Polyimide Nanocomposites Research Articles

Large interfacial polarization in metal–organic framework hollow ZIF-8/polyimide low-k nanocomposite films

Polymer films with tailored dielectric properties and large electrical displacement are required for applications in microelectronics due to the need for ultrahigh speed and low transmission delays. In this study, we developed a low-k polyimide (PI) nanocomposite incorporated with metal–organic framework hollow ZIF-8 (HZIF-8) nanocrystals to achieve a high energy storage capacity. The PI nanocomposite film was prepared by solution casting a mixture of HZIF-8/polyamide acid with thermal imidization. A dielectric constant of 2.26 was obtained at 100 Hz for the 5 wt% nanocomposite with a multi-stage pore architecture. Due to improved interfacial polarization, the 1 wt% nanocomposite had a high energy density of 12.2 J/cm3 and a charge–discharge efficiency of 70% at 600 MV/m. The PI nanocomposite film exhibited dielectric reliability with inherent flexible performance, and it is expected to be a primary candidate for polymer dielectric applications in microelectronics.

High temperature energy storage and release properties of polyimide nanocomposites simulated by considering charge trapping effects

AbstractDielectric energy storage capacitors with excellent high temperature resistance are essential in fields such as aerospace and pulse power. However, common high‐temperature resistant polymers such as polyimide (PI) and polyether sulfone have low energy storage densities and energy efficiencies at high temperature, which are greatly limited in practical applications. The polymer nanocomposites prepared by doping modification can regulate the charge injection and transport process, and improve the high‐temperature energy storage performance. However, the quantitative relationship between charge injection and charge trapping and the energy storage performance of linear polymer nanocomposites still needs further study. An energy storage and release model considering the charge trapping effects is constructed by the authors. We simulate the high‐temperature energy storage properties of polyimide nanocomposite dielectrics (PI PNCs) with different charge injection barriers and trap parameters at 150°C. A triangular voltage is applied to the electrodes at both sides of the PI PNCs, the electric displacement‐electric field loop is simulated, and the discharged energy densities and energy efficiencies are calculated. The simulation results are consistent with the experimental results. Increasing the charge injection barrier, deep trap energy and deep trap density can effectively reduce the charge injection and the carrier mobility, thereby improving the discharged energy densities and energy efficiencies of dielectric capacitors. In the case of low charge injection barrier (1.3 eV), with the increase of deep trap energy (0.7–1.5 eV) and deep trap density (1 × 1021–1 × 1025 m−3), the discharged energy density changes from 0.20 to 1.44 Jcm−3, the energy efficiency changes from 9.0% to 99.9%, and the high‐temperature energy storage performance improves significantly. This research provides theoretical and model support for the improvement of the high‐temperature energy storage performance of nanocomposites.

Research Progress and Application of Polyimide-Based Nanocomposites.

Polyimide (PI) is one of the most dominant engineering plastics with excellent thermal, mechanical, chemical stability and dielectric performance. Further improving the versatility of PIs is of great significance, broadening their application prospects. Thus, integrating functional nanofillers can finely tune the individual characteristic to a certain extent as required by the function. Integrating the two complementary benefits, PI-based composites strongly expand applications, such as aerospace, microelectronic devices, separation membranes, catalysis, and sensors. Here, from the perspective of system science, the recent studies of PI-based composites for molecular design, manufacturing process, combination methods, and the relevant applications are reviewed, more relevantly on the mechanism underlying the phenomena. Additionally, a systematic summary of the current challenges and further directions for PI nanocomposites is presented. Hence, the review will pave the way for future studies.

