scholarly journals Polyamic Acid Nanofibers Produced by Needleless Electrospinning

2010 ◽  
Vol 2010 ◽  
pp. 1-6 ◽  
Author(s):  
Oldrich Jirsak ◽  
Petr Sysel ◽  
Filip Sanetrnik ◽  
Jakub Hruza ◽  
Jiri Chaloupek
Keyword(s):  
Pressure Drop ◽  
Ir Spectroscopy ◽  
Polyamic Acid ◽  
Needleless Electrospinning ◽  
Electrospinning Method ◽  
Filtration Properties ◽  
To Receive ◽  
Polyimide Precursor ◽  
Oxydiphthalic Anhydride

The polyimide precursor (polyamic acid) produced of4,4′-oxydiphthalic anhydride and4,4′-oxydianiline was electrospun using needleless electrospinning method. Nonwoven layers consisting of submicron fibers with diameters in the range about 143–470 nm on the polypropylene spunbond supporting web were produced. Filtration properties of these nanofiber layers on the highly permeable polypropylene support—namely filtration effectivity and pressure drop—were evaluated. Consequently, these polyamic acid fibers were heated to receive polyimide nanofibers. The imidization process has been studied using IR spectroscopy. Some comparisons with the chemically identical polyimide prepared as the film were made.

Cure Studies of Fluorinated Polyamic Acids by Thermal-IR

1992 ◽  
Vol 264 ◽  
Author(s):  
Robert T. Roginski ◽  
Douglas E. Fjare
Keyword(s):  
Ir Spectroscopy ◽  
Phthalic Anhydride ◽  
Amic Acid ◽  
Back Reaction ◽  
Curing Process ◽  
Thermal Curing ◽  
Additional Mechanism ◽  
Polyamic Acid

AbstractThe thermal curing chemistry of a fluorinated polyamic acid based on 6FDA (hexafluoroisopropylidene bis(phthalic anhydride)) and APBP (4,4′-bis(4-aminophenoxy)biphenyl) was studied by thermal-IR spectroscopy. Anhydride formation was observed at intermediate cure temperatures and maximized at approximately 220°C. The degree of anhydride formation was affected by the solvent, being least in 2-methoxyethyl ether and increasing in the solvent order: 2-methoxyethyl ether < NMP < 2-(2-ethoxy)ethoxyethanol. In addition to the back reaction of amic acid to anhydride and amine, at least one additional mechanism of anhydride formation is observed. The onset of the second mechanism of anhydride formation is coincident with the onset of imidization, which leads us to propose that water generated by imidization can react with anhydride during the curing process, before escaping from the film, to form diacid. Cyclization of diacid to anhydride is proposed as the second mechanism of anhydride formation.

Positive-working photosensitive polyimide precursor based on polyisoimide using nifedipine as a dissolution inhibitor

1994 ◽  
Vol 6 (3) ◽  
pp. 225-233 ◽  
Author(s):  
Amane Mochizuki ◽  
Kazuo Yamada ◽  
Tadashi Teranishi ◽  
Koichi Matsushita ◽  
Mitsuru Ueda
Keyword(s):  
Dissolution Rate ◽  
Photochemical Reaction ◽  
Ring Opening ◽  
Exposed Area ◽  
Post Exposure ◽  
Pyridinedicarboxylic Acid ◽  
Dissolution Behaviour ◽  
Post Exposure Bake ◽  
Polyimide Precursor ◽  
Oxydiphthalic Anhydride

A positive-working photosensitive polyimide precursor based on polyisoimide (PFII) and nifedipine (1,4-dihydro-2,6-dimethyl-4-(nitrophenyl)-3,5-pyridinedicarboxylic acid dimethylester) (DHP) as a photosensitive compound has been developed. P11 was prepared by the ring-opening polyaddition of oxydiphthalic anhydride (ODPA) and 3,3' diamino diphenylsulphone (3,3'-DDS), followed by the treatment of trifluoroacetic anhydridetriethylamine in N-methyl-2-pyrrolidone (NMP). PII film showed excellent transparency at 365 nm and 436 nm. The dissolution behaviour of PII film containing 20 wt% of DHP after exposure and post-exposure bake (PEB) has been studied. It was found that the dissolution rate of the exposed area was about six times faster than that of the unexposed area due to the photochemical reaction of DHP in P11 film. The photosensitive polyimide precursor containing 20 wt% of DHP showed a sensitivity of 45 mJ cm- 2 and a contrast of 2.4 with 365 nm light when post-baked at 150C for 10 min and developed with cyclohexanone at 50C.

