Polyimide Composite Films Research Articles

Thermal conductivity enhancement of polyimide films filled with BN and AlN fillers

A series of polyimide (PI) composite films were prepared using PI as matrix and boron nitride (BN) and aluminum nitride (AlN) as the doped phases. The modification of the thermal conductive filler particles was characterized by Fourier transform infrared (FTIR). The results showed that the silane coupling agent KH550 was successfully coated on the surface of BN and AlN. X-ray photoelectron spectrometer characterization was used to further prove that silane coupling agents were successfully attached to BN and AlN surfaces, forming a new chemical bond. Scanning electron microscope (SEM) was used to analyze the dispersion of filler particles in the matrix. It was found that agglomeration phenomenon occurred when the content of BN particles were high, but this problem was improved after the surface modification of BN. The breakdown field strength and volume resistivity of PI/BN composite film increased first and then decreased with the increase of BN content and reached the maximum when the volume fraction of BN was 5%, which was 191.53 kV/mm and 8.832 × 1013 Ω·m, respectively. When the BN content was 9 vol%, the thermal conductivity of the PI/BN composite film was 0.496 W/(m·K), which was 1.4 times larger than that of the pure PI film. The thermal conductivity of the PI/BN/AlN composite film at the BN and AlN contents of 5 vol% and 1 vol%, respectively, is 0.144 W/(m·K) higher than that of 7 vol% PI/BN. It indicated that the synergistic effect of the composite fillers played a significant role, and at the same time, under the premise of ensuring higher thermal conductivity, the amount of thermally conductive particles could be reduced to some extent. After the surface modification of the filler particles, the properties of the composite film showed the same trend compared with the unmodified one, while the only difference was that there was a certain increase in the numerical value.

Microstructures and energy storage property of sandwiched BZT-BCT@Fe3O4/polyimide composites

In this paper, the sandwich structured polyimide composite films were studied, in which two layers of pure polyimide films were covered on both sides of BZT-BCT@Fe3O4/PI composite films. The result indicated that composite films with doped BZT-BCT@Fe3O4 had a significant performance in dielectric properties. The phases and microstructures of BZT-BCT@Fe3O4 and sandwiched composite films were studied by means of XRD, TEM and SEM. It was found that Fe3O4 was present and randomly coated on BZT-BCT. The measured dielectric properties of the composite films show great increased dielectric constant. The dielectric strength of the composite films decreases with the volume fraction raising, however, the relatively high values can be obtained when the fillers content is lower than 5 vol.%. The energy storage density increases significantly at small volume fractions, but decreases significantly at 7 vol.% due to reduced dielectric strength. On the whole, the composite films exhibit higher energy storage density and excellent discharge efficiency when the volume fraction is less than 7%, and the discharge efficiency is still higher than 85% at 265 kV/mm.

Hollow silica nanosphere/polyimide composite films for enhanced transparency and atomic oxygen resistance

Abstract In the low Earth orbit (LEO) space, transparent polyimide (PI) films with high transmittance and strong resistance to atomic oxygen (AO) are pursued for providing effective protection and energy harvesting for novel lightweight solar arrays in spacecraft. In this work, hollow silica nanospheres (HSNs) were inlaid in transparent PI films for the formation of an HSN/PI composite structure, where the HSNs were first generated by a solution-based removal of organic templates from PAA-silica core-shell nanospheres, free from common high-temperature treatments, and then transferred to PI substrates. The HSN/PI composite structures resulted in the higher transmittance and stronger resistance to AO than did the pristine PI: the composite flexible films showed an average transmittance of 92.43% at broad wavelengths (400–1600 nm) and an AO erosion yield of 4.67 × 10−26 cm3/atom after an AO exposure of 6.05 × 1020 atoms/cm2, which were superior to those of the pristine PI (90.80% and 1.33 × 10−24 cm3/atom, respectively). Simultaneous realization of antireflective (AR), AO resistant, and mechanically robust PI composite flexible films provides new solutions to traditional AR patterned AO-resistant PIs and insights into the multifunctionalization of PIs in the LEO space environment.

