Mixed Fillers Research Articles

Study on the polymerization shrinkage and mechanical-physical properties of dental resin composite modified by polyurethane dimechacrylate and glass flake fillers

ObjectivesWe intend to explore the polymerization shrinkage and mechanical-physical properties of the dental resin composite modified by polyurethane oligomer PU-MA and glass flakes fillers, and provide some experimental information for developing new dental materials. MethodsBased on Bis-GMA/TEGDMA, the new dental resin composite was hand fabricated by combining PU-MA with different content (65 wt% ∼ 75 wt%) of glass flakes/Si-Al-borosilicate glass mixed fillers. The kinetics of polymerization shrinkage was investigated by using an experimental set-up based on laser triangulation. The mechanical-physical properties of specimens after 60 days water immersion and 5000 times thermo-cycles were measured by three-point bending test and micro vickers hardness tester. Data were submitted to one-way ANOVA/LSD-test (α = 0.05). Independent sample T test was used to analyze the data before and after aging. Two-way ANOVA was adopted to analyze the effect of composition and aging condition on the mechanical-physical properties (α = 0.05). ResultsPU-PG-75 % performs lower volume shrinkage (1.35%). As the increase of filler content, the water sorption and solubility increased and the depth of cure decreased significantly (P < 0.05). After aging, the flexural strength, elasticity modulus and vickers hardness of commercial products dropped obviously and PU-PG-75wt% was relatively stable. Conclusions20 wt% PU-MA could decrease the volume shrinkage of dental resin composite effectively. 60 days water immersion and 5000 times thermal cycles simultaneously resulted in a significant reduction in the flexural properties for experimental materials. PU-PG-75 % may have the potential to be taken as a low shrinkage dental resin composite with good mechanical properties. Clinical SignificanceThis new synthesized composite could perform low polymerization shrinkage and better mechanical resistance, which may provide a new idea for improving the lifespan of direct restoration.

Fabrication of PVC-based electromagnetic interference shielding composite film by positively charged SMA enhancing the dispersibility of carbon nanomaterial

To address the weak binding force and poor dispersion stability of carbon (C) nanoparticles in current non-covalent modification methods, we employed organic amine-grafted styrene maleic anhydride copolymers (SMA-N) to modify C nanoparticles (C@SMA-N) through π–π conjugation and positive charge interactions. The obtained C@SMA-N has excellent dispersion in N, N-dimethylacetamide (DMAc), which is attributed to the enhanced steric hindrance and electrostatic repulsion from the grafted organic amine chains. To study the impact of surface modification on the electromagnetic interference shielding effectiveness (EMI SE), C@SMA-N was used as a conductive filler in polyvinyl chloride (PVC) composite films, which exhibits a higher EMI SE performance than pristine C nanoparticles. Particularly, the obtained C@SMA-N using polyether amine (PEA) (C@SMA-PEA) exhibits a better EMI SE performance. By optimizing the SMA-PEA grafting parameters, the PVC/C@SMA-PEA composite films transition from insulators to conductors at a C@SMA-PEA content of 0.3 wt%. To achieve a higher EMI SE performance, the filler content, mixed filler composition, and film thickness were optimized. The results indicate that with a total filler content of 20 wt% and a mixed filler comprising fibrous form carbon nanotubes (CNT) and particles form carbon black (CB) in a 10:1 mass ratio (CB@SMA-PEA to CNT@SMA-PEA), the composite film has a thickness of 0.08 mm and an EMI SE value of 20.2 dB. Increasing the thickness to 0.2 mm enhances the EMI SE value to 31.5 dB. These findings indicate that thinner films have a higher EMI SE performance and promising application prospects in the field of electromagnetic shielding.

Evaluation of Shape Recovery Performance of Shape Memory Polymers with Carbon-Based Fillers.

This study focuses on enhancing the thermal properties and shape recovery performance of shape memory polymers (SMPs) through the application of carbon-based fillers. Single and mixed fillers were used to investigate their effects on the glass transition temperature (Tg), thermal conductivity, and shape recovery performance. The interaction among the three-dimensional (3D) structures of mixed fillers played a crucial role in enhancing the properties of the SMP. These interactions facilitated efficient heat transfer pathways and conserved strain energy. The application of mixed fillers resulted in substantial improvements, demonstrating a remarkable 290.37% increase in thermal conductivity for SMPCs containing 60 μm carbon fiber (CF) 10 wt% + graphite 20 wt% and a 60.99% reduction in shape recovery time for SMPCs containing CF 2.5 wt% + graphite 2.5 wt%. At a content of 15 wt%, a higher graphite content compared to CF improved the thermal conductivity by 37.42% and reduced the shape recovery time by 6.98%. The findings demonstrate that the application of mixed fillers, especially those with high graphite content, is effective in improving the thermal properties and shape recovery performance of SMPs. By using mixed fillers with high graphite content, the performance of the SMP showed significant improvement in situations where fast response times were required.

