Filler Dispersion Research Articles

Nanocellulose‐polypropylene composites with novel antimicrobial complex salt

AbstractPolypropylene composites with different contents of zinc‐ammonium salts (3, 5 and 7 wt%) and nanocellulose (1 wt%) after enzymatic bioconversion were characterized by structural, dispersion‐morphological, thermal, antimicrobial and mechanical analysis. It was shown that the use of a newly synthesized salt significantly affected the formation of the supermolecular structure of the polymer matrix and increased the nucleation activity, thermostability and flexibility of the composite materials. Moreover, the addition of the inorganic filler allowed to obtain composites with very good antimicrobial properties against Staphylococcus aureus, Escherichia coli and Candida albicans. An interesting relationship between the degree of filler dispersion in the polymer matrix and the formation of polymorphic varieties was elucidated in the study, which contributes to the improvement of final performance characteristics of composite materials. It is noteworthy that a hybrid filler in the form of nanometric cellulose and a biocidal additive containing zinc‐ammonium complex salt was used for the first time. Research has shown that such polymer composites can find application during the manufacture of smart packaging materials with enhanced barrier properties against oxygen and water vapor as well as improved biocidal characteristics, which will notably extend food storage time. At the same time, the presented process of obtaining the innovative composite materials is an excellent example of sustainable technologies for the design of antimicrobial treatments, while guaranteeing the possibility of further processing of these composite materials through material recycling.Highlights Zinc‐ammonium complex with antimicrobial properties was obtained The strength properties and thermal stability of the composites were improved Degree of filler dispersion in polymer affects formation of polymorphic varieties The composites can be applied in the production of smart packaging materials

Preparation and Performance of PBAT/PLA/CaCO3 Composites via Solid-State Shear Milling Technology

Replacing traditional disposable, non-biodegradable plastic packaging with biodegradable plastic packaging is one of the key approaches to address the issue of “white pollution”. PBAT/PLA/inorganic filler composites are widely utilized as a biodegradable material, commonly employed in the field of packaging films. However, the poor dispersion of inorganic fillers in the polymer matrix and the limited compatibility between PBAT and PLA have led to inferior mechanical properties and elevated costs. In this work, we propose a simple and effective strategy to improve the dispersion of nano-CaCO3 in a PBAT/PLA matrix through solid-state shear- milling (S3M) technology, combined with mechanochemical modification and in situ compatibilization to enhance the compatibility between PBAT and PLA. The impact of varying milling conditions on the structure and performance of the PBAT/PLA/CaCO3 composites was investigated. During the milling process, PBAT and PLA undergo partial molecular chain fragmentation, generating more active functional groups. In the presence of the chain extender ADR during melt blending, more branched PBAT-g-PLA is formed, thereby enhancing matrix compatibility. The results indicate that the choice of milling materials significantly affects the structure and properties of the composite. The film obtained by milling only PBAT and CaCO3 exhibited the best performance, with its longitudinal tensile strength and fracture elongation reaching 22 MPa and 437%, respectively. This film holds great potential for application in the field of green packaging.

Aminated ZIF‐8 to facilitate CO2 sieving through polyvinyl alcohol/ionic liquid membranes

AbstractCO2 separation technology at low pressure is most desirable in carbon capture projects to mitigate global warming. Facilitated transport membranes offer selective and effective CO2 permeation using a wide range of carbon carriers at low pressure. Porous fillers were recently included as they can carry abundant fixed carriers besides offering open channels for CO2 permeation. This study investigates the effects of amine‐modified zeolitic imidazolate framework‐8 (ZIF‐8) with well‐defined micropores and gas sieving ability in polyvinyl alcohol (PVA) membranes containing an ionic liquid that worked as mobile carriers. The effects of amine‐modified ZIF‐8 and silica nanoparticles on membrane properties and separation performance were also compared. Fourier transform infrared spectra confirmed the incorporation of ZIF‐8, secondary amine, IL anions, and silica nanoparticles in PVA membranes. Energy dispersive analysis showed the good dispersion of inorganic fillers. The amine‐modified silica nanoparticles resulted in higher thermal stability compared to the amine‐modified ZIF‐8 in PVA membranes containing [bmin][Ac] ionic liquid, as shown in the thermogravimetric analysis. However, the CO2 separation performance of PVA membranes containing [bmim][Ac] ionic liquid was improved more significantly by the amine‐modified ZIF‐8 with microporous structure. A CO2/N2 ideal selectivity of 85.65 and CO2 permeance up to 4,502.91 GPU were attained. Unlike the CO2/N2 ideal selectivity, the CO2 permeance was not significantly affected either using [bmin][Ac] or [bmin][BF4]. The humid gas greatly enhanced the CO2 permeance without much changes in the CO2/N2 ideal selectivity due to the promotion of facilitated transport. © 2024 Society of Chemical Industry and John Wiley & Sons, Ltd.