Thermal Decomposition and Stability of Hybrid Graphene–Clay/Polyimide Nanocomposites

Polyimide matrix nanocomposites have gained more attention in recent years due to their high thermal stability, good interfacial bonding, light weight, and good wear resistance and corrosion, factors that make them find great applications in the field of aerospace and advanced equipment. Many advancements have been made in improving the thermal, mechanical, and wear properties of polyimide nanocomposites. The use of nanofillers such as carbon nanotubes, graphene, graphene oxide, clay, and alumina has been studied. Some challenges with nanofillers are dispersion in the polymer matrix and interfacial adhesion; this has led to surface modification of the fillers. In this study, the interaction between clay and graphene to enhance the thermal and thermal-oxidative stability of a nanocomposite was studied. A polyimide/graphene nanocomposite containing ~12.48 vol.% graphene was used as the base nanocomposite, into which varying amounts of clay were added (0.45-9 vol.% clay). Thermogravimetric studies of the nitrogen and air atmospheres showed an improvement in thermal decomposition temperature by up to 50 °C. The presence of both fillers leads to increased restriction in the mobility of polymer chains, and thus assists in char formation. It was observed that the presence of clay led to higher decomposition temperatures of the char formed in air atmosphere (up to 80 °C higher). This led to the conclusion that clay interacts with graphene in a synergistic manner, hence improving the overall stability of the polyimide/graphene/clay nanocomposites.

Effects of organoclay on colorless and transparent polyimide nanocomposites: thermomechanical properties, morphology, and optical transparency.

Although aromatic polyimide (PI) exhibits excellent mechanical performance and thermal stability, its dark color limits applicability in optical displays. Therefore, it is desirable to manufacture colorless, transparent PI (CPI) nanocomposite films that retain excellent physical properties. In this study, a solution intercalation method was used to disperse organoclay (Cloisite 25A; CS25A) in poly(amic acid), which was prepared using 4,4'-oxydiphthalic dianhydride and 3,4'-oxydianiline as monomers. This dispersion was then subjected to thermal imidization to synthesize CPI hybrid films. The influence of the CS25A content (0-1.00 wt%) on the thermomechanical properties, optical transmittance, and morphology of the prepared films was investigated. The hybrid film with a CS25A content of 0.50 wt% exhibited the best thermomechanical properties. However, upon further increasing the organoclay content to 1.00 wt%, the physical properties deteriorated. At 0.50 wt% CS25A, some agglomeration occurred but most of the clay was well dispersed as nano-sized particles, as revealed by transmission electron microscopy. In contrast, when the CS25A content exceeded a critical content, most of the clay was agglomerated and the physical properties were reduced. All the obtained CPI hybrid films were colorless and transparent, regardless of the organoclay content.

Aminoquinoline-functionalized fluorographene quantum dots for low-temperature curable and low-dielectric photosensitive polyimide nanocomposites

Photosensitive polyimide (PSPI) is widely used in the electronic packaging of integrated circuits (IC), organic light-emitting diodes (OLED), and optoelectronic devices. However, low-temperature curable and low-dielectric PSPI is currently required to meet new applications in electronic packaging. Herein, a multifunctional aminoquinoline-functionalized fluorographene quantum dots (QL-FGQDs) nanofiller is carefully designed to achieve these goals. The results demonstrated that the in-situ polymerized QL-FGQDs/PI nanocomposites cured at 200 °C exhibit a low dielectric constant (Dk) of 2.65@1 MHz and a dissipation factor (Df) of 0.009@1 MHz. In addition, the nanocomposites also have excellent optical, mechanical, and thermal properties (the transmittance at 550 nm is above 90%, Young's modulus is 2.95 GPa, and T5% can achieve as high as 517.2 °C), which are better than those of pure PI cured at 300 °C. Furthermore, QL-FGQDs are demonstrated to be applied as a nanofiller for PSPI with a high resolution of 3 μm under an exposure light of 365 nm. Therefore, QL-FGQDs nanofiller and PI nanocomposites exhibit excellent application potential in next-generation electronic packaging.