Chemistry of Adhesion at the Polyimide-Metal Interface

1987 ◽  
Vol 108 ◽  
Author(s):  
M. Grunze ◽  
W. N. Unertl ◽  
S. Gnanarajan ◽  
J. French
Keyword(s):  
Structural Changes ◽  
High Vacuum ◽  
Scanning Tunneling ◽  
Metal Interface ◽  
Polyimide Films ◽  
Absorption Data ◽  
Polyamic Acid ◽  
Vapor Phase Deposition ◽  
Infrared Reflection ◽  
Polyimide Precursor

ABSTRACTThis article describes recent studies of the chemistry of adhesion between thin (d ≥ 11 Å) polyimide films and silver and copper substrates, and the structural changes in the polymer when polyamic acid is imidized to polyimide. The thin polyamic acid films were formed by vapor phase deposition of 1,2,4,5-benzenetetracarboxylic anhydride (PMDA) and 4,4-oxydianiline (ODA) under high vacuum conditions and subsequent imidization by heating in vacuum. Both ODA and PMDA are at least partially dissociated upon adsorption onto clean copper and silver and with increasing film thicknesses react to form the polyimide precursor, polyamic acid. Heating to T ≥ 425 K leads to polymerization to form polyimide films which are thermally stable to about 700 K. Polyimide films with mean thicknesses as small as 1.1 nm have been fabricated in this way and their bonding to the substrate as determined by x-ray photoemission studies is su marized. Infrared reflection absorption data gives further evidence that the polyimide bonds to the substrate via fragmented PMDA. Changes in the surface topography and molecular structure of the films during imidization are demonstrated by scanning tunneling micrographs and infrared reflection absorption data.

The preparation of new poly(phenylsilsesquioxane)-polyimide hybrid films by the sol-gel process and their properties

1994 ◽  
Vol 6 (1) ◽  
pp. 53-62 ◽  
Author(s):  
Yoshitake Iyoku ◽  
Masa-aki Kakimoto ◽  
Yoshio Imai
Keyword(s):  
Nmr Spectra ◽  
Sol Gel ◽  
Tensile Modulus ◽  
Heating Process ◽  
Hybrid Films ◽  
Polyamic Acid ◽  
Sol Gel Process ◽  
Polyimide Matrix ◽  
Polyimide Precursor ◽  
Silicone Content

The preparation of poly(phenylsilsesquioxane)-polyimide hybrid films was successfully performed with phenyltriethoxysilane (PhTES) and the polyamic acid (polyimide precursor) prepared from 4.4'-oxydianiline (ODA) and pyromellitic dianhydride (PMDA). During the heating process at 300 C, the imidization of the polyamic acid and the sol-gel reaction, hydrolysis and condensation of PhTES, proceeded simultaneously. The IR spectrum and the t3C-NMR and 29Si-NmR spectra showed that the sol-gel reaction of PhTES proceeded in the polymer matrix with high conversion. The hybrid films with a silsesquioxane content up to 75 wt% were obtained as the self-standing form. The hybrid films having a silsesquioxane content of 45 wt% were yellow and transparent, and those having more silicone content were yellow and translucent. The therma] properties of the hybrid films were improved to some extent by the introduction of the silsesquioxane component into the polyimide matrix. With respect to the tensile properties. the tensile strength remained around 85 MPa up to a silicone content of 45 wt%. This value was twice that of the hybrid films based on methyltriethoxysilane. The tensile modulus decreased with increasing silsesquioxane content.

scholarly journals Synthesis of Electrospun Nanofibers Membrane and Its Optimization for Aerosol Filter Application

