Single Filler Research Articles

Study of frequency dependence properties of CCTO-BT/polymer composites

In the current study, the calcium copper titanate (CCTO)/polymer, barium titanate (BT)/polymer, and CCTO-BT/polymer composites with variable volume fractions of CCTO and BT are fabricated using hand lay-up and compression molding processes. The composites are characterized for the frequency dependence on dielectric properties, conductivity, impedance spectroscopy, and electrical modulus. X-ray diffraction (XRD) patterns of CCTO-BT/polymer composite samples confirmed the presence of both CCTO and BT ceramic samples separately. The dielectric properties of hybrid CCTO-BT/polymer composites with 10 vol% CCTO 10 vol% BT, 12 vol% CCTO 8 vol% BT, and 8 vol% CCTO 12 vol% BT was found relatively better than those of the single ceramic filler reinforced polymer composites. AC conductivity analysis shows a significant improvement in the results of hybrid filler-filled CCTO-BT/polymer composites in comparison with single filler-filled polymer composites. Thus, impedance analysis confirms higher insulating properties for 8 vol% CCTO 12 vol% BT and 12 vol% CCTO 8 vol% BT hybrid CCTO-BT/polymer composites with respect to the single and other hybrid ceramic polymer composites. The analysis suggests the hybrid CCTO-BT/polymer composites to be adopted as a possible dielectric material for energy storage devices and other electronic applications.

Thermo‐mechanical property enhancement of rigid polyurethane foam using silica and alumina as hybrid fillers over single filler

AbstractSilica and alumina particles were loaded in the rigid polyurethane foam composite as hybrid fillers. After the successful addition of silica and alumina as fillers, various properties of the foam composite were enhanced up to a particular weight percentage (7.5 wt% of silica and alumina each) with respect to alumina loaded foams. Hard urea domains are well distributed in the urethane matrix which indicates the absence of the peak representing H‐bonded urea in the Fourier‐transform infrared spectroscopy results. The addition of hybrid fillers into the rigid polyurethane foam matrix improved the compressive strength of the foam composite by 14% in comparison to alumina loaded foams due to the synergistic effect of the hybrid fillers. The foam composite at 7.5 wt% loading of hybrid fillers was successful in decreasing the thermal conductivity by 9% with respect to the thermal conductivity of the unloaded foam. There was a reduction in the gross calorific value up to 7% in the hybrid filler loaded foam composite when compared with that of the alumina loaded composite. Hence, hybrid fillers should be added to enhance the composite's properties by a greater extent.Highlights From the compressive test results, an increase in the compressive strength up to 14% was observed in the samples loaded with hybrid fillers with respect to the samples loaded with alumina due to the synergistic effects of the two fillers. For the foam composite loaded with alumina, the gross calorific value decreased up to 6% when compared to the unloaded foam. The gross calorific value decreased by a further 7% when hybrid fillers were added to the polyurethane foam composite with respect to the alumina loaded foam composite. The foam composite loaded with 7.5 weight % of hybrid fillers had lower values of thermal conductivity when compared with that of the unloaded polyurethane foam. We propose the addition of both alumina and silica as hybrid filler particles as they enhanced the various properties of the polyurethane foam composite to a greater extent than the addition of alumina particles as a single filler and have potential to replace unloaded polyurethane foams in different applications.

Thermomechanical and Dielectric Properties Relationship of Hybrid Carbon Black and Nano Silica Epoxy Composites

Multifunctional materials refer to the types of materials that possess enhanced mechanical, electrical, and thermal properties. In this work, nano silica and Carbon Black (CB) are added to epoxy polymer as an effort to improve the thermomechanical and dielectric properties of the composites. Filler loadings are varied from 0.1 wt.%, up till 5 wt.%. The thermomechanical properties are measured from Dynamic Mechanical Thermal Analysis (DMTA) while the dielectric properties are measured from Vector Network Analyser (VNA). The synergistic effects of combining both fillers (keeping them at 1:1 wt.% ratio) are also assessed. It was found that the value of glass transition temperature (Tg) increased from 56.85°C (neat epoxy) to 59.8°C (5 wt.% CB). The Tq values further increased to 64.7°C, for 5 wt.% hybrid fillers (2.5 wt.% silica + 2.5 wt.% CB), demonstrating the synergistic effects by employing dual fillers. By adding single and dual fillers, the values of storage Modulus, E’ remains almost constant for both glassy (40°C) and rubbery region (100°C), regardless of the loadings employed. The values of real permittivity, er’ was also measured for dual fillers in the frequency range between 300 kHz to 18 GHz. The highest value of er’ was 5.5 F/m, which was measured for both 1.5 mm and 2.0 mm sample thickness of 5 wt.% hybrid fillers (2.5 wt.% silica + 2.5 wt.% CB). This study highlights the thermomechanical and dielectric properties improvement of epoxy composites by incorporating dual fillers.

