Home About us Contact
|
Home About us Contact | ||
|
|
||
Polyamic Acid (polyamic + acid)
Selected AbstractsIn situ generated hydroxyl-terminated polybutadiene nanoparticles in polyimide filmsADVANCES IN POLYMER TECHNOLOGY, Issue 1 2009Anand Kumar Gupta Abstract Polyimide (PI) has been extensively investigated as matrices for blends in the search for novel materials for microelectronics and engineering application. The processing of the PI with hydroxyl-terminated polybutadiene (HTPB) offers a considerable advantage to develop a material having good mechanical and thermal stability. Taking this into account, the HTPB was blended with polyamic acid, which is precursor to PI to form PI + HTPB films. A number of properties were evaluated for PI + HTPB films with ultra low concentrations of HTPB. The films prepared with ultra low concentration (10,3,1 wt%) showed unusual synergism, which is attributed to the presence of in situ generated micro/nanostructures derived from HTPB. The microhardness study was used to elucidate the actual mechanical performance due to structure formation of HTPB in a nanometer regime within PI matrix. Atomic force microscopy analysis confirmed the dispersion of HTPB at nano regime within PI matrix. The enhanced thermal stability as determined by thermogravimetric analyzer and Fourier transform infrared spectrometry was attributed to the presence of micro/nanoparticle of HTPB within the PI matrix. The water absorption isotherms were measured and their abnormal behavior was correlated with micro-/nano-sized particles in the PI/HTPB film. © 2009 Wiley Periodicals, Inc. Adv Polym Techn 28:48,59, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20144 [source] Synthesis and characterization of novel polyimide/SiO2 nanocomposite materials containing phenylphosphine oxide via sol-gel techniqueJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010Canan Kizilkaya Abstract In this article, a series of novel polyimide/silica (PI/SiO2) nanocomposite coating materials were prepared from tetraethoxysilane (TEOS), ,-glycidyloxypropyltrimethoxysilane (GOTMS), and polyamic acid (PAA) via sol-gel technique. PAA was prepared by the reaction of 3,3,,4,4,-benzophenone tetracarboxylic dianhydride (BTDA) and bis (3-aminophenyl) phenyphosphine oxide (BAPPO) in N -methyl-2- pyrrolidone (NMP). BAPPO was synthesized hydrogenation of bis (3-nitrophenyl) phenyphosphine oxide (BNPPO) in the presence of Pd/C. The silica content in the hybrid coating materials was varied from 0 to 20 wt %. The molecular structures of the composite materials were analyzed by means of FT-IR and 29Si-NMR spectroscopy techniques. The physical and mechanical properties of the nanocomposites were evaluated by various techniques such as, hardness, contact angle, and optical transmission and tensile tests. These measurements revealed that all the properties of the nanocomposite coatings were improved noticeable, by the addition of sol-gel precursor into the coating formulation. Thermogravimetric analysis showed that the incorporation of sol-gel precursor into the polyimide matrix leads to an enhancement in the thermal stability and also flame resistance properties of the coating material. The surface morphology of the hybrid coating was characterized by scanning electron microscopy (SEM). SEM studies indicated that nanometer-scaled inorganic particles were homogenously dispersed throughout the polyimide matrix © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Simulation of dry-spinning process of polyimide fibersJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2009Gang Deng Abstract As one type of high-performance fibers, the polyimide fibers can be prepared from the precursor polyamic acid via dry-spinning technology. Unlike the dry-spinning process of cellulose acetate fiber or polyurethane fiber, thermal cyclization reaction of the precursor in spinline with high temperature results in the relative complex in the dry-spinning process. However, the spinning process is considered as a steady state due to a slight degree of the imidization reaction from polyamic acid to polyimide, and therefore a one-dimensional model based on White-Metzer viscoelastic constitutive equation is adopted to simulate the formation of the fibers. The changes of solvent mass fraction, temperature, axial velocity, tensile stress, imidization degree, and glass transition temperature of the filament along the spinline were predicted. The effects of spinning parameters on glass transition temperature and imidization degree were thus discussed. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source] Poly(vinyltriethoxysilane) modified MWCNT/polyimide nanocomposites,Preparation, morphological, mechanical, and electrical propertiesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 3 2008Siu-Ming Yuen Abstract Multi-walled carbon nanotube (MWCNT) modified by vinyltriethoxysilane (VTES) via free radical reaction has been prepared (poly (vinyltriethoxysilane) modified MWCNTs, PVTES-MWCNT). Precursor of polyimide, polyamic acid has been synthesized by reacting 4,4,-oxydianiline with 3,3,,4,4,-benzophenone tetracarboxylic dianhydride. PVTES-MWCNT were then mixed with polyamic acid and heated to 300 °C to form CNT/polyimide composite. During the imidization processes, the silanes on CNT surface reacted with each other and may be connected together by covalent bond (SiOSi). The PVTES-MWCNT was analyzed by Fourier transform infrared and X-ray photoelectron spectroscopy. The PVTES-MWCNT/polyimide composites were analyzed by CP/MAS solid state 29Si nuclear magnetic resonance (NMR) spectroscopy. Morphological properties of the PVTES-MWCNT/polyimide composites were investigated by scanning electron microscope and transmission electron microscope. Electrical conductivity increased dramatically comparing to the unmodified MWCNT/polyimide composites. Mechanical properties of nanocomposite were enhanced significantly by PVTES-MWCNT. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 803,816, 2008 [source] Nano-floating gate capacitor with SnO2 quantum dots distributed in polyimide dielectricsPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 4 2009Dong Uk Lee Abstract Self-assembled SnO2 quantum dots were fabricated by a chemical process between a BPDA-PDA polyamic acid and a Sn film. A nano-floating gate capacitor having metal,insulator,semiconductor structure has been formed on p-type Si substrate with SnO2 quantum dots and dielectric polymer layer. The size and density of fabricated SnO2 quantum dot were about 15 nm and 2.4 × 1011 cm,2, respectively. The electrical properties of the nano-floating gate capacitor have been investigated by measuring capacitance,voltage characteristics. Then, the flat-band voltage shift due to charging of the electron in SnO2 quantum dot was ranged from 1.2 V to 4 V. And the transmission electron microscopy and the optical absorption spectra have been measured to investigate the morphology and absorbance of the SnO2 quantum dots embedded in polyimide. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] In situ generated diphenylsiloxane-polyimide adduct-based nanocompositesPOLYMER ENGINEERING & SCIENCE, Issue 1 2005Manisha G. Goswami Arylsiloxane was incorporated into polyimide (PI) via electronic interaction with polyamic acid (PAA)/PI, and a wide spectrum of properties were evaluated for different compositions. The samples prepared with relatively low concentrations (0.0001,0.1%) of oligomers showed unusual synergism, which is attributed to the generation of nanostructures dispersed in the continuous PI matrix. The incorporation of siloxane with bulky phenyl groups contributed to enhanced thermal stability as determined by thermogravimetric analysis. Water uptake and methanol absorption by these composites were evaluated and correlated with the underlying micro- and nanostructures. Fourier Transform Infrared (FTIR) spectroscopy was used to elucidate the probable reaction mechanism (including in situ polymerization of arylsilanol), and to study the synthetic aspects associated with the molecular composites and nanocomposites formation. POLYM. ENG. SCI., 45:142,152, 2005. © 2004 Society of Plastics Engineers [source] Synthesis and properties of BCDA-based polyimide,clay nanocompositesPOLYMER INTERNATIONAL, Issue 6 2007P Santhana Gopala Krishnan Abstract Bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride (BCDA)-based polyimide,clay nanocomposites were prepared from their precursor, namely polyamic acid, by a solution-casting method. The organoclay was prepared by treating sodium montmorillonite (Kunipia F) clay with dodecyltrimethylammonium bromide at 80 °C. Polyamic acid solutions containing various weight percentages of organoclay were prepared from 4,4,-(4,4,-isopropylidenediphenyl-1,1,-diyldioxy)-dianiline and BCDA in N -methyl-2-pyrrolidone containing dispersed particles of organoclay at 20 °C. These solutions were cast on a glass plate using a Doctor's blade and then heated subsequently to obtain nanocomposite films. The nanocomposites were characterized using Fourier transform infrared spectroscopy, differential scanning calorimetry, thermal mechanical analysis, dynamic mechanical analysis, polarizing microscopy, scanning electron microscopy, transmission electron microscopy, wide-angle X-ray diffraction (WAXD) and thermogravimetric analysis. The glass transition temperature of the nanocomposites was found to be higher than that of pristine polymer. The coefficient of thermal expansion of the nanocomposites decreased with increasing organoclay content. WAXD studies indicated that the extent of silicate layer separation in the nanocomposite films depended upon the organoclay content. Tensile strength and modulus of the nanocomposite containing 1% organoclay were significantly higher when compared to pristine polymer and other nanocomposites. The thermal stability of the nanocomposites was found to be higher than that of pristine polymer in air and nitrogen atmosphere. Copyright © 2007 Society of Chemical Industry [source] Preparation and properties of ternary polyimide/SiO2/polydiphenylsiloxane composite filmsPOLYMER INTERNATIONAL, Issue 11 2006Zhenping Shang Abstract A series of novel ternary polyimide/SiO2/polydiphenylsiloxane (PI/SiO2/PDPhS) composite