bluuebunny/crossref_metadata_2025 huggingface dataset:
Optimization of Morphology of Polyimide–Silica Hybrids in the Production of Matrices for Carbon Fibre Composites
Authors: Xenopoulos C , Mascia L , Shaw S J
Published: August 2002

Hybrids of polyimide and silica have been produced from solutions via the sol–gel process. Compatibilization of the organic phase, originating from a polyamic acid and the inorganic phase, based on alkoxysilane solutions of tetraethoxysilane (TEOS), was achieved through the use of an epoxy-functional trialkoxysilane coupling agent, γ-glycidyloxypropyltrimethoxysilane (GOTMS). The use of GOTMS brings about the intimate inter-dispersion of the two phases, which results in the formation of nano-sized co-continuous domains. The materials were evaluated by a variety of techniques, including differential scanning calorimetry, thermogravimetric analysis, electron microscopy and dynamic mechanical tests. The gelation characteristics of the precursor solutions, the mechanical and thermal properties of the resulting hybrids as matrices for carbon fibre composites were used as parameters to assess the compatibilization efficiency. The results show notable improvements in the thermal stability and mechanical properties of hybrids over those of the base polymer. Above the optimum concentration of the coupling agent, however, properties were found to deteriorate owing to a diluting effect by the aliphatic component in its structure, as well as to the reduction in the degree of imidization of the polymeric component.
Effects of Vacuum Ultraviolet Radiation on Thin Polyimide Films
Authors: Dever Joyce A , Messer Russell , Powers Charles , Townsend Jacqueline , Wooldridge Eve
Published: August 2002

This paper describes the vacuum ultraviolet (VUV) radiation durability screening testing of thin (12.7–25.4 μm) polyimide films proposed for use on the Next Generation Space Telescope (NGST) sunshield. Materials included in this screening test were Kapton®E, Kapton®HN, Upilex®S, CP1, CP1 with vapour deposited aluminium (VDA) on its back surface, and CP2 with a VDA coating on its back surface. Samples were exposed to approximately 1000 equivalent sun hours (ESH) of VUV radiation and examined for changes in solar absorptance, thermal emittance, ultimate tensile strength, and elongation at failure. Changes in the solar absorptance were observed for some materials, and, additionally, significant changes in spectral reflectance were observed in the ultraviolet to visible wavelength region for all of the polyimide materials tested. Changes in the ultimate tensile strength and elongation at failure were within the experimental uncertainty for all samples. Longer exposures are needed to verify the observed trends and to develop performance predictions for these materials on the NGST sunshield.
Ranking of Wire Insulation for Spacecraft Use
Authors: Hoertz Frank , Koenig Dieter , Hanson Josef , van Eesbeek Marc
Published: August 2002

Insulated wires are important for the reliable supply of electrical energy in aircraft and spacecraft applications. Damage to the wire insulation in the electrical network can lead to a high-current arc burning between the metal conductors of the wire, which may cause a breakdown of the whole electrical system. In the past, numerous fault arc tests on insulated wires for space application have been performed at Darmstadt University of Technology, High Voltage Laboratory (TUD/HVL) in cooperation with the European Space Agency (ESA/ESTEC). Based on these studies a test proposal was prepared and is discussed in relevant standardization organizations up to the present time. This proposal is referred to as the ‘advanced fault arc resistance test’ Proposal International Standard 1998 Space systems–arc tracking test, cables and wires: advanced fault arc resistance test ISO/TC20/SC14/WG 1, 14N118. The insulated wires are tested under different stress and environmental conditions. The experimental results as well as their physical background are discussed.
New Poly(4-Dichloro)Maleimides: III. Synthesis and Characterization of Poly[Ether-Ester-Azomethine-(4-Chloro) Maleimides] and Poly(Azomethin Ester-Aspartimides)
Authors: Gaina C , Gaina V , Sava M
Published: August 2002

New poly[(N-ester-azo)-3-ether-4-chloro)maleimides] and poly(azomethin-ester-aspartimides) were synthesized by the reaction of N-[4-(formylphenoxy carboxylphenyl)]-3-(4-formylphenoxy)-4-chloromaleimide (3 a) or N-[4-formylphenoxycarbonylphenyl)maleimide (3 b) with various diamines. IR and elemental analyses confirmed the structures of the resulting polymers. A series of model compounds were synthesized to facilitate confirmation of the polymer structures. The polymers possess inherent viscosities in the range 0.17–0.42 dl g−1, solubility in aprotic dipolar solvents and 5% weight loss at temperatures above 300 °C.
Thermo-Processable Polyimides with HighTg and High Thermo-Oxidative Stability as Derived from 2,3,3′,4′-biphenyltetracarboxylic dianhydride
Authors: Hasegawa Masatoshi , Shi Zemin , Yokata Rikio , He Feifeng , Ozawa Hideo
Published: August 2002

