innovative products and turn the NRLF to be the disinfectant NRLF. Various specific properties were considered, particularly the structure of modified ZnOnp and the antimicrobial activity of foams. It was found that the use of ZnOnp-coated CaCO3 at a ratio of 90:10 (ZnOnp-Ca10) indicated the highest of reinforcement efficiency, crosslink density based on the observed Mooney-Rivlin, and thermal stability. This related to the smaller particles, surface contacting area to the rubber chains, and shorter band gap in the activated states relative to the ZnO and unmodified ZnOnp. This NRLF had also the highest % inhibition of bacterial activity within 1 h by killing 94.01% of gram-native E.Coli bacteria. Relating the indication of the inhibition zone, NRLF filled with ZnOnp-Ca10 also showed strong efficiency for prohibiting the E.Coli and gram-positive S.Aureus bacteria. This affirmed the achievement of the disinfectant NRLF by using less ZnO purity in the foam which can support the preparation of other end rubber foam products.

Challenges associated with cellulose composite material: Facet engineering and prospective

Cellulose is the most abundant polysaccharide on earth. It has a large number of desirable properties. Its low toxicity makes it more useful for a variety of applications. Nowadays, its composites are used in most engineering fields. Composite consists of a polymer matrix and use as a reinforcing material. By reducing the cost of traditional fibers, it has an increasing demand for environment-friendly purposes. The use of these types of composites is inherent in moisture absorption with hindered natural fibers. This determines the reduction of polymer composite material. By appropriate chemical surface treatment of cellulose composite materials, the effect could be diminished. The most modern and advanced techniques and methods for the preparation of cellulose and polymer composites are discussed here. Cellulosic composites show a reinforcing effect on the polymer matrix as pointed out by mechanical characterization. Researchers tried their hard work to study different ways of converting various agricultural by-products into useful eco-friendly polymer composites for sustainable production. Cellulose plays building blocks, that are critical for polymer products and their engineering applications. The most common method used to prepare composites is in-situ polymerization. This help to increase the yields of cellulosic composites with a significant enhancement in thermal stability and mechanical properties. Recently, cellulose composites used as enhancing the incorporation of inorganic materials in multi-functional properties. Furthermore, we have summarized in this review the potential applications of cellulose composites in different fields like packaging, aerogels, hydrogels, and fibers.

Enhancement of Mechanical, Thermal and Morphological Properties of Eleusine Indica Grass Fiber Reinforced Epoxy Composites

ABSTRACT This research focuses on developing a new material by reinforcing chemically treated Eleusine Indica (EI) fiber with epoxy resin as matrix. Composites using varying wt% of treated EI fibers were fabricated taking epoxy as matrix. The effect of chemical treatment and fiber loading on various mechanical properties, thermal, and morphology using a scanning electron microscope (SEM) was investigated. From the results obtained, it is obvious that the mechanical and thermal properties of composites reinforced with chemically treated fibers were enhanced due to fiber surface modification which helps in better bonding with matrix. Moreover, the composites with 20 wt% fiber concentration shows good tensile strength, Young’s modulus, impact strength and was found to be 79.31MPa, 3.84 GPa, 32.24 KJ/m2 respectively. At this fiber loading the composites were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and thermogravimetric (TGA) and compared with untreated fiber reinforced composites and neat epoxy. Finally, the failure analysis of fracture surface due to delimitation, pull-out of the fibers, percentage of voids, and composite fracture has been verified using scanning electron microscope. The findings provide manufacturers and engineers with a general concept of how to employ the composites to make low-weight automotive parts for improved fuel efficiency.

An experimental and computational study of a low-temperature electrolyte design utilizing iodide-based ionic liquid and butyronitrile

A designed low-temperature electrolyte of [BMIM][I]/BuCN/LiI extends the liquidus range down to −150 °C. The complex interactions between imidazolium/iodide ions and nitrile solvent molecule results in enhancement of thermal and transport properties.

