Spherical Filler Research Articles

Effects of spherical fillers reinforcement on the efficacy of thermal conductivity in epoxy and polyester matrices: Experimental validation and prediction using finite element method

AbstractThe creation of a theoretical heat conduction model for polymers embedded with spherical inclusions is described in this study. It also contains the experimental confirmation of the suggested correlation for utilizing the model to estimate the effective thermal conductivity (K) of such composites. According to ASTM‐E‐1530, composites are made with varying amounts of aluminium oxide and pine wood dust reinforced in polyester resin. The effective thermal conductivities (Keff) of the composites are then determined using the Unitherm TM model 2022. Ansys 19.R2 software is used to evaluate the effective thermal conductivity of these composites with a uniform filler distribution, while Digimat‐FE software is used determine the thermal conductivity values of such particle filled polymer composites with a random filler distribution. After comparison and validation with experimental data, these values are shown to be fairly good agreement with the theoretical values from the suggested correlation. The investigation is further expanded to determine the thermal conductivities for epoxy composites using wood apple shell dust and coir dust particle. Also epoxy and polyester composites reinforced with SiO2 and TiO2 have been investigated in the similar manner. The main thrust of this report to validate the numerical results of composites by varying numerous polymers. The thermal conductivity all the composites grow monotonically with increase in filler content. The thermal conductivity of silicon dioxide, titanium oxide, and aluminium oxide filled epoxy composites is measured as 1.5, 7, and 35 W/m‐K respectively.Highlights In this study spherical fillers are successfully used as a potential filler material in polyester composites The thermal conductivity predicted by proposed mathematical model of polyester is validated with measured value and found better agreement. The Ansys 19.R2 and digimat software are used to predict the thermal conductivity values of these composites. The mathematical model is further used to predict thermal conductivity of epoxy composites to check the accuracy of the model.

Study on the impact of hybridization of spherical fillers with size differences and sheet fillers on the thermal conductivity and anticorrosive performance of composite coatings

AbstractThe improvement of anti‐corrosion performance and enhancement of functionality in anti‐corrosion coatings are essential. Boron nitride (BN), as a two‐dimensional thermal conductive filler, is incorporated into composite coatings to provide corrosion resistance and thermal conductivity. The combination of BN with zero‐dimensional filler alumina (Al2O3) proves to be an effective method for enhancing the thermal conductivity of composite coatings. In this study, micro alumina (Micro‐Al2O3) and/or nano alumina (Nano‐Al2O3) were combined with BN to be integrated into waterborne epoxy resin (WER), resulting in different composite coatings (BN@Micro‐Al2O3/WER, BN@Nano‐Al2O3/WER, and BN@Micro‐Al2O3/Nano‐Al2O3/WER). The influence of different hybrid modes of two‐dimensional and zero‐dimensional thermal conductive fillers on corrosion resistance and thermal conductivity was discussed. The composite coating BN@Micro‐Al2O3/Nano‐Al2O3/WER exhibits the highest thermal conductivity at 0.789 W/mK with a filler loading of 30 wt% BN, 4 wt% Micro‐Al2O3, and 6 wt% Nano‐Al2O3. Meanwhile, the composite coating BN@Nano‐Al2O3 demonstrates superior anti‐corrosion performance at a filler loading of 20 wt% BN and 10 wt% Nano‐Al2O3. After immersion in a 28‐day period in a NaCl solution with a concentration of 3.5%, the impedance modulus remains above 109 Ω·cm2, while corrosion current density is measured at 7.3367 × 10−8 A/cm2. The hybrid mode involving two‐dimensional and zero‐dimensional thermal conductive fillers can effectively improve the composite coatings' corrosion resistance and thermal conductivity. There are variations in the optimal hybrid methods for incorporating two‐dimensional and zero‐dimensional thermal conductive fillers to enhance anti‐corrosion and heat conduction effectiveness of coatings.Highlights The properties of coating is improved by the incorporation of BN and Al2O3. The prepared coating performs good thermal conductivity. The synergy of BN and Al2O3 can improve thermal conductivity significantly. The obtained coating performs good corrosion resistance. The synergy of BN and Al2O3 can also improve anti‐corrosion effectively.