Aromatic copolyimides were prepared using 2,3,3′,4′-biphenyltetracarboxylic dianhydride (asymmetric BPDA or a-BPDA) and several aromatic diamines with flexible ether linkages to obtain melt-processable polyimides (PIs) with balanced properties, i.e. high Tg, high thermo-oxidative stability, low melt viscosity, and sufficient toughness. The use of a-BPDA for the present purpose is based on our previous results which showed that a-BPDA-based PIs always show both higher Tg and much higher thermoplasticity than the corresponding symmetric BPDA-derived PIs. On the basis of the structure–property relationship, a copolyimide system was focused upon as a promising candidate. The molecular weight of the selected copolyimide was controlled using an end-capping reagent to balance between Tg, the melt viscosity, and toughness. The effect of the polymerization route (one-pot and two-step) on the properties was also discussed. An a-BPDA-based copolyimide accomplished a high Tg at 249 °C, a low melt viscosity of 8200 Poise at 400 °C, and high thermo-oxidative stability concurrently with considerably high film toughness (elongation at break = 66%).
Synthesis and Biological Activity of Polyketone Resins. Part I: Systems Based on Toluene with Carbon Disulphide as Solvent
Authors: Patel N. Z. , Patel J. N. , Ray R. M. , Patel R. M.
Published: August 2002

Polyketone resins have been synthesized by reacting toluene, chloroacezyl chloride, 1,2-dichloroethane and dichloromethane using anhydrous aluminium chloride as catalyst. The polyketones thus obtained were characterized by IR analyses and number average molecular weight by vapour pressure osmometry. The thermal properties were studied by thermogravimetry and differential scanning calorimetry. All the polyketone resins were tested for their biological activity against bacteria and fungi. The results show that the growth of the tested organisms can be controlled by the polyketones.
Unique Characteristics Derived From Poly(Arylene Ether Phosphine Oxide)s
Authors: Smith C. D. , Grubbs H. , Webster H. F. , Gungör A. , Wightman J. P. , McGrath J. E.
Published: August 2002

Arylene ether phosphine oxide homopolymers were prepared via nucleophilic aromatic substitution polycondensations of bis(4-ftuorophenyl)phenyl (or methyl) phosphine oxide with various aromatic bisphenols in the presence of a weak base and an aprotic dipolar solvent. These thermoplastic materials with Tg values in the range of about 200°C-285°C showed 5% weight loss in air around 500°C with substantial amounts of char yield at 800°C, which was related to their excellent' self-extinguishing characteristics relative to other engineering thermoplastics. Additionally, the presence of phosphorus in the char after such high temperature heating implied that these materials should also be resistant to aggressive oxygen plasma environments. Indeed, these systems showed extremely low amounts of etching in oxygen plasma when compared with other engineering polymers. The presence of phosphorus residues after either burning or etching with oxygen plasma could play crucial roles in areas of commercial importance and aerospace applications.
Azo Dyes Based on Phenolic Oligomers: Acid Azo-Naphthol-Formaldehyde Oligomeric Dyes
Authors: Lad B. D. , Vyas H. S. , Patel H. S.
Published: August 2002

A series of new oligomeric acid azo dyes were prepared by coupling various aromatic diazonium salts to 1-naphthol-formaldehyde and 2-naphthol-formaldehyde oligomers. They were characteried in terms of their softening points, yields, colour, solubility and UV-vis spectral studies. The structure-property relationships were also established. Dyeing of Nylon-6,6 and wool was also investigated. The dyeing of Nylon-6,6 and wool resulted in orange, brown to red and blue shades with excellent light fastness and washing fastness properties.
Effect of Structural Features and Humidity on the Dielectric Constant of Polyimides
Authors: Mercer Frank W. , Goodman Timothy D.
Published: August 2002

A series of aromatic polyimides and partially fluorinated aromatic polyimides were prepared and investigated to determine the structural features affecting their moisture absorption, dielectric constant, and dielectric constant as a function of relative humidity. The moisture absorption of polyimides is related to the total imide content of the polymer. Polyimides with a lower weight per cent of imide have a lower moisture absorption. Both dielectric constant and moisture absorption of polyimides can be reduced by incorporation of fluorine into the polymer. However, a minimum in moisture absorption (about 0.7 wt.%) and dielectric constant (about 2.7) is approached at about 20% fluorine by weight of the polymer.
Alginate Polyelectrolyte Ionotropic Gels-XII. Chromatographic Separation of Divalent Transition Metal Ions using Alginates as Ion Exchangers
Authors: Hassan Refat M. , El-Shatoury S. A. , Makhlouf M. Th.
Published: August 2002