Synergistic enhancement in mechanical, thermal, and dielectric properties of PANI@BT/PVDF composites by adding 2D nanoplatelets

AbstractPolymer‐based dielectric composites with simultaneously improved dielectric constant and breakdown strength have great potential applications in energy storage. In this paper, polyaniline@BaTiO3 (PANI@BT) nanoparticles with core‐shell structure are first fabricated by in‐situ chemical oxidative polymerization, and deposited on the surface of two‐dimensional nanoplatelets (graphene oxide [GO] and hexagonal boron nitride nanosheets [BNNS]), which are then utilized to prepare poly(vinylidene fluoride) (PVDF)‐based composites. The presence of 2D nanoplatelets is found to significantly ameliorate the dispersion of PANI@BT particles in the PVDF matrix, and thus endowing the resultant PVDF composites with improved comprehensive performance. The dielectric constant of PANI@BT‐GO/PVDF and PANI@BT‐BNNS/PVDF composites with 50 wt% fillers increase to 124.9 and 169.5 at 100 Hz, accompanied with relatively low dielectric loss. When the filler content is 10 wt%, the breakdown strength of PANI@BT‐BNNS/PVDF achieves 133.5 kV/mm, which is 9.7% and 71.8% higher than that of the pristine PVDF and PANI@BT/PVDF composites. Meanwhile, the tensile stress also reaches the highest value of 43.38 MPa. In addition, the PANI@BT‐GO/PVDF and PANI@BT‐BNNS/PVDF composites present higher thermal decomposition temperature in comparison with PANI@BT/PVDF composites.

Thermal and Tribological Properties Enhancement of PVE Lubricant Modified with SiO2 and TiO2 Nanoparticles Additive

The addition of nanoparticles may have a positive or negative impact on the thermal and tribological properties of base lubricant. The objective of this paper is to investigate the effect of nanoparticle dispersion in lubricant base in relation to its application in refrigeration system compressors. An investigation of tribological and thermal properties of nanolubricants for rolling piston rotary systems was carried out through four-ball tribology tests and thermal conductivity measurements. Nanolubricants dispersed with SiO2 and TiO2 nanoparticles were tested at various concentrations and temperatures. The changes in thermal conductivity and coefficient of friction (COF) were analyzed while wear weight loss was also calculated from wear scar size. A regression model of thermal conductivity enhancement was proposed for both types of nanoparticles. Zeta potential results show that nanolubricants have excellent stability. The thermal conductivity increases by the increment of nanoparticle concentration but decreases by temperature. The R-square for the regression model is more than 0.9952 with an average deviation not more than 0.29%. The COF for SiO2/PVE nanolubricant at 0.003 vol.% reduced 15% from the baseline. The COF for nanolubricants exceeds the result for base lubricants when the concentration is more than the threshold value. The optimum concentration of SiO2 and TiO2 nanoparticles improved the thermal and tribological properties of PVE lubricant and may offer an advantage when applied to refrigeration systems.

Rational Design of Mesoporous Silica (SBA-15)/PF (Phenolic Resin) Nanocomposites by Tuning the Pore Sizes of Mesoporous Silica.

The development of composite materials with functional additives proved to be an effective way to improve or supplement the required properties of polymers. Herein, mesoporous silica (SBA-15) with different pore sizes were used as functional additives to prepare SBA-15/PF (phenolic resin) nanocomposites, which were prepared by in situ polymerization and then, compression molding. The physical properties and structural parameters of SBA-15 with different pore sizes were characterized by N2 adsorption-desorption, X-ray diffraction (XRD), and scanning electron microscopy (SEM). The thermal properties of the SBA-15/PF hybrid were investigated by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). The mechanical, friction, and dynamic mechanical properties of SBA-15/PF nanocomposites were also studied. The results revealed that the pore sizes of SBA-15 have a significant effect on the resulting SBA-15/PF hybrid and SBA-15/PF nanocomposites. The thermal stability of the SBA-15/PF hybrid was dramatically improved in comparison with pure PF. The friction and dynamic mechanical properties of the SBA-15/PF nanocomposites were enhanced significantly. Specifically, the glass transition temperature (Tg) of the nanocomposite increased by 19.0 °C for the SBA-15/PF nanocomposites modified with SBA-15-3. In addition, the nanocomposite exhibited a more stable friction coefficient and a lower wear rate at a high temperature. The enhancement in thermal and frictional properties for the nanocomposites is ascribed to the confinement of the PF chains or chain segments in the mesopores channels.

