Imidization Of Polyamic Acid Research Articles

Physical and Technological Characteristic Features of the Process of Installation of Dies onto a Temporary Foundation in Internal Wiring Technology

The physical and technological characteristic features of the installation of dies onto a temporary foundation in the internal wiring technology are studied. The justified selection of the material for the fixation of silicon dies active side down onto a temporary foundation from various solutions of polyamic acids (PAAs) is performed. The experimental dependence of the adhesion strength of silicon dies on the lifetime of the solutions of PAAs is found. The possible defects formed upon the imidization of PAAs in the process of creation of highly integrated microassemblies, multidie modules, and electronic modules of the “system in package” level are shown.

Preparation of PI/PTFE-PAI Composite Nanofiber Aerogels with Hierarchical Structure and High-Filtration Efficiency.

Electrospun nanofiber, showing large specific area and high porosity, has attracted much attention across various fields, especially in the field of air filtration. The small diameter contributes to the construction of filters with high-filtration efficiency for fine particulate matter (PM), however, along with an increase in air resistance. Herein, composited nanofiber aerogels (NAs), a truly three-dimensional (3D) derivative of the densely compacted electrospun mat, were constructed with the blocks of polytetrafluoroethylene–polyamideimide (PTFE–PAI) composite nanofiber and polyimide (PI) nanofiber. PI/PTFE–PAI NAs with hierarchically porous architecture and excellent mechanical properties have been obtained by thermally induced crosslink bonding. Results indicated that sintering at 400 °C for 30 min could complete the decomposition of polyethylene (PEO) and imidization of polyamic acid (PAA) into PI, as well as generate sufficient mechanical bonding between adjacent nanofibers in the NAs without extra additive. The well-prepared PI/PTFE–PAI NAs could withstand high temperature up to 500 °C. In addition, the filtration tests illustrated that the composite NAs had an excellent performance in PM filtration. More importantly, the filtration behavior could be adjusted to meet the requirements of various applications. The excellent thermal stability and high-filtration efficiency indicated its great potential in the field of high-temperature air filtration.

Magnetic properties of iron-based soft magnetic composites prepared by utilizing polyimide insulating layer

Polyimide (PI) with excellent insulating property and enhanced thermal stability was used as insulating coating material for the preparation of iron-based soft magnetic composites (SMCs), and the effect of insulating coating content and curing temperature on the magnetic properties of iron-polyimide SMCs was investigated. The results demonstrate that the insulating layer of PI shows satisfactory adhesion property on the surface of iron particles, and uniform insulating layer of PI was obtained by imidization of polyamic acid (PAA) at 200 °C. With the increase of PI content, the thickness of insulating layer increases gradually, accompanied by the increase of resistivity and the reduction of core loss. PI shows enhanced heat resistance, the SMCs can be cured at the temperature up to 400 °C, leading to the effectively release of residual internal stress generated during the compaction process. At the optimized PI content of 1.5 wt% and curing temperature of 400 °C, low core loss of 780 W/Kg (measured at 50 mT and 100 kHz) and higher maximum permeability of 305 were achieved.

Influence of curing accelerators on the imidization of polyamic acids and properties of polyimide films

In order to lower the imidization temperature of polyamic acids (PAA), the catalytic activities of the curing agents p-hydroxybenzoic acid (PHA), quinoline (QL), benzimidazole (BI), benzotriazole (BTA), triethylamine (Et3N) and 1, 8-diazabicyclo [5.4.0]undec-7-ene (DBU) were investigated in the process of thermal imidization of PAA. In addition, the effect of these various curing agents on the thermal stabilities and mechanical properties of the resultant polyimide (PI) films was determined. Quinoline was found to be an effective curing accelerator in the use of two-step method for synthesizing PI. Due to its moderate base strength, low steric crowding effect and moderate boiling point, quinoline could not only accelerate PAA to achieve imidization completely at 180 °C, but also maintain the mechanical properties and thermal stability of the ordinary PI film. Any residual quinoline could be removed from PI films by heating at 250 °C for 4 h.

