Mechanical Properties Of Polyimide Films Research Articles

Relaxation of the mechanical properties of polyimide films of the kapton H type during long-term exposure at ambient conditions

The influence of the exposure time in the initial state at room temperature, which is comparable to the time of operation in orbit (5, 8, and 10 years), on the mechanical properties of polyimide films of the kapton H type of different thicknesses and manufacturers under tensile conditions at room temperature was studied. A change in all studied characteristics (forced elasticity limit, fracture stress, total deformation before fracture, contributions of individual strain components to it, modules of elasticity, and forced elasticity at individual stages of deformation) was revealed. The changes were different for amorphous and partially crystalline films, as well as for amorphous films of the same thickness, but obtained by different manufacturers.

Mechanism analysis of PI/PEEK interface bonding properties enhanced by atmospheric plasma treatment: Experiment and DFT calculation

Due to the increase of service temperature, the bond strength of polyimide composite film will decrease significantly, the continuity of the lapped structure is broken. Therefore, this study proposed a double-layer structure consisting of a polyimide (PI) substrate and Polyetheretherketone (PEEK) coating. The PI/PEEK interface adhesion was improved by using atmospheric plasma treatment. The surface wettability, surface chemical structure, surface element analysis, surface morphology and surface roughness of PI films were studied, respectively. The Materials Studio (MS) was used to model the active groups' grafting mechanism after plasma treatment. The results shown that the surface free energy increased obviously from 27.65 mJ/m2 to 66.93 mJ/m2. Reactive groups containing oxygen, such as C = O, C–O, were generated on the surface of PI film due to etching and addition reactions during the plasma process. The mechanical properties of PI films had little change after plasma treatment. The inorganic particles on the surface of the PI film were exposed by plasma etching, which would increase the adhesion between the PI film and the PEEK coating. MS simulated the sequence, relative energy change, and energy barrier of the three functional groups, revealing that the reactivity sequence of the three groups was: –OH > –COOH > –CO–.

Effects of Electron Irradiation and Temperature on Mechanical Properties of Polyimide Film.

Polyimide (PI) is widely deployed in space missions due to its good radiation resistance and durability. The influences from radiation and harsh temperatures should be carefully evaluated during the long-term service life. In the current work, the coupled thermal and radiation effects on the mechanical properties of PI samples were quantitatively investigated via experiments. At first, various PI specimens were prepared, and electron irradiation tests were conducted with different fluences. Then, both uniaxial tensile tests at room temperature and the dynamic mechanical analysis at varied temperatures of PI specimens with and without electron irradiation were performed. After that, uniaxial tensile tests at low and high temperatures were performed. The fracture surface of the PI film was observed using a scanning electron microscope, and its surface topography was measured using atomic force microscopy. In the meantime, the Fourier-transform infrared spectrum tests were conducted to check for chemical changes. In conclusion, the tensile tests showed that electron irradiation has a negligible effect during the linear stretching period but significantly impacts the hardening stage and elongation at break. Moreover, electron irradiation slightly influences the thermal properties of PI according to the differential scanning calorimetry results. However, both high and low temperatures dramatically affect the elastic modulus and elongation at break of PI.

Overall Improvement in Dielectric, Water Resistance and Mechanical Properties of Polyimide Film via Synergy between GO and Sandwich-type Porous Structure.

Simultaneous improvement in dielectric, water resistance and mechanical properties of polyimide (PI) films is critical for their practical use, but difficult to achieve. Herein, a sandwich-type porous GO/PI film with excellent comprehensive properties was obtained through integrating a GO-containing complex, fluorine-containing porous structure and sandwich-type distribution of porous structure by a simple, low-cost and green breath figure method. With the addition of only a small amount of GO-containing complex, a low dielectric constant of 2.21, water absorption of 0.51%, increment in dielectric constant after moisture treatment of 1.60% and high tensile strength of 113.1 MPa, tensile modulus of 1.70 GPa, with 35.39%, 79.42%, 81.81% of reduction and 17.22%, 21.43% of increase compared to PI film were shown, respectively. Moreover, these properties could be adjusted through regulating the component and porous structure by changing the parameters of breath figure method. These outstanding properties make the film a promising candidate for high-performance low-dielectric materials.