Mixing carbon nanotubes with asphalt binder through a foaming process toward high-performance warm mix asphalt (WMA)

ABSTRACT This paper investigates mixing carbon nanotubes (CNTs) with asphalt binder through a foaming process to produce high-performance warm mix asphalt (WMA). Two different solvents of ethanol and a water-based surfactant are used to disperse the multi-walled CNTs. Initial morphological assessment of the two CNT solutions showed that a more homogenous dispersion of the CNTs was achieved using the water surfactant solution. The foaming performance, thermal, and rheological properties of the foamed asphalt mixed with different percentages of CNTs are further investigated. The test results showed that a very small amount of CNTs (0.06% ∼ 0.1% in weight of the binder) can effectively enhance the foaming performance for bubble stability without tangibly increasing the rheological properties of the foamed asphalt. The specific heat capacity of the foamed samples was smaller than the neat binder, whereas the glass transition temperature of the foamed samples shifted to a lower temperature as compared to that of the neat binder. The thermal conductivity of the 6% CNTs sample (0.24% wt. in asphalt binder) was improved by two-fold compared with the foamed unmodified asphalt, which indicates the potential of using CNTs in the binder for enhancement of thermal properties in asphalt pavements.

Effect of incorporating multi-walled carbon nanotube and graphene in UHMWPE matrix on the enhancement of thermal and mechanical properties

Effect of incorporating multi-walled carbon nanotube and graphene in UHMWPE matrix on the enhancement of thermal and mechanical properties

Enhanced mechanical, thermal, and barrier properties of poly(lactic acid)/starch composite films using gelatinized starch acetate‐functionalized montmorillonite

AbstractA nanostructured starch acetate–montmorillonite (SA–Mt) hybrid, where gelatinized SA was attached on the exfoliated Mt through Mt hydration expansion, ion exchange between Mt and quaternary ammonium salt, and SA intercalation, was designed and further used for reinforcing poly(lactic acid)/starch acetate (PLA/SA) composite films. Making use of the synergistic effect of SA and Mt, considerable enhancement in mechanical, thermal, and barrier properties for PLA/SA composite films was achieved. The effect of SA–Mt hybrids on structure–property relationships of PLA/SA composite films was investigated. Under an optimal loading of 7 wt% SA–Mt (SA:Mt = 1:1, w/w), the tensile strength, Young's modulus and elongation at break of SA–Mt‐filled composite films were significantly enhanced, about 104%, 73%, and 98% higher than those of PLA/SA, respectively, revealing the synergistic strengthening/toughening effect of SA and Mt; the thermal decomposition temperature and degradation activation energy of such composite film were also enhanced, implying their superior thermal stability. Moreover, the obtained PLA‐based composite films with good water/oxygen barrier performance and excellent biodegradability provide a potential for use as packaging materials.

Novel crystalline reduced graphene oxide/adhesive nanocomposites for enhanced electrical, thermal, dielectric properties and electromagnetic energy absorption application