The separation of divalent metal ion mixtures has been investigated chromatographically on columns of either gel or sol forms of alginate polyelectrolyte. Separation was obtained in the form of narrow sharp zones for the metal ions. Ion exchange selectivity indicated that Cu2+ ions were most strongly retained among the divalent metal ions studied. The factors which affect the ion exchange selectivity, such as the strength of chelation and the mobility and radii of the metal ions, are discussed. The selectivity coefficient for the separation of a mixture of Cu2+ and Co2+ ions on columns of calcium alginate gel or sodium alginate sol was determined and found to be 1.9 ± 0.1 in both ion exchangers at 25°C.
Synthesis and Thermal Stability of Unsaturated Polyamides
Authors: Patel N. R. , Patel N. Z. , Patel R. M.
Published: August 2002

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.
Synthesis and Characterization of Polybenzazoles Containing Hexafluoroisopropylidene
Authors: Hutzler Rene F. , Meurer David L. , Kimura Kunio , Cassidy Patrick E.
Published: August 2002

A series of three polybenzazoles containing hexafluoroisopropylidene (HFIP-PBZs) were produced in order to study the effect of including the HFIP group into the rigid PBZ backbone. The monomers, 2,5-diamino-1,4-benzenedithiol dihydro-chloride and 4,6-diamino-1,3-benzenediol dihydrochloride, were synthesized and puri-fied. The monomer 1,2,4,5-tetraaminobenzene tetrahydrochloride is commercially avail-able and was purified by recrystallization. These mononmers were polymerized with 2,2-his(4-carboxyphenyl)-I1,,1,3,3,3-hexafluoropropane (6F-diacid) by a polycondensation reaction in polyphosphoric acid employing the P205 adjustment method to give polymers in good yields with inherent viscosities ranging from 0.33 to 1.18 dl/g. These polymers show an increase in solubility over non-HFIlP containing PBZs and display excellent thermal stability by thermogravimetric analysis (540-568°C in argon). Isothermal aging in air of the polymers for 300 h afforded weight losses between 3.27 and 12.0%.
Polyimides Based on Furfuryl-Disulphide
Authors: Patel Harshad D. , Patel Hasmukh S.
Published: August 2002

Poly (disulphido-imides) were prepared by Diels-Alder (DA) reaction of furfuryl-disulphide (FDS) with various bismaleimides. The DA reaction was carried out in xylene as solvent, as well as in bulk, followed by aromatization of terrahydrophthalimide intermediates in the presence of acetic anhydride. All the poly (disulphido-imide)s were characterized by elemental analyses, IR spectral data and thermogravimetry. The poly (disulphido-imide)s exhibit moderate thermal stability. Preliminary test for glass reinforcement of the poly (disulphido-imide) indicate that laminates with good mechanical strength can be obtained.
Synthesis Characterization and Glass Reinforcement of Poly(urethane-imide)s-III
Authors: Patel Hasmukh S. , Shah Vipul J. , Vyas Hemant S.
Published: August 2002

Poly(urethane-imide)s (PUIs) were prepared by the intermolecular Diels-Alder (DA) reaction of methylenedi-4,1-phenylenebis(2-furanyl-methylcarb-amate) (MPBFC) with various bismaleimides. The DA reaction was carried out in 1,4-dioxane as solvent as well as in bulk, followed by aromatization of tetrahydro-phthalimide intermediates in the presence of acetic anhydride. All the polymers were characterized by elemental analysis, IR spectral studies and thermogravfmetry. The PUts exhibit moderate thermal stability. MPBFC and bismaleimides were polymerized (at 145 + 10 C) by an in situ DA intermolecular reaction into moderately thermally stable PUls-glass fibre composite (i.e. laminates) and were characterized by their chemical resistance and mechanical properties.
New polymer syntheses II--linear unsaturated polyesters containing azo groups*
Authors: Aly Kamal I
Published: August 2002

Linear unsaturated polyesters, characterized by the presence along the polymer chain of azo groups between aromatic rings, have been prepared by reacting 3,5-bis(p-hydroxybenzylidene)isopropyl piperidinone (BHIP, I) or 3,5-divanillylidene isopropylpiperidinone (DVIP, It) with 4,4'-azodibenzoyl chloride (III) and 3,3'-azodibenzoyl chloride (IV) using the interfacial polycondensation method. The polymers were characterized by elemental analyses. IR spectroscopy, solubility and viscomnetry. The thermal properties of the polymers were evaluated by thermogravimetric analysis (TGA) and correlated to their structural units. Al] the polymers dissolved readily in concentrated H2S04 or o-cresol. X-ray analysis of the polymers showed some degree of crystallinity in polymers VI and VII. Moreover, the UV-visible spectra of certain polymers were measured in NMP or in dimethyl suiphoxide (DMSO)solutions and showed characteristic absorption bands at 412 and 432 nrn due to n-7r* transition.
Synthesis and Physico-Chemical Properties of Polycyanurates of 2-(N,N-Diphenylhydrazino)4,6-Dichloro-s-Triazine with Various Aromatic Diols
Authors: Bhonsale B S , Kaula S N , Patel B V , Patel K C
Published: August 2002