Conductivity of Diblock Copolymer System Filled with Conductive Fillers

AbstractThe electrical response of the insulating diblock copolymer system (DBC) filled with conductive spherical fillers is investigated to the variation of the following factors: i) composite temperature; ii) affinities of fillers for copolymer blocks; iii) interaction between fillers. By performing the consistent phase‐field and Monte‐Carlo simulations of the filled DBC system, this article quantitatively demonstrates that the distribution of fillers in DBC essentially depends on the complicated interplay of the above three factors. The obtained distribution of filler particles, in turn, proves to be directly related to the electrical response of the DBC‐particle composite, calculated by the developed model. In particular, the order‐disorder transition in the DBC system has been found to co‐occur with the insulator‐conductor transition in the filler network providing a sufficient difference between the affinities of fillers for dissimilar DBC blocks. The order–order transition between the lamella and cylindrical morphologies of DBC has been found to cause a spike in the composite conductivity.

Soft, Tough, Antifatigue Fracture Elastomer Composites with Low Thermal Resistance through Synergistic Crack Pinning and Interfacial Slippage.

Soft elastomer composites are promising functional materials for engineer interfaces, where the miniaturized electronic devices have triggered increasing demand for effective heat dissipation, high fracture energy, and antifatigue fracture. However, such a combination of these properties can be rarely met in the same elastomer composites simultaneously. Here a strategy is presented to fabricate a soft, extreme fracture tough (3316J m-2) and antifatigue fracture (1052.56J m⁻2) polydimethylsiloxane/aluminum elastomer composite. These outstanding properties are achieved by optimizing the dangling chains and spherical aluminum fillers, resulting in the combined effects of crack pinning and interfacial slippage. The dangling chains that lengthen the polymer chains between cross-linked points pin the cracks and the rigid fillers obstruct the cracks, enhancing the energy per unit area needed for fatigue failure. The dangling chains also promote polymer/filler interfacial slippage, enabling effective deflection and blunting of an advancing crack tip, thus enhancing mechanical energy dissipation. Moreover, the elastomer composite exhibits low thermal resistance (≈0.12K cm2 W-1), due to the formation of a thermally conductive network. These remarkable characteristics render this elastomer composite promising for application as a thermal interface material in electronic devices.

Development of copper-boron nitride core-shell structured fillers and surface treatment for thermally conductive composites

Core-shell structured copper-boron nitride (Cu@BN) spherical fillers were synthesized to fabricate thermally conductive composites. To enhance the interaction between the fillers and the matrix, polysilazane (PSZ) was coated on the surface of the filler. The resultant composite exhibited remarkable characteristics, including a substantial tensile strength of 32.36 MPa, excellent electrical insulation properties, and impressive thermal conductivity of 3.47 W/mK. When applied in a light-emitting diode (LED) application, the composite effectively managed heat, reducing the operating temperature by 34 °C. The epoxy/PSZ-Cu@BN composites hold great promise for improving thermal management in electronic devices.

Thermal conductivity of composites with heterogeneous fillers under effects of interface thermal resistance

There has been significant interest in enhancing the effective thermal conductivity (ETC) of polymer by incorporating spherical hybrid fillers. However, the effect of interface thermal resistance (Rc) on the ETC of composites has not been investigated. In this paper, this effect is investigated. Meanwhile, the combined effects of filler thermal conductivities (K1, K2), filler sizes (V1, V2), the Rc sum (R*c1 + R*c2) and the Rc ratio (R*c1/R*c2) are also considered. The results show that for a given K1, K2 and R*c1 + R*c2, the ETC is largely independent of R*c1/R*c2 when the R*c1 + R*c2 is less than 10−4. However, when the R*c1/R*c2 ranges from 10−2 to 10, the competing effects of hybrid fillers Rc have a significant effect on the ETC. The ETC is not affected by the TC of filler-1 when K1 exceeds a critical value of 103, instead becoming dependent on K2. For each sum of Rc, there exists a critical value of R*c1/R*c2 where the ETC reaches its nadir, this critical value is influenced by the R*c1 + R*c2, V and K of two fillers. The Rc of fillers with high K is <10−2, it is not feasible to improve the ETC by continuing to reduce its Rc, this value is 10−4 for fillers with low K.