In-situ sol-gel process for the formulation of Bis-GMA/TEGDMA/silica dental nanocomposite

A novel dental composite based on Bis-GMA/TEGDMA resin incorporating silica nanoparticles was developed using an innovative in situ sol-gel process. This method ensures a homogeneous dispersion of fillers, effectively preventing their agglomeration during preparation. It results in an interpenetrating network in which polymer chains and silica particles are intimately mixed, thereby enhancing the structural and mechanical properties and minimizing the volumetric shrinkage of the dental restorative material.The formation of organic and inorganic network was confirmed by infrared spectroscopy. The in situ synthesis enabled uniform dispersion of silica nanoparticles within the material as evidenced by transmission electron microscopy, scanning electron microscopy and energy dispersive spectroscopy.The results showed that the prepared composite containing 50 wt% fillers achieved hardness, modulus of elasticity, compressive strength and flexural strength values of 72 HV, 10 GPa, 240 MPa, and 110 MPa, respectively. These properties are comparable to those of the commercial “Nt Premium” composite containing 75 % preformed silica nanoparticles, which has hardness, modulus of elasticity, compressive strength and flexural strength values of 68 HV, 10 GPa, 220 MPa and 95 MPa, respectively. Additionally, the study revealed a significantly reduced volumetric shrinkage of 0.5 % for our composite, compared with over 2.2 % for Nt Premium. This groundbreaking approach holds substantial promise for developing advanced dental materials, offering superior performance and enhanced longevity in clinical applications.

Influence of high cis-1,4-liquid polydienes on properties of carbon-black filled composites

High cis-1,4 liquid polybutadiene (cLBR) and polyisoprene (cLIR) with narrow molecular weight distribution were prepared by the chain-transfer coordination polymerization. The effects of cLBR and cLIR on the physical and dynamic mechanical properties of carbon-black filled composites containing single polybutadiene (PBR) or a blend of PBR/polyisoprene (PIR), were investigated. The results showed that cLBR and cLIR effectively ameliorated filler dispersion compared with the treated distillate aromatic extract (TDAE) oil. The wet skid resistance and rolling resistance of vulcanized PBR/PIR composites plasticized with 5 phr cis-1,4 liquid rubbers were significantly improved. Therefore, a new type of plasticizers cLBR and cLIR that are environmental benign and highly compatible with matrix rubbers, has been discovered to replace the conventional TDAE oil used in fabricating the “green” tyres.

Quantitative Study on Reinforcing Mechanism of Nanofiller Network in Silicone Elastomer Based on Fluorescence Labeling Technology

Although there have been many theoretical studies on the enhancement effect of nanofiller networks and their interaction with elastomer molecular chains on the mechanical properties of elastomers, its mechanism description is still not completely clear. One of the main obstacles is the lack of quantitative characterization techniques and corresponding theoretical models for the three-dimensional morphology of complex nanofiller networks. In this paper, the precipitated silica-filled silicone rubber was studied by fluorescence labeling combined with laser scanning confocal microscopy, and the real three-dimensional images of dispersion and aggregation structure of filled rubber systems were obtained. The microstructure evolution of nano-particle aggregates caused by the increase in the filler volume fraction was quantitatively described, and the reinforcement mechanism of elastomers with a distribution of aggregates and filler networks composed of nanoparticles was studied. Furthermore, a nano-composite reinforcement model based on volume fraction, particle shape, interaction, and filler dispersion has been proposed.