Various polycynaurates were synhesised by stirred interfacial polycondensation of 2-(N.N-diphenynhydrazino)-4,6-dichloro-s-triaziae (DPHDCT) with each of the aromatic diols: bisphenol-A (BPA); bisphenol-C (BPC); bisphenol-S (BPS); phenolphthalein (Ph); catechol; resorcinol; 1,5and 2.7-dihydroxynaphthalene (DHN-1,5 and DHN-2,7) and 1,8-dihydroxyanthraquinone (DHA-1,8). Interfacial polycondensation of DPHDCT with BPA was investigated in detail in order to select optimum reaction conditions. The yield of polycyanurates varies from 6 I% to 79%. The polycyanurates are soluble in chlorinated solvents such as chloroform, dichloroethane. dichloromethane and chlorobenzene. The reduced viscosity for polycyanurates, determined with a 1 g disolution in chloroform at 25 + 3°C was found to be in the range 0.50-0.68 dl g. All the polycyanurates were characterized by IR spectra. The densities of the polycyanurates, determined using the suspension method at 25 3°C, range between 1.196 and 1.330 g cm. The overall reactivity of diols, based on reduced viscosity values, was found to decrease in the following order: PCBPA> PCPh> PCBPC> PCR>PCDHN-2,7 > PCDHN-I,5 > PCC > PCDHA-1.8 > PCBPS. The thermal stability of polycyanurates, derived from various temperature characteristics, was found to decrease in the following order: PCBPA> PCBPS> PCBPC > PCC PCR> PCDHN-2,7 PCDHN-.l 5 > PCDHA-1,8 > PCPh.
Co-crystallization in PEEK Copolymers
Authors: Mehmet-Alkant A A , Hayt J N , Blundell D J , Parker D G
Published: August 2002

Thermal and wide-angle x-ray scattering (wAxs) studies of a new set of copolymers of polyether ether ketone (PEEK) with ether diphenyl ether ketone (EDEK) have been undertaken. The copolymerization modifies the properties of PEEK. At low levels of comonomer content the incorporation of the comonomer unit lowers the melting temperature and reduces the degree of crystallinity. At higher levels the melting point increases towards that of the PEDEK homopolymer.

The x-ray structure is very similar to that of PEEK, consistent with rejection of the comonomer at low levels of comonomer content. At high levels the structure is very similar to that of PEDEK while at intermediate levels the structure is found to 'swtich' from that of PEEK to that of PEDEK, consistent with co-crystallization of the two monomer units.
Poly(ether-imide)s based on epoxy resin: I
Authors: Patel Hasmukh S , Patel Nimisha R
Published: August 2002

Novel poly(ether-imide)s were prepared by Diels-Alder (DA) reaction of 1, l'-(1-methylethylidene)bis[4-{l-(2-furanylmethoxy)-2-propanolyloxy}]benzene with the bismaleimrnides N, N'-hexamethylenebismaleimide and N-N'-1, 4-phenylenebismaleimide. The DA reaction was carried out in solution using tetrahydrofuran as solvent, as well as in bulk. The post-polymerization, involving aromatization of tetrahydrophthalimide intermediates, was accomplished in the presence of acetic anbydride. 'All the poly(ether-imide)s were characterized by elemental analyses, infrared spectrometry and thermogravimetry.
Poly[1,3(2-ethoxy-4-hydroxy-5-propylphenylene)propylene] copolymer as an ion exchanger
Authors: Patel Jayesh R , Sutaria Dipan H , Patel Magan N
Published: August 2002

The present paper reports the synthesis and characterization of a copolymer, The copolymer sample was synthesized by Friedel-Crafts polycondensation of 2-hydroxy-4 ethoxypropiophenone with 1,3-propane diol in the presence of polyphosphoric acid catalyst. The copolymer was characterized by elemental analysis, IR spectroscopy and viscosity study, and its number-average molecular weight (M) was determined by non-aqueous titration and found to be 2855 g mol- 1. Chelation ion-exchange properties have also been studied, employing a batch-equilibration method. It was employed to study selectivity of metal ion uptake over a wide pH range and in media of various ionic strengths. The overall rate of metal uptake follows the order UOl + > Fe3 + > Cu2 + > Ni2 +.
The use of bisfuroic acid derivatives in the curing of bismaleimides
Authors: Hawthorne D G , Hodgkin J H , Jackson M B , Morton T C
Published: August 2002