Frequency-Selective Radar-Absorbing Composites Using Hybrid Core-Shell Spheres.

Radar-absorbing materials (RAMs) covering the exterior surfaces of installed parts and assembled devices are crucial in absorbing most incident electromagnetic (EM) waves. This absorption minimizes reflected energy, thereby enhancing pilot safety and the stability of operating electronic devices without interference. Particularly, active stealth aircraft require effective protection from near- and far-field EM radiation across a wide spectrum of frequencies from both highly integrated electronic components and advanced enemy radars. Studies of RAMs often prioritize absorption over crucial tunability in frequency selectivity, revealing a research gap. In this study, we propose smart RAMs with frequency-selective absorption capabilities. Our approach involves incorporating two types of core-shell spheres in a polymer matrix, which feature shells of either wave-diffuse reflecting metal or wave-absorbing graphene. The key innovation lies in the ability to tailor absorption frequencies in the X-band range (8.2-12.4 GHz) by adjusting the interstitial spaces between the metallic spheres while the scattered waves are efficiently attenuated by graphene networks in the composites. On a metal substrate, a 2 mm-thick composite with an optimized structural composition and ratio of the two types of spheres exhibits a maximum absorption efficiency of 99.3%, effectively trapping and extinguishing incident waves. Combined with the structural tunability and frequency-selective properties of spherical fillers, our approach provides a scalable and effective method for creating functional isotropic coverings on various metallic surfaces.

Shape engineering for improved gas separation: Computation-driven insights on harnessing platonic particles in mixed-matrix membranes

Recently, there has been a growing focus on the significance of mixed matrix membranes (MMMs) in the domain of gas separation processes. It is well known that, the integration of structurally diverse porous materials into a polymeric matrix intensifies the influence of filler structural sensitivity during the performance evaluation of MMMs. In this study, a computational approach utilizing voxel-based finite element method (FEM) was employed for a systematic investigation of the impact of Platonic shapes used as fillers on the criteria that dictate the design of optimal membranes. The assessment of single gas transport in MMMs containing randomly distributed fillers has confirmed that filler particles with varying sphericity, but the same volume, can significantly influence the effective permeability of MMMs. A reduction in filler particle sphericity, such as in the case of a tetrahedral structure compared to a spherical one, results in a substantial enhancement of effective permeability, primarily due to the introduction of more interconnected pathways. This effect becomes increasingly pronounced at higher filler loading fractions and filler-to-polymer ratios. Furthermore, binary gas transport assessments of MMMs established that filler particle shapes have a considerable influence over the optimal filler–matrix combination, particularly in the context of phase gas transport compatibility, aimed at achieving maximal selectivity in gas mixtures. Filler particles with lower sphericity yield a higher maximum selectivity; however, this is achieved with a partially higher filler-to-polymer permeability for faster gas flow compared to spherical filler particles. This research offers valuable insights for the strategic enhancement of permeability and selectivity in MMMs through the integration of structurally diverse porous materials.

Regulated orientation and exfoliation of flaky fillers by close packing structures in polymer composites for excellent thermal conduction and EMI shielding

Efficient heat dissipation and electromagnetic interference (EMI) shielding are essential demands on packaging intensively integrated circuits in advanced electronics. Multicompetent polymer composites with thermal conduction and EMI shielding capacity have attracted tremendous interest in the material science community. Herein, we report the preparation of thermally conductive polymer composites with superior EMI shielding effectiveness (SE) by building a 3D interconnected conductive network under close-packing circumstances. The build of the 3D network relies on the coordinated stacking of flaky and spherical fillers, where the asymmetric graphite flakes (FG) are confined in the interstitial regions of the close-packing structures of hollow glass microspheres (HGμS). The “rigid” close-packing structure of HGμS inhibits the in-plane orientation of FG along the flow direction during melt processing and facilitates the exfoliation of FG under external forces producing a conductive network with enhanced interconnectedness. The model system comprised of thermoplastic polyurethane (TPU), FG and HGμS has attained in-plane and through-plane thermal conductivity of 20.54 W m−1 K−1 and 6.55 W m−1 K−1 with 30 vol% FG (while maintaining a low mass density of 1.15 g cm−3, identical to neat TPU). Meanwhile, a high EMI SE of 69 dB has been achieved at a thickness of 1 mm.

