Search

Nonwoven materials are fashioned from polyimide (PI) and its copolymer derivative (urethane–imide) (CPUI) through the formation of electrical fibers, referred to as electrospinning (ES). Diaminobiphenyl ether (DABPE) and pyromellitic anhydride (PMA) are chosen as monomers in the synthesis of polyimide. Diamine dianhydride and toluene di-isocyanate (TDI) are used in the synthesis of copoly(urethaneimide), as is polycaprolactone (Mn = 2000). A nonwoven polyimide material is obtained from an aqueous–ethanolic solution of the triethylammonium salt of polyamide acid (SPAA) with subsequent thermal imidization of the nonwoven prepolymer at 250°C. A nonwoven material based on SPAA is obtained from a solution of copoly(urethaneamidoacid) in dimethyformamide (DMF) using a catalytic mixture consisting of triethylamine and acetic anhydride. Optimum conditions are selected for the formation of nonwoven fibers in electrospinning. The chemical structure of nonwovens is confirmed via IR spectroscopy. The morphology of the microstructure of nonwovens is studied by means of scanning electron microscopy (SEM). The thermal and mechanical properties of the obtained nonwovens are determined using TGA, DSC, and DMA, and their deformation and strength characteristics are determined. Membrane filtration properties of the obtained nonwovens are studied. It is concluded that nonwovens can be used as membranes that operate in nonaqueous organic media. [ABSTRACT FROM AUTHOR]

To enhance PI films' triboelectric nanogenerator(TENG) performance , we synthesized amino-functionalized reduced graphene oxide (FRGO)/polyimide (PI) composite films via in-situ polymerization. As a charge capturer, FRGO significantly increases the film's charge density and storage capacity, offering a novel method to boost the TENG performance of PI films. [Display omitted] As a promising sustainable power source in intelligent electronics, Triboelectric Nanogenerators (TENGs) have garnered widespread interest, with various strategies explored to enhance their output performance. However, most optimization methods for triboelectric materials have focused solely on tuning chemical compositions or fabricating surface microstructures. Here, we have prepared amino-functionalized reduced graphene oxide (FRGO)/polyimide (PI) composite films (PI-FRGO) via in-situ polymerization, aimed at enhancing PI materials' nanotribological power generation performance. By varying the doping levels of amino groups and controlling the FRGO proportion during synthesis, we can explore the optimal FRGO/PI composite film ratio. At a p-Phenylenediamine: reduced Graphene Oxide (PPDA: RGO) ratio of 1:1 and an FRGO addition of 0.1 %, the output electrical performance peaks with a voltage of 58 V, a charge of 33 nC and a current of 12 μA, nearly 2 times that of a pure PI film. We have fabricated a TENG with an optimally formulated PI-FRGO composite to explore its application potential. Under a 10 MΩ external load resistance, the TENG can deliver a power density of 3.5 mW/m2 and can be powering small devices. This work presents new effective strategies to significantly enhance TENG output performance and promote their widespread application. [ABSTRACT FROM AUTHOR]

Abstract This paper introduces a novel, cost-effective solution designed to achieve large absorption bandwidth within the THz spectrum employing a miniaturized, single-layer metamaterial structure. The designed structure features a single circular ring composed of an ohmic resistive sheet with notably higher sheet resistance than traditional metallic resonators. This distinctive design is implemented on a lossy dielectric polyimide substrate with a backing of metallic gold. Our developed absorbing structure demonstrates the capability to achieve a substantial absorption bandwidth ranging from 3.78 to 4.25 THz, maintaining a consistent absorption rate of over 90%. Moreover, we conducted an analysis to assess its absorption performance under various sheet resistance values within the top layer. Additionally, we characterized its angular stability and polarization insensitivity through oblique incident and polarization angle analysis. Finally, an RLC circuital and interference theory approach is adopted to justify its simulated results. The proposed absorber shows potential for a broad spectrum of applications, encompassing communication, imaging, and diverse integrated circuits operating within the THz band.

It is important to understand tribological characteristics of components operating in a hydrogen atmosphere. For instance, piston rings used in reciprocating compressors require strength, heat resistance and wear resistance, hence resins containing fillers are used. Particularly at high-pressure stages, PEEK- or polyimide (PI)-type composite resins are often introduced. In this study, focusing on PI and its composites, we investigated sliding properties of the resin in the hydrogen environment and the structure of transfer film. It was confirmed that some PI without fillers had good sliding properties and this unfilled PI exhibited sliding properties which was equivalent to other graphite-filled PI. A cross-sectional TEM EELS analysis revealed that the transfer film was a layer mainly composed of carbon. Raman analysis suggested that, in case of unfilled PI, the transfer film of carbon was formed by the decomposition of the PI due to wear, whereas in case of graphite-rich PI resin, the film was created mainly by decomposition of graphite. These results suggest that the carbon layer of the transfer film, which comes from sliding in the hydrogen environment, improves friction and wear properties, indicating that the origin of the layer may be irrespective of whatever it is (e.g., PI, graphite, etc.).

The world cannot counter climate change without the automobile industry becoming far more environmentally sustainable than it is today. With the realization that electrified mobility will take decades, not years, and that internal combustion engines (ICE) will continue to power vehicles in the near future, we need to step up the focus on improving fuel efficiency of ICE vehicles. In this report, we have confirmed that, in timing chains for automobile engines, the sliding area can be reduced by changing the arrangement of the arms & guides from continuous contact to a segmented one and by using an aromatic polyimide (PI) that can withstand the high contact surface pressure, thereby reducing friction loss. Through bench test monitoring, we confirmed that the friction loss was reduced in comparison to that by the conventional arms & guides in ICEs. The conventional arms & guides in the layout of the timing chains are placed with a curvature of ~ R2000 mm (at least R500 mm). In this study, the layout of the arms & guides was investigated. Each arm or guide is divided into two or three segments in the direction of travel and each curvature is reduced to about R100 mm. In addition, the material has been changed from polyamide (PA66) to PI. By these changes, the contact surface is decreased, and the surface pressure is increased. This means that on the Stribeck diagram, the lubrication conditions move in the direction of the smaller Sommerfeld number and the friction loss decreases. The use of the high compressive modulus material reduces the amount of deformation of the arms & guides contact surface, leading to the reduction of the friction loss.

As one single membrane material could not fulfill the requests of chemical stability, mechanical strength, and resistance to pollution in practical applications. Modifications of the membrane to improve its separation performance were of great significance. In this study, UV irradiation grafting modification was employed and butyl acrylate was selected as a modification monomer for polyimide membrane to improve its lipophilicity and separation efficiency in lubricant solvent recovery. And effects of monomer concentration, irradiation distance, and grafting time on the grafting results and separation properties of modified polyimide membranes were investigated. The results exhibited that modified polyimide membranes obtained an enhanced lubricant retention rate compared with raw membranes, which increased from 66.5% to 93.1%. The industrial test for 40 days proved the great stability of modified polyimide membranes. Overall, this work confirmed the good industrial utilization potential of modified polyimide membranes and offered an effective way for lubricant solvent recovery.

The present study aims to assess the impact of alfa and date palm natural fibers as reinforcement for epoxy, vinyl ester, and polyimide polymer (AlfaDate palm/epoxy, Alfa-Date palm/vinyl ester, and Alfa-date palm/polyimide) through a genetic approach. The study employs a genetic simulation rooted in the Weibull formalism, employing genetic operators such as selection, crossing, and mutation for a nuanced evaluation of the damage at the fibermatrix interface across the studied materials. The genetic algorithm results authentically capture the intrinsic behaviour of these materials, emphasising key mechanical properties like Young's Modulus, deformation, and stress at break. The obtained results highlight that the matrix showing the highest Young's modulus value at its fiber-matrix interface exhibits superior strength. These conclusions align with contemporary advancements in natural fiber-reinforced composite materials tailored for diverse industries and eco-friendly applications.

Aluminum‐doped ZnO (AZO) were successfully prepared on polyimide (PI) film using electrochemical deposition. Field emission scanning electron microscopy (FESEM) analysis revealed that as the aluminum concentration increased, the morphology of AZO nanostructures changed from pellets to nanorods. X‐ray photoelectron spectrometry (XPS) was employed to study the chemical states of undoped and Al‐doped ZnO on a polyimide substrate. The X‐ray diffraction (XRD) patterns of the PI/AZO nanostructures showed a polycrystalline wurtzite structure with a crystallographic orientation along the (002) plane. The XRD analysis also indicated that the average crystallite size decreased from 50.5 nm to 31.0 nm with increasing aluminum concentration (from 0.05 mM to 10 mM). Transmittance analysis revealed that with increasing aluminum concentration, the average optical transmittance in the visible region decreased from 90 % to 75 %. The aluminum concentration has a significant effect on the electrical properties of the samples, as shown by current‐voltage (I–V) and Hall measurements. Among the samples, the AZO/PI film prepared with 5 mM aluminum concentration exhibited the minimum electrical resistivity (4.14×10−2 Ω.cm), the highest carrier density (1.10×1021 cm−3) and the Hall mobility (5.40 cm2 V−1 s−1). We also discuss the possible mechanisms underlying these results compared to undoped ZnO films. This study contributes to the potential applications in flexible electronics and optoelectronics by demonstrating the tunability of AZO nanostructures on a flexible polyimide substrate through controlled aluminum doping. [ABSTRACT FROM AUTHOR]

The continuous upgrading of electronic technology has facilitated the integration and miniaturization of electronic and electrical equipment, as well as putting great pressure on the multifunctional demand for internal materials. Developing insulating materials with both low permittivity and high thermal conductivity has become imperative. This perspective focuses on polyimide (PI), which is the top material of the polymer material pyramid, discusses the characteristic parameters that affect its dielectric property and thermal conductivity. A series of basic schemes to regulate the dielectric/thermal properties of PI are summarized, revealing the bottlenecks and drawbacks of the current research. Future development trends of PIs featured low permittivity-high thermal conductivity are anticipated, and novel ideas are proposed for the development of new generation of multifunctional PIs. [ABSTRACT FROM AUTHOR]

This paper introduces a novel, cost-effective solution designed to achieve large absorption bandwidth within the THz spectrum employing a miniaturized, single-layer metamaterial structure. The designed structure features a single circular ring composed of an ohmic resistive sheet with notably higher sheet resistance than traditional metallic resonators. This distinctive design is implemented on a lossy dielectric polyimide substrate with a backing of metallic gold. Our developed absorbing structure demonstrates the capability to achieve a substantial absorption bandwidth ranging from 3.78 to 4.25 THz, maintaining a consistent absorption rate of over 90%. Moreover, we conducted an analysis to assess its absorption performance under various sheet resistance values within the top layer. Additionally, we characterized its angular stability and polarization insensitivity through oblique incident and polarization angle analysis. Finally, an RLC circuital and interference theory approach is adopted to justify its simulated results. The proposed absorber shows potential for a broad spectrum of applications, encompassing communication, imaging, and diverse integrated circuits operating within the THz band. [ABSTRACT FROM AUTHOR]

This paper introduces a novel, cost-effective solution designed to achieve large absorption bandwidth within the THz spectrum employing a miniaturized, single-layer metamaterial structure. The designed structure features a single circular ring composed of an ohmic resistive sheet with notably higher sheet resistance than traditional metallic resonators. This distinctive design is implemented on a lossy dielectric polyimide substrate with a backing of metallic gold. Our developed absorbing structure demonstrates the capability to achieve a substantial absorption bandwidth ranging from 3.78 to 4.25 THz, maintaining a consistent absorption rate of over 90%. Moreover, we conducted an analysis to assess its absorption performance under various sheet resistance values within the top layer. Additionally, we characterized its angular stability and polarization insensitivity through oblique incident and polarization angle analysis. Finally, an RLC circuital and interference theory approach is adopted to justify its simulated results. The proposed absorber shows potential for a broad spectrum of applications, encompassing communication, imaging, and diverse integrated circuits operating within the THz band. [ABSTRACT FROM AUTHOR]

A lithium‐ion battery separator facilitates lithium‐ion transportation and prevents direct contact between the cathode and anode. Polyimide separators exhibited superior thermal stability and electrolyte wettability. In this study, carboxylated polyimide separators were prepared by electrospinning carboxyl group‐containing monomers. Polyimide separators were prepared with different content of carboxyl group‐containing monomer. Moreover, the thermal property, mechanical property, and electrochemical performance of separators were studied. The carboxylated polyimide separators exhibited lower interfacial resistance and higher ionic conductivity compared with polyimide separators. Moreover, the LiFePO4/Li half‐cell assembled using the carboxylated polyimide exhibited enhanced cycling stability and rate capability. Therefore, carboxylated polyimide separators with superior electrochemical performances are promising candidates for lithium‐ion batteries. [ABSTRACT FROM AUTHOR]

Highlights A fluorinated polyimide (PI‐FTD) was synthesized for preparing a thermally conductive PI matrix and composites. Additionally, surface‐treated boron nitride (BN) was incorporated into the PI‐FTD via the solution casting method to form efficient heat paths along the through‐plane direction. The resultant composite demonstrated remarkable characteristics, including an impressive through‐plane thermal conductivity of 3.6 W mK−1, a substantial tensile strength of 69.4 MPa, and excellent thermal stability. When this composite was applied to light‐emitting diodes, it effectively managed heat, reducing the operating temperature by 29°C. The PI‐FTD/BN‐OH composites can potentially improve thermal management in electronic devices. A novel fluorinated polyimide (PI‐FTD) was fabricated. Introducing CF3 functionalities in the PI‐FTD provides high thermal stability. BN‐OH reinforced the thermal and mechanical properties of the composites. The PI‐FTD/BN‐OH composites achieved excellent thermal management. [ABSTRACT FROM AUTHOR]

Metalized plastic current collectors (MPCCs) have shown potential in improving the energy density and safety of lithium‐ion batteries (LIBs). However, the poor mechanical strength, weak interfacial adhesion force, and surface metal corrosion have impeded the practical application of MPCCs. Here, an innovative engineering of MPCCs is proposed by incorporating halloysite nanotubes (HNTs) as fillers into polyimide (PI) polymer layer, which is further coated with two thin copper (Cu) layers. Because of the strong bonding between HNTs surface and the PI precursor, HNTs improve the mechanical strength of PI‐HNTs composite film, reinforce the interfacial adhesion force between the PI‐HNTs film and the coated Cu layer, and suppress the Cu corrosion by electrolyte. The prepared MPCCs exhibit a low mass density and only account about one‐fifth of the density of commercial Cu CCs. Furthermore, the PI‐HNTs‐Cu composite demonstrates significantly enhanced interfacial adhesion force doubled to 4 N cm−1 along with prolonged stability under electrolyte immersion and electrochemical reaction conditions, and delivers a high fracture strength of 125 MPa. LIBs assembled with MPCCs deliver a twice higher discharge capacity compared to battery with Cu CCs and reach a long‐term cycle capacity retention as high as 92.9% at 0.5 C after 500 cycles. [ABSTRACT FROM AUTHOR]

A novel fluorinated diamine monomer (FPMDA ) was synthesized from p-fluorobenzaldehyde and 2, 6-dimethylaniline, and then reacted with pyromellitic anhydride to obtain a fluorinated polyimide (FPI). The structures of the synthesized FPMDA diamine monomer and polyimide were characterized by FTIR, nuclear magnetic hydrogen spectroscopy, and mass spectrometry (MS) ;the thermal properties of the polyimide film were characterized using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The results showed that FPI has excellent solubility in solvents such as DMF, NMP, and THF. FPI also shows good thermal stability, under nitrogen environment, with thermal decomposition temperature Td5% of 550 °C, Td10% of 580 °C, and char yield of 58.7% at 1 000 °C, its glass transition temperature is greater than 400 °C . [ABSTRACT FROM AUTHOR]

The traditional high-temperature preparation process of polyimide can cause many problems and limits the wider application in extreme conditions. An important challenge to be solved urgently is the reduction of imidization temperature. In this work, twelve kinds of polyimide films with different chain rigidity were prepared at low temperature of 200 °C, in the absence or presence of imidazole used as the catalyst. The molecular rigidity and free volume were theoretically calculated, and relationship between structure and properties were systematically studied. The results show that imidization reaction under low temperatures is significantly affected by the rigidity of molecular chains. The rigid structure of polyimide is not conducive to the low-temperature imidization, but this adverse effect can be eliminated by adding catalyst, resulting the notably increased imidization degree. The optical and thermal properties can be improved to a certain extent for the chemically catalyzed system, resulting in relatively higher heat resistance and thermal stability. While the mechanical performance could be determined by complicating factors, greatly different from polyimide films prepared by high temperature method. To investigate aggregation structures of films, the effect of chain rigidity and catalyst on the stacking or orientation of molecular chains was further elaborated. This work can contribute to the understanding of chemically catalyzed imidization that is rarely reported in the existing research, and will provide guidance for the low-temperature preparation of high-performance polyimides. [ABSTRACT FROM AUTHOR]

In order to improve the PI resin's processability and thermal properties, a novel diamine monomer bis(p-aminophenylethynyl)dimethylsilane was designed and synthesized by introducing silicon and alkyne groups in this paper. And a new thermosetting polyimide resin SiOPI with silicon and alkynyl structures in the main chain was prepared using 4,4′-oxobis (phthalic anhydride) (ODPA) as the dianhydride monomer with this diamine monomer. The structures of the diamine monomer and the polyimide were characterized by H nuclear magnetic resonance spectroscopy (1H NMR), Fourier transform infrared spectroscopy (FT-IR), mass spectrometry (MS), and X-ray diffraction (XRD), respectively. The incorporation of silyl groups into the PI increases the flexibility of the resin and provides good solubility and processability. The SiOPI is well soluble in DMF, DMSO and THF. The resin has a viscosity of less than 200 Pa·s at 50–88°C and has a wide processability range. By virtue of the introduction of alkyne groups, the cured polyimide forms dense reticulated structures, analogous to the benzene ring, giving the resin excellent heat resistance and mechanical property. The glass transition temperature (Tg) of SiOPI reached 367°C, and the heat loss temperature at 5% (Td5) is 540.9°C, the heat loss temperature at 10% (Td10) is 592.2°C, and the residual carbon rate at 800°C (R800°C) is 65.76% in a nitrogen atmosphere. The tensile strength of c-SiOPI is 257.6 MPa at room temperature and 232.9 MPa with a retention rate of 90.41% at 300°C, respectively. [ABSTRACT FROM AUTHOR]

In this study, 4-biphenyl-3,5-diaminobenzoate (E- m -PDA) was synthesized by three steps using 3,5-dinitrobenzoic acid as a starting material. Two series of colorless polyimides (CPIs) PI-(1a-1d) and PI-(2a-2d) were prepared by traditional two-step polycondensation of m -phenylenediamine (m -PDA) based diamines with different pendant groups (-H, CF3, COOH and biphenyl ester) with aromatic dianhydrides BPADA and 6FDA, respectively. All of the prepared CPIs exhibited high thermal stability with 5% weight loss at temperatures ranging from 428 to 539°C in nitrogen, and glass transition temperatures (T gs) ranging from 228 to 332°C. These PI films displayed a UV-vis absorption cut-off wavelength at 338–376 nm and transparency of 76%–89% at a wavelength of 450 nm. Both series of colorless PI films also showed low birefringence values of 0.0021–0.0100. In addition, the optical retardations of these CPIs were extremely low (48–220 nm), indicating low optical anisotropy of these CPI films. Colorless PI film PI-2d prepared based on E- m -PDA and 6FDA had good comprehensive properties of low birefringence (∆ n of 0.0064), high T g (319°C) and excellent transparency (T 450 of 88%). [ABSTRACT FROM AUTHOR]

Copyright of Journal of Tiangong University is the property of Journal of Tianjin Polytechnic University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Polymer Materials Science & Engineering is the property of Sichuan University, Polymer Research Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Acta Materiae Compositae Sinica is the property of Acta Materiea Compositae Sinica Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of China Plastics / Zhongguo Suliao is the property of Journal Office of CHINA PLASTICS and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

2D conjugated metal–organic frameworks (2D c‐MOFs) with large pore sizes and high surface areas are advantageous for adsorbing iodine species to enhance the electrochemical performance of aqueous dual‐ion batteries (ADIBs). However, most of the reported 2D c‐MOFs feature microporous structures, with few examples exhibiting mesoporous characteristics. Herein, we developed two mesoporous 2D c‐MOFs, namely PA‐TAPA−Cu‐MOF and PA‐PyTTA−Cu‐MOF, using newly designed arylimide based multitopic catechol ligands (6OH‐PA‐TAPA and 8OH‐PA‐PyTTA). Notably, PA‐TAPA−Cu‐MOF exhibits the largest pore sizes (3.9 nm) among all reported 2D c‐MOFs. Furthermore, we demonstrated that these 2D c‐MOFs can serve as promising cathode host materials for polyiodides in ADIBs for the first time. The incorporation of triphenylamine moieties in PA‐TAPA−Cu‐MOF resulted in a higher specific capacity (423.4 mAh g−1 after 100 cycles at 1.0 A g−1) and superior cycling performance, retaining 96 % capacity over 1000 cycles at 10 A g−1 compared to PA‐PyTTA−Cu‐MOF. Our comparative analysis revealed that the increased number of N anchoring sites and larger pore size in PA‐TAPA−Cu‐MOF facilitate efficient anchoring and conversion of I3−, as supported by spectroscopic electrochemistry and density functional theory calculations. [ABSTRACT FROM AUTHOR]

Air pollution containing microorganisms poses a major hazard to human health. It is critical to develop air filters that are both highly efficient for indoor use and suitable for use in industrial settings. Developing long‐lasting electrostatic force‐assisted filtration while keeping high‐temperature resistance and antibacterial qualities is still challenging. Here, centrifugal spinning is used to fabricate fiber mats consisting of polyimide with silver incorporation (PI/Ag). The electrostatic force remained over –700 V after 330 days. The strong electrostatic effect improves the filtration efficiency, resulting in a high PM0.3 removal efficiency of 99.1% with a low‐pressure drop of 103.67 Pa. The high filtration efficiency remains above 91.3% for PM0.3 after placing it for 330 days and heating it at 280 °C. The PI/Ag fiber mats also show antimicrobial properties against the E. coli (Gram‐negative) and S. aureus (Gram‐positive) with prominent bacteriostatic zones >1.2 mm. The PI/Ag fiber mat filters are expected to have great potential for multi‐scenario air filtration. [ABSTRACT FROM AUTHOR]

Relationship between the temperature of the electric field treatment (EFT) and the improvement of the effective thermal conductivity (TC) in the out‐of‐plane direction of the carbon nanofiber (CNF)/cured silicone rubber composite sheet was investigated to elucidate the appropriate operation of the EFT. Two types of silicone rubber precursors, with viscosities of 1.3 and 58 Pa∙s, were used. The effective TC gradually increased as the temperature during EFT increased from 40 to 80 °C. However, beyond 80 °C, the effective TC started to decrease and reached the same value as that of the sheet without EFT at 100 °C. This trend was observed regardless of the rubber species or CNF content. The influence of the EFT temperature was also discussed regarding the temperature dependency of the viscoelastic properties: storage modulus, loss modulus, and complex viscosity of the uncured precursor solution. When the temperatures were set at 80 °C, no significant changes were observed in the three‐viscoelastic properties for 60 min. On the other hand, a significant increase in the viscoelastic properties was observed after 10 min at 100 °C because of the start of the curing reaction, which supported the relationship between the temperature of the EFT and effective TC. [ABSTRACT FROM AUTHOR]

Aerogels are widely used as thermal insulation materials because of their high porosity and low bulk density. However, the insulation performance of aerogels is limited to a narrow temperature range. Besides, the preparation of aerogel materials with precisely controlled and complex architectures is still challenging. Here, we report 3D printed polyimide/silica aerogel particle (PI/SAP) composite aerogels for thermal insulation in a wide range of temperature with customized applications. The printability and shape fidelity of 3D printed composite aerogels is improved by adding hydrophilic SAP as a rheology modifier. The resulting PI/SAP composite aerogel exhibits excellent flame-retardant properties and thermal insulation from −50 °C to 1300 °C. Moreover, the PI/SAP composite aerogel with customized shape can be applied for battery insulation at subzero temperatures, promising to be used as customizable and stable insulating materials in a variety of complex and extreme applications. [ABSTRACT FROM AUTHOR]

Recently, PI as high-performance polymer with high glass transition temperature have been regarded as promising matrix for high-temperature dielectric nanocomposites. As such, the review aimed to summarize the influence of nanoceramic fillers on the characteristics of polyimide-based nanocomposites for high-temperature energy storage. Herein, it is worth noting that SiO2, TiO2, AlN, and BN remain favorable reinforcement materials for improving thermal stability, breakdown strength, and energy density of PI-matrix for high-temperature energy storage. Thus, as they depict the potential properties needed in high-temperature dielectrics, the authors concluded the study with challenges/recommendations for further enhancement of PI-based nanocomposites for high-temperature energy storage. [ABSTRACT FROM AUTHOR]

Researching and manufacturing materials that possess both electromagnetic interference (EMI) shielding and infrared stealth capabilities is of great significance. Herein, an ultrathin polyimide-based nonwoven fabric with low-reflection EMI shielding/infrared stealth performance is successfully fabricated by in-situ loading of Fe3O4/Ag nanoparticles on the surface of polyimide (PI) fiber (PFA), and followed by bonding with a commercial Cu/Ni mesh. The synergistic assembly of PFA and Cu/Ni promotes the rational construction of hierarchical impedance matching, inducing electromagnetic waves (EMW) to enter the composite and be dissipated as much as possible. Meanwhile, the existence of Cu/Ni mesh on back of PFA facilitates the formation of electromagnetic resonance and destructive interference of EMW reflected from composite, leading to a lower-reflectivity (0.26) EMI shielding performance of 58 dB within 24–40 GHz at a thinner thickness (430 µm). More importantly, the fluffy PFA nonwoven fabric and metal Cu/Ni mesh endow composite with good thermal insulation and low infrared emissivity, resulting in excellent infrared stealth performance in various environments. As a result, such excellent compatibility makes it possible to become a promising defense material to be applied in military tent for preventing electromagnetic and infrared radiation. [ABSTRACT FROM AUTHOR]

Copyright of Polymer Materials Science & Engineering is the property of Sichuan University, Polymer Research Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Lubrication Engineering (0254-0150) is the property of Editorial Office of LUBRICATION ENGINEERING and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Carbon-based conductive polymer composites (CPCs) have significant potential for fabricating low-cost and high-performance flexible electric heating films in deicing applications. However, the inferior high-temperature resistance and low heating power density seriously restrict their large-scale commercial application. Herein, a series of polyimide (PI)/carbon black (CB) composite electrothermal films with excellent high-temperature stability and high-power density are prepared by a simple slurry coating method. With successfully introducing the high-temperature resistance and high mechanical strength PI as polymer matrix, the PI/CB composite electrothermal films with a low percolation threshold of 10.8% have a broad operating temperature ranging from 40°C to 270°C under low applied voltages (< 60 V) at room temperature. Impressively, these PI/CB composite electrothermal films with a uniform thin thickness of 45 μm exhibit high operating temperature (> 200°C), rapid heating response speed (< 10 s), remarkable long-term working stability, and superior low-temperature operating reliability even at −30°C. The simulated deicing experiment indicates that the PI/CB composite electrothermal film dislodges an ice cube (thickness = 10 mm) within 280 s. This work not only provides a universal strategy for the design and fabrication of high-operating-temperature CPCs, but also verifies the great potential for use in deicing applications. [ABSTRACT FROM AUTHOR]

Thermoplastic polyimides (TPIs) can meet the requirements of advanced electronic packaging such as flexible copper clad laminate (FCCL) applied under extreme conditions, attributed to their excellent thermal stability, mechanical properties, electrical insulation and chemical resistance. With the increasing demands for electronic devices, such as applications in high‐frequency communication, it is highly desirable to develop high‐performance TPI with good thermoplasticity, thermal stability, mechanical properties and dielectric properties. However, there is a trade‐off between thermoplasticity and other properties. Herein, we introduce an effective strategy to afford TPIs with good performance by copolymerization of a diamine monomer consisted of a coplanar aromatic carbazole group and a short flexible linkage methylene group. On the one hand, short flexible linkages help improve the flexibility of polymer chains and are not too much to enable small‐scale molecular motions below Tg. On the other hand, coplanar aromatic donor groups benefit to strong charge transfer complex (CTC) interaction and π‐π stacking interaction. Based on this strategy, the resultant TPI possesses good thermoplasticity with a proper Tg of 348 °C. Meanwhile, it preserves a low coefficient thermal expansion of 48 ppm K−1, low dielectric constant/dielectric loss factor of 3.27/0.0073 at 10 GHz, and tensile strength of ca. 78 MPa. [ABSTRACT FROM AUTHOR]

Proton exchange membranes (PEMs) are the core components of fuel cells, and research has long focused on how to balance their proton conductivity and durability. In this work, a series of homogeneous blend of sulfonated polyimide (SPI) and sulfonated polyether ether ketone (SPEEK) hybrid membranes with were constructed refined with sulfonated MoS 2 (H–MoS 2) and sodium lignosulfonate (SLS). The results showed that the tensile strength of the films was enhanced by 39.4% (67.84 MPa) compared to the base film. The composite films incorporating 1 wt% H-MoS 2 and 2 wt% SLS has excellent proton conductivity, which can reach 50.24 mS/cm at 80°C and 100% humidity. The embed hybrid structure constructed by H–MoS 2 and SLS, which not only effectively solves the limitations of the proton transport channel of traditional polymer materials, but also provides abundant proton transport sites, which provides a new strategy for preparing high-performance PEM. [Display omitted] • The stability of composite films was improved by organic/inorganic co-modification • H–MoS 2 and SLS together construct a continuous proton transport channel • The tensile strength of the best composite film is up to 67.84 MPa [ABSTRACT FROM AUTHOR]

Titanium oxide (TiO2) coated polyimide has broad application prospects under extreme conditions. In order to obtain a high-quality ultra-thin TiO2 coating on polyimide by atomic layer deposition (ALD), the polyimide was activated by in situ oxygen plasma. It was found that a large number of polar oxygen functional groups, such as carboxyl, were generated on the surface of the activated polyimide, which can significantly promote the preparation of TiO2 coating by ALD. The nucleation and growth of TiO2 were studied by x-ray photoelectron spectroscopy monitoring and scanning electron microscopy observation. On the polyimide activated by oxygen plasma, the size of TiO2 nuclei decreased and the quantity of TiO2 nuclei increased, resulting in the growth of a highly uniform and dense TiO2 coating. This coating exhibited excellent resistance to atomic oxygen. When exposed to 3.5 × 1021 atom cm−2 atomic oxygen flux, the erosion yield of the polyimide coated with 100 ALD cycles of TiO2 was as low as 3.0 × 10−25 cm3/atom, which is one order less than that of the standard POLYIMIDE-ref Kapton® film. [ABSTRACT FROM AUTHOR]

Silicon carbide (SiC) is a wide-band gap semiconductor that exceeds other semiconducting materials (except diamond) in electrical, mechanical, chemical, and radiation stability. In this paper, we report a novel approach to fabrication of SiC nano films on a Si substrate, which is based on the endotaxial growth of a SiC crystalline phase in a graphite-like carbon (GLC) matrix. GLC films were formed by carbonization of rigid rod polyimide (PI) Langmuir–Blodgett (LB) films on a Si substrate at 1000 °C in vacuum. After rapid thermal annealing of GLC films at 1100 °C and 1200 °C, new types of heterostructures SiC(10 nm)/GLC(20 nm)/Si(111) and SiC(20 nm)/GLC(15 nm)/SiC(10 nm)/Si(111) were obtained. The SiC top layer was formed due to the Si-containing gas phase present above the surface of GLC film. An advantage of the proposed method of endotaxy is that the SiC crystalline phase is formed within the volume of the GLC film of a thickness predetermined by using PI LB films with different numbers of monolayers for carbonization. This approach allows growing SiC layers close to the 2D state, which is promising for optoelectronics, photovoltaics, spintronics. [ABSTRACT FROM AUTHOR]

Polyimide (PI) has good mechanical properties and thermal stability, while high coefficient (COF) and wear rate limit its wide application. In order to endow PI with better friction and wear resistance, Mo2Ti2C3 MXene was used as solid lubricant to prepare Mo2Ti2C3/PI nanocomposites with different content of Mo2Ti2C3. The effect of the amount of Mo2Ti2C3 on the tribological behavior of PI was explored and the tribological mechanism was also analyzed Tribological tests showed that at 1.2 wt% of Mo2Ti2C3 addition, the composite material demonstrated superior friction and wear resistance, exhibiting a 19.9% decrease in the COF and a 79.7% decrease in the wear rate compared to single PI due to the good self‐lubricating properties of Mo2Ti2C3 MXene. Moreover, Mo2Ti2C3 can also effectively assist PI to form sleek transfer films without interruption or gaps on the steel balls, resulting in a reduced friction COF and wear rate of the material. This work demonstrates that Mo2Ti2C3 MXene is an aussichtsreich additive for polymers to improve the tribological properties and broadens the applications of Mo2Ti2C3/PI composites in friction material area. Highlights: Mo2Ti2C3 significantly improves the tribological performance of polyimide.The thermal properties of Mo2Ti2C3/polyimide are enhanced by the introduction of Mo2Ti2C3.The minimum coefficient of Mo2Ti2C3/PI composites was only 0.246 at the 1.2 wt% content of Mo2Ti2C3.The wear rate of Mo2Ti2C3/PI composites was decreased by 79.7% at the 1.2 wt% addition of Mo2Ti2C3.Mo2Ti2C3 promotes the establishment of tribo‐film to protect the Mo2Ti2C3/PI composites from friction. [ABSTRACT FROM AUTHOR]

The triboelectric nanogenerator (TENG) has been considered as an effective way to convert various mechanical energies into electrical energy. However, the energy output needs continuous improvement for potential applications. In this study, triboelectric layers composed of polyimide (PI) matrix and carbon nanotube@barium titanate (CNT@BTO) nanoparticles were developed to achieve the performance enhancement through the synergistic coupling of piezoelectric and triboelectric effects as well as the microcapacitor function. To achieve the purpose, CNT@BTO nanoparticles were synthesized by the chemical vapor deposition method and then incorporated into a flexible PI triboelectric layer prepared using electrospinning technology and thermal imidization. The results showed that when the BTO content was 26 wt % and the CNT content was 2 wt %, the open-circuit voltage and short-circuit current of a TENG based on a PI/CNT@BTO nanofiber membrane reached 305 V and 104 μA, which were 3 times higher than those of a pure PI-based TENG. The TENG demonstrated sufficient power to drive small electronic devices, such as calculators, and to light up 124 commercial green LED and 18 blue COB light sources. Additionally, the TENG was integrated into a real-time temperature-sensing alarm system, showcasing its potential application in safety-related fields. The study demonstrated the feasible methods for TENGs' performance enhancement and provided potential application fields of energy-harvesting and self-powered sensing systems. [ABSTRACT FROM AUTHOR]

The excellent electrical properties of graphene have received widespread attention. However, the difficulty of electron transfer between layers still restricts the application of graphene composite materials to a large extent. Therefore, in this study, graphene/polyimide films were subjected to a Joule heating treatment to improve the electrical conductivity of the film by ~76.85%. After multiple Joule thermal cycle treatments, the conductivity of the graphene/polyimide film still gradually increased, but the increase in amplitude tended to slow down. Finally, after eight Joule heat treatments, the conductivity of the graphene/polyimide film was improved by ~93.94%. The Joule heating treatment caused the polyimide to undergo atomic rearrangement near the interface bonded to the graphene, forming a new crystalline phase favourable for electron transport with graphene as a template. Accordingly, a model of the bilayer capacitive microstructure of graphene/polyimide was proposed. The experiment suggests that the Joule heating treatment can effectively reduce the distance between graphene electrode plates in the bilayer capacitive micro-nanostructures of graphene/polyimide and greatly increases the number of charge carriers on the electrode plates. The TEM and WAXS characterisation results imply atomic structure changes at the graphene/polyimide bonding interface. [ABSTRACT FROM AUTHOR]

With the increasing demand for innovative electronic products, LED transparent screens are gradually entering the public eye. Polyimide (PI) materials combine high temperature resistance and high transparency, which can be used to prepare flexible copper-clad laminate substrates. The physical and chemical properties of PI materials differ from copper, such as their thermal expansion coefficients (CTEs), surface energy, etc. These differences affect the formation and stability of the interface between copper and PI films, resulting in a short life for LED transparent screens. To enhance PI-copper interfacial adhesion, aminopropyl-terminated polydimethylsiloxane (PDMS) can be used to increase the adhesive ability. Two diamine monomers with a trifluoromethyl structure and a sulfone group structure were selected in this research. Bisphenol type A diether dianhydride is a dianhydride monomer. All three of the above monomers have non−coplanar structures and flexible structural units. The adhesion and optical properties can be improved between the interface of the synthesized PI films and copper foil. PI films containing PDMS 0, 1, 3, and 5 wt% were analyzed using UV spectroscopy. The transmittance of the PI-1/3%, PI-1/5%, PI-2/3%, and PI-2/5% films were all more than 80% at 450 nm. Meanwhile, the Td 5% and Td 10% heat loss and Tg temperatures decreased gradually with the increase in PDMS. The peel adhesion of PI-copper foil was measured using a 180° peel assay. The effect of PDMS addition on peel adhesion was analyzed. PIs-3% films had the greatest peeling intensities of 0.98 N/mm and 0.85 N/mm. [ABSTRACT FROM AUTHOR]

To provide polyimide (PI) with high heat resistance and ultra-low coefficient of thermal expansion (CTE) for use in flexible display substrates, a novel diamine with bisbenzimidazole and bisamide groups, namely N,N'-(1H,1'H-[5,5'-bibenzo[d]imidazole]-2,2'-diyl)bis(4-aminobenzamide) (BZBA), was designed and successfully synthesized. Several poly(benzimidazole-amide-imide) (PBIAI) films were prepared by thermal imidization with 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 4,4'-oxydiphthalic anhydride (ODPA), 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA), and 4,4'-(hexafluoroisopropylindene)-diphthalic anhydride (6FDA), respectively. Among them, BZBA-BPDA has a high glass transition temperatures (T g = 345 °C) while achieving an extremely low coefficients of thermal expansion (CTE = 1.9 ppm K−1), meeting the processing requirements of polymer flexible substrates in OLED devices. The effects of different dianhydrides on the performance of PBIAIs were compared, providing a meaningful reference for further adjusting the PI molecular structure to meet specific requirements for industrial polymer films. [ABSTRACT FROM AUTHOR]

With the advent of the 5G era, the demand for heat dissipation using high thermal conductivity (TC) materials is becoming increasingly urgent. The electrical insulation and thermal stability of dielectric polymer composites are also notable in electrical and electronic applications. Nevertheless, the improvement in TC of dielectric polymer composites is typically accomplished at the expense of electrical insulating capabilities. Herein, we fabricated polyimide (PI) composites with ordered structure by combining electrostatic spinning, vacuum filtration deposition and blade-coating. The modified boron nitride nanosheets (mBN) not only enhanced the interaction between filler and PI matrix, but also reduced the interface thermal resistance. Benefiting from the hierarchical structure, the in-plane TC of prepared composite was 17.44 W/mK at 18.79 vol% mBN content, which is 9.6 times higher than that of pure PI. Moreover, the composites were electrically insulating, with the volume resistivity of about 1013 Ω cm, and exhibited great flexibility, exceptional thermal stability (T HRI ＞ 269 °C), excellent thermal dissipation capability and low dielectric characteristics. In summary, this work offers a novel perspective to design highly thermally conductive composites and these composites have vast application potential in flexible electronic devices or circuits. [ABSTRACT FROM AUTHOR]

The present study aims to assess the impact of alfa and date palm natural fibers as reinforcement for epoxy, vinyl ester, and polyimide polymer (Alfa-Date palm/epoxy, Alfa-Date palm/vinyl ester, and Alfa-date palm/polyimide) through a genetic approach. The study employs a genetic simulation rooted in the Weibull formalism, employing genetic operators such as selection, crossing, and mutation for a nuanced evaluation of the damage at the fibermatrix interface across the studied materials. The genetic algorithm results authentically capture the intrinsic behaviour of these materials, emphasising key mechanical properties like Young's Modulus, deformation, and stress at break. The obtained results highlight that the matrix showing the highest Young's modulus value at its fiber-matrix interface exhibits superior strength. These conclusions align with contemporary advancements in natural fiber-reinforced composite materials tailored for diverse industries and eco-friendly applications. [ABSTRACT FROM AUTHOR]

Copyright of Plastics Science & Technology / Suliao Ke-Ji is the property of Plastics Science & Technology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Orientation film is a key material in liquid crystal displays, and the technology of inducing liquid crystal molecular orientation through polyimide photoorientation film is widely studied. In this work, polyimide is a random copolymer synthesized from a mixture of cyclobutanetetracarboxylic dianhydride and pyromellitic dianhydride, 4,4' ‐ diaminodiphenylmethane, 3,3', 5,5'‐ tetramethylbenzidine, and Methanone, bis (4‐aminophenyl) ‐, homopolymer. In this study, we investigated the pre‐inclination of a series of photo‐crosslinked diamine structures for the polymerization of RM monomers by PSVA (Polymer Stabilized Vertical Alignment) technology, and mainly investigated the pre‐inclination of a series of light‐oriented films with different molar fraction reaction monomers polymerized on the backbone. The results show that the polymerization of 2‐(methacrylate)ethyl ester 3,5‐diaminobenzoic acid reaction monomer with 6.3% molar fraction of polyimide photooriented film achieves high pre‐tilt adjustment under low light accumulation conditions, and successfully achieves excellent optical & reliability performance. [ABSTRACT FROM AUTHOR]

The irreversible threshold voltage (Vth) shift by polyimide (PI) charging is experimentally demonstrated. The Vth of device without PI electrode is positively moved during the release. Interestingly, the shifted Vth is not recovered to initial value up to one month. The mechanism for the irreversibility is suggested. [ABSTRACT FROM AUTHOR]

Copyright of Polymer Materials Science & Engineering is the property of Sichuan University, Polymer Research Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Nitrogen-doped carbon is a major class of high-performance electrode materials for the electrochemical supercapacitor. Herein, nitrogen-doped carbon was obtained by pyrolysis to graphene-grafted polyimide precursors on carbon cloth through in situ polymerization. The morphology, structure, and electrochemical properties of flexible electrodes were investigated in detail. Scanning electron microscopy (SEM) confirmed the preparation of nitrogen-doped carbon on carbon cloth. X-ray photoelectron spectroscopy (XPS) characterization showed the doping of the N heteroatom. Flexible electrodes obtained with the optimized mass graphene delivered high specific capacitance of 669 F g−1 at 0.5 A g−1 and good cycle stability, with retention of 122.3% capacitance after 6000 cycles in a three-electrode system. These typical flexible electrodes show great potential in wearable energy storage devices. [ABSTRACT FROM AUTHOR]

Bio‐compatible strain sensors are indispensable for human monitoring devices, requiring a delicate balance of robustness, flexibility, and sensitivity. However, achieving these attributes concurrently remains a formidable challenge. This article presents a pioneering approach to fabricate three‐dimensional flexible strain sensors using laser‐induced graphene (LIG) on polyimide (PI) substrates. Through a one‐step laser direct writing (LDW) technique, durable LIG/CuSO4 composites with closed‐pore porous structures are synthesized. The integration of copper sulfate within the closed‐cell architecture of LIG establishes a resilient conducting pathway, enhancing sensitivity to deformation under tensile stress. The resulting sensor exhibits exceptional performance in monitoring a wide range of human movements, from vigorous activities to subtle oscillations and physiological signals. Notably, the sensor boasts a remarkable sensing range of up to 25% strain, coupled with a high sensitivity characterized by a gauge factor of approximately 597. Rapid response times of 175 ms and quick recovery times of 200 ms further underscore its efficiency. Moreover, the sensor demonstrates outstanding stability and durability, maintaining consistent performance over 5600 cyclic experiments. This innovative approach represents a significant advancement in bio‐compatible strain sensor technology, offering a versatile solution for diverse monitoring applications. [ABSTRACT FROM AUTHOR]

This work is dedicated to the development and investigation of the properties of low‐dielectric‐constant nonwoven materials obtained by electrospinning from a polyimide‐based polymer, PMDA‐ODA, which is composed of pyromellitic dianhydride (PMDA) and 4,4′‐oxydianiline (ODA). The influence of the molar mass of PMDA‐ODA on the structural, mechanical, and dielectric properties of the resulting samples has been investigated. The molar mass of the polyimide has been determined through light scattering and viscosity measurements of polyamic acid solutions. As the molar mass of PMDA‐ODA increases from 13.400 to 49.300 g/mol, the glass transition temperature of the produced nonwoven samples increases, and their tensile mechanical properties are improved. The dielectric constant of PMDA‐ODA nonwoven polyimide materials varies from 1.55 to 1.91 at a temperature of 30°C in a frequency range from 1 Hz to 1 MHz, depending on the molar mass of the polymer used. [ABSTRACT FROM AUTHOR]

Abstract The threat to information security from electromagnetic pollution has sparked widespread interest in the development of microwave absorption materials (MAMs). Although considerable progress has been made in high‐performance MAMs, little attention was paid to their absorption frequency regulation to respond to variable input frequencies and their stability and durability to cope with complex environments. Here, a highly compressible polyimide‐packaging carbon nanocoils/carbon foam (PI@CNCs/CF) fabricated by a facile vacuum impregnation method is reported to be used as a dynamically frequency‐tunable and environmentally stable microwave absorber. PI@CNCs/CF exhibits good structural stability and mechanical properties, which allows precise absorption frequency tuning by simply changing its compression ratio. For the first time, the tunable effective absorption bandwidth can cover the whole test frequency band (2−18 GHz) with the broadest effective absorption bandwidth of 10.8 GHz and the minimum reflection loss of −60.5 dB. Moreover, PI@CNCs/CF possesses excellent heat insulation, infrared stealth, self‐cleaning, flame retardant, and acid‐alkali corrosion resistance, which endows it high reliability even under various harsh environments and repeated compression testing. The frequency‐tunable mechanism is elucidated by combining experiment and simulation results, possibly guiding in designing dynamically frequency‐tunable MAMs with good environmental stability in the future.