At present times electromagnetic (EM) pollution is increasing due to a lot of progress and achievements in the electronics field. There is a dire need to develop materials that have greater EM energy absorption/emission properties. We report here the synthesis of a nanocomposite of carbonaceous material, reduced graphene oxide (rGO) with Chloroprene (CP) grafted polymethyl methacrylate (CP-g-pMMA), i.e. rGO/CP-g-pMMA. FTIR confirms the grafting of Chloroprene rubber and the presence of rGO. XRD shows the crystallinity of rGO alone and in the composites as well. SEM images showed smooth texture for neat polymer while nanocomposite showed a leafy appearance of the reduced graphene oxide (rGO). The viscosity of pure CP was 3740 cps while CP-g-pMMA was 1644 cps. A slight decrease was observed after the addition of rGO. Enhancement in thermal properties from 264 °C to 269 °C showed that the composites were thermally more stable than the virgin CP and CP-g-pMMA. The permittivity and alternating current conductivity were checked by Radio Frequency (RF) impedance and material analyzer in the range of (1–1000 MHz) X-band and (1–3 GHz) S-band. The nanocomposites showed the lowest percolation (0.32 vol. %) yet reported. The nanocomposites showed low real and absolute permittivity. The electrical and permittivity analysis of the rGO/CP-g-pMMA nanocomposites revealed that they can be potential candidates for their applications in electronic devices as an absorber.

Enhancement of solar thermal storage properties of phase change composites supported by modified copper foam

Metallic foams, especially copper foams (CF), have been investigated to solve the problems of leaking and low thermal conductivity of phase change materials (PCMs), which helps to promote the application in solar thermal energy storage and thermal management. In this paper, the surface and pore structure of commercial CF was modified by in-situ formed copper nanowires and the introduction of flake graphite (FG). The copper nanowires and embedded FG not only provide greater capillary absorption force to prevent the leakage of liquid paraffin but also enhance the thermally conductive and photothermal conversion efficiency of the phase change composites. The thermal conductivity of the modified CF supported composite PCM reaches 4.1 W m−1 k−1, which is 1.6 times of the un-modified CF supported composite PCM and 20.5 times of paraffin. These results indicate the great application prospects in the fields of solar thermal energy storage and thermal management.

Enhancing the thermal stability and mechanical properties of phenyl silicone rubbers by controlling BN addition and phenyl content

Silicone rubber matrix composites with high thermal stability and flexibility are widely used in electronics and aerospace industries. In this work, boron nitride (BN) was added into the phenyl silicone rubber matrix as the reinforcement, and the influence of both the BN content and phenyl content on the thermal stability and mechanical properties of as-prepared composites was studied. The results showed that the thermal stability and mechanical properties were efficiently enhanced by BN addition, regardless of the phenyl content in the matrix. When the filler content was fixed at 40 wt%, the composite with 20 mol% phenyl showed the highest initial decomposition temperature (T5%) of 454 °C and good flexibility (tensile strength, elongation at break and hardness reached 3.10 MPa, 145% and 56 A). However, the decomposition temperature of 30% weight loss, mass retention rate at 800 °C and mechanical properties were improved for the composite with 50 mol% phenyl. The enhancement in thermal stability and mechanical properties was ascribed to the coupled effects of the interfacial force between the matrix and BN particles as well as the pores inside the composite, which was verified by Fourier transform infrared spectroscopy and scanning electron microscopy.

Anisotropic highly conductive joints utilizing Cu-solder microcomposite structure for high-temperature electronics packaging

The miniaturization of power conversion systems requires high-power density operation of power modules, causing the heat-density increase. Therefore, it is essential to develop bonding technology to realize highly thermally conductive and reliable high-temperature joints. In this study, we propose a novel anisotropic microcomposite (AMC) joint that integrates a lotus-type porous Cu (LPC) sheet and Sn-based solder for high-temperature electronic applications. The AMC joint was successfully fabricated by infiltrating the molten solder into the unidirectional pores of the LPC sheet during a simple reflow process. Steady-state thermal conductivity measurements for a uniquely designed specimen revealed its equivalent thermal conductivity (142.4 W/m·K), 2.5 times higher than the solder. Finite element simulations supported its excellent thermal performance by investigating the heat flux distribution and thermal conductivity prediction that utilize a three-dimensional image-based constructed model. In addition, the aging test at 200 °C for 1008 h clarified a stable shear strength of over 46 MPa. This indicates a reliable mechanical performance at 200 °C, which is only 20 °C below the melting point of the solder. These experimental and numerical studies proved the potential of the novel joint as a high-temperature electronics joint and offered possible mechanisms for its thermal and mechanical property enhancement.