Reactive extrusion for efficient preparation of high temperature resistant PA6T/66/BN composites with great thermal management and mechanical properties

High temperature resistant polymer-based composite with high thermal conductivity and great mechanical properties are highly demanded in the field of electronic devices for simultaneously meeting surface mounting process and high-power operation. The key to achieving this goal is to balance the contradiction between the high melt viscosity of high-temperature resistant polymers and the dispersibility of fillers. In this work, the high-performance polyamide 6T/66/hexagonal boron nitride (PA6T/66/BN) composites were fabricated successfully via the method combining prepolymerization and reactive extrusion. Results demonstrated that this method not only significantly improves the preparation efficiency of high temperature resistant polyamide and its composites, but also enables the prepared composites to reach 3.6 W/(m⋅K), over 299 °C and 67.8 MPa in thermal conductivity, melting point and tensile strength respectively. Furthermore, the prepared composite exhibits excellent thermal management effects on LED and CPU. Therefore, the results of this work are of great significance for the efficient preparation and wide application of high-temperature resistant polymer based thermally conductive composites.

Enhanced Dielectric, Thermal, Energy Storage, Quality Factor, Impedance, and Conductivity Properties of Novel PVDF/PAN/ZrO2 Polymer Nanocomposites for Flexible Electronics Applications

ABSTRACTIn this study, novel polymer nanocomposite films based on polyvinylidene fluoride/polyacrylonitrile/zirconium dioxide (PVDF/PAN/ZrO2) were prepared using a solution casting technique. The structural modifications and morphological properties were analyzed by x‐ray diffraction (XRD) and high resolution scanning electron microscopy (HRSEM). The obtained results verified the filler‐polymer interactions and uniform dispersion of the ZrO2 filler in the host polymers (PVDF and PAN). Thermal stability of up to 46% leftover residue for 30% ZrO2 nano‐filler loading in the blend polymer nanocomposite was analyzed by thermogravimetric analysis (TGA). The dielectric properties such as dielectric constant and dielectric loss values and impedance, Q‐factor, and AC conductivity were analyzed using an impedance analyzer. The decrement in impedance with increasing nano‐filler content with improved dielectric, thermal, Q‐factor, energy density and conductivity properties signifies the prepared novel PVDF/PAN/ZrO2 polymer nanocomposite as an effective material for flexible electronics applications.

Protective graphene-based coatings for Zamak: Physical and electrochemical analysis

Concerns surrounding the widespread use of hazardous materials have increased over time and have led numerous states to implement regulations aimed at preserving human and environmental health. In response, industries like metallurgy have gradually transitioned from traditional, hazardous technologies to safer alternatives, such as using polymeric coatings to protect metals from corrosion. This study focuses on evaluating the protective properties of non-functionalized graphene oxide-based coating (GC) and functionalized graphene oxide-based coating (FGC) on the zamak samples. First, the powders were analyzed from structural, morphological, and spectroscopic perspectives. The formation of amino-silica groups on the graphene oxide sheets was confirmed through SEM-EDS, XRD, and FTIR analyses, validating the success of the functionalization process. Granulometric analysis demonstrated a good dispersion of fillers in the mixtures. Cross's theoretical model was applied to the rheological experiments to find the optimum way of coating application on metallic substrates. The corrosion resistance of the coatings was evaluated using OCP, LSV, PS, EIS, and salt spray experiments. The results revealed that the functionalized graphene oxide coating provided superior corrosion protection compared to other coatings on Zamak samples. AFM topographic images, along with roughness measurements, indicated a significantly less corroded surface when using the functionalized graphene oxide coating. Additionally, Raman spectroscopy confirmed the protective effectiveness of the FGC coating against corrosion.