Influence of metallization on the mechanical properties of polyimide films

The need to obtain and study the properties of metallized polymeric materials is associated with their wide application in space exploration, electronics, and the production of consumer goods. The main directions in the search for new materials are aimed at obtaining composite films with different distributions of the metal phase over the thickness while maintaining the mechanical characteristics. The most promising metallized polymer materials are polyimides with high thermal stability, good dielectric properties, and low expansion coefficient. Therefore, the study of viscosity, strength, and other mechanical characteristics of metallized polymeric materials, the determination of the effect of the coating structure on their mechanical behavior, and the development of methods for predicting their behavior are currently relevant and important tasks. Methods for improving the mechanical properties of polyimide films by silver plating have been studied. The thickness of the metal layer of the polyimide base, which is part of the structure, ranged from 1 to 5 μm. Surface coatings were 80–97% of comparable silver mirrors in the visible and infrared regions. The deformation of the samples was carried out at room temperature on an Instron 5982 universal testing machine in the uniaxial tension mode. As a result of the metallization of the films, a significant increase in mechanical characteristics was observed compared to a pure polyimide film. An increase in ultimate strength by ∆σ = 105 MPa and plasticity by ∆ε = 75% was obtained, which is associated with a change in the structure of metallized films and the conditions of their chemical treatment.

Synergistic effect of electron and proton on the mechanical properties of polyimide films

Polyimide film can be used in spacecraft thermal control multilayer and large-scale deployment structure, and its mechanical properties will be degraded by the influence of space radiation environment such as electron and proton. In this paper, the mechanical properties of polyimide film under the synergistic effect of electron and proton was studied using the space integrated irradiation test facility in Beijing Institute of Spacecraft Environment Engineering. It is found that the combined irradiation of electron and proton damages the polyimide film more than the single environment of electron or proton. The synergistic effect of electron and proton causes the exponentially decrease of rupture elongation and the tensile strength of the polyimide film with. With the increase of the electron and proton irradiation fluence until its properties reaches a steady state.

Effects of pre-imidization on rheological behaviors of polyamic acid solution and thermal mechanical properties of polyimide film: an experiment and molecular dynamics simulation

Effects of pre-imidization on rheological behaviors of polyamic acid solution and thermal mechanical properties of polyimide film: an experiment and molecular dynamics simulation

Comparison of nanostructure and nanomechanical properties of cast and air sides of polyimide films from different manufacturers

Polyimide films are widely applied in harsh environments because of their outstanding performance. High-quality polyimide films are often manufactured through a two-step process. The complicated procedure results in different properties on the two sides, i.e., the air side and cast side of the films, and the quality of products from different manufacturers varies notably. In the present work, polyimide films with two thicknesses (1 and 2 mm) from four manufacturers were investigated. Atomic force microscope and FT-IR spectrometer were employed to monitor morphology, roughness, nanomechanical properties, and corresponding relative imidization degree on the two sides of each film. Statistical tools were applied to analyze the data. T-test suggests that the two sides of the same film were significantly different in roughness, DMT modulus, and relative imidization degree (p < 0.05). The roughness on the air side was consistently smaller than that of the cast side. ANOVA was used to compare differences among the manufacturers. Manufacturer B provided the smoothest films with the highest DMT moduli and imidization degrees. A positive correlation was found between the DMT modulus and imidization degree (r = 0.7330). Nanostructure and nanomechanical properties could affect the quality of the film. Striped morphology and adhesion were found on the cast side of the 2-mm film from manufacturer D, which compromised the film tension in the direction perpendicular to the strips. Investigations of morphology and mechanical properties of polyimide film at the nanoscale would help us better characterize the film, assure its quality, and select suitable film and side for proper applications.

Facile strategy for low dielectric constant polyimide/silsesquioxane composite films: structural design inspired from nature

It is important for the development of high-performance dielectric materials to reduce the dielectric constant and water uptake simultaneously, with the maintenance of mechanical properties. Herein, sandwich-type composite film was prepared through coating the both sides of flat polyimide (PI) film with polyhedral oligomeric silsesquioxanes (POSS) contained hierarchical porous structure using the microemulsion method, in which water droplets were used as the template for patterned pores. Due to the introduction of two layers of hierarchical porous structure with patterned pores and POSS, the dielectric constant of PI film was significantly reduced, accompanied by the low dielectric loss. In addition, the water uptake was also greatly reduced, thus contributing to its excellent durability under high humidity. More importantly, even with the introduction of porous structure, the mechanical properties of PI film can still be maintained, or even improved by optimizing POSS content. Through varying the POSS content from 10 to 50%, low dielectric constant of 2.28–2.42, dielectric loss of 0.005–0.009, water uptake of 0.56–0.62%, increment of dielectric constant under high humidity of 1.19–2.35%, with 26–32%, 43–69%, 77–80% and 31–37% of reduction, respectively, compare to flat PI film were achieved. These results indicate the potential of our sandwich-type composite film as low dielectric material in microelectronics.