Rheology of Highly Filled Polymer Compositions-Limits of Filling, Structure, and Transport Phenomena.

The current state of the rheology of various polymeric and other materials containing a high concentration of spherical solid filler is considered. The physics of the critical points on the concentration scale are discussed in detail. These points determine the features of the rheological behavior of the highly filled materials corresponding to transitions from a liquid to a yielding medium, elastic-plastic state, and finally to an elastic solid-like state of suspensions. Theoretical and experimental data are summarized, showing the limits of the most dense packing of solid particles, which is of key importance for applications and obtaining high-quality products. The results of model and fine structural studies of physical phenomena that occur when approaching the point of filling the volume, including the occurrence of instabilities, are considered. The occurrence of heterogeneity in the form of individual clusters is also described. These heterogeneous objects begin to move as a whole that leads to the appearance of discontinuities in the suspension volume or wall slip. Understanding these phenomena is a key for particle technology and multiphase processing.

High‐Yield‐Stress Particle‐Stabilized Emulsion for Form‐Factor‐Free Thermal Pastes with High Thermal Conductivity, Stability, and Recyclability

AbstractThermal pastes, thermally conductive fillers dispersed in liquid matrices, are widely used as thermal interface materials (TIMs). TIMs transfer heat generated from electronics to the surroundings, ensuring optimal operating temperatures. Thus, it is crucial to obtain high thermal conductivity (TC) by forming a continuous heat‐conduction pathway through interconnected filler‐networks within the TIM. Therefore, for paste‐type TIMs with spherical fillers, high TC can only be realized at sufficiently high filler loadings (&gt;60 vol%). However, the pastes bearing such high filler loadings are thick, stiff, and less applicable. To these ends, particle‐stabilized emulsions composed of immiscible liquids (silicone oil and glycerol) and spherical alumina are utilized as thermal pastes. Owing to this structure, the resulting form‐factor‐free thermal paste exhibits higher TC and stability than a simple mixture consisting of alumina and a single‐liquid‐matrix (either silicone oil or glycerol). Furthermore, the high applicability of the emulsion‐type pastes enables syringe extrusion, 3D printing, multiple cycles of reprocessing/molding, and eco‐friendly recycling.

Morphology engineering of heterogeneous carbon particles toward boosted dielectric polarization for ultrathin and strong loss absorber

Micron-carbon particles with polymorphous concave polyhedron have been easily prepared via high-efficiency spray drying-carbonization process, which is aimed at boosting dielectric polarization toward the feature of high the real part of the complex permittivity accompanied with low level dielectric loss for achieving ultrathin absorber. In addition, the effect of geometry on the microstructure and microwave absorption (MA) performances was systematically studied for the first time. A minimum reflection loss (RLmin) of −55.07 dB under ultrathin thickness of 1.23 mm and a broad effective absorption bandwidth (<-10 dB) of 4.0 GHz at 1.3 mm were obtained for composites filled with polymorphous concave polyhedral carbon particles, meanwhile the loading contents have been reduced from 30 wt% spherical filler to 22.5 wt% polymorphous concave polyhedral filler. Optimized MA performance with strong loss and ultrathin thickness has been identified as attenuation mechanism dominated by interference cancellation and assisted by dielectric loss for the first time. This work not only provides an insight to realize engineering applications of carbonaceous absorbents but also reveals the intrinsic attenuation mechanism of microwave absorbing materials.