Bioinspired surface modification of mussel shells and their application as a biogenic filler in polypropylene composites

This study explores the potential of mussel shells (MS) as biogenic fillers in polymer composites. The chemical composition and crystal structures of MS were characterised. To improve MS filler dispersion and adhesion within a polypropylene (PP) matrix, three surface modification methods were evaluated: polydopamine (PDA) coating, maleic anhydride-grafted polypropylene (MAPP) modification, and PDA/MAPP co-modification. The PDA coating, inspired by the adhesive properties of mussel foot proteins, successfully functionalized the MS surface, as confirmed by X-ray photoelectron spectroscopy (XPS). Thermodynamic analysis, based on contact angle measurements, revealed that MAPP and PDA/MAPP modifications reduced surface energies and potential energy differences. These changes enhanced filler dispersion and interfacial bonding by increasing hydrophobicity and reducing agglomeration in the PP matrix. Consequently, PP composites with 20% PDA/MAPP-modified MS fillers exhibited a 2.9% increase in tensile strength and a 7.5% increase in flexural strength compared to neat PP. Scanning electron microscopy (SEM) also showed reduced filler-matrix debonding and fewer voids. The proposed mechanism attributes these macroscopic property enhancements to the ability of the PDA coating to facilitate chemical and hydrogen bonding between MS fillers and MAPP.

Grafting of maleic anhydride onto waste acrylonitrile butadiene styrene (ABS) and its application for compatibilization of ABS blends

AbstractIncorporating recycled plastics into the manufacturing process is an essential way to establish a sustainable plastics economy. However, current processes are limited by the degradation of mechanical properties, high cost, and inconsistent product quality compared with their virgin counterparts. Here, we present an upcycling strategy for waste plastics where waste acrylonitrile‐butadiene‐styrene (reABS) is first grafted with maleic anhydride (MAH), then utilized to compatibilize nylon 6(PA6)/ABS and PA6/ABS/CaCO3 blends. The reABS‐g‐MAH exhibits improved Young's modulus and tensile strength, but lower strain at break and impact strength compared with reABS. As an additive, reABS‐g‐MAH effectively compatibilizes PA6/ABS and PA6/ABS/CaCO3 blends, indicated by greatly decreased PA6 domain size, homogeneous dispersion of fillers, and narrowed glass transition temperature regions between PA6 and ABS. Adding only 5 wt% reABS‐g‐MAH increases the Young's modulus, strain at break, and impact strength of PA6/ABS blends by 26%, 180%, and 110%, respectively, compared with uncompatibilized samples. Similarly, for PA6/ABS/CaCO3 blends, the strain at break and impact strength increase by 370% and 150%, respectively, while the Young's modulus and tensile strength show increases of 5% and 10%. The results show that this strategy of using polar groups to functionalize waste plastics as compatibilizers may open numerous opportunities for upcycling waste plastics.

Enhanced abrasion resistance of NR/BR/TBIR composites through the synergistic reinforcement of carbon black and graphene oxide: Structural influence and mechanistic insights

AbstractCarbon black (CB) with different structural parameters together with graphene oxide were formed into uniformly dispersed filler network for enhancing the abrasion resistance of natural rubber/cis‐1,4‐polybutadiene rubber/trans‐1,4‐poly(isoprene‐butadiene) rubber blended composites. It showed that the CB structural parameters, such as specific surface area, surface activity and structural degree affected the formation of bound rubber. With the increase of bound rubber content, the homogeneity of filler network structure was improved and the filler‐rubber interaction was enhanced, resulting in a remarkable increase in the mechanical properties, thermal performance and abrasion resistance of the composites. Among the different types of CB, the composites filled with high‐structural‐degree CB of N134 had DIN wear volume as low as 76 mm3 and exhibited 19.5% higher abrasion resistance than N330. Wear surface observations and wear mechanism analyses showed that the increase in abrasion resistance was related to the improvement in tear resistance, hardness and thermal properties of the composites. Multiple linear regression analyses yielded that the structural degree in the structural parameters of CB had a significant correlation effect on the formation of bound rubber, and there was a strong linear relationship between the abrasion resistance of the composites and the content of bound rubber.Highlights Trans‐1,4‐poly(isoprene‐butadiene) rubber as compatibilizer for NR/BR blends. Synergistic enhancement of rubber using carbon black and graphene oxide. Carbon black with high structural degree promotes the formation of bound rubber. Described correlation between CB structural parameters and abrasion resistance of rubber.