Mechanical Property Evolution Model of Polyimide Film by Far Ultraviolet Irradiation

The deuterium lamp was used as simulation source to study the Mechanical property of polyimide film in space far ultraviolet environment, thermo gravimetric and XPS was used to analyze the evolution mechanism of polyimide film in different exposures. It was found that the mechanical properties such as tensile strength and rupture elongation of polyimide film decrease firstly and then exponent increase until to stable. From XPS analysis, it can be found that there were rupture and crosslink of chemical bond in polyimide film. In early stage of far ultraviolet radiation, the rupture of C-N, C=O, C-O, C-C bond is for the decrease of mechanical properties of polyimide film, and as the increase of far ultraviolet exposure, the release of N, and formation of C-N bond is for the increase of mechanical properties of polyimide film.

Degradation Mechanism of Polyimide Film Irradiated by Gamma Rays

The Co-60 radiation ground simulation test was conducted on the Mechanical property of polyimide film, thermo gravimetric and XPS was used to analyze the evolution mechanism of polyimide film in different dosages. It was found that the mechanical properties such as tensile force, tensile strength and rupture elongation of polyimide film in gamma ray radiation increase firstly and then exponent decrease. The corresponding initial decomposition temperature of the gamma ray-radiated polyimide film changed from 570°C to 590°C for weight-loss ratio of 2%. From XPS analysis, it can be found that there were rupture and crosslink of chemical bond in polyimide film. In early stage of gamma ray radiation, the rupture of C-N bond and following crosslink is for the increase of mechanical properties of polyimide film, and as the increase of radiation, the rupture of C=O and –N(CO) bond, formation of C-N bond, release of N was for the decrease of mechanical properties of polyimide films.

Enhancement of the Mechanical Properties of Polyimide Film by Microwave Irradiation.

Polyimide films have conventionally been prepared by thermal imidization of poly(amic acid)s (PAAs). Here we report that the improvement of tensile strength while increasing (or maintaining) film flexibility of polyimide films was accomplished by simple microwave (MW) irradiation of the PAAs. This improvement in mechanical properties can be attributed to the increase in molecular weight of the polyimides by MW irradiation. Our results show that the mechanical properties of polyimide films can be improved by MW irradiation, which is a green approach that requires relatively low MW power, very short irradiation time, and no incorporation of any additional inorganic substance.

Электронмен сәулелендірудің және күміспен қаптау процестерінің полиимидті үлдірлердің деформациялануына әсері

The effect of silver metallization and electron irradiation on the physical and mechanical properties of polyimide films is studied. The metal layer of the polyimide base impregnated into the structure was from 1 to 5 µm thick. The coatings on the surface contained 80÷97 % of the relative silver mirror in the visible and infrared regions. The irradiation was carried out on a linear accelerator ELU-6 with an average electron beam energy of 2 MeV, an integral current of up to 1000 µa with a pulse frequency of 200 Hz and a pulse duration of 5 µs. The absorbed dose by the samples was: 10, 20, 30 and 40 MGy. Deformation of the samples was performed at room temperature in the uniaxial tension mode on the universal testing machine Instron 5982. Study of Structural changes in composite materials in the result of the impact of these physical factors was studied in the x-ray diffractometer type DRON–2M in air at 293 K, CuKa radiation (laCu=1.5418 A). A significant increase in the mechanical characteristics as a result of metallization of films compared to the pure film, so the increase in the tensile strength by ∆σ=105 MPa and plasticity by ∆e=75%, which is associated with the peculiarities of changes in the structure of metallized films and the conditions of their chemical etching. Electronic irradiation of the metallized polyimide film worsens its elastic and strength parameters, which is caused by the formation of new phases in the coating in the form of silver oxide, the concentration of which increases with increasing dose, and is also caused by a violation of the ordered structure of the material in the form of a rupture of the macromolecules of polyimide and the formation of new phases of silver in the coating. The mathematical model, which is in good agreement with the experimental data and allows to predict the elastic properties of silver metallized polyimide films, is obtained.

Electrical and mechanical properties of polyimide films treated by plasma formed in water and isopropanol

Fluorinated aromatic polyimide films were treated by pulse electrical discharges formed in water or isopropanol. The relative permittivity, measured in large domains of frequencies and temperatures by broadband dielectric spectroscopy, slightly decreased after plasma discharge in both types of liquids. The dipolar relaxation calculated by Arrhenius equation showed that the liquid plasma treatment decreases the rotational potential energy barrier for non-cooperative motions of dipoles, as a consequence of an increased free volume of plasma exposed films. Higher values of hardness, Young's modulus, and an improved elongation were also measured for the plasma treated samples, indicating molecular rearrangements that occur after plasma treatment.

Degradation and Mechanism of Mechanical Properties of Polyimide Film Irradiated by Gamma Ray

Polyimide (PI) films might be damaged under space high energy particle irradiation. In this paper, the mechanical properties and mechanism of polyimide film is studied with the 60Co radiation source, the thermo-gravimetric analysis and the XPS analysis. Significant total dose effect is found in the mechanical properties of the PI film under gamma ray radiation. The tensile strength and rupture elongation of polyimide film increase first and then decrease exponentially with the increase of irradiation dose. The corresponding initial decomposition temperature of the gamma ray-radiated polyimide film changed from 570°C to 590°C for weight-loss ratio of 2%. From XPS analysis, it can be found that there were rupture and crosslink of chemical bond in polyimide film. In early stage of gamma ray radiation, the rupture of C-N bond and following crosslink is for the increase of mechanical properties of polyimide film, and as the increase of radiation, the rupture of C=O and −N(CO)bond, formation of C-N bond, release of N was for the decrease of mechanical properties of polyimide films.

Morphology and Mechanical Properties of Polyimide Films: The Effects of UV Irradiation on Microscale Surface.

As an attractive dielectric material, polyimide has been widely used in the field of electronics, aerospace, and automobiles due to its useful mechanical properties and good chemical resistance. UV irradiation was considered to be the main factor related to the damage and failure of polyimide. Here the effects of UV irradiation on the surface morphology and microscale mechanical properties of polyimide films are characterized by atomic force microscopy (AFM). The surface roughness of the UV-irradiated samples developed and the mechanical properties degraded with the radiation dose increased. For comparison, uniaxial tensile test was performed to obtain the macroscale Young’s modulus of polyimide film. The UV-irradiated damaging depth was simulated with finite element method (FEM).

Impact of silver metallization and electron irradiation on the mechanical deformation of polyimide films

The impact of silver metallization and electron irradiation on the physical and mechanical properties of polyimide films has been studied. The metal that impregnated the structure of the polyimide substrate was 1–5 μm. The surface coatings contained 80–97% of the relative silver mirror in the visible and infrared regions. Irradiation was performed at the ELU-6 linear accelerator with an average beam electron energy of 2 MeV, an integral current of up to 1000 μA, a pulse repetition rate of 200 Hz, and a pulse duration of 5 μs. The absorbed dose in the samples was 10, 20, 30, and 40 MGy. The samples were deformed at room temperature under uniaxial tension on an Instron 5982 universal testing system. The structural changes in the composite materials that result from the impact of the physical factors were studied using an X-ray diffractometer DRON-2M in air at 293 K using CuKα radiation (λαCu = 1.5418 A). A substantial growth of mechanical characteristics resulting from the film metallization, as compared to the pure film, was observed. The growth of the ultimate strength by Δσ = 105 MPa and the plasticity by Δe = 75% is connected with the characteristics of the change of structure of the metallized films and the chemical etching conditions. The electron irradiation of the metallized polyimide film worsens its elastic and strength characteristics due to the formation of new phases in the form of silver oxide in the coating. The concentration of these phases increased with increasing dose, which was also the result of the violation of the ordered material structure, namely, the rupture of polyimide macromolecule bonds and the formation of new phases of silver in the coating. A mathematical model was obtained that predicts the elastic properties of silver metallized polyimide films. This model agrees with the experimental data.

