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Moisture absorption and hydrothermal aging of phenylethynyl-terminated pyromellitic dianhydride-type asymmetric polyimide and composites
摘要： The effects of moisture on a polymerized monomeric reactant (PMR)-type polyimide (TriA X) and associated composites were investigated. Water uptake tests were performed on the polyimide at various temperatures and relative humidity levels to investigate moisture absorption behavior. Two-stage moisture absorption was observed, in which the first stage was diffusion controlled, whereas the second stage was moisture plasticization controlled. As exposure temperature increased, the equilibrium moisture content of the polyimide decreased, indicating an exothermic absorption process. The Arrhenius temperature dependence and moisture saturation as functions of temperature and humidity in the neat polymer were determined using curve fitting based on the published mathematical models. Long-term hydrothermal aging at 95°C was conducted on the neat polyimide and associated carbon fiber composites. Reversible hydrolytic reactions and a trace of irreversible hydrolysis were observed in the long-term exposure. The tensile ductility of the neat polyimide and the short-beam shear strength of the composites decreased with increasing aging time, while the tensile strength and modulus and thermal properties of the polyimide exhibited little change after 2000-h aging, demonstrating hydrothermal stability. The decrease in the ductility of the neat polymer after long-term moisture exposure was attributed to the network structure change, driven by hydrolysis and moisture plasticization.
关键词： β-relaxation,hydrothermal aging,moisture absorption,thermal properties,hydrolysis,Polyimide,composite,mechanical properties,plasticization
更新于2025-09-04 15:30:14
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Graphene oxide enwrapped polyimide composites with efficient photocatalytic activity for 2,4-dichlorophenol degradation under visible light irradiation
摘要： In this study, graphene oxide (GO) enwrapped polyimide (PI) composite photocatalyst was prepared via a facile ultrasonic chemical method. The as-synthesized GO/PI hybrid composite can serve as a stable metal-free photocatalyst for 2,4-dichlorophenol (2,4-DCP) degradation under visible-light irradiation. After loading of GO, the GO/PI composites displayed enhanced photocatalytic performance. The apparent rate constant for 2,4-DCP degradation of the composites was approximately 4.5 times as high as that of bare PI. The results of radical trapping experiments and electron spin resonance indicated that the photogenerated hole (h+) and O2? were the main responsible for the 2,4-DCP degradation. The energy band diagram derived from Mott-Schottky and UV–vis diffuse absorption spectra revealed that the formed heterojunction between PI and GO is type-II. The formed heterojunction with well matched energy levels leads to an efficient injection of photoinduced electrons from PI to GO, and facilitates the separation of photoinduced charge carrier. The combined transient photocurrent and electrochemical impedance spectroscopy results further verified the enhancement was mainly ascribed to the improved charge carrier separation performance of composite.
关键词： Photocatalysis,2,4-dichlorophenol,Heterojuction,Polyimide,GO
更新于2025-09-04 15:30:14
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Modeling Spin Coating over Topography and Uniformity Improvements through Fill Patterns for Advanced Packaging Technologies
摘要： An empirical model is proposed for predicting surface variations following dielectric spin coating (DSC) as applied to existing underlying topography in redistribution layer (RDL) fabrication. Test structures that represent a wide range of underlying feature widths, spacings, and heights are designed and fabricated. These are coated with multiple thicknesses of polyimide, and their surfaces are profiled and analyzed. An empirical model based on spatial filtering over underlying features is developed, with model parameters fit to coatings over a single feature for each set of process parameters. The model predicts post-coating thicknesses at the chip-scale. Comparisons between predictions and experimental results show an RMS error of 4.4% of the feature heights when averaged over each region profiled. Finally, fill patterns are designed and new test structures are simulated using these patterns. Simulation results suggest that global variations can be substantially reduced using such fill patterns, and these results are confirmed experimentally.