Investigation on the microstructure, mechanical and electrical properties of Ti3SiC2/Cu joint obtained by Ti25Zr25Ni25Cu25 amorphous high entropy alloy and Ag composite filler

Ti3SiC2/Cu brazed joint has an important application in the pantograph of high-speed trains, but excessively continuous intermetallic compounds (IMC) and thick diffusion reaction zone (DRZ) in the joint are detrimental to both the mechanical and electrical properties of the joint. Therefore, regulating the interfacial microstructure is an effective way to acquire an excellent brazed joint. In this study, Ti25Zr25Ni25Cu25 amorphous high entropy alloy (HEA) was fabricated, and the brazing of Ti3SiC2 to Cu was carried out by the Ti25Zr25Ni25Cu25 HEA and Ag foil composite filler. The hysteresis effect of the HEA effectively slowed down the interfacial atomic diffusion and metallurgical reactions, which is conducive to the formation of relatively thin DRZ. Due to the combination of Ag foil and the HEA, the IMC distribution in the joint obtained at a relatively low temperature is more dispersed and uniform. Under the optimal brazing conditions, the maximum shear strength of the brazed joint obtained with the Ti25Zr25Ni25Cu25 and Ag composite filler is 34.85% higher than that obtained with Ag-26.7Cu-4.5Ti conventional filler. In particular, the electrical resistance of the joint obtained with the composite filler is 20.35% lower than that obtained with the single Ti25Zr25Ni25Cu25 HEA filler.

Fillers Influence on Hot-Mix Asphalt Mixture Design and Performance Assessment

Filler’s presence in hot-mix asphalt (HMA) is even though minimal but they do affect its durability characteristics. Many natural and waste materials in the form of fillers have been studied for their effectiveness on HMA mix design and performance characteristics. However, in practice, stone dust (SD) is the preferred filler due to its abundance, ease of availability, and cost-effectiveness. Thus, the major objective of this study was to investigate the effect of locally available materials: stone dust (SD)- natural, hydrated lime (HL) – processed, rice-husk ash (RHA) and fly-ash (FHA)-waste materials on HMA properties based on the factors such as availability, field utilization, cost, and sustainability, while at the same time identify the anomalies of those selected fillers on HMA mix if any. A viscosity grade (VG-30) binder was selected and checked for its fundamental consistency characteristics set forth in Indian standards. In this study, aggregate gradation structure specified as bituminous concrete grading 1 (BC1) in India was designed for the preparation and evaluation of four HMA mixes: (a) BC1 with SD (BC1-SD), (b) BC1 with RHA (BC1-RHA), (c) BC1 with FA (BC1-FA), and d) BC1 with HL (BC1-HL). Fillers: RHA, FA, and HL were studied for their physico-chemical properties. The most recommended filler dosage of 4% by weight of mix was selected and kept uniform for the various BC1 mixes. Marshall method of mix design was performed to identify the optimum asphalt content (OAC) of four different BC1 mixes. The test results of methylene blue value (MBV), german filler value (GFV), and fineness modulus (FM) indicated that RHA includes more micron-to-nano sized particles than the other two fillers (HL and FA). The scanning electron microscope coupled with energy dispersive X-ray results showed that the RHA and FA exhibited similar chemical composition, while HL was identified to be a calcium-based compound. The BC1-RHA mix resulted in non-cohesive mix for the binder content ranging from 4.5 to 6.5%. Additionally, for the binder contents in the range of 7 to 9% the BC1-RHA compacted samples failed to yield air voids of 4% required to arrive at the OAC. The BC1- FA mix showed the highest Marshall stability (26.97 KN) followed by BC1-HL (23.97 kN), and BC1-SD (17.9 kN). Also, retained stability test results of all the three different mixes were in close proximity to each other indicative of the affinity of the fillers to asphalt. The resistance to moisture susceptibility results indicated that HL is the better anti-stripping element followed by FA, and SD. Among the three different filler-based BC1 mixes, BC1-HL mix was adjudged as an effective moisture resistant mix followed by BC1-FA, and BC1-SD. However, a single filler that not only tends to improve the various performance parameters of the mix but be available in abundance and cost-effective is yet to be explored.