Molecular mechanism of temporal physico/chemical changes that take place during imidization of polyamic acid: Coupled real-time rheo-optical and IR dichroism measurements

Multiple overlapping physical and chemical changes often take place during casting/drying and imidization from PMDA-ODA polyamic acid precursors from cast solutions. To shed light into details of these complex phenomena, we designed a unique real time measurement system that combines true stress, true strain, in-plane birefringence and temperature with polarized ultra-rapid scan FT-IR spectrometry (URS-FT-IR). At the early stages of heating (21°C–130 °C), initially isotropic solution cast film was observed to develop stress and birefringence as the solvent decomplexed and evaporated without showing any imidization as it was held in uniaxially constrained state. At a temperature around 130 °C, the onset of imidization reaction was detected while the stress went through a maximum. Beyond this stage, the evaporation of bound solvent and chemical conversion was observed to take place simultaneously and this is accompanied by a steady increase in birefringence. As the majority of the bound solvent evaporated, the stress and birefringence values started leveling off at long times.

Retraction notice to “Electrical conduction of polyimide films prepared from polyamic acid (PAA) and pre-imidized polyimide (PI) solution”

Electrical conduction characteristics in two different polyimide films prepared by the imidization of polyamic acid (PAA) and pre-imidized polyimide (PI) solution were investigated. It is found that the current density of the polyimide film from PAA was higher than that of the polyimide film from PI at the same electric field, even though the conduction mechanism in both polyimide films follows the ionic hopping model. The hopping distance was calculated to be 2.8 nm for PAA type and 3.2 nm for PI type polyimide film. It is also found that the decay rate of the residual electrostatic charges on the polyimide films becomes faster in the PAA type than in the PI type polyimide film.

Gas Separation Properties of Polyimide Membranes Based on 2,2-Bis(<i>3-amino-4-hydroxyphenyl</i>)hexafluoropropane

A series of polyimides (PIs) by thermal imidization of polyamic acid (PAA) were prepared in order to investigate the gas separation property. The single gas permeability of He, H2, CO2, O2, N2 and CH4 were measured and compared in order to determine the effect of the reaction content and thermal imidization temperature on the gas separation properties. The results showed that the higher the thermal imidization temperature is, the more beneficial for the gas separation properties of the PI membranes. The optimum polycondensation reaction content on preparing PI was 25 wt%. The highest ideal selectivity of He/CH4, H2/CH4, CO2/CH4 and H2/N2 is 2814.88, 1652.38, 216.63 and 191.58, respectively.

Two Step Synthesis of Hydroxyl Group Polyimide Based on 2,2-Bis(<i>Amino-4-Hydroxyphenyl</i>)hexafluoropropane

The feasibility of using two step procedures with thermal imidization of polyamic acid (PAA) for synthesizing hydroxyl group polyimide (PI), based on 2,2-Bis(3-amino-4-hydroxyphenyl)hexafluoropropane (Bis-AP-AF), was studied. It was found that a high molecular weight PAA could be successfully synthesized from Bis-AP-AF with 3,3',4,4'-Benzophenone tetracarboxylic dianhydride (BTDA). The optimum polycondensation reaction time on synthesizing molecular weight of the PAA was 4 hours. The PI films could be successfully prepared by thermal imidization of the PAA. The higher the inherent viscosity of the PAA is, the more beneficial for the tensile properties of the PI films. All the results indicate that two step procedures with thermal imidization of the PAA under appropriate conditions represented a promising way for preparation PI films, with a reasonable level of mechanical properties.

Synthesis and Imidization of Polyamic Acid

Polyamic acids (PAA) were synthesized by solution polycondensation of aromatic diamine with dianhydride and PAA were readily soluble in polar organic solvents (N-methylpyrrolidinone, N, N-dimethylacetamide and DMF). It was found that the most appropriated reaction conditions of synthesis of PAA solution were the ratio of dianhydride with diamine being 1.02:1and 3h reaction time at ambient temperature in both N-methylpyrrolidinone and N, N-dimethylacetamide polar organic solvents. PAA thin films were prepared by PAA solution spread on the glass plate and PI thin films were obtained by the casted thin films which underwent a special high-temperature (300°C, 2h) heat curing. The structures of PAA and PI films were characterized by FT-IR spectra and degree of imidization of PAA solution was indicated from IR spectra. The thermal stability was studied by thermogravimetric analysis (TGA) and the thermal behaviors were investigated by differential scanning calorimetry (DSC) in this paper. It was shown that PAA solution were imidization at 200°C mostly and PI had higher thermal stability.