关键词： Process Modeling,2.5D Integration,Polyimide,Spin Coating,Fill Patterns,Dielectric Spin Coating,Re-Distribution Layers,RDLs,Packaging
更新于2025-09-04 15:30:14
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Z‐scheme Polyimide/AgBr@Ag aerogel with excellent photocatalytic performance for degradation of oxytetracycline
摘要： A novel Z-scheme Polyimide (PI)/AgBr@Ag aerogel photocatalyst has been successfully synthesized by combining in-situ precipitation method and supercritical drying method. The as-prepared PI/AgBr@Ag-50 (50 wt% of AgBr@Ag in PI/AgBr@Ag) aerogel photocatalyst exhibited excellent photocatalytic activity for oxytetracycline degradation with a rate constant of 0.025 min-1, which was 6.9 and 2.6 times as many as that of PI aerogel and AgBr@Ag nanoparticles, respectively. More significantly, PI/AgBr@Ag-50 aerogel photocatalyst showed stable cycling, which could be attributed to the high mechanical strength and 3-D network of PI aerogel. The introduction of AgBr@Ag on PI with the formed hetero-junction structure efficiently promoted the separation of electron-hole pairs by a Z-scheme mechanism. The reduced metallic Ag nanoparticles were found to function as the center for the accumulation of electrons from AgBr to PI. This work found a new application of PI/AgBr@Ag aerogel photocatalyst in environmental protection.
关键词： Aerogel photocatalyst,Polyimide,Oxytetracycline,Stability,AgBr@Ag
更新于2025-09-04 15:30:14
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[IEEE 2018 International Conference on Diagnostics in Electrical Engineering (Diagnostika) - Pilsen, Czech Republic (2018.9.4-2018.9.7)] 2018 International Conference on Diagnostics in Electrical Engineering (Diagnostika) - Study on the trap properties of nano-ZnO modified polyimide based on surface potential decay method
摘要： The space environment will charge the surface of the spacecraft. Due to the low discharge ability of the dielectric material, it may cause the surface discharge of the spacecraft and affect the normal work of the spacecraft. Polyimide is a typical dielectric material on the spacecraft, this paper attempts to improve the surface discharge ability by modifying polyimide with nano-ZnO. The research method is based on the surface potential decay platform, which is an intuitive approach to evaluate the states of surface charging. The surface potential decay characteristics of pure polyimide and its modified samples are tested. The surface potential decay mechanism of the dielectric is analyzed by calculating the trap characteristics. Results show that the surface potential of ZnO modified polyimide has less decrement and rate of decay than that of the pure polyimide. The deep trap density of electron trap and hole trap density is less than that of pure polyimide, the shallow trap of pure polyimide is the lowest. The change of electron trap level is small, while the hole trap level increases.
关键词： polyimide,hole trap,ZnO,electron trap,Surface potential decay
更新于2025-09-04 15:30:14
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Organosoluble and transparent cardo polyimides with high <i>T</i> <sub/>g</sub> derived from 9,9-bis(4-aminophenyl)xanthene
摘要： 9,9-Bis(4-aminophenyl)xanthene (BAPX) was prepared simply and effectively via one-pot, two-step procedure using xanthenone and aniline as main substrates. The monomer BAPX was reacted with six aromatic dianhydrides in N,N-dimethylacetamide (DMAc) to yield the corresponding polyimides (PIs) via the poly(amic acid) precursors and subsequent thermal or chemical imidization. The resulting PIs exhibited good thermal stability with glass transition temperatures of 308–348°C, initial decomposition temperatures of 470–510°C, 10% weight loss temperatures of 540–565°C, and char yields of 55–59% at 800°C in nitrogen, respectively. All polymers were amorphous and readily soluble in organic solvents such as N-methyl-2-pyrrolidone and DMAc. The PI films had tensile strengths of 71–92 MPa, tensile moduli of 1.91–2.35 GPa, and elongations at break of 5–13%. Meanwhile, these polymer films also had high optical transparency with a cutoff wavelength in the range of 367–415 nm, lower dielectric constants (3.02–3.34 at 10 MHz), and low water uptake of 0.30–0.52%.