Mechanical Bonding Properties of Solderable Anisotropic Polymer Composite containing Low-Melting-Point and High-Melting-Point Solder Fillers

In this papers, to enhance the mechanical bonding properties of solderable anisotropic polymer composites (SAPCs) containing low-melting-point solder filler only, a new low-melting-point solder and high-melting-point solder mixed filler filled SAPCs (LH-SAPCs) was proposed, and the influence of the high-melting-point solder filler on the conduction path formation and mechanical bonding properties of the LH-SAPC were investigated. Two types of LH-SAPC were synthesized by adding high-melting-point solder within the low-melting-point solder/high-melting-point solder mixed filler at mixing ratios of 0 and 50 vol% (the volume fraction of low-melting-point solder/high-melting-point solder mixed filler in the polymer composite was 20%), and a bonding test was conducted using QFP. The results exhibited that the LH-SAPC containing high-melting-point solder formed a wide and stable conduction path due to the proper selective conduction path formation behavior by the interaction between molten low-melting-point solder and solid-state high-melting-point solder fillers within the polymer composite with low viscosity condition. Furthermore, the mechanical bonding properties of the LH-SAPC joints containing high-melting-point solder were enhanced compared to that of LH-SAPC containing low-melting-point solder only owing to the precipitation hardening and dispersion strengthening effects due to the increase of fine Bi-rich, Cu&lt;sub&gt;6&lt;/sub&gt;Sn&lt;sub&gt;5&lt;/sub&gt;, and Ag&lt;sub&gt;3&lt;/sub&gt;Sn intermetallic compound particles inside the conduction path.

Biological denitrification performance of a novel sulfur-slow-release carbon source mixed filler

Long-term operation of the sulfur autotrophic denitrification (SAD) process leads to pH reduction, nitrite accumulation, a low nitrogen removal efficiency and excessive sulfate in the effluent. Two slow-release carbon source (SRC) fillers (reactors S2 and S3) consisting of different ratios of hydroxypropyl methyl cellulose, disodium fumarate, polyhydroxy fatty acid ester and Fe3O4 powder were designed to couple SAD with heterotrophic denitrification by using SRC and sulfur particles (reactor S1) as components, combining the advantages of both processes while avoiding secondary pollution. During reactor operation, S3 showed the best denitrification performance. Under the optimal hydraulic retention time of 4 h, different influent nitrate concentrations of 39.92 ± 0.59 mg/L and 20.22 ± 0.45 mg/L achieved average nitrate removal efficiencies up to 88.01 ± 3.62 % and 94.28 ± 2.52 %, and the average denitrification strength were 8.78 mg N/(L·h) and 4.77 mg N/(L·h), respectively. 16S rRNA gene analysis at the genus level showed that the coupled reaction had the highest relative abundance of Thiobacillus associated with SAD, and SAD dominated the coupled system.

Preparation and performance study of thermally conductive coatings with mixed fillers

Preparation and performance study of thermally conductive coatings with mixed fillers

Investigation on the improvement method of ampacity for cable in duct bank: Using the mixed filler with high thermal conductivity material and phase change material

Duct laying is a common cable laying way for the case of not meeting excavation conditions. However, due to the slow air flow rate in the duct, the cable section laying the duct becomes one ampacity bottleneck. Backfilling the duct with the mixed filler of high thermal conductivity material and phase change material is an effective method to solve the problem. In this paper, the simulation models of cable in ducts with backfilling the mixed filler were used to analysis the effect of relative position of cable and duct on temperature distribution and guide the thermal modeling of external environment. Then, the thermal model of cable in duct was conducted and the layered method was adopted to optimize the model. The real cable experiment was designed to verify the accuracy of proposed model. The improvement effect of mixed filler with different thermal conductivity and phase transition region on the cable ampacity were discussed by using the proposed model. The investigations in this paper show that the use of mixed filler material can have a great contribution to ensure the safe operation of cable in duct.