Engineering Thermal and Light Dual‐Triggered Thermosetting Shape Memory Polyimide Nanocomposites with Superior Toughness and Rapid Remote Actuation Properties

To meet a variety of application scenarios, high‐performance shape memory polymers require not only excellent mechanical and shape memory properties but also a multistimulus response. Herein, this article reports a near infrared (NIR) light‐triggered thermosetting shape memory polyimide (PI)/reduced graphene oxide (rGO) nanocomposite with a high transition temperature, excellent shape memory behaviors, superior robustness, and fast light‐induced shape recovery. The nanocomposite exhibits unexceptionable mechanical properties with breaking strain up to 44.1% and toughness up to 41.7 MJ m−3 at a low content of GO (1 wt%) on account of the good dispersion of GO in the PI matrix and the formed hierarchical structure similar to Nacre. The nanocomposites also have high glass transition temperatures above 200 °C and exhibit a great high‐temperature shape memory effect with a shape fixation rate above 99% and a shape recovery rate above 98%. In addition, with the aid of the efficient photothermal conversion property of rGO, enabling the induction of a temporary shape that completely recovers to the original shape within 7 s by sequential NIR irradiation. It is envisioned that high‐performance nanocomposites with high‐temperature shape memory and excellent mechanical and multistimuli properties will be widely applied in harsh environments, such as alarms, actuation, and so on.

Enhanced mechanical and electrical properties of ECR-glass reinforced polyimide composites with incorporation of TiO2 for insulation applications

This paper presents the mechanical behaviour of novel class composites consisting of ECR-glass type reinforced polyimide (PI) composite loaded with TiO2 nanoparticles. ECR glass reinforced PI composites were fabricated by adding TiO2 particles at three different concentrations namely; 2, 4, and 6 wt% using 3D-Turbula dispersion and Spark Plasma Sintering (SPS) method. The morphologies, crystallinity, mechanical, and electrical properties of the produced composites were evaluated using scanning electron microscope (SEM), X-ray diffractometer, nanoindentation test, and LCR meter device. The SEM results revealed that the TiO2 nanoparticles were homogenously dispersed into the PI composites. The mechanical properties, such as hardness, stiffness, and elastic modulus of the pure PI and ECR glass reinforced PI composite was improved by the incorporation of TiO2 nanoparticles. Maximum hardness and elastic modulus values of 2.19 GPa and 13.99 GP, respectively, was observed in ECR reinforced PI composited loaded with 6 wt% TiO2 nanoparticles. In addition, ECR glass reinforced PI composites with 6 wt% TiO2 nanoparticles depicted the lowest dielectric constant (1.18), dielectric loss (1.14) and electrical conductivity (3.16 × 10−6 S/cm). Finally, the findings suggest the easy processability of PI nanocomposites and their potential for mechanical and electrical insulation applications.

Improved energy storage performance of polyimide nanocomposites by constructing the meso- and macroscopic interfaces

Polyimide (PI) is a promising material for the dielectric capacitor due to its excellent electrical insulation and mechanical properties and so on. However, the low dielectric constant limits the enhancement of energy storage density and its further practical application. Here, we construct the sandwich-structured PI/BaTiO3 nanocomposites by in-situ synthesis and solution casting techniques. The energy density of the sandwich-structured nanocomposites reaches the maximum value of 7.44 J/cm3, contributed by the synergistically enhanced breakdown strength and dielectric constant (486.34 kV/mm and 7.24), while keeping a good charge-discharge efficiency. Combined with the three-dimensional simulation results, it can be seen that the organic/inorganic interfacial polarization in polarized layer and the interlayer polarization can significantly increase the dielectric constant. Meanwhile, the sandwich structure can redistribute the electric field and mitigate the electric field concentration in the polarized layer. The outer insulation layer can block the high current and heat breakdown paths caused in the middle layer. Consequently, the breakdown strength and dielectric constant are improved synergistically, leading to an enhancement in the energy density. The work provides a new paradigm to explore polyimide nanocomposites with enhanced energy density based on the combination of experiments and simulations.