Effect of fillers on the microphase separation in polyurethane composites: A review

AbstractThe microphase separation behavior of polyurethane (PU) strongly affects its mechanical, thermal, electrical, and other functional properties. Adding fillers to change the degree of microphase separation (DPS) in PU is a convenient and efficient method. Although many scholars have tried to regulate the microphase separation of PU by adding fillers, there are still many controversies about the effect. In this review, we classify commonly used fillers into three categories according to their morphology: spherical fillers, fibrous fillers, and layered fillers, and summarize their effects on the microphase separation behavior of PU. We explore the similarities and differences in the mechanisms by which different fillers affect the microphase separation of PU, and find that the polarity, morphology, size of fillers, and preparation method have a significant impact on the degree of microphase separation in PU. The impact of microphase separation on the mechanical properties of PU has also been summarized to illustrate their close relationship. We hope that these summaries will provide some guidance for the development of new high‐strength and multifunctional PU composites.Highlights Summarized recent research progress on effect of common fillers on DPS of PU. Common fillers are classified into three categories based on their morphology. Common laws of the fillers impact on the DPS are classified and discussed. The close relationship between DPS and mechanical properties is reviewed. Provided information for high‐strength and multifunctional PU development.

Conformal BN coating to enhance the electrical insulation and thermal conductivity of spherical graphite fillers for electronic encapsulation field

Herein, we provided a structural design strategy of constructing boron nitride (BN) conformal coating on the surface of the spherical graphite (SG) particles via precursors deposition and high-temperature pyrolysis method to achieve improved electrical insulation. The dissolved and reprecipitated BN precursors were uniformly deposited on the surface of polydopamine-modified SG through strong adhesion and hydrogen bonding of polydopamine. Then, the homogeneous and dense BN ceramic coating was formed on the surface of SG via slow pyrolysis at high temperature. The complete encapsulation of BN coating prevents the SG particles directly contacting with each other in the silicon rubber (SR) matrix to retain electrical insulation of SR composites. Furthermore, the BN coating flattens the uneven surface of SG so that the fillers are better infiltrated by the SR matrix. The small specific surface area of SG@BN filler particles is beneficial to significantly reduce the generation of the filler/matrix interfaces and weaken phonons scattering, thus decreasing the thermal boundary resistance. As a result, the thermal conductivity of prepared SG@BN/SR composites is up to 3.65 W m−1 K−1, which is 20.2-fold of that of pure SR with 0.18 W m−1 K−1. And the SG@BN/SR composites exhibit a satisfactory breakdown voltage of 5.6 kV mm−1, which is much higher than 1.1 kV mm−1 for the original SG/SR composites. This strategy is worth using for reference to extend the application of graphite-type fillers in the electronic encapsulation field.

A Multiscale Hollow Spherical LATP Active Filler Improves Conductivity and Mechanical Strength in Composite Solid Electrolytes

The performance of composite solid electrolytes (CSEs) composed of poly(ethylene oxide) and ceramic oxide-type solid electrolyte fillers has been shown to be highly dependent on the available surface area of filler inside of the composite. This is due to the formation of new transport pathways in the polymer-ceramic interphase, a region some tens of nanometers between the bulk polymer and ceramic surface. The small volume of this interphase relative to the size of traditional particles presents a design problem: Using micron-scale filler particles, a nm-thick interphase can never occupy a meaningful volume fraction of the composite. Thus, nanoparticles are often used in CSEs. However, the inevitable agglomeration of nanoparticles prevents a continuous interphase from forming even in the best dispersion conditions. Therefore, efforts to explore and exploit this synergistic transport mechanism have so far relied on careful, slow, and expensive methods designed to yield a continuous polymer-ceramic interphase between electrodes, e.g., cast nanowires, infiltrated 3D-structures, or templating.In this work we report a ceramic solid electrolyte, Li1.3Al0.3Ti1.7(PO4)3 or LATP, with a multiscale hollow spherical microstructure, designed to maximize the available continuous interphase volume in the composite. The hollow spherical structure is achieved by synthesizing LATP particles onto 10-15 μm carbon spheres, then subsequently pyrolyzing the carbon to achieve micron-scale hollow spheres composed of nano-scale LATP particles. This structure effectively prevents the bulk agglomeration of individual LATP particles, while still allowing for long, continuous interphase pathways. Importantly, the non-directionality of the filler means that the manufacture of the films remains simple.The hollow spherical microstructure of the filler had significantly enhanced the room temperature conductivity of the composite solid electrolyte, to 1.64 x 10-4 S/cm – the highest reported for an LATP-containing CSE with micron-scale filler particles. The mechanical properties, thermal stability, and electrochemical stability of the composite solid electrolyte were also significantly enhanced. This approach is a promising method to exploiting the synergistic transport in composite solid electrolytes while maintaining their excellent manufacturability.