Progress in preparation, processing, and application of high dielectric polypropylene matrix composite materials

AbstractCurrently, in the era of highly advanced information technology, dielectric materials exhibit extensive potential applications in the realms of energy storage and information transmission. Polypropylene stands as one of the most prevalent plastics, lauded for its exceptional mechanical, thermal, electrical, and processing attributes. This article expounds upon the intricate essence and energy storage principles underpinning dielectric materials while pinpointing the areas in which the current dielectric materials necessitate enhancements. It further delves into the study's selection of polypropylene as the base material, with a focus on the impact of individual fillers (ferroelectric ceramics, carbon materials, etc.) and mixed filler nanoparticles on augmenting the dielectric properties of polypropylene. We also delve into pertinent fabrication techniques and methodologies, such as the solution blending method, melt blending method, and in situ polymerization method. In the context of existing polypropylene‐based composite dielectric materials, this article introduces two quintessential applications: insulation materials for direct current cables and metal capacitor films. Finally, it concludes by summarizing the obstacles and challenges that high‐performance polypropylene‐based dielectric composites confront and offers insights into potential avenues for future research.

Review on Frontal Polymerization Behavior for Thermosetting Resins: Materials, Modeling and Application.

The traditional curing methods for thermosetting resins are energy-inefficient and environmentally unfriendly. Frontal polymerization (FP) is a self-sustaining process relying on the exothermic heat of polymerization. During FP, the external energy input (such as UV light input or heating) is only required at the initial stage to trigger a localized reaction front. FP is regarded as the rapid and energy-efficient manufacturing of polymers. The precise control of FP is essential for several manufacturing technologies, such as 3D printing, depending on the materials and the coupling of thermal transfer and polymerization. In this review, recent progress on the materials, modeling, and application of FP for thermosetting resins are presented. First, the effects of resin formulations and mixed fillers on FP behavior are discussed. Then, the basic mathematical model and reaction-thermal transfer model of FP are introduced. After that, recent developments in FP-based manufacturing applications are introduced in detail. Finally, this review outlines a roadmap for future research in this field.

Challenges and recent advances in MOF-based gas separation membranes.

Membrane-based gas separation, characterized by a small footprint, low energy consumption and no pollution, has gained widespread attention as an environmentally friendly alternative to traditional gas separation. Metal-organic-frameworks (MOFs) are considered to be one of the most promising membrane-based gas separation materials because of their large specific surface area and high porosity. One of the hottest studies at the moment is how to utilize the characteristics of MOFs to prepare higher performance gas separation membranes. This paper provides a review of gas separation membranes used in recent years. Firstly, the synthesis methods of MOFs and MOF membranes are briefly introduced. Then, methods to improve the membrane properties of MOFs are described in detail, and include applications of lamellar MOFs, ionic liquid (IL) spin coating, functionalization of MOFs, defect engineering and mixed fillers. In addition, the challenges of MOF-based gas separation membranes are presented, including pore size, environmental disturbances, plasticization, interfacial compatibility, and so on. Finally, based on the current development status of the MOF membranes, the development prospects of MOF gas separation membranes are discussed. It is hoped to provide reliable and complete ideas for researchers to prepare high-performance gas separation membranes in the future.

Interlayer growth of SiC nanowires in graphene aerogel for thermal conductivity enhancement of epoxy resin and its mechanism

AbstractThe chemical reduction method is a simple and popular way to contrast the graphene network to improve the polymer matrix's thermal conductivity. And hybrid thermal conductive fillers composed of two or more mixed fillers through chemical synthesis usually have better thermal conductivity because of the synergistic effort. In this work, silicon carbide nanowires (SiC NWs) in graphene aerogels are synthesized with the chemical vapor deposition method, acting as bridges for phonon transmission between adjacent graphene sheets. The RGO/SiC NWs aerogel‐endowed EP composites have a high thermal conductivity of 3.79 W/mK at a filler loading of 5.5 wt%, and 4.23 W/mK at a filler loading of 7.5 wt%, which is 1895% and 2126% higher than pure EP resin, respectively. Finite element analysis (FEA) is utilized to analyze the heat conduction mechanism of composites at last.

Effects of filler on the microstructure and corrosion of similar and dissimilar gas inert tungsten arc welding aluminum alloys joints

Welding of dissimilar aluminum alloys has been widely used in many industrial applications. However, the selection of filler type still attracts significant interest in the welding research area. The present work concerns the effect of filler metal on the microstructure and corrosion of weld joints of dissimilar aluminum alloys. AA 5083 and AA 6082 alloys were welded by tungsten inert gas welding (GTAW) using filler metals ER 4043 and ER 5356. The microstructure observations and the corrosion test of the weld joints were carried out. Solidification cracks were observed in the ER 4043 weld zone, whereas defect-free joints were obtained using a mix filler welding process. A galvanic corrosion was observed on the boundary between the filler rod ER 4043 weld zone and AA 5083 base alloy. From the corrosion standpoint of view, the using of ER 4043 electrodes is not preferred for welding 5000 series aluminum alloys, whereas ER 5356 filler electrode is more favorable than ER 4043 filler electrode either for dissimilar welding of AA 5083 and AA 6082 alloys or individual welding of both aluminum alloys. No galvanic corrosion is observed between ER 4043 fillers and AA 6082 base alloy.