Study on the Enhancement Effect of Synergy between Multi-Size Functionalized Boron Nitride and Graphene Oxide on the Thermal Properties of Phase Change Composites.

Boron nitride nanosheet (BNNS) and graphene oxide (GO) as a single filler can effectively improve the thermal conductivity of the composites, and the synergistic mechanism of BNNS and GO was investigated in this paper. In this study, BNNS was first surface-functionalized and the multi-sized (50 nm, 200 nm, 500 nm) modified BNNS (A-BN) were attached to GO through non-covalent bonding interactions to form a cross-linked structure. Then, A-BN and GO were used as thermal fillers and support material adsorption eutectic phase change materials (PCMs) to prepare composite phase change material (CPCM). Characterization results show that small-size A-BN was more likely to form dense thermal networks with good compatibility and interface connectivity between PCMs, A-BN, and GO, ensuring that PCMs can be stored in the network without leaking. When the size of the BNNS was greater than 200 nm, the advantage of thermal conductivity obtained by A-BN was no longer obvious, and the phase change behavior of CPCM was inhibited. In general, the prepared CPCM has the ideal thermal response and thermal stability, which is very suitable for energy storage and thermal management applications.

New Reinforcing Approach for Biobased UV-Curing Resins: Hybrid Lignocellulose Fillers with Improved Synergy and Wood Structure Mimics

Lignocellulosic fillers have been widely investigated for various polymer resin applications since they have great potential for using wood biomass and recycled plastics. However, besides cellulose nanocrystals (CNC) and nanofibrils (CNF), not much of the other lignocellulose has been used for UV-curing resins. Even more so, none has been used in hybrid lignocellulose combination compositions. In the present work, the effects of hybrid lignocellulose fillers such as lignin (LN)/CNC/CNF/hemicellulose (HC) with ratio-varying compositions on UV-curing biobased resins have been investigated for wood-mimic material coating applications. The hybrid filler effects on the macromolecular chain network, surface morphology, thermomechanical properties, and thermostability were carefully studied. A combination of scanning electron microscopy, DMA Cole–Cole plot, contact angle, etc., allowed getting a sense of hybrid filler distribution and interaction within the polymer matrix. It was identified that an increase in the HC content of up to 38% contributes to more even particle distribution and achieves a maximum double bond conversion rate of about 80%. HC also contributes to porous surface structure, while CNC smooths surface morphology, and, in turn, CNF increases defects. Thermomechanical testing revealed the unique benefit of hybrid reinforcement, showing higher results than single-filler compositions despite the general decrease after incorporation of 5 wt % LN. The storage modulus showed a fourfold increase for 5 wt % LN composition. The observed enormous property enhancement has been attributed to the benefits of hybrid fillers, which mitigate characteristic radical scavenging properties of LN and strongly reduce general filler aggregation, allowing more even filler dispersion while also improving filler–matrix interface synergy. Seventeen different compositions clearly, in comparison to single fillers, show the benefit of hybrid lignocellulosic reinforcement and testify to the ability to precisely tune up material performance and achieve wood structure-mimicking coating materials.

Synergistically toughened silicone rubber nanocomposites using carbon nanotubes and molybdenum disulfide for stretchable strain sensors

Stretchable rubber nanocomposites have been investigated for detection in piezoresistive strain sensors. Tensile toughness must be improved while maintaining stretchability to realize high-performance, robust, stretchable nanocomposites. We investigate a stretchable and synergistically toughened silicone nanocomposite-based, piezoresistive strain sensor using multiwalled carbon nanotubes (MWCNTs) and molybdenum disulfide (MoS2). One-dimensional MWCNTs mechanically reinforce the silicone rubber matrix, improving tensile strength by 95% but decreasing fracture strain by 27% at 5 phr, providing an electrical percolation network. Adding two-dimensional nanolayers of MoS2 as a single filler increases fracture strain from 205% (unfilled) to 320% (5 phr MoS2), possibly due to cure retardation in the silicone rubber, preventing over-curing. Silicone nanocomposites exhibit improved tensile toughness at 8.46 kJ/m3 for 5-phr MWCNT-MoS2 hybrids due to the synergistic effects of the hybrid filler, a 125% improvement over unfilled rubber. Nanocomposites maintain a low elastic modulus (<0.45 MPa) suitable for stretchable sensors. The nanocomposite utility is demonstrated as body-attachable, piezoresistive strain sensing with a gauge factor of ∼25.95 (100%<Δε<155%), stretchability of up to 155%, and durability of over 5000 cycles. Toughened nanocomposites with MWCNT and MoS2 hybrid fillers could be useful for applications requiring robust stretchability and sensitivity.

Dermal fillers: History 101

AbstractIntroductionDermal fillers are an efficacious option for treating age‐related volume deficiency, as well as scars and wrinkles. Additionally, they are useful for facial sculpting and contouring, and to augment anatomical structures such as the lips.DiscussionThe start of the search for an ideal dermal filler can be traced back to the late 1800s. Characteristics of this ideal filler product include nontoxic, nonmigratory, noncarcinogenic, easily applied, noninfectious, painless, and long‐lasting. It would also have predictable and consistent results, feel natural, and require no patient downtime. Over the past century and a half, numerous products have been used or developed in an attempt to achieve a filler possessing these characteristics. However, only in the past few decades have safe, injectable filler products approved by the US Food and Drug Administration (FDA), been developed. Herein, we discuss the various injectable agents used in the past, as well as the most commonly used agents of present day.ConclusionReflecting upon the history of dermal filler development serves as an important reminder to proceed with caution, as serious complications may occur with their use. Importantly, no single filler is ideal for all patients or indications, therefore optimal treatment requires awareness of the properties and characteristics of each available product, and discretionary use by providers.

Dielectric, Mechanical, and Thermal Properties of Crosslinked Polyethylene Nanocomposite with Hybrid Nanofillers

Crosslinked polyethylene (XLPE) nanocomposite has superior insulation performance due to its excellent dielectric, mechanical, and thermal properties. The incorporation of nano-sized fillers drastically improved these properties in XLPE matrix due to the reinforcing effect of interfacial region between the XLPE-nanofillers. Good interfacial strength can be further improved by introducing a hybrid system nanofiller as a result of synergistic interaction between the nanofiller relative to a single filler system. Another factor affecting interfacial strength is the amount of hybrid nanofiller. Therefore, the incorporation amount of hybridising layered double hydroxide (LDH) with aluminium oxide (Al2O3) nanofiller into the XLPE matrix was investigated. Herein, the influence of hybrid nanofiller content and the 1:1 ratio of LDH to Al2O3 on the dielectric, mechanical, and thermal properties of the nanocomposite was studied. The structure and morphology of the XLPE/LDH-Al2O3 nanocomposites revealed that the hybridisation of nanofiller improved the dispersion state. The dielectric, mechanical, and thermal properties, including partial discharge resistance, AC breakdown strength, and tensile properties (tensile strength, Young's modulus, and elongation at break) were enhanced since it was influenced by the synergetic effect of the LDH-Al2O3 nanofiller. These properties were increased at optimal value of 0.8 wt.% before decreasing with increasing hybrid nanofiller. It was found that the value of PD magnitude improvement went down to 47.8% and AC breakdown strength increased by 15.6% as compared to pure XLPE. The mechanical properties were enhanced by 14.4%, 31.7%, and 23% for tensile strength, Young's modulus, and elongation at break, respectively. Of note, the hybridisation of nanofillers opens a new perspective in developing insulating material based on XLPE nanocomposite.

A reconfigurable and automatic platform for the on-demand production of stretchable conductive composites

Stretchable conductive composites (SCCs) have been widely used as interconnects and sensors in stretchable electronic devices due to their tunable electromechanical properties and intrinsically high stretchability compared to solid metals. SCCs can be readily made by mixing (or breaking bulk) conductive fillers within an elastomeric polymer, which are subsequently cured. Despite the simplicity of this, most fabrication methods follow customized protocols and lack precise automatic control. These methods also require bulky and costly equipment (e.g. stirrers, mixers, ovens, and vacuuming machines). Also, variations in the production process make it challenging to maintain the consistency of SCC’s electrical and mechanical properties produced in different batches. To solve this problem, this work develops an automatic SCC production platform (ASPP) that can be programmed to produce SCCs with high consistency in properties. The versatility of ASPP is demonstrated by fabricating SCCs with single and hybrid fillers, and porous structures. The consistency of SCCs’ electromechanical properties is examined using samples fabricated in different batches following the same protocol. We further utilize the fabricated SCCs to realize various intelligent tactile sensing and heating platforms. The capability demonstrated for the ASPP shows its potential in fabricating SCCs for applications in soft robotics and wearable devices.