Silica nanofillers-reinforced polyimide composites for mechanical, thermal, and electrical insulation applications and recommendations: a review

Owing to the specific properties of polyimide, its nanocomposites have in recent years shown to be a promising polymer composite for mechanical, thermal, and electrical insulation applications. Studies have in many ways revealed the utilization of the polyimide reinforced nanofillers in the area of insulation practice be it thermal or electrical insulation. However, reinforced polyimide nanocomposites were observed to undergo interfacial bonding issues that have badly influenced their insulation behaviour during service. Dielectric properties and electrical discharge (corona discharge) resistance lifespan of polyimide composites are found degrading during long periods of exposure to elevated temperature conditions. Notwithstanding, efforts have been made on improving the electrical and thermal insulation behaviour of polyimide nanocomposites. As such, the current review study focused on the influence of silica nanoparticles on the thermal, electrical, and mechanical characteristics of polyimide matrix composites for insulation practice and applications. Thus, the vision of the authors is to contribute to the future trend of designing and processing polyimide nanocomposites for insulation applications. Thus, the authors ended the article with furtherance, challenges, and recommendations of further enhancement of polyimide nanocomposites as a candidate material for insulation (electrical and thermal). Hence, the study will pave the way for future studies.

Preparation and properties of polyimide dielectric nanocomposites containing polyvinylpyrrolidone chemically functionalized barium titanate by in‐situ synthesis compounding

AbstractThis work employed polymer active agent polyvinylpyrrolidone (PVP) treated barium titanate (BT) nanoparticles (PVP@BT) as functional nanofillers to fill polyimide (PI) matrix to fabricate PI nanocomposite films. The microstructure, dielectric properties, and heat resistance of PI, PI/BT, and PI/PVP@BT dielectric nanocomposite films were investigated. Fourier transform infrared spectrometer (FTIR) indicated that PVP has been successfully coated on the surface of BT nanoparticles. Due to the enhanced aggregation of monomers on the PVP@BT nanoparticles, higher molecular weight and viscosity of PI/PVP@BT nanocomposite films were achieved. Compared with PI/BT nanocomposite films, the dispersion of PVP@BT nanoparticles in PI/PVP@BT nanocomposite films was better, as verified by field emission scanning electron microscope and high‐resolution transmission electron microscopy. Filling a small amount of PVP@BT nanoparticles into the PI matrix improved the dielectric properties of the resultant nanocomposite films. The dielectric constant of the nanocomposite films with 10 wt% filler loading was up to 7.1 at 1000 Hz, which was 2.5 times higher than that of pure PI (2.9). PI nanocomposite film dielectric loss was generally lower than 0.015. Thermogravimetric analysis (TGA) tests verified that both pure PI and PI nanocomposite films showed excellent thermal stability. This work can be expected to provide a new strategy for designing and manufacturing PI dielectric nanocomposite films for energy storage applications.

Enhanced mechanical, thermal and dielectric properties of polyimide nanocomposites containing SiCp (SiCw) nanofillers for high energy-storage applications

Enhanced mechanical, thermal and dielectric properties of polyimide nanocomposites containing SiCp (SiCw) nanofillers for high energy-storage applications

Cetyltrimethylammonium bromide decorated MXene/polyimide nanocomposites with enhanced dielectric properties, thermostability, and moisture resistance

AbstractUnder extreme conditions, the polymer dielectric materials are expected to have good dielectric properties and heat resistance. Polyimide (PI) has high service temperature (>250°C) and low dielectric loss, but its low dielectric constant limits its further application. The addition of MXene can significantly improve the dielectric constant of PI, but the poor compatibility between MXene and weak polar matrix leads to Bénard‐Marangoni (BM) instability in the process of thermal imidization. This issue can be solved by the surface modification of MXene. Therefore, in this work, a new cetyltrimethylammonium bromide (CTAB) decorated MXene/PI nanocomposite film was prepared by in‐situ polymerization. With the addition of 7 wt% MXene@CTAB, the PI nanocomposite shows improved dielectric constant (k = 7.8 at 100 Hz), which is 2.4 times that of pure PI due to the formation of micro‐capacitors structure and Maxwell‐Wagner‐Sillars (MWS) interfacial polarization. Its dielectric loss keeps at an ultra‐low level (0.027 at 100 Hz) while that of 7 wt% MXene/PI nanocomposite is 3.027. It is owing that CTAB inhibits the agglomeration of MXene. In addition, MXene@CTAB/PI composites have excellent thermal stability, good hydrophobicity, and low water absorption. The above properties ensure MXene@CTAB/PI composites wide application in various extreme situations.