Preparation of nonwoven polyimide/silica hybrid nanofiberous fabrics by combining electrospinning and controlled in situ sol–gel techniques

A controlled in situ sol–gel synthesis combined with the electrospinning technique and postspun imidization was applied in the fabrication of polyimide/silica hybrid nonwoven nanofiberous fabrics with excellent thermal and mechanical performance. The nanofiberous fabrics were prepared by electrospinning of the solution of tetraethoxysilane (TEOS) and polyamic acid (PAA). The different silica contents in the fabrics were achieved by varying the amount of TEOS while fitting the solid content of PAA. The final polyimide/silica fabrics was obtained after imidization of PAA and gelation of silica phase simultaneously accomplished through a step-wise heating process. Some specific IR techniques and other characterizations indicated the successful incorporation of the silicon dioxide (SiO 2) into the PI matrix and the relatively even distribution of the SiO 2 in the fabrics. An increase of 133 °C in the decomposition temperature and 4-fold enhancement of the ultimate tensile strength were achieved for the hybrids with a 6.58 wt.% of SiO 2 content, compared to the pure PI fabric. The excellent performance could be attributed to the good compatibility between the polyimide and silica, and good adhesion among the fibers, which resulted from the controlled TEOS hydrolysis and the simultaneous imidization and gelation process.

Electrical conduction of polyimide films prepared from polyamic acid (PAA) and pre-imidized polyimide (PI) solution

AbstractElectrical conduction characteristics in two different polyimide films prepared by the imidization of polyamic acid (PAA) and pre-imidized polyimide (PI) solution were investigated. It is found that the current density of the polyimide film from PAA was higher than that of the polyimide film from PI at the same electric field, even though the conduction mechanism in both polyimide films follows the ionic hopping model. The hopping distance was calculated to be 2.8 nm for PAA type and 3.2 nm for PI type polyimide film. It is also found that the decay rate of the residual electrostatic charges on the polyimide films becomes faster in the PAA type than in the PI type polyimide film.

Synthesis of duplex nanoparticles in polyimide by the reaction of polyamic acid with Cu–Zn alloy films

Nanoparticle formation resulting from the reaction between polyamic acid (PAA) and alloy films during imidization of PAA was investigated. A Cu–Zn alloy film was deposited on a silicon and glass substrates by DC magnetron sputtering. A PAA solution was spin-coated onto the Cu–Zn alloy films and the PAA/alloy film samples were cured at 250, 300 and 350 °C, respectively for 2 h. The nanoparticles were characterized by transmission electron microscopy. Fourier transform infrared (FT-IR) spectroscopy was used to analyze the curing behavior of PAA into polyimide (PI). The optical properties were measured using the ultraviolet visible spectrometer. The results showed that the very fine Cu 2O and ZnO nanoparticles were distributed in the PI film and the size and density of the particles increased with increasing curing temperature. FT-IR results showed that the degree of the imidization increased as the curing temperature was increased.