The use of 2,2-bis(4-[(2-carboxy-5-furyl)oxy]phenyl)propane as a Diels-Alder based co-reactant for curing bismaleimides was investigated. Differential scanning calorimetry and thermal gravimetric analysis were used to study the thermal behaviour of this reactant on its own and in the presence of 1,1'-(4methylene-4,1-phenylene)bismaleimide. The range of products formed under different cure conditions was determined by vFnR spectroscopy. The DMTA characteristics and thermal stability of cured laminates made from this resin system have been investigated. It is concluded that the thermal stability and other properties of laminates made from this system are only comparable to those of a typical commercial bismaleimide system.
Solvent-resistant polyetherimide network systems via phenylethynylphthalic anhydride endcapping
Authors: Meyer G W , Tan B , McGrath J E
Published: August 2002

The synthesis and characterization of a highly processable thermosetting polyimide system based on 22'-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride or bisphenol A dianhydride (BPA-DA) endcapped with 4-phenylethynylphthalic anhydride is described. The system afforded oligomers that were readily melt processable at high curing temperatures (380-420 CC). Imide oligomers ranging from MR = 2000 to 40 000 g molI and copolyimides were synthesized using the ester acid of the dianhydrides and either meta- and/or para-phenylene diamines as comonomers via solution imidization techniques. The oligomers were shown to display low melt viscosity values and to flow under low pressure during compression moulding. The thermally cured polymers formed tough creasable films and displayed excellent solvent resistance which was correlated to their high gel fractions (>95%). Very significant increases in glass transition temperatures were observed after cure of a 3000., oligomer. The mera-phenylene diamine-based polymer exhibited a cured Ts approximately 30C lower (233C) than the para:meta (70:30) system (267C). The all para-phenylene diamine-based homopolymers could be completely cyclized in solution but crystallized at room temperature to produce fine insoluble powders. The resulting moderately semicrystalline homopolymer showed a TM of up to 321 'C which was not observed on the second heating. These polyimides also show excellent thermal stability as judged by thermogravimetric analysis (TGA) and are being examined as structural adhesives and matrix resins.
New high-temperature polyimides based on [5]helicene dianhydride
Authors: Frimer Aryeh A , Cavano Paul J , Alston William B
Published: August 2002

The new anhydride, [5]helicene-5,6,9, 10-tetracarboxylic 5,6:9,10-dianhydride (HLDA) was thermally imidized with four diamrnines: methylenedianiline (AAFIII), xylylenedianifine (AAFIV). 3,3'-hexafluoroisopropylidene)dianiline (AAFV) and 4",4"'-(hexafluoroisopropylidene)bis(4-phenoxyaniline)(AAFVI). In thecase of AAFIII and AAFIV, a nadic endcap was added and the n value formulated for 2.087; for AAFV and AAFVI no endcap was used, Moulding powders were prepared either by imidizing these diamines in refluxing methanolic solutions of esterified HLDA followed by compression moulding at about 315 °C, or alternatively, in the case of AAFV and AAFVL, by imidizing in cold or refluxing NMP followed by compression moulding at about 365 °C. While the weight loss. results for AAFIII and AAFIV at 343 °C prove to be poorer than PMR-15, AAFV and AAFVI moulding powders prepared in cold or hot NMP result in resins which substantially outperform PMR-15. Indeed. the lowest rates of weight loss (mg cm -2)from AAFV (cold NMP) and AAFVI (hot NMP). respectively, were 1/5 and 1/2 that of PMR-15 at either 343 °C or 371 °C. The outstanding performance of AAFV approaches that of PMR-II-50, now considered one of the high-temperature polymer weight-loss standards.
IM7/LARCTM-IA polyimide composites
Authors: Hou T H , Johnston N J , St Clair T L
Published: August 2002

LARCTM-IA (Langley Research Center-Improved Adhesive) aromatic polyimide, based on oxydiphthalic anhydride and 3.4'-oxydianiline, was evaluated as a matrix for high-performance composites. Six poly(amide acid)solutions in N-methylpyrrolidone (NMP), end-capped with phthalic anhydride to various theoretical molecular weights, were synthesized and their molecular weights and molecular weight distributions determined, Importantly, high concentrations of low-molecular-weight species were found in all the offset compositions. Except for the 1% offset polymer, all fully imidized films failed a solvent resistance test which involved immersion in acetone, methyl ethyl ketone, toluene, dimethylacetamide and chloroform for 1 min followed by a fingernail crease. Unidirectional prepreg was fabricated from each of the six resins by both standard drum winding procedures and the LARC multipurpose prepreg machine. The consolidation cycle developed previously for IM7/LARCTM-ITPI composites was found to be equally applicable for IM7/LARCTM-IA composites since both materials are similar and were prepared in and prepregged from NMP. An optimal end-capped resin composition was identified (4% stoichiometric imbalance) by using, as a screening tool, initial composite mechanical properties (short-beam shear strength, longitudinal flexural strength and flexural modulus) at room temperature, 93, 150 and 177°C. Composite engineering properties for the 4% offset composition were obtained, including longitudinal tension, transverse flexural, longitudinal compression, interlaminar shear, short block compression, open hole compression and compression strength after impact. Notably, the CAI strength was 303.2 MPa (44 Ksi) showing that the LARCTM-IA composites have good damage tolerance.