Thermal and dielectric properties of flexible polyimide nanocomposites with functionalized nanodiamond and silver nanoparticles

Thermal and dielectric properties of flexible polyimide nanocomposites with functionalized nanodiamond and silver nanoparticles

Synthesis, characterization and properties of polyimide nanocomposite thin films reinforced with TiO2/Al2O3 hybrid nanoparticles

Highly flexible PI (polyimide) nanocomposite thin films were successfully synthesized incorporating surface functionalized TiO2/Al2O3 hybrid nanoparticles. The as-prepared composite films were characterized by different techniques. The FTIR spectra revealed that the Al2O3/TiO2 hybrid nanoparticles showed characteristic peaks of the individual fillers in a single spectrum. Amino groups grafted on the surface of the hybrid nanoparticles were also confirmed by FTIR. PI composites with 2 wt% TiO2/Al2O3 hybrid nanoparticles showed an increment of T5 (temperature of 5% weight loss) by about 37.2 ℃ compared to the neat PI films. The T10 (temperature of 10% weight loss) of PI composites with 2 wt% TiO2/Al2O3 hybrid nanoparticles was also increased by approximately 36.1 ℃ compared to the neat PI films. The PI composite films with TiO2/Al2O3 hybrid nanoparticles showed an increment of Tg by about 93.1 °C compared to the neat PI films. The tensile strength and tensile modulus of PI nanocomposite films incorporating TiO2/Al2O3 hybrid nanoparticles was improved by approximately 157.2% and 113.7%, respectively compared to the neat PI films.

Comparison of Properties of Colorless and Transparent Polyimide Nanocomposites Containing Chemically Modified Nanofillers: Functionalized-Graphene and Organoclay.

Poly(amic acid) (PAA) was synthesized from dianhydride 4,4-(4,4-isopropylidenediphenoxy)bis(phthalic anhydride) and diamine bis [4-(3-aminophenoxy) phenyl] sulfone. Colorless and transparent polyimide (CPI) hybrid films were synthesized through thermal imidization after dispersing nanofillers using an intercalation method in a PAA solution. C16-GS and C16-MMT, in which hexadecylamine (C16) was substituted on graphene sheet (GS) and montmorillonite (MMT), respectively, were used as nanofillers to reinforce the CPI hybrid films. These two nanofillers were admixed in varying loadings of 0.25 to 1.00 wt%, and the morphology, thermal properties, and optical transparency of the hybrid films were investigated and compared. The results suggest that the thermal properties of the CPI hybrid films can be improved by adding only a small amount of nanofiller. Transmission electron microscopy results of the CPI hybrid film containing two types of fillers suggested that the fillers were well dispersed in the nano-size in the matrix polymer; however, some of the fillers were observed as agglomerated particles above the critical concentration of 0.50 wt%.

Triboelectric Nanogenerator Based on Polyimide/Boron Nitride Nanosheets/Polyimide Nanocomposite Film with Enhanced Electrical Performance

Triboelectric nanogenerators (TENGs) that convert mechanical energy into electricity have attracted tremendous attention and kinds of strategies are proposed to optimize the electrical performance of TENG. In this work, we fabricated a TENG based on a sandwich-structured polyimide (PI)/boron nitride nanosheet (BNNS)/PI nanocomposite film (named PBP). The PBP-TENG exhibits an optimized open-circuit voltage of 65.9 V and a short-circuit current of 4.5 μA. When the load resistance was 10 MΩ, the introduction of a BNNS interlayer raised the power density of the TENG up to 21.4 μW/cm2, which is 15 times higher than that of TENG without a BNNS interlayer (PP-TENG). It is found that the relatively high dielectric constant of BNNS leads to enhancing the output performance of the TENG. More importantly, PBP-TENG also maintains excellent output even in a high-humidity environment.