关键词： Aromatic polyimide,9,9-bis(4-aminophenyl)xanthene,bulky pendent xanthene cardo group,thermal property,optical transparency,solubility
更新于2025-09-04 15:30:14
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Synthesis and characterization of thianthrene-containing preimidized soluble polyimide resins and the derived films with high refractive indices and good optical transparency
摘要： A series of organo-soluble polyimide (PI) resins were prepared from a newly designed and synthesized aromatic thianthrene-containing diamine, 2,7-bis(3-aminophenoxy)thianthrene (APOT) and various aromatic dianhydrides via a one-step high temperature polycondensation procedure with N-methyl-2-pyrrolidone (NMP) as the solvent. The derived PI resins were soluble in polar aprotic solvents, including NMP and N,N-dimethylacetamide (DMAc). For comparison, several unsoluble sulfur-containing PIs were prepared from another para-substituted thianthrene-containing diamine, 2,7-bis(4-aminophenylenesulfanyl)thianthrene (APTT) and aromatic dianhydrides by a two-step polycondensation procedure via poly(amic acid) (PAA) precursors at elevated temperatures as high as 300 °C. Flexible and tough PI films with the tensile strength higher than 88 MPa were successfully cast from the APOT-PI resin solution at a relatively low curing temperature of 250 °C. The meta-substituted molecular skeleton in the APOT- PIs endowed the films good optical transparency with the transmittance higher than 83% at a thickness around 10 um, which was apparently higher than those of the para-substituted APTT-PI analogues. The sulfur-rich thianthrene moiety with high molar refraction endowed the APOT-PI films high refractive indices up to 1.7147 at 632.8 nm and low birefringence in the range of 0.0064–0.0133. In addition, the PI films showed good thermal stability with the glass transition temperatures (Tg) higher than 198.3 °C and 5% weight loss temperatures higher than 510 °C in nitrogen.
关键词： Thermal properties,High refractive index,Polyimide,Optical properties,Thianthrene
更新于2025-09-04 15:30:14
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43.1: <i>Invited Paper:</i> Advances in Flexible Display Materials
摘要： One of the trends in today’s Display technology is flexible displays. It enables consumer electronic products to have form factors of being curved, foldable, bendable and rollable. DowDuPont Electronics & Imaging Display Technology has been heavily investing in flexible technologies. It provides liquid polyimide for customers’ high-quality flexible substrates on which display devices are built.
关键词： Flexible display,Polyimide (PI),Colorless,OLED
更新于2025-09-04 15:30:14
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Novel polyimide nanocomposites enhanced by covalent modified graphene nanosheets based on Friedel–Crafts reaction
摘要： We report a new approach to fabricate novel polyimide (PI) nanocomposites using amine-functionalized graphene nanosheets (AGNS). AGNS was successfully prepared by Friedel–Crafts (F–C) reaction and nitroreduction. The PI nanocomposites with outstanding strength and high tribological performance were obtained though in situ polymerization in the presence of different contents of AGNS. The thermal stability, mechanical performance, and the tribological properties of PI/AGNS nanocomposites were significantly enhanced compared with that of pristine PI and PI/graphene nanosheets (GNS) blends, resulting from the strong covalent bonds between AGNS with PI matrix. Particularly, given that the friction coefficient and wear rate were reduced separately by 20.5% and 90.5% under dry sliding condition, the PI/AGNS nanocomposite with 0.5 wt% AGNS manifested the optative friction performance. The combined exclusive friction resistance and mechanical performance were the paramount factors which illustrate the applications of the resultant PI/AGNS nanocomposites in the wear-resistant field or another high-performance material.
关键词： graphene nanosheets,mechanical properties,polyimide nanocomposites,tribological performance,Friedel–Crafts reaction
更新于2025-09-04 15:30:14