A minor modification of LARCTM-IA polymer backbone which did not alter the consolidation cycle, designated as LARCTM-IAX, improved solvent resistance measurably. Mechanical properties of IM7/LARCTM-IAX composites were shown to be comparable to those exhibited by the baseline IM7/LARCTM-IA composites.
Preparation and properties of optically active aromatic polyamides derived from newly prepared chiral phenylindanediamine
Authors: Morikawa Atsushi , Kakimoto Masa-Aki , Imai Yoshio
Published: August 2002

Chiral phenylindanediamnine (+)-2 was synthesized starting from chiral phenyl-indanedicarboxylic acid by a Schmidt rearrangement. Ordered amine-acid AB-type monomers, 8 and 9, were also prepared by a controlled reaction of (+)-2 with diacid chlorides. Disordered and ordered polyamides were synthesized by the reaction of (+)-2 with dicarboxylic acids, and the self-condensation of 8 and 9, respectively. Both the ordered and disordered polyamides were soluble in various solvents. The polyamides composed of the same dicarboxylic acid prepared by the different routes showed the same circular dichroism spectra. X-ray diffraction of the polyamide films indicated that all of the polyamides were amorphous. The glass transition and decomposition temperatures ranged from 170 to 340°C and from 320 to 400 °C, respectively. Additionally, polyamides containing the same diacids displayed nearly equivalent physical properties.
Study of the polymerization of high-performance polymers by electrons and x-rays: 2. The case of bismaleimide/N-vinylpyrrolidone
Authors: Grenier-Loustalot Marie-Florence , Denizot Vincent , Beziers Daniel
Published: August 2002

In the context of radiation-induced polymerization of bismaleimide monomers, we have investigated the polymerization mechanisms and kinetics of a bismaleimide/vinyl-pyrrolidone system. Several parameters were considered, including the type of dose (electrons or x-rays), power, presence of a catalyst and the carbon fibre filler.

To this end, we developed a methodology based on physicochemical studies by infrared absorption spectroscopy and solid state 3CNMR (CP-MAS) in order to quantify the chemical species created or residuals in the cross-linked network. The results (progression of the reaction and structure of the network formed) were correlated with thermal behaviour and compared with those obtained by thermal polymerization.

Using an optimized formulation, we determined the thermal and mechanical properties of these radiation-polymerized prepolymers and composites.
Synthesis of a new photoreactive polyester by addition reaction of bisepoxide with f-truxiloyl chloride and chemical modification of this polymer
Authors: Nishikubo Tadatomi , Kameyama Atsushi , Hayashi Nobuyuki , Nakagome Riou
Published: August 2002

A new reactive polyester (P-I) containing a cyclobutane ring in the main chain and a pendant chloromethyl group in the side chain was synthesized successfully by the addition reaction of diglycidyl ether of bisphenol A (DGEBA) with fi-truxiloyl chloride (TC). The addition reaction of DGEBA with TC proceeded smoothly to give P-1 with a relatively high molecular weight using quaternary onium salts or a crown ether complex as catalysts at 90-C for 15 h. However, the reaction did not occur without a catalyst. Substitution reactions of the obtained P-I with (4-dimethy Iamino)cinnamic acid (MACA), [(4-dimethylamino)-a-cyano]cinnamic acid (MACCA) and (4-dimethylamino4'-hydroxy)chalcone (MACH) were carried out to synthesize certain new multifunctiqnal photosensitive polymers with positive-working groups in the main chain and negative-working groups in the side chains. The reaction of P-I with MACA proceeded very smoothly with 99% conversion to form the corresponding polymer (P-2a) using 1,8-diazabicyclo[5.4.0]-7-undecene (DBU) as a base in DMF. The reaction with MACCA gave the corresponding polymer (P-2b) containing a pendant [(4-dimethylamino)-a-cyano]cinnamJc ester moiety with 26% conversion. The reaction with MIACH produced the corresponding polymer (P-2c) containing a pendant (4-dimethy]amino)chalcone ether moiety with 32% conversion. Photochernical reaction of the thus-obtained P-2a-c was also performed in the film state.
Low-temperature piezoelectric and dielectric properties of aromatic polyureas prepared by vapour deposition polymerization
Authors: Wang Xian-Shan , Takahashi Yoshikazu , Lijima Masayuki , Fukada Eiichi
Published: August 2002