2016 ◽  
Vol 1 ◽  
Author(s):  
Abdul Rajak
Keyword(s):  
Pressure Drop ◽  
Fiber Diameter ◽  
Polymer Concentration ◽  
Electrospun Nanofibers ◽  
Diameter Distribution ◽  
Air Filtration ◽  
Sem Image ◽  
Aerosol Filtration ◽  
Electrospinning Method ◽  
Fiber Diameter Distribution

Nanofibers membranes were synthesized using electrospinning method for air filtration application. Polyacrylonitrile (PAN) with three different concentrations as the polymeric matrix of the nanofibers membrane is used. In the aerosol filtration, the pressure drop is one of the most important parameters, which is determined by the membrane characteristics. One of the parameters that influence the characteristics of membrane is concentration of polymer solution, in which it will determine the diameter of fiber. In this study, the relation between the PAN concentration and the pressure drop in air filtration test was examined. Three different concentrations of PAN solution (6, 9, and 12 wt.%) were employed under the same process parameters of electrospinning. The fiber diameter distribution of each membrane was measured from its scanning electron microscope (SEM) image. The three concentrations resulted in significant different effect to the pressure drop that proved the existing correlation between the polymer concentration and the air pressure drop.

Optimization of air permeability of spunlaced filter fabrics using the Box–Behnken experimental design

2019 ◽  
Vol 50 (5) ◽  
pp. 675-691 ◽  
Author(s):  
Lebo Maduna ◽  
Asis Patnaik ◽  
Mlando Mvubu ◽  
Lawrance Hunter
Keyword(s):  
Pressure Drop ◽  
Air Permeability ◽  
Water Jet ◽  
Polyphenylene Sulfide ◽  
Dust Particles ◽  
Fiber Types ◽  
Independent Variables ◽  
Good Filter ◽  
Filtration Properties ◽  
Filter Fabric

One of the most important characteristics that a filter must possess is high air permeability. A good filter fabric must be able to capture the dust particles while maintaining a good airflow through it in order to reduce high pressure drop. Therefore, producing a filter fabric with the desired air permeability can be challenging as several process parameters such as fiber types, area weight and water jet pressure will interact with each other during spunlacing process and influence the fabric air permeability. To study the effects of these independent variables on the air permeability of three different types of spunlaced fabrics, the Box–Behnken design was used to model their effects. The fibers used were polyacrylonitrile, polyphenylene sulfide and blend of polyphenylene sulfide/polyimide. In addition, filtration properties of some of the filter samples were also evaluated. Based on the effects of the fiber types, area weight and water jet pressure on the fabric air permeability, the optimum conditions for achieving higher air permeability were fiber types (+1 level), area weight (0 level) and pressure (−1 level), respectively. The air permeability of the fabrics decreased with increasing water jet pressure for all fiber types and increasing area weight decreased the air permeability. It was observed that the independent variables had a significant effect on the air permeability. Filtration efficiency of the selected filters samples were ≥95%. Among the selected samples, polyphenylene sulfide/polyimide (440 g/m2) fabric has the lowest pressure drop whereas polyacrylonitrile (560 g/m2) has the highest pressure drop.

Electrospinning of PVA/Carbon Nanotube Composite Nanofibers: The Effect of Processing Parameters

2008 ◽  
Vol 589 ◽  
pp. 221-226 ◽  
Author(s):  
Kolos Molnár ◽  
Eva Košt’áková ◽  
László Mészáros
Keyword(s):  
Carbon Nanotube ◽  
Composite Nanofibers ◽  
Lower Surface ◽  
Processing Parameters ◽  
Poly Vinyl Alcohol ◽  
Conductivity Measurements ◽  
Needleless Electrospinning ◽  
Electrospinning Method ◽  
Carbon Nanotube Composite ◽  
Scanning Electron

Poly(vinyl alcohol)/carbon nanotube (CNT) composite nanofibers were processed by both conventional and needleless electrospinning method. The effect of the processing parameters on the possibility of manufacturing was investigated. The results were evaluated by surface tension and conductivity measurements. For the investigation of surface morphology scanning electron microscopy (SEM) was used. It was concluded that surface treatment of carbon nanotubes was necessary for needleless electrospinning. Lower surface tensions were better for this process but the effect of conductivity was not so significant.

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