The Effect of Porosity on the Thermal Conductivity of Highly Thermally Conductive Adhesives for Advanced Semiconductor Packages.

This study suggests promising candidates as highly thermally conductive adhesives for advanced semiconductor packaging processes such as flip chip ball grid array (fcBGA), flip chip chip scale package (fcCSP), and package on package (PoP). To achieve an extremely high thermal conductivity (TC) of thermally conductive adhesives of around 10 Wm-1K-1, several technical methods have been tried. However, there are few ways to achieve such a high TC value except by using spherical aluminum nitride (AlN) and 99.99% purified aluminum oxide (Al2O3) fillers. Herein, by adapting highly sophisticated blending and dispersion techniques with spherical AlN fillers, the highest TC of 9.83 Wm-1K-1 was achieved. However, there were big differences between theoretically calculated TCs that were based on the conventional Bruggeman asymmetric model and experimentally measured TCs due to the presence of voids or pores in the composites. To narrow the gaps between these two TC values, this study also suggests a new experimental model that contains the porosity effect on the effective TC of composites in high filler loading ranges over 80 vol%, which modifies the conventional Bruggeman asymmetric model.

Isolated effect of filler particle size on surface properties of experimental resin composites before and after toothbrush abrasion.

This study aimed to isolate the relationship between filler size and the surface properties of roughness and gloss before and after toothbrush abrasion for experimental resin-based composites (RBCs) containing uniform spherical fillers. Five experimental light-cured RBCs with different spherical filler sizes and three commercial RBCs were studied. Forty specimens were polished using silicon carbide papers. Gloss was measured after 0, 90, 180, and 360 min of simulated toothbrushing, and surface roughness was measured before and after 360 min of toothbrushing. Two-way ANOVA/Tukey's multiple comparison tests were used to compare the RBCs, and the correlation between particle size and surface roughness or gloss was also determined. After polishing and toothbrushing, RBCs with smaller fillers exhibited significantly higher gloss and lower surface roughness, and RBCs with larger fillers exhibited lower gloss and higher surface roughness. A significant correlation was found between filler particle size and gloss and surface roughness both before and after toothbrush abrasion. Gloss of RBCs containing fillers with larger particle sizes was significantly reduced. After toothbrushing abrasion, the surface roughness increased for all RBCs, except those containing the finest-sized fillers. The particle size of the filler is a critical determinant of the surface roughness and gloss of RBCs, after polishing and after toothbrushing. Increased surface roughness caused by toothbrush abrasion reduces the gloss of resin-based composites. Resin-based composites containing finer fillers best maintain glossiness after routine tooth brushing.

Elastomer Nanocomposites: Effect of Filler-Matrix and Filler-Filler Interactions.