Thin films of aromatic polyurea were prepared by vapour deposition of a diisocyanate tmonomer and a diamine monomer. Three kinds of aromatic polyurea were synthesized by combining 4,4'-dipheny Lnethane diisocyanate (MDI) with 4,4'-diamino-3,3'-dimethyldiphenylmethane (MeMDA), 4,4'-diaminodiphenylether (ODA), and 4,4'-diamino-diphenylmethane (MDA). After poling, for example applying a field of 120 MV m -I at 210C for 10 min, these films acquired piezoelectric activity. The piezoelectric constant (13-26 x 10 3 C m' 2) and dielectric constant (3-4) were almost constant over a temperature range between -150C and 50 C. Infrared spectra observed for as-deposited, poled and annealed films indicated that CO and NH dipoles were oriented along the poling field and that hydrogen bonds were formed between adjacent molecular chains.
Synthesis and characterization of aramids containing a-terthienylene units by palladium-catalysed polycondensation of dibromo-a-terthiophene, aromatic diamines and carbon monoxide
Authors: Ueda Mitsuru , Lahagu Ivonne Mesalina , Okada Takashi
Published: August 2002

Aramids containing,-terthienylene units were prepared by palladium-catalysed polycondensation of dibromo-a-terthiophene, aromatic diamnines and carbon monoxide. Polymerizations were carried out in N,N-dimethylacetamide (DMAc) with triphenyl-phosphine and 1,8-diazabicyclo[5,4,0)-7-undecene (DBlU) in the presence of palladium catalyst, and gave a series of aramids with inherent viscosities up to 0.87 dl g-J under mild conditions. The structures of the polymers were determined by IR and '3C NMR spectroscopy. The polymers were soluble in strong acids and dipolar aprotic solvents. Thermogravimetry of the polymers showed excellent thermal stability, and the 10% weight losses of the polymers in air were observed to be above 410C. The glass transition temperatures of the polymers ranged from 185 to 231C.
High-performance heat resistant insulation materials for coils
Authors: Koyama Tohru , Sugawara Katuo , Kanno Chikasi , Maruyama Syouichi , Kashiwamura Yoshikiyo
Published: August 2002

A new impregnating epoxide resin has been developed by optimizing cross-linking densities. The resin satisfies the thermal index of 210C: this is the first time an epoxide system without a heterocyclic ring has done so. Thermal class 220C insulating systems of traction motor coils are developed by interaction of the impregnating epoxide resin and epoxide binding resin in a new insulating tape. The newly developed epoxide impregnating resin has low viscosity and very good workability. Therefore, electrically insulated coils of various classes of heat resistance, such as class C (> 180C), class H (180 C) and class F (155C), can be prepared by using only a single kind of impregnating resin, by selecting the insulating tape and hardening conditions. It is unnecessary to keep various kinds of impregnating resin corresponding to the different beat resistant grades and it is possible to decrease drastically the amount of waste generated by using several different impregnating resins.
Effects of catalysts on the model reactions of several maleimide resin systems (II): amine-modified maleimide/epoxy resin system
Authors: Enoki Takashi , Takeda Toshiro , Ishii Keiichiro
Published: August 2002

A detailed investigation on the effects of catalysts on the curing reactions of amine-modified maleimide/epoxy resin systems was carried out by using model reactions. N-phenylmaleimide (PMI), phenyl glycidyl ether (PGE), aniline (AN) and N,N'-diphenylaspartimide (API) were chosen as the model compounds. Imidazole accelerates the oligomerization of PMI in the presence of PGE excessively. In this system, a zwitterion is first produced from one imidazole molecule and two PGE molecules, then this zwitterion accelerates the oligomerization of PMI selectively and effectively. These results would be useful in maleimide chemistry and its application.
Thermotropic copolyesters from phenylhydroquinone, hydroquinone, 4,4'-diphenyldicarboxylic acid and p-hydroxybenzoic acid
Authors: Inoue Toshihide , Yamanaka Toru , Tabata Norikazu , Okita Shigeru
Published: August 2002

Copolyesters from phenylhydroquinone (Ph-HQ), hydroquinone (HQ), 4.4'diphenyldicarboxylic acid (BB) and p-hydroxybenzoic acid (HBA) were prepared and their thermal and mechanical properties were investigated.

As-spun fibres and injection moulded specimens from Ph-HQ/BB,'HBA exhibited low moduli. whereas those from Ph-HQHQ/BB/HBA exhibited high moduli probably due to the high packing density of the polymer chain caused by incorporation of HQ structural unLts. Although the modulus of as-spun fibres from Ph-HQ'BBHBA did not correlate with the number of HBA units, the modulus of injection moulded specimens decreased with increase in the number of HBA units. It is most likely that rigidity of the polymer chain was reduced by incorporation of HBA units. Thus, packing density and rigidity of the polymer chain seem to be influential factors in determining the modulus of injection moulded specimens.
LC-polyimides 24. Cholesteric copoly(ester-imide)s derived from 4-aminobenzoic trimellitimide and isomannide or 1,3-butanediol
Authors: Probst Nicolas , Kricheldorf Hans R
Published: August 2002