Formation of unique three-dimensional interpenetrating network structure with a ternary composite

Ternary composite of reduced graphene oxide/multi-walled carbon nanotubes (RGO/MWCNT)/polyimide (PI) with high-performance mechanical and electrical properties was synthesized via in situ polymerization. The unique three-dimensional interpenetrating network structure conferred the conductive pathways for electrons, resulting from the strong interfacial covalent bonds between RGO/MWCNT and the PI matrix. The electrical conductivity of (RGO/MWCNT)/PI reached 4.4 × 10− 4 S m−1 with the filler loading concentration at an extremely low value (0.2 wt%), which was significantly higher than that of the neat PI. The (RGO/MWCNT)/PI composite films exhibited high tensile strength (up to 462 MPa) and tensile modulus (260 MPa). Furthermore, the introduction of RGO/MWCNT enhanced the thermal stability of the (RGO/MWCNT)/PI composites (from 579 to 623 °C). The composite film is expected to be extensively applied in the field of electronics, solar cells and biosensors.

Ionic liquid embedded polyimides with ultra-foldability, ultra-flexibility, ultra-processability and superior optical transparency

New generation spacecraft technology requires more and more deployable, light-weight, thin polymer films, in particular novel polyimide materials with high optical transparency, excellent foldability and superior flexibility. In this work, we develop a highly transparent, ultra-foldable, ultra-flexible and ultra-processable polyimide composite material by incorporating 5–8 wt% of ionic liquid 1-ethyl-3-methylimidazolium bis((trifluoromethyl)sulfonyl)imide into colorless polyimide matrices. This 23-μm-thick polyimide composite film exhibits a high optical transmittance of 90.4% even at 450 nm wavelength and an incredibly low cutoff wavelength of 273 nm. It is an extremely strong and flexible material, with a tensile modulus of 844.6 MPa, a tensile strength of 48.2 MPa, a high elongation at break of 108.4%, and an extraordinary minimum bend radius of 1 μm. It can be easily folded in half 4 times or twisted by 900° without any crack damages. Moreover, it has a low expense cost and good film processability for industrialization manufacturing. All of these superior performances render this ionic liquid/polyimide composite an ideal structural material for solar sails, solar arrays and thin-film photovoltaics, etc.

Multifunctional super-aligned carbon nanotube/polyimide composite film heaters and actuators

Polyimide (PI) is a high-performance polymer with ultrahigh heat stability while carbon nanotube (CNT) possesses high mechanical strength, excellent electrical and thermal conductivity. Here we report a facile and low-cost method free from CNT pre-dispersion for fabricating super-aligned carbon nanotube (SACNT)/PI composite film which combines the advantages of both SACNT and PI. Flexible and scratch-resistant composite film with high CNT content, uniform dispersion of CNTs, and controlled patterned CNT structures can be fabricated easily via in situ imidization. The SACNT/PI composite film exhibits improvement in mechanical strength, Young's modulus, electrical conductivity compared with pristine PI, and shows good thermal stability. Thanks to these superb properties, a flexible, stable, addressable, electromagnetic wave permeable, and high-temperature fast-response multifunctional heater as well as a thermo-mechanical actuator based on SACNT/PI composite film have been demonstrated in this paper. And it also shows great potential in a variety of applications such as flexible/wearable electronics, RFID, other thermo-related devices and so on.

Preparation of Fluorinated Graphene Oxide/Polyimide Composites with Low Dielectric Constant and Moisture Resistance

Fluorinated graphene oxide (FGO) was successfully prepared in this paper, and the chemical structure of FGO was characterized. A series of polyimide (PI) composite films with different content of FGO was prepared by in situ polymerization. Because of the homogeneous dispersion of FGO and the strong interfacial interaction between FGO and the PI matrix, the resulting composite films that contained FGO exhibited effects of mechanical properties, thermal properties and dielectric properties that were even better than the pure PI. Furthermore, due to the hydrophobic properties of FGO, the water absorption of the composite films were reduced. The result showed when the 0.6[Formula: see text]wt.% FGO was filled into the PI, the tensile strength was increased about 66.3%, the decomposition temperature was increased from 540∘C to 570∘C, and the dielectric constant (Dk) decreased with the increasing content of FGO, and a Dkvalue of 2.28 was achieved when the content of FGO was 1.0[Formula: see text]wt.%.