High-value application of kaolin by wet mixing method in low heat generation and high wear-resistant natural rubber composites

In this study, a silane coupling agent and kaolin, a natural mineral resource, were introduced into the wet mixing process of natural rubber latex, the high wear-resistant and low-generation heat natural rubber composites were prepared. The sputtering, collision, and deposition of coupling agent/fillers/natural rubber latex mixed emulsion onto the roller effectively could break up the filler aggregates, enable fillers to be better infiltrated, distributed, and dispersed in the rubber. The effects of dry/wet mixing processes and the ratio of kaolin to silica on the crosslinking density, filler dispersion, extrusion rheological properties, gas barrier properties, dynamic mechanical properties and thermal stability of NR composites were investigated, and the silanization mechanism was summarized by FTIR and XRD. The experimental results showed that kaolin improved the crosslinking density and failure temperature, reduced the Payne effect, extrusion swell, and rolling resistance. Compared with 60 phr silica-filled natural rubber, the gas barrier property and wear resistance of 60 phr kaolin-filled natural rubber were improved by 64 % and 27 %, respectively, and the rolling resistance was reduced by 57 %. When the ratios of silica to kaolin were both 20:40, the crosslinking density, gas barrier property, and wear resistance of wet mixing were improved by 24 %, 45 %, and 9 %, respectively, compared with dry mixing. This study provided a new method for the high-value application of kaolin in wet mixing and green tires.

Effect of silane coupling agent on mechanical properties, flame retardancy, and ceramifiable behavior of ceramifiable flame‐retardant silicone rubber composite

AbstractIn order to improve the dispersibility of inorganic fillers and enhance its ceramifiable flame‐retardant efficiency, the ceramifiable flame‐retardant silicone rubber composites were prepared using glass powder, zinc borate, ammonium polyphosphate, mica powder, platinum catalyst as ceramifiable flame‐retardant agent, and various silane coupling agents as interfacial modifier. The micromorphology, mechanical properties, flame retardancy, thermal stability, and combustion behavior of ceramifiable flame‐retardant silicone rubber composites, as well as the flexural strength of the corresponding ceramics generated after pyrolysis of the composites were examined. The results reveal that the inclusion of silane coupling agents improves the dispersibility of ceramifiable flame‐retardant agents substantially. The mechanical properties, flame retardancy, thermal stability, and combustion behavior of ceramifiable flame‐retardant silicone rubber composites are all improved. When compared to a composite without a silane coupling agent, the tensile strength of the composite can be improved by up to 1.9 times. Only 0.5phr silane coupling agent is required to raise the vertical combustion rating from V‐1 to V‐0, and the composite with 3 phr KH570 has a LOI value of 38.6. Meanwhile, the heat release rate of the composite is reduced to a certain extent, and the time to ignition and residue are dramatically enhanced after the addition of silane coupling agent in the cone calorimetry test. Moreover, flexural strength of the corresponding ceramics generated after pyrolysis of the composites rapidly increases with increasing silane coupling agent content, which can reach to 24.7 MPa with addition of 3 phr KH570.

Facile and fast construction of biomimetic, waterborne, and superhydrophobic coatings via spraying strategy

Typically, the preparation of superhydrophobic coatings may release a large amount of volatile organic compounds (VOCs), which will be potentially harmful to the environment. In this condition, waterborne coatings have gradually become the main method to replace the traditional organic solvent-based coatings in recent years. Inspired by natural superhydrophobic phenomena, biomimetic, waterborne, and superhydrophobic coatings with multi-functional integration have been prepared via a one-step pneumatic spraying technique in this paper. The coatings were mainly composed of solvent (water), low surface energy substances (polytetrafluoroethylene emulsion (PTFE)), binding agents (waterborne silicone resin (WSR)), rough structure maker (polyphenylene sulfide (PPS) and graphene powder (GP)), and filler dispersion agent (dodecyl phenyl polyoxyethylene (OP-10)). Owing to the formation of hierarchical micro/nano-scaled structure covered with low surface energy, the water contact angle (WCA) and water sliding angle (WSA) values of as-prepared coatings can reach 155.5° ± 1.1° and 9.2° ± 0.3°, respectively. This is feasible for endowing the coatings with rich surface functionalities such as self-cleaning properties, anti-icing ability, anti-corrosion properties, and oil-water separation. Furthermore, the adequate durability and stability of as-prepared coatings have been confirmed by a series of mechanical and chemical damage tests. The super-hydrophobicity can be retained even after 12 m sandpaper abrasion, 24 h continuous UV irradiation and acid/alkali immersion tests. Thus, this article has provided an effective and simplified strategy for preparing multifunction-integrated and waterborne superhydrophobic coatings, which will extend its potential application in many daily life and industrial fields.