Investigation of interconnection properties of solderable isotropic polymer composite filled with low- and high-melting-point solder mixed fillers

Investigation of interconnection properties of solderable isotropic polymer composite filled with low- and high-melting-point solder mixed fillers

Thermally Conductive and Electrically Insulating Epoxy Composites Filled with Network-like Alumina In Situ Coated Graphene.

With the rapid development of the electronics industry, there is a growing demand for packaging materials that possess both high thermal conductivity (TC) and low electrical conductivity (EC). However, traditional insulating fillers such as boron nitride, aluminum nitride, and alumina (Al2O3) have relatively low intrinsic TC. When graphene, which exhibits both superhigh TC and EC, is used as a filler to fill epoxy resin, the TC of blends can be much higher than that of blends containing more traditional fillers. However, the high EC of graphene limits its application in cases where electrical insulation is required. To address this challenge, a method for coating graphene sheets with an in situ grown Al2O3 layer has been proposed for the fabrication of epoxy-based composites with both high TC and low EC. In the presence of a cationic surfactant, a dense Al2O3 layer with a network structure can be formed on the surface of graphene sheets. When the total content of Al2O3 and graphene mixed filler reached 30 wt%, the TC of the epoxy composite reached 0.97 W m-1 K-1, while the EC remained above 1011 Ω·cm. Finite element simulations accurately predicted TC and EC values in accordance with experimental results. This material, with its combination of high TC and good insulation properties, exhibits excellent potential for microelectronic packaging applications.

Mechanical Properties of Solderable Polymer Composites with Low- and High-Melting-Point Solder Mixed Filler

A solderable polymer composite (SPC) with a low-melting-point solder (LMPS)/high-melting-point solder (HMPS) mixed filler was formulated to solve the bonding property and reliability problems in an SPC system with an LMPS filler. In addition, the possibility of enhancing the mechanical bonding properties of SPC with LMPS/HMPS mixed fillers was investigated. Three types of SPCs (mixing ratios for LMPS and HMPS: 100:0, 50:50, and 0:100) were prepared, and two types of mechanical property investigations (i.e., ball shear and microhardness tests) were performed to measure the mechanical bonding properties of SPCs according to the LMPS/HMPS mixing ratios. The SPC with an LMPS/HMPS mixed filler exhibited enhanced mechanical bonding properties compared with the Sn-58Bi solder paste and SPC with LMPS or HMPS only due to the change in composition and subsequent microstructure transformation of the solder joint after adding HMPS.

Cyclic thermoresistivity of resin-based carbon fiber bars modified with mixed carbon powder and nano-silica

The addition of conductive fillers to the carbon fiber bar reduces its resistivity and improves electrical stability. Unstable conductivity and susceptibility to ambient temperature change impede the application of this technique in engineering, unless such influence can be eliminated by technical means or precisely predict. In this paper, modified epoxy Resin based carbon fiber bars with 4 sets of different mixed fillers have been designed to evaluate the temperature-resistance effect under different temperature cycles. Results show that the initial volume resistivity reduces due to the incorporation of carbon powder(CP) and nano-silica(NS), and meets the lowest when the CP and NS mass ratio is 1:0.6. The volume resistivity increases linearly with the temperature rising, and reaches the maximum temperature sensitivity coefficient of 78.8%. During the temperature cycle process, the volume resistivity of all specimens first decreases and then increases with the increasing temperature uniformly. The three groups (CP/NS ratio 1:0.2, 1:0.6, and 1:0) share the same PTC effect transition temperature range, from 30 to 60 °C. And for the 1:1 group, the transition temperature is about 0 °C, which is the lowest. Altogether, these enhancements provide avenues for future self-sensing carbon fiber composites in engineering structures.

Impact of Natural Graphite Flakes in Mixed Fillers on the Irradiation Behavior of Fine-Grained Isotropic Graphite

Two forms of fine-grained isotropic graphite, derived from mixed fillers by the isostatic pressing method, NG (filler with 100% natural graphite flake) and 75N25C-G (mixed filler with 75 wt.% natural graphite flake and 25 wt.% calcined coke) were prepared and irradiated with 7 MeV Xe26+ to investigate its irradiation behaviors. Grazing incidence X-ray diffraction and Raman spectra show that the initial graphitization degree of 75N25C-G is lower than that of NG, but the crystallite sizes are larger due to calcined coke in the filler particles. After irradiation, the stacking height of crystallite sizes along c-axis directions (Lc) of NG increased, and Lc of 75N25C-G decreased. This can be attributed to irradiation-induced catalytic graphitization of calcined coke, and is also the reason that the dislocation density of 75N25C-G increases slower than that of NG. After irradiation, the crystallite sizes along a-axis directions (La) of NG and 75N25C-G reduced, but this trend was more obvious in irradiated 75N25C-G; this was closely related to the change of the surface morphology. The results show that the effect of the content of natural graphite flakes in the filler on the initial graphitization degree determines the difference in microstructure evolution caused by irradiation.

Synergistic effects of boron nitride sheets and reduced graphene oxide on reinforcing the thermal conduction, SERS performance and thermal property of polyimide composite films

AbstractPolyimide (PI) composite films with hybrid fillers containing hBN (hexagonal boron nitride) sheets and rGO (reduced graphene oxide) were successfully fabricated by in‐situ polymerization. Herein, hBN sheets and rGO were obtained by ball milling and chemical reduction, respectively. In PI composite films, hBN can be tightly attached onto the surface of rGO via π‐π interaction, which can benefit the construction of heat‐conduction pathways and reduce boundary of heat resistance. The results show that the addition of rGO and hBN could enhance the thermal conductivity by synergistic effects. Specially, hBN and rGO are at the weight ratio of 1:1 and at the total loading of 33 wt%, thermal conductivity of PI composites can reach up to 1.19 Wm−1 K−1, which is 5.61 times higher than that of pure PI. Thermal property and dynamic mechanical property of composite films were also investigated. Besides, compared with pure PI, mixed fillers have obvious surface‐enhanced Raman scattering signals, indicating the synergistic effect of the mixed fillers. Overall, this study gives insights into heat dissipative and high sensitivity analysis components which may be used in the field of high‐temperature micro fabrication.

Hybrid composites based on carbon nanotubes and graphene nanosheets outperforming their single-nanofiller counterparts

The electrical properties of epoxy hybrids filled with Graphene Nanosheets (GNs) and Multi-Wall Carbon Nanotubes (MWCNTs) were investigated by Tunneling Atomic Force Microscopy (TUNA) to understand the correlation between electrical conductivity, on a micro/nano space scale, and the arrangement of the electrically conductive paths through the sample. Two different amounts of mixed fillers, namely below 0.1 wt% and above 0.5 wt%, were dispersed by ultrasonication into a tetrafunctional epoxy matrix at five different MWCNTs:GNs mix ratios. At a low amount of nanoparticles, 0.1 wt%, the hybrid nanofiller concentration allows for detecting a very interesting synergy toward an increase in the electrical conductivity of several orders of magnitude, and a lowering of the Electrical Percolation Threshold (EPT). Both the computational and experimental results highlight that, owing to the hybrid MWCNT/GNs network formation, the hybrid nanocomposites outperform their single-nanofiller counterparts.

A computational model for characterizing electrical properties of flexible polymer composite filled with CNT/GNP nanoparticles

Ultrasensitive flexible sensors with a high sensitivity in a broad pressure range are required for various applications in flexible electronics era. Hybrid nanocomposites reinforced by carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs) have shown improvements in cost-effectiveness and electrical properties. Simulating the hybrid nanocomposites is of vital significance since it offers an insight into the functional and electrical performance of flexible sensors. In this paper, the structural evolution of CNT and GNP nanocomposites in response to mechanical deformation is theoretically modeled to clarify the synergy mechanism of two nanofillers. The influence of the microstructure parameters including the aspect ratio (AR) and volume ratio of CNT and GNP on the conductivity and sensitivity of the flexible composites are comprehensively analyzed and discussed. Analytical simulation and experimental results show that the conductivity of the mixed filler system fails to outperform any individual system, but shows superiority regarding to the piezoresistive sensitivity. Besides, the Poisson's ratio of the polymer is innovatively introduced to characterize the elastic deformation of the nanocomposites. It was found that the Poisson's ratio of the polymer had the negative correlation with the sensitivity of the CNT/GNP nanocomposite. This work provides considerable guidance for the design and manufacture of flexible piezoresistive sensors.