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Volume 54, Issue 9
Displaying 1-8 of 8 articles from this issue
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Koichi KITAO1997 Volume 54 Issue 9 Pages 519-525
Published: September 25, 1997
Released on J-STAGE: June 11, 2010
JOURNAL FREE ACCESSThe brittle-ductile transition temperature (BDTT) of polyethylene was evaluated using the Charpy impact test. The effect of the crystallinity on BDTT was the main concern in this study. Higher density resins revealed lower BDTT. On the other hand, whitening of the deformed region during the tensile test and craze-like failure during the tensile test with a notch increased for higher density resins more than for lower density resins. Therefore, a crack shielding effect by microvoid formation at yielding zone near the notch is proposed as the toughening mechanism on Charpy impact test for higher density resins.View full abstractDownload PDF (2547K) -
Tadatomo KAWAI, Shinya TERAMACHI, Takahiro SAKAI, Tuyoshi HIBINO1997 Volume 54 Issue 9 Pages 526-536
Published: September 25, 1997
Released on J-STAGE: June 11, 2010
JOURNAL FREE ACCESSThe molecular characterization of cellulose derivatives is very complicated. It is important to determine the distribution of degree of substitution (DS), that is, the intermolecular heterogeneity of the average DS of each molecule (corresponding to the chemical composition distribution of copolymer). Distributions of DS of the acetyl cellulose samples were determined by reversed-phase absorption high-performance liquid chromatography (HPLC). First, the optimum condition for HPLC fractionating the samples according to the DS was investigated using various combinations of columns and eluents. The combination of a phenyl modified silica gel column and liner gradient elution of acetone and mixture of water and methanol (3vs. 1 by volume) was found to be more effective than other combinations. The samples were eluted from low acetyl content to high acetyl content, according to reversed-phase adsorption mechanism. Next, we tried to determine distributions of DS of the samples using this separation system. Since the samples have no UV absorption, evaporative light scattering detector (ELSD) was used for the detection. The response of ELSD does not depend only upon sample concentration. Therefore, the chromatograms were converted to the distributions of DS by the optimization method using calibration curves for concentration and DS. The distribution curve of DS thus obtained becomes narrower as the DS increases, in accordance with theoretical consideration.View full abstractDownload PDF (1612K) -
Yasuharu YAMADA, Nobuyuki FURUKAWA1997 Volume 54 Issue 9 Pages 537-543
Published: September 25, 1997
Released on J-STAGE: June 11, 2010
JOURNAL FREE ACCESSThree types of low molecular weight bis-imide additives containing fluorine and siloxane were synthesized. The effects of the additives for polyimides on dielectric constant, thermal, and mechanical properties were studied. Theaddition of these additives for aromatic polyimide lowered the dielectric constant of the polyimide with increasing the amount of the additives up to 10wt%. However, the addition of additives with more than 10wt% did not show any further effect. Bis-imide additives containing fluorine were more effective than the bis-imide additive containing siloxane to lower the dielectric constant for polyimide. In contrast, the additives did not show any effect on lowering dielectric constant for siloxane-imide block copolymer with microphase separated structure. The glass transition temperature (Tg), thermal decomposition temperature (Td), tensile modulus (TM), tensile strength, and elongation were lowered with increasing the amount of additives for aromatic polyimide, while Tg, Td, and TM were slightly increased by the addition of fluorine containing additives for siloxane-imide block copolymer. It was found that the effect of additive into the polyimide on dielectric constant, thermal, and mechanical properties was different according to the structure of the polyimide.View full abstractDownload PDF (1087K) -
Masafumi YAMATO, Ritsuko MUROHASHI, Tsunehisa KIMURA, Eiko ITO1997 Volume 54 Issue 9 Pages 544-551
Published: September 25, 1997
Released on J-STAGE: June 11, 2010
JOURNAL FREE ACCESSDielectric β relaxation processes were measured for a series of ethylene terephthalate/p-hydroxybenzoic acid (ET/ PHB) copolymers with different PHB contents. The copolymers with the PHB content lower than 30% were in an isotropic amorphous glass phase, while those with higher PHB contents were in a liquid crystalline glass phase. The latter exhibited a larger dielectric strength than the former. This observation was not fully explained in terms of onlythe difference in the correlation length of the torsional vibration of the main chains. The orientation distribution of the main chains relative to the electric field direction was assumed to obtain a reasonable explanation. To confirm this assumption, the dielectric measurements were carried out on two film samples with different orientations: one with parallel orientation and the other with perpendicular orientation with respect to the film surface, both prepared by using a magnetic field. The results of the dielectric measurements for these two samples were in favor of the assumption.View full abstractDownload PDF (1378K) -