Green and energy-saving tread rubber by constructing chemical cross-linking interface between graphene oxide and natural rubber

The dispersibility of fillers and interfacial interaction are crucial for polymer nanocomposites. Developing a simple, efficient and green method to simultaneously reduce and functionalize graphene oxide (GO) for preparing graphene/rubber composites with excellent dispersibility and enhanced interfacial interactions remains one of the main trends in developing and expanding the application of graphene in the rubber industry. In this work, VOC (volatile organic compound) -free and environmentally friendly L-methionine (L-Met) was selected as the functional modifier of GO. Then, L-Met-modified GO (MGO) was blended with natural rubber (NR) in an aqueous phase to prepare MGO/NR composites. The amphiphilic property of L-Met not only reduced GO but also endowed it with less agglomeration and excellent water dispersibility, which was a prerequisite for achieving uniform dispersion of GO in the NR matrix. In addition, the amino acids on the surface of MGO enhanced the compatibility between GO and the protein-phospholipid layer on the outer layer of NR latex particles. Meanwhile, L-Met containing sulfur bonds promoted rubber vulcanization, resulting in the formation of a cross-linked network between the modified GO and NR molecular chains. Compared to unmodified GO/NR composites, MGO/NR composites exhibited excellent mechanical properties and low heat build-up. More importantly, the solid tire prepared by using L-Met as the interface modifier for GO filled rubber showed lower rolling resistance and temperature rise, and the energy saving efficiency was improved. This strategy is expected to provide a new insight into the green production of organically modified graphene and the preparation of low-energy-consumption green graphene tires.

Lignin dispersion in polybutadiene rubber (BR) with different mixing parameters

There is a strong need to replace carbon black and silica as a reinforcing filler in rubber industry. Lignin is a promising option as a replacement, because of its wide availability, complex chemistry and sustainable source. Typically, the reinforcing effect of lignin is weak and one major cause is the poor dispersion of filler. In this study, typical dispersion parameters in mixing are tested in a systematic way to validate their effect on kraft lignin dispersion in polybutadiene rubber. Tested mixing variables are temperature, rotor speed, mixing time, fill ratio and shear forces. The effect of variables to dispersion are analyzed from electron microscopy images with an image analysis software. With this novel method exact number of particles and their properties could be calculated. Unlike for conventional fillers (carbon black and silica), the results show clearly that only the mixing temperature has an effect on lignin dispersion in rubber. With high mixing temperatures, dispersion and hence mechanical properties improved. The better dispersion is especially seen as decreasing number of large (>Ø 5 μm) particles. Other mixing variables did not have significant effect on dispersion and the number of large particles.

Surface one-step modification of graphene oxide with N-cyclohexylbenzothiazole-2-sulfonamide to enhance the wear resistance of natural rubber/butadiene rubber composites

Natural rubber (NR) and butadiene rubber (BR) composites are frequently used in manufacturing tires and conveyor belts, which are susceptible to severe wear, leading to product failure and significant losses. To enhance the wear resistance of NR/BR composites, we prepared NR/BR composites reinforced with a synergy of N-cyclohexylbenzothiazole-2-sulfonamide surface one-step modified reduced graphene oxide (CZ-rGO) and carbon black N234 (CB) using a latex co-precipitation method. This study explored the effects of GO content and CZ modification on the structure, wear resistance, thermal conductivity, and mechanical properties of the NR/BR blended composites. It showed that adding 2 phr of GO resulted in excellent filler dispersion, significantly improving the tensile strength, elongation at break, tear strength, thermal conductivity, and wear resistance of the composites. The incorporation of CZ-rGO further increased the crosslinking density, vulcanization performance, and filler dispersion with enhanced mechanical properties, thermal conductivity, and wear resistance of the composites. Notably, the DIN abrasion volume was reduced to 77.88 mm³, surpassing the ISO 10247 standard for conveyor belt cover rubber in terms of wear resistance. The wear resistance of NR/BR/CZ-rGO composites is not only significantly higher than that of single NR- or SBR-based rubber composites, but also significantly higher than that of other binary rubber blend composites, and the CZ-rGO filler is simpler in composition and structure and exhibits a more prominent wear enhancement. This work provides guidance for an efficient and environmentally friendly approach to GO surface modification, as well as useful insights for the development of high wear-resistant rubber composites with excellent overall performance.