Polymeric Fe3O4 Nanoparticle/Carbon Nanofiber Hybrid Nanocomposite Coatings for Improved Terahertz Shielding

With the rapid advancement in THz technology and continuously increasing number of electrical and electronic devices in this frequency band, highly efficient and functional THz shielding materials are required to ensure the intended working of these devices. Polymeric composites of hybrid nano-fillers including CNFs and magnetic nanoparticles possess distinctive capability of providing high shielding efficiency primarily absorptive in nature with field functional properties. In this article, lightweight polymeric nanocomposite coatings of continuous carbon nanofibers and magnetite (Fe3O4), as potential shielding material for the THz frequency band, have been prepared using a cost-effective conventional air-spray coating method. The obtained results are quite exclusive, as the sample with 40 wt % Fe3O4 outperforms at a very low thickness value of 540 μm, showing the highest SE value of ∼60 dB. These results are superior compared to the results obtained from most of the contemporary polymer composite materials, which usually provide good shielding at high thickness values in the mm range. Also, this study establishes that shielding performance of the polymeric hybrid nanocomposites (Fe3O4 + CNFs) is substantially better than a single nanocomposite CNF filler previously synthesized and characterized through the same approach.

New nanocomposites based on poly(benzoxazine-co-epoxy) matrix reinforced by novel graphene single and mixed blend fillers

We report new nanocomposites with poly(benzoxazine-co-epoxy) matrix reinforced with 1 wt% graphene. Curabox 24-111, a benzoxazine resin was copolymerised with Epilok 60-566, a mixture of epoxy resins. Copolymerisation was also carried out in the presence of different graphene powders, namely, Nanene-001 and Nanene-002, used as single fillers and as mixture (relative weight ratio 70:30 or 30:70). DSC results showed the addition of either single filler caused a delay in polymerisation and an increase in the exothermic peak temperature of the curing reaction with a related reduction in ΔH Total. compared to the neat copolymer. Copolymerisation showed a 38% reduction and 24% increase in tensile modulus (E) compared to the neat polybenzoxazine and epoxy polymer, with a respective 18% and 30% reduction in tensile strength (TS). Nanocomposites with 0.7wt% Nanene-002 + 0.3 wt% Nanene-001 showed the highest increase of 35% in TS, a 1.6% reduction in E and 36% increase in elongation at break (EB) compared to the neat copolymer matrix. Samples with 1 wt% Nanene-001 showed the largest reduction of 21% in E, a 27% increase in TS and a 45% increase in EB. Additionally, TGA thermographs showed a 22°C increase in the onset of degradation (300°C–322°C) improving the materials thermal stability.

Effect of crack and vibration of waste tyre rubber hybrid composite for energy absorption applications

Composites reinforced with landfill waste materials have find the applications in engineering materials and they can lead to reduce the environmental pollutions. Waste tyre rubber, broken ceramic tiles and wood particles are creating the environmental hazard to the surroundings. In particular, the recycling of used tyre rubber is highly challenging, but it has very good property to absorb the energy. The reinforcement of rubber as single filler in composite has the limitations in processing and applications. Hence, the above waste materials are incorporated to prepare the composite in the present work. The fracture toughness and shear strength of composites were evaluated and compared with other combinations along with pure epoxy specimen. In order to find the application of composite in dynamic conditions the vibration analysis were done. The presents of rubber decreased the fracture toughness and at the same time the incorporation of ceramic largely improved the fracture toughness of epoxy composite. The shear strength of composites increased with the addition of ceramic and wood particles. But the rubber particle has the great influence on the damping behavior of ceramic base epoxy composites. The addition of ceramic with the epoxy increased the natural frequency and decreased the damping factor. This can be compensated by the inclusion of rubber with ceramic in epoxy resin matrix. 15 wt % addition of rubber with ceramic and epoxy increased the natural frequency of 18.52% and damping factor of 288% than 5 wt % of rubber with ceramic and epoxy. The natural frequency and damping factor of ceramic and rubber based epoxy composite have the highest amount of all combinations and can be used for vibration applications to absorb the energy at high frequencies.

Tunable Head-Conducting Microwave-Absorbing Multifunctional Composites with Excellent Microwave Absorption, Thermal Conductivity and Mechanical Properties

Developing composite materials with both thermal conductivity and microwave absorption is an effective strategy to solve the problems of heat dissipation burden and microwave radiation interference caused by the development of miniaturization and high performance of portable electronic equipment. However, these properties are not easy to simultaneously implement due to the limitation of single type fillers with a single particle size, inspiring the possibility of realizing multifunctional composites with the introduction of composite fillers. In this work, using alumina (Al2O3) and zinc oxide (ZnO) as head-conducting fillers, carbonyl iron (Fe(CO)5) as microwave-absorbing fillers, silicone rubber (SR) composites (Al2O3/ZnO/Fe(CO)5/SR) with enhanced microwave absorption, high thermal conductivity and good mechanical properties were successfully mass prepared. It was found that the composites can achieve a thermal conductivity of 3.61 W·m−1·K−1, an effective microwave absorption bandwidth of 10.86–15.47 GHz. Especially, there is an effective microwave absorption efficiency of 99% at 12.46–14.27 GHz, which can realize the integration of electromagnetic shielding and heat dissipation. The compact microstructure, formed by the overlapping of large particle size fillers and the filling of their gaps by small particle size fillers, is helpful to enhance the thermal conduction path and weaken the microwave reflection. The heat-conducting microwave-absorbing Al2O3/ZnO/Fe(CO)5/SR composites also have the advantages of thermal stability, lightness and flexibility, providing a certain experimental basis for the research and development of high-performance and diversified composites.

Normalization of impact energy by different layer arrangement for kenaf-glass hybrid composite laminates

An increase of interest to mesh up two or more fillers in the matrix is increasing. The main objective is to improve the performance of a single filler reinforced matrix with other fillers that have higher strength as compared to the initial fibre. Thus, in this study, kenaf fibre plies have been hybridised with woven glass fibre mats in order to improve its post impact tensile properties. These hybrid composite materials were fabricated by hand lay-up and cold press techniques. Two different systems were fabricated based on specific fibre layer arrangements of kenaf-glass fibre reinforced polymer (KGFRP) hybrid composites. The results revealed that the woven glass fibre at the outer layer arrangement produced better strength than having kenaf fibre at the outer layer as shown in Normalized Stress curve. This arrangement helps to sustain more impact, as a consequence, exhibits more resistance to crack growth.

Core-Shell Engineering of Conductive Fillers toward Enhanced Dielectric Properties: A Universal Polarization Mechanism in Polymer Conductor Composites.

Flexible dielectric and electronic materials with high dielectric constant (k) and low loss are constantly pursued. Encapsulation of conductive fillers with insulating shells represents a promising approach, and has attracted substantial research efforts. However, progress is greatly impeded due to the lack of a fundamental understanding of the polarization mechanism. In this work, a series of core-shell polymer composites is studied, and the correlation between macroscopic dielectric properties (across entire composites) and microscopic polarization (around single fillers) is investigated. It is revealed that the polarization in polymer conductor composites is determined by electron transport across multiple neighboring conductive fillers-a domain-type polarization. The formation of a core-shell filler structure affects the dielectric properties of tpolymer composites by essentially modifying the filler-cluster size. Based on this understanding, a novel percolative composite is prepared with higher-than-normal filler concentration and optimized shell's electrical resistivity. The developed composite shows both high-k due to enlarged cluster size and low loss due to restrained charge transport simultaneously, which cannot be achieved in traditional percolative composites or via simple core-shell filler design. The revealed polarization mechanism and the optimization strategy for core-shell fillers provide critical guidance and a new paradigm, for developing advanced polymer dielectrics with promising property sets.