Matrimid polyimide membranes for the separation of carbon dioxide from methane

AbstractThree types of polyimide membranes viz., Matrimid, Kapton and P84, were prepared by solution casting and solvent evaporation method to study the permeation of CO2 and CH4 gases. Barrier properties were investigated as a function of feed pressure for pure gases and feed composition for the binary mixtures of CO2 and CH4. Kapton polyimide, prepared by imidization of polyamic acid, showed an increase in permeability, but reduction in selectivity, due to the occurrence of plasticization at higher feed CO2 concentrations. Matrimid was found to exhibit the highest permeability and was studied in greater detail, due to the feasibility in its scale‐up into a hollow fiber modular configuration for commercial application. Matrimid was characterized by Fourier transform infrared (FTIR) spectroscopy and X‐ray diffractometry (XRD) to assess the intermolecular interactions and to understand the separation profiles. The effect of feed flow was evaluated by studying the permeation behavior of flat sheet membrane in dead‐end operation mode with the hollow fiber module operated in crossflow feed mode. For pure gases, Matrimid hollow fiber membrane exhibited a CO2 permeability of 12.7 Barrers with a CO2/CH4 selectivity of 40 at the feed pressure of 20 bar. At the same pressure, for binary mixture feed of 5 mol % CO2 in methane, the module gave a permeability of 7.4 Barrers with a selectivity of 21. The total binary mixture permeability was determined at the feed CO2 concentrations varying from 0 to 20 mol % to demonstrate the preferential sorption of CO2 in Matrimid membrane. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007

Simultaneous Preparation of PI/POSS Semi‐IPN Nanocomposites

AbstractSummary: This investigation presents a simultaneous and convenient approach to produce a high‐performance polyimide with a low dielectric constant by introducing the octa‐acrylated polyhedral oligomeric silsesquioxane (methacrylated‐POSS) into a polyimide matrix to form polyimide semi‐interpenetrating polymer network (semi‐IPN) nanocomposites. The differential scanning calorimetry (DSC) and Fourier‐transform infrared (FT‐IR) results indicate that the self‐curing of methacrylated‐POSS and the imidization of polyamic acid (PAA) occurs simultaneously. The morphology of a semi‐IPN structure of polyimide/POSS‐PI/POSS nanocomposites with POSS nanoparticles embedded inside the matrix is elucidated. The POSS particles are uniform and are aggregated to a size of approximately 50–60 nm inside the polyimide matrix. The interconnected POSS particles are observed at high POSS content. The structure is highly cross‐linked, so the PI/POSS nanocomposites have an enhanced glass transition temperature. The high porosity of the PI/POSS nanocomposites markedly reduces the dielectric constant of PI because of the nanometer‐scale porous structure of POSS.FT‐IR spectra of the various compounds of A) methacrylate‐POSS before curing, B) methacrylate‐POSS after curing, C) PAA containing 15 wt.‐% POSS, and D) PI/POSS containing 15 wt.‐% POSS.magnified imageFT‐IR spectra of the various compounds of A) methacrylate‐POSS before curing, B) methacrylate‐POSS after curing, C) PAA containing 15 wt.‐% POSS, and D) PI/POSS containing 15 wt.‐% POSS.

Preparation, structure and properties of porous polyimide films via PAA/PU alloy

A new route to porous polyimide (PI) films with pore sizes in the nanometer regime was developed. A polyamic acid (PAA)/polyurethane (PU) blend with PU as the disperse phase was first prepared via in situ polymerization of pyromellitic dianhydride and 4,4-oxydianiline in PU solutions. Porous PI films were obtained from PAA/PU films by thermolysis of PU at 360°C and imidization of PAA at 300°C, respectively. Fourier transform infrared spectroscopy and thermal gravimetric analysis were used to detect the imidization and thermolysis processes of PAA/PU blends under thermal treatment. The microporous structure of the PI films was observed by transmission electron microscopy. It was found that the size and content of pores increased with an increase in the PU mass fraction in the PAA/PU blend up to 20%. Because of the existence of nanopores, the dielectric constant of PI films decreased by a wide margin and was less than 2.0 at a PU mass fraction of 20%. It implies that this is an effective means to reduce the dielectric constant of PI, but it also causes the decrease of tensile strength and the rise of water absorption.

Nanoparticles fabricated by selective reaction of Fe 100− xPt x alloy films during imidization of polyamic acid

Nanoparticles with different morphology and composition were fabricated inside a polyimide (PI) matrix based on selectively oxidizing a layer of Fe 100− x Pt x alloy metal film sandwiched between two PI precursor layers. γ-Fe 2O 3, Pt, and Fe 3Pt nanoparticles were formed in a monolayer between two PI layers, depending on the alloy film composition and curing conditions. These particles were well-crystallized and sized between 4 and 10 nm. X-ray photoelectron spectroscopy confirmed that Fe in the film preferentially reacted with the organic matrix whereas Pt remained metallic throughout the curing process, which enabled fabrication of particles different morphology and composition. This process can be easily extended to other alloy films, which provides an opportunity to fabricate nanoparticles relatively easily with desired composition and morphology embedded in an inert organic matrix.