Yoshio WADA, Hideaki SUGIURA, Masashi OHARA, Shinzaburo ITO, Masahide ...1997 Volume 54 Issue 9 Pages 552-559
Published: September 25, 1997
Released on J-STAGE: June 11, 2010
JOURNAL FREE ACCESSThe photochemical reaction of N-methyldiphenylamine (MDPA) and carbon tetrabromide (CTB) yields a triphenylmethane dye (TPMD). The mechanism of the reaction was ivestigated by product analysis and UV-VIS spectroscopy. MDPA and CTB in a polymer matrix formed a charge transfer complex in the ground state. The reaction proceeded through an exciplex produced by photo-excitation of the complex, providing a cationic intermediate of MDPA substituted with CBr2 group, a cationic dimeric intermediate of MDPA connected with CBr group, and finally TPMD. The reaction in a matrix to form TPMD is rather efficient compared to that in solution. The results obtained here allows one to analyze the reaction of a photosensitive polymer system containing diphenylamine chromophore and CTB.View full abstractDownload PDF (1518K) -
Yoshio WADA, Hideaki SUGIURA, Shinzaburo ITO, Masahide YAMAMOTO1997 Volume 54 Issue 9 Pages 560-565
Published: September 25, 1997
Released on J-STAGE: September 28, 2010
JOURNAL FREE ACCESSA photosensitive polymer film doped with diphenylamine (DPA) and carbon tetrabromide (CTB) yields a triphenylmethine dye of DPA trimer by a multi-step reaction of DPA with CTB. In the current study, we applied this reaction for polymer systems of poly (N, N-diphenylaminoethyl methacrylate) with CTB (CTB/PDPAEMA). The irradiation of CTB/PDPAEMA film induced the dimerization between two DPA chromophores, which was monitored by the increase of absorption at 650nm. Since the reactive intermediate of DPA substituted with CBr2 was stable, the dimerization proceeded gradually in the dark. The CTB/PDPAEMA system formed no triphenylmethine dye of DPA chromophores, but the dimerization reaction of the chromophoric groups resulted in photocrosslinking of the polymer films, accompanied with coloring. The rate of reaction was discussed in terms of the glass transition temperature of the examined polymer film.View full abstractDownload PDF (1117K) -
Hiroshi NIWA, Masatoshi NAGATA1997 Volume 54 Issue 9 Pages 566-570
Published: September 25, 1997
Released on J-STAGE: June 11, 2010
JOURNAL FREE ACCESSThe short-chain branched structure of ethylene-vinyl chloride copolymer obtained from suspension copolymerization was studied by using 13C NMR spectroscopy. The 13C NMR chemical shifts of short chain branched structures in the ethylene-vinyl chloride copolymer were calculated from substituent increments of a chemical shift. 13C NMR spectra showed the C4 branch having the ethylene residue as a branch end group in the copolymer. The C4 branch having the ethylene residue in the branch end was presumed to be the characteristic structure in ethylene-vinyl chloride copolymer.
On the other hand, the ethylene residue was not observed in the C2 branch. The C2 and C4 branch structures were detected by the 13C NMR spectra of the copolymer after dechlorination with tri-n-butyltin hydride at the part of vinyl chloride units. The C2 branch in ethylene-vinyl chloride copolymer was thought to be formed only from vinyl chloride propagation. The C4 branch having the ethylene residue in the branch end group could not induce the second back-biting reaction associated with the C2 branch formation.View full abstractDownload PDF (608K) -
Yoshiharu KONDO, Naofumi WAKAO, Kimiaki ITAKURA, Mikio TAKAKI1997 Volume 54 Issue 9 Pages 571-578
Published: September 25, 1997
Released on J-STAGE: September 28, 2010
JOURNAL FREE ACCESSA monomer having a silacyclopentene ring, 1-methy1-3, 4-diphenyl-1- (p-vinylphenyl) -1-silacyclopent-3-ene (VPSiCP), was synthesized by a coupling reaction of 2, 3-diphenyl-1, 3-butadiene-magnesium complex with p-vinylphenylmethyldichlorosilane. The VPSiCP was obtained in a high yield of 80.1% as white needles (mp, ca. 103°C) by recrystallization from acetone. The initial rate of homopolymerization of VPSiCP in benzene was found to be ca. 21times higher than that of styrene in spite of its highly bulky substituent. The radical copolymerization of VPSiCP (M1) with styrene (St) or methyl methacrylate (MMA) were carried out in benzene by AIBN at 60°C. Monomer reactivity ratios in the copolymerizations with the comonomers (M2) were determined by Kelen-Tudos method: r1=0.67±0.06, r2=0.65±0.05for st; r1=0.85, r2=0.47 for MMA. Q and e values were also calculated by Alfrey-Price equation; Q=0.74, e=0.11 for St comonomer; Q=1.08, e=-0.56 for MMA comonomer.View full abstractDownload PDF (1258K)
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