Photopolymerization of ceramic/zeolite reinforced photopolymers: Towards 3D/4D printing and gas adsorption applications

Normally, 3D printed objects via photopolymerization usually don’t have fully optimized mechanical properties and functions. In this context, the addition of single filler usually can improve these properties through the access to composite materials. However, the addition of filler inevitably has a negative influence on the light penetration inside the composites strongly reducing the depth of cure. Hence, the fabrications of photo-composites based on a combination of two inorganic fillers (alumina Al2O3 and zeolite LTA-5A) are reported in this work. Compared to pure poly(ethylene glycol) diacrylate (PEGDA) and its other corresponding single filler-based composites, PEGDA with 25 wt% LTA-5A and 25 wt% Al2O3-200 had several improved properties: better depth of cure (DOC), good mechanical properties (the storage modulus, tensile strength, the Young’s modulus). Direct laser write (DLW) was used to manufacture 3D patterns and 3D cross-shaped objects with good resolution. Under the hydrothermal stimuli, a 4D printing behavior (reversible shape change) was observed on the 3D cross-shaped objects. In addition, the 3D object with the condition of 4D printing had the ability of withstand a heavy stuff (the mass difference was more than 100 times). This is the first time to report the fabrication of the double filler-based (50 wt%) composite (ceramic and zeolite) with 4D printing behavior and good mechanical properties. Interestingly, calcinated composites had a certain structure strength and good CO2 adsorption performance. Therefore, this work not only paves the way for the investigation of photo-composites filled with multiple fillers combinations (how to improve the mechanical properties and keep good depth of cure for composites via photopolymerization), but also shows us the potential applications in the field of 3D/4D printing, microlithography and functional composites.

Probing the Carrier Dynamics of Polymer Composites with Single and Hybrid Carbon Nanotube Fillers for Improved Thermoelectric Performance

The incorporation of carbon nanotubes (CNTs) within polymer hosts offers a great platform for the development of advanced thermoelectric (TE) composite materials. Over the years, several CNT/polymer composite formulations have been investigated on an effort to maximize the TE performance. Meanwhile, several studies focused on the decay dynamics of the charged excitons within CNTs itself and therefrom derived structures, aiming to investigate the lifetimes and the corresponding recombination processes of free charge carriers. The latter physical phenomena play a crucial role in the performance of various types of energy converting and scavenging materials. Nevertheless, up to this date, there is no systematic study on the combination of TE parameters and the critical charge carrier dynamics within CNT containing TE polymer composites. Herein, a variety of composites with single and hybrid CNT fillers based on polycarbonate (PC) and polyether ether ketone (PEEK) polymer matrices were prepared by melt-mixing in small scale. At the same loading, the addition of single fillers in PC results in higher Seebeck coefficients and similar conductivities when compared to the use of hybrid filler systems. In contrast, with hybrid filler systems in PEEK composites, higher power factors could be reached than in single filler composites. Moreover, the PC-based composites are studied using ultrafast laser time-resolved transient absorption spectroscopy (TAS), for the investigation of the exciton lifetimes and the physical origins of free charge carrier transport within the TE films. The findings of this study reveal interesting links between the TE parameters and the obtained charge carrier dynamics.

Conducting and stretchable emulsion styrene butadiene rubber composites using SiO2@Ag core-shell particles and polydopamine coated carbon nanotubes

In the present scenario of development in technology, the applications of stretchable conductive elastomers in modern electronic equipments have aroused great interest. Non-covalent bonding modification of carbon nanotubes (CNTs) using dopamine has improved the dispersion of CNT@PDA and interfacial interaction with the rubber matrix. The SiO2@Ag core-shell particles were prepared by coated with silver nanoparticles (AgNPs) on the surface of SiO2 using dopamine oxidation self-polymerization and electroless plating process. ESBR composites were prepared by latex co-coagulation method, where CNT@PDA and SiO2@Ag were used to develop an 1D-3D synergistic conductive network in ESBR composites. One-dimensional (1D) CNT@PDA were incorporated in three-dimensional (3D) spherical SiO2@Ag core-shell particles, which effectively prevented the agglomeration of SiO2@Ag and CNT@PDA. Again, 1D CNT@PDA could also be used as bridges to interact with 3D SiO2@Ag to develop the charge transfer more effectively in ESBR composites. The optimum electrical conductivity of the ESBR/CNT@PDA/SiO2@Ag composites was 0.2 S/cm, which was found to be higher than that of single filler. Moreover, the high electrical conductivity can be controlled at low tensile strain. The mechanical property of ESBR/CNT@PDA/SiO2@Ag composite was also improved by 105.4% as compared by ESBR/CNTs. This work provides a new idea for the fabrication of stretchable conductive elastomer composites with high performance.