Aramid Paper Research Articles

Interface engineering via non-thermal atmospheric plasma for highly tensile insulating epoxy-impregnated aramid composite paper

Epoxy-impregnated aramid composites, notable for their excellent mechanical and insulation qualities, are pivotal in electrical engineering and electronics. However, their performance is severely restrained by interface issues. This research proposes an effective modification strategy for improving interface property by employing non-thermal atmospheric plasma to introduce active functional groups onto aramid paper. The modified composites demonstrated a 26 % increase in tensile strength and a 20 % enhancement in breakdown strength at best, alongside inhibited charge transport properties and reduced partial discharge under operational electric fields. Molecular simulation suggests that plasma treatment bolsters interface hydrogen bonding, restricting the chain mobility of the resin molecular, and thus augmenting inter-phase compatibility. This study offers a factual perspective on improving resin-impregnated composites, laying a theoretical foundation for advancing high-performance materials in power industries.

Nacre-inspired composite papers with enhanced mechanical and electrical insulating properties: Assembly of aramid papers with aramid nanofibers and basalt nanosheets

Aramid papers (AP), made of aramid fibers, demonstrate superiority in electrical insulation applications. Unfortunately, the strength and electrical insulating properties of AP remain suboptimal, primarily due to the smooth surface and chemical inertness of aramid fibers. Herein, AP are modified via the nacre-mimetic structure composed of aramid nanofibers (ANF) and carbonylated basalt nanosheets (CBSNs). This is achieved by impregnating AP into an ANF-CBSNs (A-C) suspension containing a 3D ANF framework as the matrix and 2D CBSNs as fillers. The resultant biomimetic composite papers (AP/A-C composite papers) exhibit a layered “brick-and-mortar” structure, demonstrating superior mechanical and electrical insulating properties. Notably, the tensile strength and breakdown strength of AP/A-C5 composite papers reach 39.69 MPa and 22.04 kV mm−1, respectively, representing a 155 % and 85 % increase compared to those of the control AP. These impressive properties are accompanied with excellent volume resistivity, exceptional dielectric properties, impressive folding endurance, outstanding heat insulation, and remarkable flame retardance. The nacre-inspired strategy offers an effective approach for producing highly promising electrical insulating papers for advanced electrical equipment.

Impact of Defect Structures on Interfacial and Insulation Properties in Epoxy-Impregnated Aramid Paper

Impact of Defect Structures on Interfacial and Insulation Properties in Epoxy-Impregnated Aramid Paper

Research on The Dielectric Property of Nano-doped Aramid Paper

Oil-paper insulation systems are widely used in high-voltage equipment. Reducing the dielectric constant of insulating paper can improve the dielectric coordination of the oil-paper combination system. At present, a large number of new synthetic insulation materials have been produced, and some new composite insulation papers have low dielectric constant and high electrical strength properties. This article studied the optimal process flow for preparing aramid paper in the laboratory, trial-produced laboratory hand sheets with three types of nanofillers at different doping concentrations, and conducted relative dielectric constant and dielectric loss tests to select Laboratory samples with the best performance; the main research results achieved in the paper are as follows: ①Researched and determined the optimal process flow for making aramid paper in the laboratory, explored the effects of different rolling pressures and rolling temperatures on the dielectric properties of the paper, and determined the optimal rolling temperature and temperature of meta-aramid paper. The pressures are 200℃and 0.3Mpa respectively. ②Meta-aramid paper doped with SiO2, TiO2 and x nanoparticles was prepared, and the relative dielectric properties of the three nanoparticles at the optimal doping amounts (15%, 3% and 4%, respectively) were compared. Constant and dielectric loss, it is determined that the dielectric properties of 4% C3N4 nanoparticle-doped paper are at a relatively excellent level. Compared with pure paper, its relative dielectric constant is not much different, and it can better cooperate with transformer oil. At the same time The dielectric loss is reduced, so nanoparticles of this type and concentration are used as fillers to improve the electrical properties of aramid paper.

Femtosecond laser precision machining of carbon film based on aramid paper substrate

Carbon film has many applications in flexible electronic devices (FED) due to its low cost and high conductivity. However, it is difficult to remove carbon film from the substrate without damaging it. This research explores the use of femtosecond laser, which has minimal thermal effect and non-contact processing, for carbon film ablation. The main objectives are to determine the ablation threshold of carbon film and aramid paper, to optimize the laser ablation parameters and scanning path, and to analyze the ablation mechanism and quality. The results show that the optimal laser fluence is between 0.22 J/cm2 and 1.45 J/cm2, and the optimal scanning method is grid scanning method. The laser ablation achieves a removal depth of 9.4 μm and a minimum Sa of 3.0 μm. Raman spectroscopy confirms the complete removal of carbon film and the transformation of graphite to amorphous carbon. The ablation process is mainly governed by combustion and evaporation. A resistance strain gauge is fabricated using laser ablation to demonstrate its potential in carbon film FED manufacturing.

A new interface bonding improvement method combined with precipitation and hot-pressing process to ameliorate the defects of para aramid paper

At present, the mechanical properties of para aramid paper (PPTA paper) are still severely challenged since interface bonding defects. In this work, a novel method for improving the interface bonding of PPTA paper was proposed by introducing m-phenylenediamine (MPD) into PPTA molecular chain by copolymerization. Result showed that the addition of MPD could monitor the rigidity and glass transition temperature (Tg) of PPTA. The Tg generated by the copolymerized modified PPTA precipitated fibers (MAPFs) realized micro-melting bonding with adjacent fibers during hot-pressing process. Further optimization of MAPFs precipitation and hot-pressing process improved the tensile strength of paper. Results indicated that the tensile strength of paper made of MAPFs with 60% MPD far beyond PPTA paper (PAP), and was 1.07 times of Nomex paper. The method provides a reference value for the application of high performance PAP in lightweight and high strength fields, broadening the application field of PAP as well.

Hydrophobic Composite Foams with Asymmetric Gradient Sandwich Structure for Excellent Electromagnetic Interference Shielding and Photothermal Response.

The evolution of contemporary electronics urgently requires the use of versatile electromagnetic interference (EMI) shielding materials in complex environments. Interlayer polydimethylsiloxane (PDMS)/Fe3O4@multiwalled carbon nanotubes (MWCNTs) foams were prepared by a simple physical foaming method with excellent flexibility and electromagnetic wave absorption. The bottom nickel aramid paper (NiP) layer creates a dense conductive network by chemical plating technology, which ensures excellent EMI effectiveness. The upper carbon black (CB)/Fe3O4 layer further improves the absorption performance via conductive loss and magnetic loss. With the effective layout of the impedance matching layer, absorbing layer, and conductive shielding layer, the CB/Fe3O4-PDMS/Fe3O4@MWCNTs-NiP composite material achieves an EMI shielding effectiveness (EMI SE) of 61.7 dB and an absorption coefficient of 0.58 at X-band. In addition, the composite foam provides photothermal conversion and hydrophobicity due to the effective stacking of PDMS and CB/Fe3O4. Thus, the multifunctional composite foam presents a broad range of possible applications, benefiting EMI shielding as well as other specific areas.

Thermal decomposition and charring behavior of polyphenylene sulfide/para-amrid fiber composite paper with excellent fireproof property

A charring behavior was found during the combustion of para-aramid chopped fibers/polyphenylene sulfide (ACFs/PPS) composite paper, which formed a highly graphitized carbon layer structure with specific mechanical properties. This sturdy structure is composed of a dense carbon layer mixed evenly between the inner and outer layers, the outer layer can effectively block the spread of oxygen and degradation products, as well as external heat radiation, while safeguarding the inner layer's structural integrity. Herein, we systematically researched the flame retardancy and thermal degradation properties of ACFs/PPS composite paper. In combustion testing, the char of ACFs/PPS composite paper could support a weight of 50 g, while the neat aramid paper was burned through by fire, which indicates the Charcoal-forming property of ACFs/PPS composite paper is better than that of neat aramid paper, and ACFs/PPS composite paper has better fire resistance because of its good char formation. Meanwhile, we further showcase the application in electrically insulating and firefighting clothing interlayers.

Mechanically strong, flexible, and flame-retardant Ti3C2Tx MXene-coated aramid paper with superior electromagnetic interference shielding and electrical heating performance

Undesirable electromagnetic interference (EMI) created by modern electronic devices has detrimental effects on the performance of high-precision electronic devices, information security, and human health. Therefore, lightweight, flexible, robust, and easy-to-fabricate EMI shielding materials with integrated functions are highly desirable to combat electromagnetic pollution. Herein, we report a scalable and facile strategy to prepare a flexible Ti3C2Tx MXene-coated aramid paper (MAP) with high-efficiency EMI shielding and excellent electrical heating performance. The intertwined network by aramid fibers endows the aramid paper (AP) with superior mechanical properties. After selectively single/dual coating with MXene onto AP, the MAP maintains a superior tensile strength of 73.6 MPa and enormous folding endurance of 4156 times. Owing to the exceptional electrical conductivity of MXene, the MAP with a relatively low MXene content (∼9.0 wt%) exhibits excellent overall performance with an EMI shielding effectiveness (SE) of 38 dB and SE/t of 422.2 dB mm−1. It’s noteworthy that the EMI SE of the MAP remains almost unchanged (37.4 dB) even after experiencing 5,000 repeated bending cycles. Additionally, the MAP shows satisfactory Joule electric-heating capability (a heating temperature rise of 130 °C at a low driving voltage of 5 V) and excellent flame-retardancy. This work provides a feasible strategy for large-scale production of flexible EMI shielding paper with multifunctional properties for future wearable facilities.

Protect aramid materials from UV‐induced damage by ANF and ANF/light stabilizer composites

AbstractAramid materials have been applied in many important civil and military fields. But a major drawback to aramid materials is the susceptibility to UV‐induced damage. In this work, aramid nanofibers (ANFs) and ANF/nano‐ZnO composites were used to protect aramid materials from UV‐induced damage. ANF protective layer was created on the surface of aramid fibers, and the ANF‐coated aramid fibers could be further prepared to aramid paper. Moreover, ANF/nano‐ZnO composites were synthesized and used for stronger UV‐blocking ability. ANFs provided effective protection to aramid material. The properties after UV exposure (about 9.3 years in the natural environment) were largely improved: ANFs improved the retention rate of strength by 17.96% for aramid fibers and by 16.93% for aramid paper. ANFs also showed synergistic effect with UV‐absorbing inorganic nanoparticles. After UV exposure, the tensile strength of aramid paper with ANF/nano‐ZnO composites was even higher than the initial value (121.55%), and the retention rate of strength was 2.43 times higher than the original aramid paper.

Light-weight wideband electromagnetic wave absorber based on aramid paper

A lightweight wideband honeycomb absorber is theoretically and experimentally investigated. The proposed absorber is constructed of aramid paper, which contains carbon fibers to absorb partially the incident electromagnetic wave. Graded silver paste circuits are also printed on aramid paper to improve the impedance matching properties and, thus, achieve wideband absorption performance. An absorber sample was fabricated and measured to verify the design strategies. The designed absorber has a fractional absorption bandwidth of 133% from 3.6–18 GHz, with a thickness of 0.19λL at the lowest frequency. The total weight of the absorber is 18.2 g, with a density of 28.4 kg/m3.

Large-area, highly thermally conductive, but electrically insulative industrial aramid papers with hierarchical multiscale compositing structures

The rapid development of emerging 5G electrical fields has put forward high requirements to the thermal dissipation performance of industrial aramid papers (IAPs), which are commonly used as the insulation layers of electrical equipment. Herein, we reported a facile method for preparing large-area (>7000 cm2), thermally conductive, but electrically insulative IAPs by compounding multiscale boron nitride nanosheets (BNNSs), industrial diamond microparticles (DMPs), and industrial aramid micropulps and microfibers (AMPs & AMFs) towards hierarchical compositing structures. Specifically, BNNSs can adhere to the surface of DMPs through electrostatic interaction and reduce the thermal resistance between neighboring DMPs, which ultimately ensures high in-plane thermal conductivity (11.66 W/(mK)) of IAPs, which is about 7 times that of pure aramid papers. Meanwhile, IAPs also exhibit high volume resistivity of 4.95 × 1015 Ω·cm. At last, the IAPs were successfully applied in a transformer for insulation and thermal conducting, demonstrating their high potential in industrial electrical equipment.

Asymmetric conductive structure design for stabilized composites with absorption dominated ultra-efficient electromagnetic interference shielding performance

Structurally asymmetric melamine foam (MF)/Polyaniline (Pani)/Fe3O4@reduced graphene oxide (rGO)/Ag-plated aramid paper (AgP)/Polydimethylsiloxane (PDMS) stabilized composites were successfully designed with controlled distribution of the conductive network to accomplish harmonization of electromagnetic absorption and shielding. Wherein, the upper MF/Pani/Fe3O4@rGO/PDMS foam combines in-situ polymerization and dip coating methods utilizing the synergistic effect of conductive Pani and Fe3O4@rGO to achieve superior impedance matching and absorption performance, while the dense conductive network formed in the bottom AgP by electroless plating technique ensures superior electromagnetic shielding effectiveness (EMI SE). With the rational arrangement of the absorptive and conductive shielding layers, MF/Pani/Fe3O4@rGO/AgP/PDMS composites demonstrate of 70 dB and extremely high absorption coefficient (A) of 0.86 at X-band. Notably, benefiting from the asymmetric structural design and PDMS wrapping, the composites possess superior thermal stability, mechanical strength and stable EMI SE. This valid work delivers a useful concept for the rational regulation of conductive networks in shielding composites, improving the applicability in practical environments.

High-Performance Cladophora-Algae-Based Paper for Honeycomb Core in Sandwich-Structured Composite: Preparation and Characterizations

Cellulose is classified as one of the most abundant biopolymers in nature. Its excellent properties have gained a lot of interest as an alternative material for synthetic polymers. Nowadays, cellulose can be processed into numerous derivative products, such as microcrystalline cellulose (MCC) and nanocrystalline cellulose (NCC). MCC and NCC have demonstrated outstanding mechanical properties owing to their high degree of crystallinity. One of the promising applications of MCC and NCC is high-performance paper. It can be utilized as a substitute for the aramid paper that has been commercially used as a honeycomb core material for sandwich-structured composites. In this study, MCC and NCC were prepared by extracting cellulose from the Cladophora algae resource. MCC and NCC possessed different characteristics because of their distinct morphologies. Furthermore, MCC and NCC were formed into a paper at various grammages and then impregnated with epoxy resin. The effect of paper grammage and epoxy resin impregnation on the mechanical properties of both materials was studied. Then, MCC and NCC paper was prepared as a raw material for honeycomb core applications. The results showed that epoxy-impregnated MCC paper outperformed epoxy-impregnated NCC paper with a compression strength of 0.72 MPa. The interesting result from this study is that the compression strength of the MCC-based honeycomb core was comparable to the commercial ones despite being made of a natural resource, which is sustainable and renewable. Therefore, cellulose-based paper is promising to be used for honeycomb core applications in sandwich-structured composites.

Hierarchical construction of CNT networks in aramid papers for high-efficiency microwave absorption

Hierarchical construction of CNT networks in aramid papers for high-efficiency microwave absorption

A novel and effective approach to enhance the interfacial interactions of meta-aramid fibers

Meta-aramid paper exhibits some unique properties, including high temperature resistance, electrical insulation. However, due to the inherent chemical inertness of aramid fibers, the interfacial bonding between fibers is weak, which negatively affect the properties of aramid paper. Herein, we report a simple, effective and scalable process for substantially improving the interfacial bonding between aramid fibers, thus, mechanical and insulating properties of the meta-aramid composite paper, and it was achieved by surface coating of aramid paper with meta-aramid stock solution that contains N, N dimethylacetamide (DMAc)-CaCl2 and high molecular weight poly (m-phenylene isophthalamide) polymers. Results show that the tensile strength, modulus, internal bond strength and tearing index of the resultant all-PMIA paper increased by 83 %, 58 %, 173 % and 89 %, respectively, in comparison with those of the control. The breakdown strength of the improved aramid paper is 190 % higher than that of the control paper, attaining 26.46 KV/mm. This work provides a simple, economical, efficient, and scalable method to improve the overall performance of meta-aramid paper, which has great potential to be implemented at the industrial scale.

Design of sandwich-structured para-aramid paper with polyphenylene sulfide non-woven fabric for enhancing mechanical properties and breakdown strength

The rapid development of national defense, military industry, and aerospace puts forward higher requirements to the mechanical property, breakdown strength, dielectric properties, and heat resistance of high-performance aramid paper. However, the vast majority of aramid paper-based materials can hardly have a combination of satisfactory high mechanical properties and breakdown strength due to the porous structure of paper-based materials. Herein, we report a para-aramid chopped fibers/polyphenylene sulfide (ACFs/PPS) composite paper with a sandwich structure by designing the structure of aramid paper. Dense PPS microfiber membrane as robust armor filled and repaired the voids and defects on ACFs/PPS composite paper. Additionally, strong barrier interfaces between PPS film and ACFs/PPS composite paper effectively slow down the transmission of voltage to the inside of the composite paper. Thus we obtain the sandwich-structured ACFs/PPS composite paper with excellent mechanical strength (158.7 MPa) and breakdown strength (55 kV/mm), which are almost 1.5 and 2.5 times higher than ACFs/PPS composite paper, respectively. Besides, excellent mechanical properties and breakdown strength are wonderfully integrated with superior dielectric properties (tanδ <0.0035), chemical stability, and thermal stability (DTGmax > 575 °C), far superior to reported aramid paper-based materials. This work plays an important role in fabricating fabulous multi-attribute combinations of aramid paper-based materials and can also be extended to other materials and structures.

Equivalent mechanical model of resin-coated aramid paper of Nomex honeycomb

Nomex honeycomb, as the core part of sandwich structure, has been widely used in the aviation and aerospace industries. Ultrasonic cutting, as a technology that can reduce machining defects, has been highlighted in recent years, but some problems in the cutting process still need to be investigated significantly. Finite element method (FEM) offers an alternative way of in-depth understanding of the problems. However, the multi-layer structure of the Nomex honeycomb cell wall, which is the resin-coated aramid paper, makes it difficult to establish a detailed multi-layered finite element (FE) model at a macro-scale level. Therefore, a novel segmented material mechanical model, which is applicable to the equivalent single-layer model, is proposed based on the analysis of the mechanical behaviour of the multi-layer structure of the resin-coated aramid paper. Moreover, the calculating method of equivalent mechanical parameters of the multi-layer structure are proposed theoretically. The proposed method is first verified by FE models at a micro-scale level in both single-layer and multi-layer approaches. Additionally, simulations and experiments are performed to verify that the proposed method performs well in the simulation of ultrasonic cutting for Nomex honeycomb, and the difficulty of modelling and CPU time of simulation are reduced significantly.

Performance Analysis of Chopped Fiber Composite Meta-Nano-Aramid IP for Transformer Bushings and to Analyze Environmental Impact

To study the effect of nano-SiO2 doping content on the properties of chopped fiber composite meta-nano-aramid insulating paper (IP) for transformer bushings, the laboratory-prepared chopped fiber composite meta-nano-aramid IP with different nano-SiO2 doping content is analyzed to assess its impact on the environment. The study has been carried out by considering crystallographic properties and morphology of chopped fiber composite meta-nano-aramid fiber, the influence-mechanism of nano-SiO2 doping content on the mechanical properties, the thermal stability and insulating properties of aramid paper. The experimental results show that the appropriate graft modification of nano-SiO2 enhances the thermal stability and mechanical properties of the meta-aramid (MA) insulating paper. It also shows lesser carbon emissions. When the results are compared with SiO2 without grafted silane coupling agent, SiO2 with a surface graft ratio of 6%, the former method (SiO2 without grafted silane coupling agent) shows a greater increase in the glass transition temperature of the MAIP. At the same time, it shows weakened molecular weight in terms of MSD. The proposed method shows more prominence in terms of the chain kinematic ability, the resistance to deformation, and shearing in terms of mechanical properties. When SiO2 with the graft ratio of 12% is observed, it does not show any improvement, and also the effects on thermal stability and mechanical properties of IP are not significant which is similar to grafting. After hot pressing at 245°C, 30 MPa for 5 min, the breakdown strength, and volume resistivity can reach as high as 37 kV/mm and 1.34 × 1015 Ω·cm respectively. The proposed method shows a significant environmental impact in terms of less emission of CO and CO2.

Enhanced Aramid/Al2O3 interfacial properties by PDDA modification for the preparation of composite insulating paper

To further improve the electrical insulation properties of meta-aramid paper, polydimethyldiallyl ammonium chloride (PDDA) was used for the modification of nano-Al2O3 in this work. The modified products were characterized by means of transmission electron microscopy, Fourier transform infrared spectrometer and liquid Zeta potential. The original and PDDA-modified nano-Al2O3 was doped into the aramid fiber composite, and the effects of PDDA and filler mass fraction on several properties such as electrical conductivity, breakdown strength and surface charge dissipation rate of insulating paper were studied. Finally, the interfacial properties of the composites were investigated using molecular dynamics. The results showed that PDDA was successfully coated on the surface of nano-Al2O3, and its surface potential was changed from negative to positive, which could improve the interface characteristics between filler and matrix and enhance the dielectric strength of aramid paper. Besides, saturation effect of PDDA modification was observed, and when the amount of PDDA was 10% and the content of modified nano-Al2O3 was 3%, the breakdown strength of aramid paper was increased by 20%, and the volume conductivity was decreased by 68%. The simulation result revealed that PDDA could improve the insulation performance of aramid paper by reducing the interfacial binding energy between aramid and filler.