films were prepared through co-hydrolysis and condensation between tetramethoxysilane, diphenyldimethoxysilane (DDS) and aminopropyltriethoxysilane-terminated polyamic acid, using an in situ sol,gel method. The composite films exhibited good optical transparency up to 30 wt% of total content of DDS and SiO2. SEM analysis showed that the PDPhS and SiO2 were well dispersed in the PI matrix without macroscopic separation of the composite films. TGA analysis indicated that the introduction of SiO2 could improve the thermal stability of the composite films. Dynamic mechanical thermal analysis showed that the composite films with low DDS content (5 wt%) had a higher glass transition temperature (Tg) than pure PI matrix. When the content of DDS was above 10 wt%, the Tg of the composite decreased slightly due to the plasticizing effect of flexible PDPhS linkages on the rigid PI chains. The composite films with high SiO2 content exhibited higher values of storage modulus. Tensile measurements also showed that the modulus and tensile strength of the composite films increased with increasing SiO2 content, and the composite films still retained a high elongation at break due the introduction of DDS. The density and water absorption of the composite films were also characterized. Copyright © 2006 Society of Chemical Industry [source] Synthesis and properties of novel polyimides derived from 2,2,,3,3,-benzophenonetetracarboxylic dianhydrideJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 9 2004Xing-Zhong Fang Abstract A new synthetic route to 2,2,,3,3,-BTDA (where BTDA is benzophenonetetracarboxylic dianhydride), an isomer of 2,3,,3,,4,-BTDA and 3,3,,4,4,-BTDA, is described. Single-crystal X-ray diffraction analysis of 2,2,,3,3,-BTDA has shown that this dianhydride has a bent and noncoplanar structure. The polymerizations of 2,2,,3,3,-BTDA with 4,4,-oxydianiline (ODA) and 4,4,-bis(4-aminophenoxy)benzene (TPEQ) have been investigated with a conventional two-step process. A trend of cyclic oligomers forming in the reaction of 2,2,,3,3,-BTDA and ODA has been found and characterized with IR, NMR, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, and elemental analyses. Films based on 2,2,,3,3,-BTDA/TPEQ can only be obtained from corresponding polyimide (PI) solutions prepared by chemical imidization because those from their polyamic acids by thermal imidization are brittle. PIs from 2,2,,3,3,-BTDA have lower inherent viscosities and worse thermal and mechanical properties than the corresponding 2,3,,3,,4,-BTDA- and 3,3,,4,4,-BTDA-based PIs. PIs from 2,2,,3,3,-BTDA and 2,3,,3,,4,-BTDA are amorphous, whereas those from 3,3,,4,4,-BTDA have some crystallinity, according to wide-angle X-ray diffraction. Furthermore, PIs from 2,2,,3,3,-BTDA have better solubility, higher glass-transition temperatures, and higher melt viscosity than those from 2,3,,3,,4,-BTDA and 3,3,,4,4,-BTDA. Model compounds have been prepared to explain the order of the glass-transition temperatures found in the isomeric PI series. The isomer effects on the PI properties are discussed. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2130,2144, 2004 [source] Synthesis and characterization of novel polyimide from bis-(3-aminophenyl)-4-(trifluoromethyl)phenyl phosphine oxideJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 19 2001Kwang Un Jeong Abstract A novel diamine, bis-(3-aminophenyl)-4-(trifluoromethyl)phenyl phosphine oxide (mDA3FPPO), containing phosphine oxide and fluorine moieties was prepared via the Grignard reaction from an intermediate, 4-(trifluoromethyl)phenyl diphenyl phosphine oxide, that was synthesized from diphenylphosphinic chloride and 4-(trifluoromethyl)bromobenzene, followed by nitration and reduction. The monomer was characterized by Fourier transform infrared (FTIR), 1H NMR, 31P NMR, 19F NMR spectroscopies; elemental analysis; melting point measurements; and titration and was used to prepare polyimides with a number of dianhydrides such as pyromellitic dianhydride (PMDA), 5,5,-[2,2,2-trifluoro-1-(trifluoromethyl)ethyliden]-bis-1,3-isobenzofuranedione (6FDA), 3,3,,4,4,-benzophenone tetracarboxylic dianhydride (BTDA), and 4,4,-oxydiphthalic dianhydride (ODPA). Polyimides were synthesized via a conventional two-step route; preparation of polyamic acids, followed by solution imidization, and the molecular weight were controlled to 20,000 g/mol. Resulting polyimides were characterized by FTIR, NMR, DSC, and intrinsic viscosity measurements. Refractive-index, dielectric constant, and adhesive properties were also determined. The properties of polyimides were compared with those of polyimides prepared from 1,1-bis-(4-aminophenyl)-1-phenyl-2,2,2-trifluoroethane (3FDAm) and bis-(3-aminophenyl) phenyl phosphine oxide (mDAPPO). The polyimides prepared from mDA3FPPO provided high glass-transition temperatures (248,311 °C), good thermal stability, excellent solubility, low birefringence (0.0030,0.0036), low dielectric constants (2.9,3.1), and excellent adhesive properties with Cu foils (107 g/mm). © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3335,3347, 2001 [source] | ||||||||||