• Analytical Science and Technology
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• v.6 no.1
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• pp.121-129
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• 1993

UV/VIS spectrophotometer interfaced with HPIC(High Performance Ion Chromatography) has been applied to the determination of lanthanide elements. The separation of lanthanide elements with HPIC helped to avoid erroneous analytical results due to interferences. Individual lanthanide elements at ppm level were separated on a HPIC CS5 column using pyromellitic acid and oxalic acid. The individual lanthanide elements were detected at 520nm following post-column reaction with PAR. Sm, Eu, Gd, Y, Tb, Dy, Ho, Er, Tm, Tb, and Lu were separated by pyromellitic acid. La, Ce, Pr and Nd were separated by oxalic acid. Appropriate pH of pyromellitic acid for separation was at pH 2.99.

• Fibers and Polymers
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• v.5 no.2
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• pp.83-88
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• 2004

In order to assess the potential of the hydroxy-containing polyamic acid (PHAA) synthesized from 3,3'-dihydroxy benzidine and pyromellitic dianhydride for a fire-safe polymer, the cyclization pathway of PHAA has been investigated using a model compound prepared from 2-aminophenol and phthalic anhydride. The reaction was monitored. by $^1{H-nuclear}$ magnetic resonance. N-(2-hydroxyphenyl) phthalamic acid is converted to N-(2-hydroxyphenyl) phthalimide at ca. 175$^{\circ}C$, showing endothermic reaction. The imide structure is rearranged to the benzoxazole structure over ca. $400^{\circ}C$. These results are similar with that of PHAA. According to pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) data, water and carbon dioxide are released during the cyclization and rearrangement reaction. One DMAc molecule is complexed with one carboxyl acid group in PHAA, which accelerates the imidization process to release more easily the flame retardant, water.

• Korean Chemical Engineering Research
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• v.50 no.2
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• pp.300-303
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• 2012

Phase change of calcium carbontae crystals in crystallization of precipitated calcium carbonate was researched by adding additives such as ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), citric acid (CIT) and pyromellitic amid (PMA). At low temperature $20^{\circ}C$, calcite crystal was made. At high temperature $80^{\circ}C$, aragonite crystal was made without additives. At middle temperature $40^{\circ}C$ and $60^{\circ}C$, Aragonite crystal also made by adding EDTA, DTPA. The crystal growth of Aragonite was retarded by the presence of CIT, PMA and the single phase of calcite was made. It was found that additives were important factors to make the single phase of calcium carbonate.

• Applied Chemistry for Engineering
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• v.27 no.1
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• pp.50-55
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• 2016

Aromatic diamines containing hexafluoroisopropylidene and ester moiety were synthesized from 4,4'-hexafluoroisopropylidene diphenol and nitrobenzoyl chloride. The reaction of aromatic diamines with hexafluoroisopropylidene phthalicdianhydride (6FDA) or pyromellitic dianhydride (PMDA) gave four kinds of poly(amic acid)s. Their inherent viscosities ranged from 0.196 to 0.346 dL/g. Poly(amic acid)s were converted to polyimides by thermal imidization. The glass transition temperatures ($T_g$) of polyimides were between 241 and $289^{\circ}C$. The 5% weight loss temperatures were recorded in the range of $430{\sim}492^{\circ}C$. The tensile strength of polyimide films were measured as 29.84~64.38 MPa.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.10
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• pp.4069-4074
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• 2010

Phase change of calcium carbontae crystals in crystallization of precipitated calcium carbonate was researched by adding additives such as ethylenediaminetetraacetic acid(EDTA), diethylenetriaminepentaacetic acid(DTPA), citric acid(CIT) and pyromellitic amid(PMA). At low temperature $20^{\circ}C$, calcite crystal was made. At high temperature $80^{\circ}C$, aragonite crystal was made without additives. At middle temperature $40^{\circ}C$ and $60^{\circ}C$, Aragonite crystal also made by adding EDTA, DTPA. The crystal growth of Aragonite was retarded by the presence of CIT, PMA and the single phase of calcite was made. It was found that additives were important factors to make the single phase of calcium carbonate.

• Textile Coloration and Finishing
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• v.8 no.2
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• pp.49-55
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• 1996

Poly(4, 4'-diphenyl ether pyromellitamic acid) was prepared from pyromellitic anhydride with 4, 4'-diamino diphenyl ether by means of low-temperature solution polymeriztion. The reation was exothermic and very fast when carried out at room temperature. The synthesized poly(4, 4'-diphenyl ether pyromellitamic acid) was converted to poly(4, 4'-diphenyl ether pyromellitimide) by thermal dehydrocyclization. FTIR analysis was widely used as a means of determining the course of imidization from intensity of characteristic bands of the imide ring at $1790cm^{-1}$ and $1490cm^{-1}$. The density of poly(4, 4'-diphenyl ether pyromellitimide) was higher than poly(4, 4'-diphenyl ether pyromellitamic acid) indicating the greater crystallinity, perhaps because of the reduction of molar volume of polymers

• Journal of the Korean Ceramic Society
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• v.39 no.11
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• pp.1063-1068
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• 2002

Polyimide/silica(PI/silica) hybrid materials having physical or chemical bonds between the PI and silica network were prepared using sol-gel process through hydrolysis and polycondensation of tetraethoxysilane with the polyamic Acid(PAA) or end-capped PAA solution. PAA solution was synthesized by ring opening reaction of pyromellitic dianhydride and oxydianiline monomers in dimethyl acetamide solution. End-capped PAA solution was synthesized by the addition of 3-aminopropyltriethoxysilane in PAA solution. PI/silica hybrid samples were characterized by infrared spectroscopy, differential thermogravimetry, X-ray diffractometry, scanning electron microscopy, and tensile tester. It has been demonstrated that the properties of hybrid samples were affected by the silica content and the bond type between PI and silica.

• Textile Coloration and Finishing
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• v.8 no.2
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• pp.43-48
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• 1996

Condensation type aromatic polyimides were synthesized in DMF solvent by two step low temperature solution polymerization. By employing monomers as p-phenylene 3diamine and 3 kinds of dianhydrides such as pyromellitic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride and trimellitic anhydride chloride, poly(amic acid) precursors were sythesized. These reactions were exothermic and very fast. When synthesized poly(amic acid)s were dissolved in DMF solvent and stood long time, the polymers were hydrolyzed and their degradation reactions were accelerated as the solution concentrations were dilute. Also, when water is added there-to the degradation rates were accelerated 8faster. In addition, in a very dilute solution state, the reduction viscosity is greatly increased to show properties of conventional polyelectrolytes. This also showed properties sensitive to the concentration change as carboxyl groups per unit segment are increased.

• Bulletin of the Korean Chemical Society
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• v.35 no.11
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• pp.3349-3352
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• 2014

• Bulletin of the Korean Chemical Society
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• v.28 no.2
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• pp.303-306
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• 2007