Polyimide Hybrid Nanocomposites with Controlled Polymer Filling and Polymer-Matrix Interaction.

Polyimide hybrid nanocomposites with the polyimide confined at molecular length scales exhibit enhanced fracture resistance with excellent thermal-oxidative stability at low density. Previously, polyimide nanocomposites were fabricated by infiltration of a polyimide precursor into a nanoporous matrix followed by sequential thermally induced imidization and cross-linking of the polyimide under nanometer-scale confinement. However, byproducts formed during imidization became volatile at the cross-linking temperature, limiting the polymer fill level and degrading the nanocomposite fracture resistance. This is solved in the present work with an easier approach where the nanoporous matrix is filled with shorter preimidized polyimide chains that are cross-linked while in the pores to eliminate the need for confined imidization reactions, which produces better results compared to the previous study. In addition, we selected a preimidized polyimide that has a higher chain mobility and a stronger interaction with the matrix pore surface. Consequently, the toughness achieved with un-cross-linked preimidized polyimide chains in this work is equivalent to that achieved with the cross-linking of the previously used polyimide chains and is doubled when preimidized polyimide chains are cross-linked. The increased chain mobility enables more efficient polymer filling and higher polymer fill levels. The higher polymer-pore surface interaction increases the energy dissipation during polyimide molecular bridging, increasing the nanocomposite fracture resistance. The combination of the higher polymer fill and the stronger polymer-surface interaction is shown to provide significant improvements to the nanocomposite fracture resistance and is validated with a molecular bridging model.

Polyimide Copolymers and Nanocomposites: A Review of the Synergistic Effects of the Constituents on the Fire-Retardancy Behavior

Carbon-based polymer can catch fire when used as cathode material in batteries and supercapacitors, due to short circuiting. Polyimide is known to exhibit flame retardancy by forming char layer in condensed phase. The high char yield of polyimide is attributed to its aromatic nature and the existence of a donor–acceptor complex in its backbone. Fabrication of hybrid polyimide material can provide better protection against fire based on multiple fire-retardancy mechanisms. Nanocomposites generally show a significant enhancement in mechanical, electrical, and thermal properties. Nanoparticles, such as graphene and carbon nanotubes, can enhance flame retardancy in condensed phase by forming a dense char layer. Silicone-based materials can also provide fire retardancy in condensed phase by a similar mechanism as polyimide. However, some inorganic fire retardants, such as phosphazene, can enhance flame retardancy in gaseous phase by releasing flame inhibiting radicals. The flame inhibiting radicals generated by phosphazene are released into the gaseous phase during combustion. A hybrid system constituted of polyimide, silicone-based additives, and phosphazene would provide significant improvement in flame retardancy in both the condensed phase and gas phase. In this review, several flame-retardant polyimide-based systems are described. This review which focuses on the various combinations of polyimide and other candidate fire-retardant materials would shed light on the nature of an effective multifunctional flame-retardant hybrid materials.

A surface modification of KTa0.5Nb0.5O3 by APDS and its enhanced dielectric properties for polyimide nanocomposites

In this work, KTN-NH2/PI nanocomposites with high breakdown strength and low dielectric loss were obtained by modifying the KTa0.5Nb0.5O3 surface with 3-(2-aminoethylamino) propylmethyldimethoxysilane (APDS). Compared with KTN/PI, the loss tangent (tanδ) of KTN-NH2/PI was decreased. The breakdown strength (Eb) could reach to 242.12 kV/mm, which is about 1.49 times higher than that of KTN/PI. Based on the molecular dynamics simulation, the interaction between the modified KTN-NH2 and the PI matrix was higher than the KTN/PI, which would reduce the tanδ by restraining the dipole orientation polarizations. Moreover, the increase of hydrogen bonds improve the interfacial compatibility, which reduce the electric field distortion of organic-inorganic interface and improve Eb.