Trisilanolphenyl-POSS nano-hybrid poly(biphenyl dianhydride-p-phenylenediamine) polyimide composite films: miscibility and structure-property relationship

A partially condensed polyhedral oligomeric silsesquioxane (POSS) compound, trisilanolphenyl-POSS (TSP-POSS) was prepared via a modified two-step procedure with phenyltrichlorosilane as the starting material. The solubility of the TSP-POSS in polyimide (PI) solvents, including N-methyl-2-pyrrolidone (NMP) and N,N-dimethylacetamide (DMAc) was first evaluated. TSP-POSS could be dissolved in the test solvents with a solid concentration higher than 50 wt% and the obtained solution was stable both at room temperatures and in refrigerator at -18 °C for more than 1 month. TSP-POSS was then physically blended with a poly(amic acid) (PAA) obtained from 3,3′,4,4′-biphenyltetracarboxylic acid dianhydride (BPDA) and para-phenylenediamine (PDA) with various adding proportions of 0, 5, 10, 15, 20, and 25 wt% (TSP-POSS in total solids). The obtained clear and homogeneous PAA/TSP-POSS solution was then thermally imidized at elevated temperatures to afford six PI/TSP-POSS composite films (PI-BP-0~PI-BP-25). For comparison, analogous composite films were prepared by blending TSP-POSS with another PI matrix, poly(pyromellitic anhydride-oxydianiline) (PIPMDA-ODA) at the same hybrid proportion (PI-0~PI-25). TSP-POSS exhibited quite different miscibility with these two PI matrixes. All of the composite films based on PIPMDA-ODA and TSP-POSS showed homogeneous nature and the films were optically transparent even at the high POSS loading of 25 wt%; however, the PIBPDA-PDA analogues showed poor compatibility with the POSS additive when the adding proportion was over 10 wt%. PI-BP-20 and PI-BP-25 films were thoroughly opaque with the haze values of 100%. In addition, the residual weight ratio of the composite films at 760 °C in nitrogen increased from 62.0 wt% (PI-BP-0) to 74.1 wt% (PI-BP-25).

Enhanced Thermal Conductivity of Polyimide Composites with Boron Nitride Nanosheets

A strategy was reported to prepare boron nitride nanosheets (BNNSs) by a molten hydroxide assisted liquid exfoliation from hexagonal boron nitride (h-BN) powder. BNNSs with an average thickness of 3 nm were obtained by a facile, low-cost, and scalable exfoliation method. Highly thermally conductive polyimide (PI) composite films with BNNSs filler were prepared by solution-casting process. The in-plane thermal conductivity of PI composite films with 7 wt% BNNSs is up to 2.95 W/mK, which increased by 1,080% compared to the neat PI. In contrast, the out-of plane thermal conductivity of the composites is 0.44 W/mK, with an increase by only 76%. The high anisotropy of thermal conductivity was verified to be due to the high alignment of the BNNSs. The PI/BNNSs composite films are attractive for the thermal management applications in the field of next-generation electronic devices.

Effect of trace diphenyl phosphate on mechanical and thermal performance of polyimide composite films

Abstract How to achieve polyimide (PI) with better thermal and mechanical properties is a great challenge. In this study, flame-retardant diphenyl phosphate (DPhP), was incorporated in to heterocyclic diamine contained PI films to form phosphorus-polyimide composite films (P-PIs). The structures, element distribution, thermal and mechanical properties of P-PIs were characterized by FT-IR, SEM, EDS, DMA, TGA, and tensile test. The results indicated that the incorporation of phosphorus can significantly enhance the thermal and mechanical properties. The 5% weight loss temperature in air and the glass transition temperature ( Tg) of P0.6-PI film were 577 and 405 °C, which were 50 and 16 °C larger than the neat PI film, respectively. In addition, the P0.6-PI film also showed improved tensile strength , modulus and toughness by 47%, 57% and 76%, respectively, as compared to the neat PI film.

Preparation and Characterazition of Copolyimide/Carboxylated Multiple-walled Carbon Nanotubes Composite Films

The copolyimide/MWCNTs-COOH composites were synthesized by pyromellitic dianhydride (PMDA), 3,3'4,4'-biphenyltetracarboxylic dianhydride (BPDA), 4,4'-diaminodiphenyl ether (ODA) and the carboxylated multiple-walled carbon nanotubes (MWCNTs-COOH) through ultrasonic dispersion in situ polymerization. And the mechanical and thermal properties of the composite films were studied. The results showed that the carbon nanotubes were well dispersed in the polyimide composite films, the tensile properties and thermal stability were improved significantly.