Polydopamine‐coated iron‐nickel alloy and epoxy composites for electromagnetic interference shielding

AbstractWith the development of electronic devices and wireless communication technology, the quality of human life has improved. However, shielding from electromagnetic interference (EMI) is required due to device malfunctions and harmful effects on human health. Polymer‐based shielding materials getting much attention due to their light weight, flexibility, good processability, and other desirable traits. However, achieving consistent dispersion of conductive fillers and optimizing the balance between electrical, mechanical, and thermal properties remain challenges despite the advantages of polymer‐based materials. Especially, epoxy resins are promising polymer materials for EMI shielding applications due to their excellent mechanical strength, chemical resistance, and excellent adhesive properties. Additionally, epoxy resin exhibits remarkable processability allowing for various fabrication techniques such as casting, molding, and three‐dimensional printing. However, one of the significant drawbacks of epoxy resin is the difficulty in achieving uniform dispersion of conductive fillers within the epoxy matrix. In this study, we propose an iron‐nickel alloy (FeNi) embedded in an epoxy matrix (FeNi/Epoxy) for EMI shielding material. It is manufactured by facile fabrication process due to the advantages of epoxy, which has excellent processability. EMI shielding effectiveness at 12 GHz is enhanced from 9.12 to 17.86 dB by the increase of FeNi concentrations. Furthermore, thermal and mechanical properties were improved by the increase of FeNi concentration. Thermal conductivity for efficient heat dissipation is increased from 0.63 to 1.49 Wm−1 K−1. Moreover, polydopamine (PDA) was employed as a surface coating material for FeNi to overcome the non‐uniform dispersion of FeNi particles in the epoxy matrix. Surface coating by PDA significantly enhanced the dispersion uniformity and strengthened the adhesion between the filler and matrix. Elastic modulus is greatly increased from 83.03 MPa to 1.29 GPa by the surface coating. The enhancement of mechanical properties is derived from the chemical bonds between the filler and matrix.

Precise Needle and Cannula Placement in the Forehead During Aesthetic Procedures: Can Device and Angulation Influence Accuracy? A Fresh Frozen Specimen Study.

Myomodulation is a technique aimed at enhancing the dynamics of muscle contraction and relaxation through methods like hyaluronic acid (HA) injection. Achieving optimal outcomes depends on the precise placement of the injected product within the targeted anatomical plane. This is particularly important in the forehead, an area with elevated vascular risk. The selected treatment techniques must ensure both efficacy and safety. This study aims to assess the anatomical precision of HA injections in the forehead using different techniques and devices. Four fresh frozen specimens were injected with HA by five experienced board-certified plastic surgeons using three different techniques/devices: (1) a 50mm, 22G microcannula; (2) a 13mm, 27G needle with the bevel down at a 45-degree angle; and (3) the same needle positioned at a 90-degree angle. Ultrasound analysis was used to evaluate the precision of each approach. Both the cannula technique and the needle technique with the bevel down at a 45-degree angle consistently delivered the filler to the supraperiosteal layer in 100% of cases without spreading. However, the 90-degree needle technique, despite correct placement on the periosteum, resulted in filler dispersion across multiple layers. The accuracy of filler placement in the forehead is influenced by the choice of device and its angulation. It is recommended to use a cannula with the entry point at the frontalis crest or a needle angled at 45 degrees to the skin. The use of a needle at a 90-degree angle should be avoided to ensure precise placement and avoid filler migration. This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .