Reduced Coefficients of Linear Thermal Expansion of Colorless and Transparent Semi-Alicyclic Polyimide Films via Incorporation of Rigid-Rod Amide Moiety: Preparation and Properties

Semi-alicyclic colorless and transparent polyimide (CPI) films usually suffer from the high linear coefficients of thermal expansion (CTEs) due to the intrinsic thermo-sensitive alicyclic segments in the polymers. A series of semi-alicyclic CPI films containing rigid-rod amide moieties were successfully prepared in the current work in order to reduce the CTEs of the CPI films while maintaining their original optical transparency and solution-processability. For this purpose, two alicyclic dianhydrides, hydrogenated pyromellitic anhydride (HPMDA, I), and hydrogenated 3,3’,4,4’-biphenyltetracarboxylic dianhydride (HBPDA, II) were polymerized with two amide-bridged aromatic diamines, 2-methyl-4,4’-diaminobenzanilide (MeDABA, a) and 2-chloro-4,4’-diaminobenzanilide (ClDABA, b) respectively to afford four CPI resins. The derived CPI resins were all soluble in polar aprotic solvents, including N-methyl-2-pyrrolidone (NMP) and N,N-dimethylacetamide (DMAc). Flexible and tough CPI films were successfully prepared by casing the PI solutions onto glass substrates followed by thermally cured at elevated temperatures from 80 °C to 250 °C. The MeDABA derived PI-Ia (HPMDA-MeDABA) and PI-IIa (HBPDA-MeDABA) exhibited superior optical transparency compared to those derived from ClDABA (PI-Ib and PI-IIb). PI-Ia and PI-IIa showed the optical transmittances of 82.3% and 85.8% at the wavelength of 400 nm with a thickness around 25 μm, respectively. Introduction of rigid-rod amide moiety endowed the HPMDA-PI films good thermal stability at elevated temperatures with the CTE values of 33.4 × 10−6/K for PI-Ia and 27.7 × 10−6/K for PI-Ib in the temperature range of 50–250 °C. Comparatively, the HBPDA-PI films exhibited much higher CTE values. In addition, the HPMDA-PI films exhibited good thermal stability with the 5% weight loss temperatures (T5%) higher than 430 °C and glass transition temperatures (Tg) in the range of 349–351 °C.

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Preparation of polyimide-graphite composite and evaluation of its friction behavior at elevated temperatures

Science and Engineering of Composite Materials ◽

10.1515/secm-2014-0322 ◽

2017 ◽

Vol 24 (1) ◽

pp. 81-86 ◽

Cited By ~ 1

Author(s):

Taoqi Zhang ◽

Xueliang Qiao ◽

Fatang Tan ◽

Wei Wang ◽

Hongfei Lu ◽

...

Keyword(s):

Thermal Stability ◽

Solid Lubricant ◽

Elevated Temperatures ◽

Infrared Spectrometry ◽

Friction Behavior ◽

Graphite Composite ◽

Good Thermal Stability ◽

Spectrometry Analysis ◽

Reducing Ability ◽

Load Carrying

AbstractIn this paper, polyimide-graphite (PG) composite was prepared and used as a solid lubricant at elevated temperatures. PG composite was characterized by X-ray diffraction, and its thermal stability was evaluated based on thermogravimetric/differential thermal analysis and Fourier transform infrared spectrometry analysis. The results show that in PG composite, there was some interaction between the graphite (GR) and the polyimide (PI) matrix. Consequently, the PG composite exhibited better thermal stability than PI. The friction behavior of the PG composite sliding against steel at elevated temperatures (300–600°C at an interval of 100°C) was evaluated with a ring-on-ring tribometer. It was found that the PG composite exhibited excellent friction-reducing ability and good load-carrying capacity in the temperature range of 300–600°C and applied loads of 300–700 N. Moreover, this excellent lubricating performance of the PG composite might be attributed to its good thermal stability as a result of the interaction between the GR and the PI matrix. Therefore, PG composite could be used as an excellent solid lubricant under the high-temperature conditions.

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Synthesis and Thermal Stability of Unsaturated Polyamides

High Performance Polymers ◽

10.1088/0954-0083/4/2/001 ◽

1992 ◽

Vol 4 (2) ◽

pp. 67-71

Author(s):

N. R. Patel ◽

N. Z. Patel ◽

R. M. Patel

Keyword(s):

Thermal Stability ◽

Differential Scanning Calorimetry ◽

Thermogravimetric Analysis ◽

Scanning Calorimetry ◽

Aromatic Diamines ◽

Good Thermal Stability ◽

Kinetics Of Decomposition ◽

Glutaconic Acid ◽

Kinetics Of ◽

Thermal Stability Of

Unsaturated polyamides were prepared by condensing /3(4-ethoxyphenyl) glutaconic acid with various aromatic diamines. The polycondensates were characterized by IR spectroscopy, vapor phase osmometry, thermogravimetric analysis, differential scanning calorimetry and elemental analysis. All resins were found to decompose in the range '-210-600 °C. The kinetics of decomposition were studied. The results indicated that the resins possess reasonably good thermal stability.

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Effect of aggregate type on linear thermal expansion of self-consolidating concrete at elevated temperatures

Science and Engineering of Composite Materials ◽

10.1515/secm-2012-0015 ◽

2012 ◽

Vol 19 (3) ◽

pp. 259-269 ◽

Cited By ~ 4

Author(s):

Tayfun Uygunoğlu ◽

İlker Bekir Topçu

Keyword(s):

Thermal Expansion ◽

Thermal Properties ◽

Elevated Temperatures ◽

Coefficient Of Thermal Expansion ◽

Linear Thermal Expansion ◽

Thermal Tests ◽

Linear Change ◽

Volcanic Tuff ◽

Self Consolidating Concrete ◽

Cement Ratio

AbstractIn this study, the effects of aggregate type on the coefficient of thermal expansion of self-consolidating concrete (SCC) produced with normal and lightweight (porous) aggregate (SCLC) were investigated. In experiments, three aggregate types, gravel, volcanic tuff, and diatomite, were used. Different combinations of water/cement ratio and superplasticizer dosage levels were prepared for the SCC and SCLC mixtures. Thermal tests were performed to accurately characterize the coefficient of thermal expansion (CTE) of SCC and SCLC aged 28 days using the dilatometer. The CTEs of SCC and SCLC were defined by measuring the linear change in length of concrete specimens subjected to a range of temperatures from 20°C to 1000°C. The results, in general, showed that SCLC has a lower CTE than that of SCC above 100°C. Moreover, CTE values of SCC and SCLC were decreased with increase in porous structure. The aggregate type has significant influence on the thermal properties of SCC.

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Preparation and Characterization of Semi-Alicyclic Polyimide Resins and the Derived Alignment Layers for Liquid Crystal Display Technology

Polymers ◽

10.3390/polym12010217 ◽

2020 ◽

Vol 12 (1) ◽

pp. 217

Author(s):

Hong-sheng Bi ◽

Xin-xin Zhi ◽

Peng-hui Wu ◽

Yan Zhang ◽

Lin Wu ◽

...

Keyword(s):

Liquid Crystal ◽

Liquid Crystal Display ◽

Weight Ratio ◽

Volume Resistivity ◽

Solid Content ◽

Processing Temperature ◽

Aromatic Diamines ◽

Good Thermal Stability ◽

Rigid Rod ◽

Alignment Layers

Uniform alignment of rigid-rod liquid crystal (LC) molecules under applied voltage is critical for achievement of high-quality display for thin-film transistor-driven liquid crystal display devices (TFT-LCDs). The polymeric components that can induce the alignment of randomly aligned LC molecules are called alignment layers (ALs). In the current work, a series of organo-soluble polyimide (SPI) ALs were designed and prepared from an alicyclic dianhydride, hydrogenated 3,3′,4,4′-biphenyltetracarboxylic dianhydride (HBPDA), and various aromatic diamines, including 4,4′-methylenedianiline (MDA) for SPI-1, 4,4′-aminodianiline (NDA) for SPI-2, 3,3′,5,5′-tetramethyl-4,4′-diaminodiphenylmethane (TMMDA) for SPI-3, and 3,3′-diethyl-5,5′-dimethyl-4,4′-diaminodiphenylmethane (DMDEDA) for SPI-4. The derived SPI resins were all soluble in N-methyl-2-pyrrolidone (NMP). Four SPI alignment agents with the solid content of 6 wt.% were prepared by dissolving the SPI resins in the mixed solvent of NMP and butyl cellulose (BC) (NMP/BC = 80:20, weight ratio). Liquid crystal minicells were successfully fabricated using the developed SPI varnishes as the LC molecule alignment components. The SPI ALs showed good alignment ability for the LC molecules with the pretilt angles in the range of 1.58°–1.97°. The LC minicells exhibited good optoelectronic characteristics with voltage holding ratio (VHR) values higher than 96%. The good alignment ability of the SPI ALs is mainly attributed to the good comprehensive properties of the SPI layers, including high volume resistivity, high degree of imidization at the processing temperature (230 °C), good rubbing resistance, good thermal stability with glass transition temperatures (Tgs) higher than 260 °C, and excellent optical transparency with the transmittance higher than 97% at the wavelength of 550 nm.

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Effect of Mn on Microstructure and Mechanical Properties of Al-4Ni Alloy

JOM ◽

10.1007/s11837-021-04908-3 ◽

2021 ◽

Author(s):

Jiao Fang ◽

Xixi Dong ◽

Shouxun Ji

Keyword(s):

Mechanical Properties ◽

Thermal Stability ◽

Tensile Strength ◽

Aluminum Alloys ◽

Yield Strength ◽

Elevated Temperatures ◽

Strength Loss ◽

Good Thermal Stability ◽

Microstructure And Mechanical Properties

AbstractThe application of aluminum alloys at elevated temperatures has been attractive for decades, and Al-Ni-based alloys have recently been recognized as potential candidates. The effect of Mn on Al-4Ni alloy has been investigated in this work. Addition of Mn transformed the eutectics from Al3Ni/α-Al to Al9(Ni,Mn)2/α-Al phases. Mn also improved the tensile strength at both 25°C and 250°C. The yield strength at 25°C increased from 48 MPa to 92 MPa with 1.87% Mn and then to 117 MPa with 3.77% Mn. At 250°C, the yield strength increased from 35 MPa to 82 MPa with 1.87% Mn and then to 101 MPa with 3.77% Mn. The alloys with Mn also showed less strength loss than Al-4Ni alloy at 250°C. The eutectic Al9(Ni,Mn)2 phase showed good thermal stability. No coarsening was observed after 2000 h at 250°C.

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Crystal structure, thermal and electrotransport properties of NdBa1–xSrxFeCo0.5Cu0.5O5+δ (0.02 ≤ x ≤ 0.20) solid solutions

Chimica Techno Acta ◽

10.15826/chimtech.2021.8.3.01 ◽

2021 ◽

Vol 8 (3) ◽

pp. 20218301

Author(s):

A. I. Klyndyuk ◽

Ya. Yu. Zhuravleva ◽

N. N. Gundilovich

Keyword(s):

Crystal Structure ◽

Thermal Stability ◽

Electrical Conductivity ◽

Thermal Expansion ◽

Solid Solutions ◽

Electrical Transport ◽

Linear Thermal Expansion ◽

Solid State Reactions ◽

Partial Substitution ◽

Cell Parameters

Using solid-state reactions method, the solid solutions of layered oxygen-deficient perovskites NdBa1–xSrxFeCo0.5Cu0.5O5+δ (0.02 ≤ x ≤ 0.20) were prepared; their crystal structure, thermal stability, thermal expansion, electrical conductivity and thermopower were studied. It was found that NdBa1–xSrxFeCo0.5Cu0.5O5+δ phases crystallize in tetragonal syngony (space group P4/mmm) and are p-type semiconductors, whose conductivity character at high temperatures changed to the metallic one due to evolution from the samples of so-called weakly-bonded oxygen. Partial substitution of barium by strontium in NdBaFeCo0.5Cu0.5O5+δ leads to the small decreasing of unit cell parameters, thermal stability and thermopower of NdBa1–xSrxFeCo0.5Cu0.5O5+δ solid solutions, increasing of their electrical conductivity values and slightly affects their linear thermal expansion coefficient and activation energy of electrical transport values.

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Aromatic Poly(ether imide oxadiazole)s

High Performance Polymers ◽

10.1088/0954-0083/4/2/002 ◽

1992 ◽

Vol 4 (2) ◽

pp. 73-80 ◽

Cited By ~ 19

Author(s):

F. W. Mercer

Keyword(s):

Thermal Stability ◽

Glass Transition ◽

Aprotic Solvent ◽

Dielectric Constants ◽

Aromatic Diamines ◽

Glass Transition Temperatures ◽

Good Thermal Stability ◽

Polar Aprotic Solvent ◽

Carbonate Reaction ◽

Poly Imide

Two oxadiazole containing aromatic diamines were synthesized. The diamines were prepared by reaction of aminophenols with 2,5-bis(4-fluorophenyl)-4l3,4-oxadiazole in a polar aprotic solvent in the presence of potassium carbonate. Reaction of the resulting 2,5-bis(4-(aminophenoxy)phenyl)-1,3,4-oxadiazoles with dianhydrides gave a series of polymeric amic acids. Thermal treatment yielded poly(imide ether oxadazole) films which displayed good thermal stability, flexibility, and glass transition temperatures ranging from 241 to 344C. The dielectric constants of the films were characterized as a function of relative humidity.

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Preparation and Properties of Inherently Black Polyimide Films with Extremely Low Coefficients of Thermal Expansion and Potential Applications for Black Flexible Copper Clad Laminates

Polymers ◽

10.3390/polym12030576 ◽

2020 ◽

Vol 12 (3) ◽

pp. 576 ◽

Cited By ~ 1

Author(s):

Yao-yao Tan ◽

Yan Zhang ◽

Gang-lan Jiang ◽

Xin-xin Zhi ◽

Xiao Xiao ◽

...

Keyword(s):

Thermal Expansion ◽

Dimensional Stability ◽

Elevated Temperatures ◽

Coefficient Of Thermal Expansion ◽

Optical Transmittance ◽

Molecular Structures ◽

Molar Ratio ◽

Optical Parameters ◽

Aromatic Diamines ◽

Potential Applications

In the current work, a series of black polyimide (PI) films with excellent thermal and dimensional stability at elevated temperatures were successfully developed. For this purpose, two aromatic diamines including 4,4′-iminodianline (NDA) and 2-(4-aminophenyl)-5- aminobenzimidazole (APBI) were copolymerized with pyromellitic dianhydride (PMDA) to afford PIs containing imino groups (–NH–) in the molecular structures. The referenced PI film, PI-ref, was simultaneously prepared from PMDA and 4,4′-oxydianiline (ODA). The introduction of imino groups endowed the PI films with excellent blackness and opaqueness with the optical transmittance lower than 2% at the wavelength of 600 nm at a thickness of 25 μm and lightness (L*) below 10 for the CIE (Commission International Eclairage) Lab optical parameters. Meanwhile, the introduction of rigid benzimidazole units apparently improved the thermal and dimensional stability of the PI films. The PI-d film based on PMDA and mixed diamines (NDA:APBI = 70:30, molar ratio) showed a glass transition temperature (Tg) of 445.5 °C and a coefficient of thermal expansion (CTE) of 8.9 × 10−6/K in the temperature range of 50 to 250 °C, respectively. It is obviously superior to those of the PI-a (PMDA-NDA, Tg = 431.6 °C; CTE = 18.8 × 10−6/K) and PI-ref (PMDA-ODA, Tg = 418.8 °C; CTE: 29.5 × 10−6/K) films.

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Study on Dependability and Repeatability of Measurement Method of Mean Linear Thermal Expansion Coefficients of Glasses

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.694-697.1271 ◽

2013 ◽

Vol 694-697 ◽

pp. 1271-1275 ◽

Cited By ~ 1

Author(s):

Ying Liang Tian ◽

Zhu Cui ◽

Chun Mei Yuan ◽

Xin Hui Liang ◽

Shi Bing Sun ◽

...

Keyword(s):

Thermal Stability ◽

Thermal Expansion ◽

Thermodynamic Property ◽

Measurement Method ◽

Initial Temperature ◽

Linear Thermal Expansion ◽

Physical Property ◽

Thermal Expansion Coefficients ◽

Measurement Results ◽

Expansion Coefficients

Coefficient of mean linear thermal expansion is an important physical property of glasses. It is the key thermodynamic property to evaluate the thermal stability and matching sealing of glasses. The measurement results of coefficient of mean linear thermal expansion obtained by different dilatometers showed that glass expands slowly with nonlinearity below 50 °C. It suggested that the initial temperature of measurement would be set above 50 °C, as behaves better repeatability and reliability of measurement than 20 °C as standard method set.

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Thermal Expansion of Triaxially Stressed Mudstone at Elevated Temperatures up to 400°C

Advances in Materials Science and Engineering ◽

10.1155/2020/8140739 ◽

2020 ◽

Vol 2020 ◽

pp. 1-8

Author(s):

Zi-jun Feng ◽

Meng-meng Qiao ◽

Fu-ke Dong ◽

Dong Yang ◽

Peng Zhao

Keyword(s):

Thermal Expansion ◽

Thermal Expansion Coefficient ◽

Expansion Coefficient ◽

Coal Gasification ◽

Elevated Temperatures ◽

Linear Thermal Expansion Coefficient ◽

Linear Thermal Expansion ◽

Underground Coal Gasification ◽

Machine Model

In order to study the thermal deformation of the rock that surrounds underground engineering projects with elevated temperatures (e.g., underground coal gasification, coal in situ pyrolysis, in situ oil and gas extraction from oil shale, geothermal energy extraction from rock, among others), a servocontrolled machine (model IMT-HTP 100F) was used to examine the thermal expansion of triaxially stressed mudstone at temperature up to 400°C. Two distinct stages of thermal expansion were found at temperatures up to 400°C: very small thermal expansion below 50°C, followed by almost constant thermal expansion at 50–400°C. This linear thermal expansion coefficient of triaxially stressed mudstone did not increase in the range 50–400°C. The effect of the applied triaxial stress was on both close cracks and impeded grain expansion and the swelling of the rock. Mudstone had a larger linear thermal expansion coefficient than either sandstone or limestone, in that order. The potential energy theory was used to explain the intrinsic variation of thermal expansion of the different rock types.

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