Transparent Electrode Based on Silver Nanowires and Polyimide for Film Heater and Flexible Solar Cell.

Transparent, conductive, and flexible Ag nanowire (NW)-polyimide (PI) composite films were fabricated by a facile solution method. Well-dispersed Ag NWs result in percolation networks on the PI supporting layer. A series of films with transmittance values of 53–80% and sheet resistances of 2.8–16.5 Ω/sq were investigated. To further verify the practicability of the Ag NWs-PI film in optoelectronic devices, we utilized it in a film heater and a flexible solar cell. The film heater was able to generate a temperature of 58 °C at a driving voltage of 3.5 V within 20 s, indicating its potential application in heating devices that require low power consumption and fast response. The flexible solar cell based on the composite film with a transmittance value of 71% presented a power conversion efficiency of 3.53%. These successful applications proved that the fabricated Ag NWs-PI composite film is a good candidate for application in flexible optoelectronic devices.

Evaluation of Polyimide/Carbon Composite Films for Capsule Support

Capsules in National Ignition Facility targets are conventionally supported by thin polymer films. Recent experiments have shown that these films add significant perturbations to the implosion. Here, we evaluate stiffer polyimide composite films for use in a new target design that has been predicted to reduce these perturbations. The films are evaluated by their contact radius to the capsule for different deflections and the force they generate at those deflections to center the capsule. We find that a composite film with a single-sided coating of carbon produces the best results and show the performance of these films in target assemblies, highlighting the importance of the indentation depth.

Preparation and Thermal Properties of Silicon-containing Polyimide Composite Films

Aromatic polyimide is a kind of polymer material with high temperature resistance, low temperature resistance, radiation resistance, excellent chemical stability, excellent electrical properties and good mechanical strength. It has been widely used in aerospace, electrical and electronic fields. At present, the synthesis, properties and application of polyimide containing silicon is one of the hot spots in the research field of polyimide. The processing property of polyimide can be greatly improved by introducing silicon group or polysiloxane segment into the main chain structure. And it has been given a good solubility, permeability, impact resistance, UV resistance and anti-degradation in oxygen rich environment. The introduction of siloxane chain segments or silicon containing groups in polyimide framework can enhance the adhesion between polyimide and inorganic materials, including the adhesion of metal materials and other substrates. A variety of polyimide hybrid materials can be prepared by the excellent bonding properties. A series of polyimide / silicon containing polyimide / BaTiO3 nanocomposite films were prepared and their structures and properties were studied in this paper. In addition, the preparation, structure and properties of polyimide / mesoporous silica composite films were studied. Silicon containing polyimide/silane mesoporous silica composite films have low infrared emissivity compared with bulk polyimide. Under the same content of mesoporous silica, the composite films prepared by copolymerization have lower infrared emissivity. Moreover, the infrared emissivity decreases with the increase of the content of silica. In short, silicon containing polyimides and their composite films with excellent performance differ from other traditional polyimides, and it has broad application prospects in the technological field of aerospace, electrical and electronic, gas separation, absorbing material preparation.

Carbonization behavior of polyimide films hybrid with different metal catalyst

Carbon films were fabricated by the carbonization of polyimide composite films with the incorporation of different metal catalyst. The carbonization process and the properties of the carbon films were investigated by X-ray diffraction, scanning electron microscopy, four-point-probe device and vibrating sample magnetometer. It was found that the metal complex in the polyimide films promoted the carbonization of matrix polyimide and resulted in the increase of electrical conductivity of the films. The change from para-magnetic to ferromagnetic behavior was also observed with the increase of carbonization temperature.

Conductive mechanism of carbon black/polyimide composite films

Abstract During the fabrication of black polyimide composite films, it is common to introduce carbon black (CB) into this composite system. The introduction of CB significantly decreases the resistivity of the films and consequently has a great effect on the inherent insulation property of polyimide. Here, the exploration of the conductive mechanism of CB/polyimide composite films is aimed to explain the change on resistivity fundamentally. In this study, two kinds of representative CBs were chosen to prepare CB/polyimide composite films. The rudiment of the conductive mechanism was built up based on the resistivity curves, and scanning electron microscopy (SEM), tensile, thermal gravimetric analysis, Fourier transform infrared (FT-IR) spectroscopy, UV, Raman and X-ray diffraction (XRD) were conducted to confirm it. The experimental results further verified the mechanism and gave us a chance to propose an integrated conductive mechanism including three sections (tunneling effect mechanism, conductive network mechanism and doping mechanism) for CB/polyimide composite films. As the conductive mechanism has been understood, it paves the way for optimization of the fabrication of conductive black polyimide films and insulating black polyimide films, even other colorful polyimide composite films.