Fabrication of Ni nanoparticles by selective oxidation of permalloy thin film during imidization of polyamic acid.

Ni nanoparticles embedded in a polyimide (PI) matrix were fabricated by selectively oxidizing a layer of Ni(80)Fe(20) metal film sandwiched between two PI precursor layers. Ni nanoparticles, formed in a monolayer between two PI layers, had an average particle size of approximately 5 nm. X-Ray photoelectron spectroscopy confirmed that Fe in the film was preferentially consumed, resulting in the formation of Ni nanoparticles.

Preparation and properties of aromatic polyimides based on 4,4?-(2,2,2-trifluoro-1-phenylethylidene)diphthalic anhydride

Aromatic polyimides were synthesized from aromatic carboxylic acid dianhydrides, 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA), 4,4′-(2,2,2-trifluoro-1-phenylethylidene)diphthalic anhydride (3FDA), and pyromellitic dianhydride (PMDA), with four typical aromatic diamines. These included polyimide (PI) from 2,2-bis(4-aminophenyl)hexafluoropropane (4BDAP) by two-step procedures; amidation to polyamic acid (PAA), followed by thermal imidization of PAA. The chemical and physical properties of the newly prepared polyimides were compared in terms of their chemical structures, inherent viscosity, thermal property, transmission, dielectric constant, UV cutoff, water absorption, and refractive index. PIs 3FDA/4BDAP and 6FDA/4BDAP were soluble in common organic solvents, whereas others were not. In particular, it was found that the solubility was dependent on the temperature of imidization. The chemical and physical properties of the newly prepared polyimides derived from 3FDA were similar to the polyimides derived from 6FDA. The solubility of polyimide containing an ether functional group in the dianhydride moiety was better than that of the ether functional group in the diamine moiety. The polymers with ether linkage in dianhydride moiety exhibited lower glass transition temperature than their functionality-reversed analogous polymers with ether linkage in diamine moiety. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 38–44, 2002

Structure analysis of a soluble polysiloxane-block-polyimide and kinetic analysis of the solution imidization of the relevant polyamic acid

A series of polysiloxane-block-polyimides were synthesized by solution imidization of the polyamic acids derived from the combination of 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride (DSDA), 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP), and diamino(polysiloxane) (PSX (M u , = 750)) in N-methyl-2-pyrrolidone (NMP). Their structures were analyzed by 1 H-, 13 C-, and 29 Si-NMR spectra as well as by IR spectroscopy. The solid-state NMR spectrum was also measured to determine the spin-lattice relaxation time of the copolyimides. The observed relaxation times of both aromatic and polysiloxane segments were similar in the copolyimides having 10-30 wt % of PSX, while those in the copolyimide with 50 wt % of PSX was significantly different. This may be attributed to the morphology change due to the increase in PSX composition in the polymer backbone. The reduced viscosity of the copolyimides could be controlled by changing the monomer ratio in the feed or by adding an end-capping reagent such as phthalic anhydride into the polymerization system. The kinetic study of the solution imidization revealed that the imidization reaction obeyed second-order kinetics. The activation energy calculated for this imidization was 99.2 kJ/mol, being similar to that for the imidization of the DSDA-based aromatic polyimides.

Study on the imidization kinetics of polyether-ester polyamic acid in solid phase by microwave radiation

The polyether-ester polyamic acid imidization process in a solid state was studied by microwave radiation. The imidization content at different radiation times was calculated quantitatively by FTIR and was confirmed by the results of dynamic mechanical analysis (DMA). The microwave radiation imidization may drop the reaction temperature and cut the reaction time down in comparison with the thermal imidization. It may be expected theoretically that the microwave radiation may generally be suitable for the condensation polymerization reaction and facilitates the reaction, especially at its later stage.