The reinforcement of elastomers is essential in the rubber industry in order to obtain the properties required for commercial applications. The addition of active fillers in an elastomer usually leads to an improvement in the mechanical properties such as the elastic modulus and the rupture properties. Filled rubbers are also characterized by two specific behaviors related to energy dissipation known as the Payne and the Mullins effects. The Payne effect is related to non-linear viscoelastic behavior of the storage modulus while the Mullins or stress-softening effect is characterized by a lowering in the stress when the vulcanizate is extended a second time. Both effects are shown to strongly depend on the interfacial adhesion and filler dispersion. The basic mechanisms of reinforcement are first discussed in the case of conventional rubber composites filled with carbon black or silica usually present in the host matrix in the form of aggregates and agglomerates. The use of nanoscale fillers with isotropic or anisotropic morphologies is expected to yield much more improvement than that imparted by micron-scale fillers owing to the very large polymer-filler interface. This work reports some results obtained with three types of nanoparticles that can reinforce rubbery matrices: spherical, rod-shaped and layered fillers. Each type of particle is shown to impart to the host medium a specific reinforcement on account of its own structure and geometry. The novelty of this work is to emphasize the particular mechanical behavior of some systems filled with nanospherical particles such as in situ silica-filled poly(dimethylsiloxane) networks that display a strong polymer-filler interface and whose mechanical response is typical of double network elastomers. Additionally, the potential of carbon dots as a reinforcing filler for elastomeric materials is highlighted. Different results are reported on the reinforcement imparted by carbon nanotubes and graphenic materials that is far below their expected capability despite the development of various techniques intended to reduce particle aggregation and improve interfacial bonding with the host matrix.

Enhancement of Isotropic Heat Dissipation of Polymer Composites by Using Ternary Filler Systems Consisting of Boron Nitride Nanotubes, h-BN, and Al2O3.

In this research article, a poly(dimethylsiloxane) (PDMS)-based composite was postulated adapting an interactive ternary filler system consisting of Al2O3, hexagonal boron nitride (h-BN), and boron nitride nanotubes (BNNT) to construct a continuous three-dimensional (3D) structure for thermal attenuation. Al2O3 was imposed as a main filler, while h-BN and BNNT were assimilated to form interconnected heat conduction pathways for effective thermal dissipation. The structured framework articulates a profound improvement in isotropic thermal conductivity considering both axial and radial heat dissipation. The presence of h-BN entails uniform heat distribution in a planar mode, eliminating the occurrence of hotspots, while BNNT constructed a connecting phonon pathway in various directions, which insinuates effective overall thermal transport. The generated ternary filler composites attained an isotropic ratio of 1.35 and a thermal conductivity of 7.50 W/mK, which is a 36-fold (∼3650%) increase compared to neat PDMS resin and almost 3-fold (∼297%) that of the Al2O3 unary filler composite and ∼53% that of its binary counterpart, partaking interfacial thermal gaps of ∼36.15 and ∼62.24% on practical heating performance relative to its counterparts. Moreover, the incorporation of BNNT on a traditional spherical and planar filler offers an advantage not only in thermal conductivity but also in thermal and structural stability. Improvement in thermal stability is stipulated due to a melting point (Tm) shift of ∼11 °C upon the assimilation of BNNT. Mechanical permeance reinforcement was also observed with the presence of BNNT, showcasing a 31.5% increase in tensile strength and a 53% increase in Young's modulus relative to the singular filler composite. This exploration administers a new insight into heat dissipation phenomena in polymeric composites and proposes a simple approach to their design and assembly.

Preparation and Characterization of Thermal-Insulating Microporous Breathable Al/LLDPE/CaCO3 Composite Films.

Breathable films were prepared based on linear low-density polyethylene (LLDPE), calcium carbonate (CaCO3), and aluminum (Al; 0, 2, 4, and 8 wt.%) using extrusion molding at a pilot scale. These films must generally be able to transmit moist vapor through pores (breathability) while maintaining a barrier to liquids; this was accomplished using properly formulated composites containing spherical CaCO3 fillers. The presence of LLDPE and CaCO3 was confirmed by X-ray diffraction characterization. Fourier-transform infrared spectroscopy results revealed the formation of Al/LLDPE/CaCO3 composite films. The melting and crystallization behaviors of the Al/LLDPE/CaCO3 composite films were investigated using differential scanning calorimetry. Thermogravimetric analysis results show that the prepared composites exhibited high thermal stability up to 350 °C. Moreover, the results demonstrate that surface morphology and breathability were both influenced by the presence of various Al contents, and their mechanical properties improved with increasing Al concentration. In addition, the results show that the thermal insulation capacity of the films increased after the addition of Al. The composite with 8 wt.% Al showed the highest thermal insulation capacity (34.6%), indicating a new approach to transform composite films into novel advanced materials for use in the fields of wooden house wrapping, electronics, and packaging.