Effect of adjustable molecular chain structure and pure silica zeolite nanoparticles on thermal, mechanical, dielectric, UV-shielding and hydrophobic properties of fluorinated copolyimide composites

A series of polyimide (PI) films, polyimide/pure silica zeolite nanoparticles (PSZN) blend films and polyimide/amine-functionalized pure silica zeolite nanoparticles (APSZN) composite films were successfully prepared by random copolycondensation. Thereinto, PSZN were synthesized by hydrothermal method. The polyimides were derived from 4,4′-diaminodiphenyl ether (ODA), and three adjustable molar ratios (3:1, 1:1, 1:3) of 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl] propane dianhydride (BPADA) and 4,4′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA). The effects of PSZN, APSZN and different chain structure on PI films were specifically evaluated in terms of morphology, thermal, mechanical, dielectric and UV-shielding properties, etc. Comparison was given among pure PI flims, PI/PSZN blend films and PI/APSZN composite flims. The results showed that the thermal and mechanical properties of PI films were drastically impaired after adding PSZN. On the contrary, the strength, toughness and thermal stability were improved after adding APSZN. Moreover, the dielectric constants of the PI/APSZN composite flims were lowered but UV-shielding properties were enhanced. Interestingly, we found that the greatest effects were obtained through introducing APSZN in PI derived by the 1:1 ratio of BPADA:6FDA. The corresponding PI/APSZN composite flim exhibited the most reinforced and toughened properties, the largest decrement of dielectric constant and the best UV-shielding efficiency, which made the composite flim be used as ultraviolet shielding material in outer space filled with high temperature and intensive ultraviolet light. Meanwhile, this work also provided a facile way to synthesize composite materials with adjustable performance.

Simulation of mechanical strain of metallic electron-irradiated polyimide films

The impact of silver metallization and electron irradiation on the physical and mechanical properties ofpolyimide films has been studied. The metal that impregnated the structure of the polyimide substrate was1–5 μm. The surface coatings contained 80–97% of the relative silver mirror in the visible and infraredregions. Irradiation was performed at the ELU-6 linear accelerator with an average beam electron energyof 2 MeV, an integral current of up to 1000 μA, a pulse repetition rate of 200 Hz, and a pulse duration of5 μs. The absorbed dose in the samples was 10, 20, 30, and 40 MGy. The samples were deformed at roomtemperature under uniaxial tension on an Instron 5982 universal testing system. A substantial growth of mechanicalcharacteristics resulting from the film metallization, as compared to the pure film, was observed.The growth of the ultimate strength by Δσ = 105 MPa and the plasticity by Δε = 75% is connected with thecharacteristics of the change of structure of the metallized films and the chemical etching conditions. Theelectron irradiation of the metallized polyimide film worsens its elastic and strength characteristics due tothe formation of new phases in the form of silver oxide in the coating. The concentration of these phasesincreased with increasing dose, which was also the result of the violation of the ordered material structure,namely, the rupture of polyimide macromolecule bonds and the formation of new phases of silver in thecoating. A mathematical model agrees with the experimental data.

The dominant factor for mechanical property of polyimide films containing heterocyclic moieties: In‐plane orientation, crystallization, or hydrogen bonding

ABSTRACTCrystallization, in‐plane orientation, and hydrogen bonding interactions are three vital factors for enhancing mechanical properties of polyimide (PI) films. However, which is the dominant factor? In this study, three PI films containing heterocyclic moiety, poly(benzoxazole‐imide), poly(benzimidazole‐imide), and poly(pyrimidine‐imide) were chosen to comparative study. The crystallinity of poly(benzoxazole‐imide), poly(benzimidazole‐imide), and poly(pyrimidine‐imide) PI films are 36, 24, and 15%, respectively. The results of small angle X‐ray scattering indicate poly(benzoxazole‐imide) and poly(benzimidazole‐imide) films show periodical lamellar structures, while poly(pyrimidine‐imide) shows no long period due to low crystallinity. In‐plane orientation (P200) is calculated from polarized attenuated total reflection (ATR)‐Fourier transform infrared and refractive indices. The order of in‐plane orientation is poly(benzimidazole‐imide) &lt; poly(benzoxazole‐imide) &lt; poly(pyrimidine‐imide). Hydrogen bonding interactions, which restrict chain motion and hinder spontaneous in‐plane orientation, are only formed in poly(benzimidazole‐imide). The relationship between mechanical properties and three influence factors are discussed, and the order of influence extent for mechanical properties of PI films is hydrogen bonding interactions &lt; degree of crystallization &lt; in‐plane orientation. Two structure models for PI films are proposed in order to further confirm the dominant effect of in‐plane orientation on the mechanical properties. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 44000.