Surface Fabrication of Block Copolymer-Templated Polyimide Films by Reactive Ion Etching

In this study, we demonstrated fabrication of polyimide composite films with periodic nanostructure on the surface by oxygen plasma reactive ion etching (RIE). Poly(2-vinylpyridine)-block-poly(methyl methacrylate) (P2VP-b-PMMA) was used as a template for formation of periodic nanostructure. The templating block copolymer formed self-assembled structure including the poly(amic acid) (PAA), as a precursor of polyimide, in only the P2VP domain. After the imidization of PAA, PMMA domain was etched selectively by RIE. Thereby, well-ordered hexagonally-packed pores with a d-spacing of approx. 50 nm and a diameter of approx. 25 nm were obtained on the surface of the film.

Dielectric and mechanical properties of polyimide composite films reinforced with graphene nanoribbon

Graphene nanoribbon (GNR) was introduced into in the polyimide (PI) composite films. The effects on dielectric and mechanical properties of PI/GNR composites were investigated. Results show that the dielectric and mechanical properties of the composite films are significantly enhanced compared to pure PI. This can attribute the excellent dispersion of and the strong interfacial interaction between GNR and the PI matrix. Tensile strength of PI/GNR composite films shows a first increasing and then decreasing trend with increased GNR content. With 0.1wt% loading, the tensile strength is increased from 120.1MPa to 166.7MPa, and the dielectric constant of PI/GNR composite film is decreased from 3.6 to 3.1 compared to pure PI, respectively. The success of this preparation is believed to afford new avenue for the development of high strength polyimide based composites.

Heat dissipation properties of polyimide nanocomposite films

In development of modern electric fields, the growth of kinds of electronic devices has made the supply and research on heat dissipating films become important. To synthesize heat dissipation films with high thermal resistance for possible use in electronics applications, carbon black is doped into polyimide to increase the dissipating rate of films, at loadings of 50, 100, and 150 wt%. The resulting films display excellent thermal properties; the thermal conductivity of the film with 150 wt% carbon black is 5.59W∙m−1K−1, a value that is 35 times higher than that of pure polyimide (0.16W∙m−1K−1). To theoretically confirm the increased dissipating ability of composite films, the Nielsen equation is used for verification. The experimental results show an excellent fit with the theoretical values calculated by the Nielsen equation. The great thermal stability of polyimide composite film with carbon black is verified by using TGA and DSC, the temperature for 1% thermal decomposition of the 150wt% film is 541°C, and the glass transition temperature is 315 °C. The heat conduction results also show high heat dissipation data, which make the carbon black composite polyimide films an excellent candidate for use in electric devices to deplete the heat generated.

Preparation and characterization of high dielectric calcium copper titanate/polyimide composite films

Calcium copper titanate (CaCu3Ti4O12; CCTO)/polyimide (PI) composite films were synthesized by 4,4′-oxydianiline, CCTO, and 3,3′,4,4′-biphenyltetracarboxylic dianhydride through ultrasonic dispersion in situ polymerization. Scanning electron microscopic images clearly confirmed that 10 wt% CCTO particles dispersed uniformly in composite films. When the content was 20–80 wt%, CCTO particles were coated by PI in good condition, and globular particles dispersed in the composite films. PI and CCTO/PI were found to exhibit excellent thermal stability. The addition of CCTO has influence on the thermal properties of PI. Weight loss temperatures (5% and 10%) of the composite films containing 70 wt% CCTO reached 612°C and 673.9°C, respectively. The strong interfacial interaction between PI and CCTO improved the dielectric properties of the composite films. The dielectric permittivity and conductivity of the CCTO/PI composite films increase with the increase of CCTO content. In addition, the dielectric permittivity of films containing 40–70 wt% increased rapidly.