Two homopoly(ester-imide)s and a series of copoly(ester-imide)s were prepared by polycondensation of N-(4'-carboxyphenyl)trimellitimide dichtoride with isomannide and phenylhydroquinone. A new synthetic method was successfully tested, based on the cocondensation of silytated isomannide and silylated phenylhydroquinone. Furthermore, two copoly(ester-imide)s derived from phenylhydroquinone and (S)-1,3-butanediol were prepared. The copolyesters are non-crystalline. Those rich in chiral diols form an isotropic melt, whereas those containing more than 50mol% of phenyihydroquinone form a liquid-crystalline melt. The formation of a 'Grandjean texture' was never observed.
LC-polyimides 26. Photoreactive, nematic or cholesteric poly(ester-imide)s derived from 4-aminocinnamic acid trimellitimide, isosorbide and various diphenols
Authors: Kricheldorf Hans R , Probst Nicolas
Published: August 2002

A photoreactive and mesogenic dicarboxylic acid was prepared from 4-aminocinnamic acid and trimellitic anhydride. Its dichloride was polyeondensed with isosorbide and methylhydroquinone, phenylhydroquinone, 4,4'-dihydroxydilhenylether or 1.644'-dihy-droxyphenoxy)hexan. The copolyesters containing < 50 mol% of isosorbide form a cholesteric melt and the homopolyesters of the diphenols are nematie. WAXD powder patterns and DSC measurements agree in that all four homopoly(ester-imide)s are semicrystalline. Incorporation of isosorbide reduces and finally eliminates the crystallinity. The solid state of these copoly(ester-imide)s is a cholesteric glass. Copolyesters containing phenylhydroquinone and 5-10 mol% of isosorbide exhibit a Grandjean texture above 250C. The poly(ester-imide)s of unsubstituted diphenols undergo thermal cross-linking above 350C and all poly(ester-imide)s are sensitive to photocross-linking upon irradiation at wavelengths <360 nm.
Synthesis and characterization of new silicon-containing poly(arylene-1,3,4-oxadiazole)s
Authors: Sava I , Schulz B , Zhu S , Bruma M
Published: August 2002

New silicon-containing aromatic polyhydrazides were synthesized by low-temperature solution polycondensation reaction of bis(p-chlorocarbonylphenyl)diphenylsilane with various aromatic dihydrazides, or of bis(p-carbohydrazidophenyl)diphenylsilane with diacid chlorides. The corresponding poly(arylene-1,3,4-oxadiazole)s wvere prepared by thermal cyclodehydration in the solid state. The cyclization process takes place at temperatures in the range of 250-300 IC. The resulting silicon-containing poly(arylene-1,3,4-oxadiazole)s are soluble in common organic solvents and have good film-forming abilities. They are stable up to 420-480 'C and their glass transition temperature is in the range of 262-278C.
Phase Separation in Thermosetting Blends Studied by Dynamic Dielectric Analysis
Authors: Partridge Ivana K , Maistros George M
Published: August 2002

Phase separation in unreinforced reactive blends has been studied using a variety of experimental techniques. A brief review of such studies is given, followed by a detailed description of the theory and practical applications of the new technique of dynamic dielectric analysis, DDA, as used in this context. Methods of data analysis and the extent of information available from in situ, real-time, measurements by dynamic dielectric analysis are illustrated by examples of results on model blends of simple epoxy/hardener mixtures with CTBN or POP rubber, or thermoplastic PES or PMMA. Deliberate ion doping is shown to enhance the phase separation features in the dielectric signal. Data are also presented on complex commercial thermoset/thermoplastic blends utilized as the resin matrices in carbon fibre pre-preg systems. Phase separation in a blend of epoxy and thermoplastic PEI can be studied by DDA within a glass fibre composite; this presents no additional difficulty compared with the studies of the corresponding unreinforced blend.
Damping Characteristics of Polyurethane-Based Simultaneous Interpenetrating Polymer Networks
Authors: Hourston Douglas J , Schäfer Franz-Ulrich
Published: August 2002

A brief overview of damping with polymers is given. The highest energy absorbing potential of polymers is centred around their glass transition temperature ( T g). In order to broaden the transition, partially miscible polymer pairs with fairly widely separated T gs can be used to give broad and high transition regions. This can be obtained by the use of interpenetrating polymer network (IPN) technology. The damping ability of the IPNs was assessed from the tan δ and loss modulus versus temperature curves. The area under the linear tan δ curve (TA) and the loss modulus equivalent (LA) were calculated and correlated with the IPN composition. An incompatible polyurethane/polystyrene IPN was chemically modified by internetwork grafting and the use of compatibilizers, resulting in a high and broad transition with tan δ values > 0.3 over 80°C and 135°C respectively. Conducting a stirred polymerization of a 60:40 PUR/PS IPN resulted in a very complicated morphology with phases within phases within phases, Values for tan δ were greater than 0.3 from −19°C to 145°C combined with a high TA area of 85.4 K. The influence of the composition on the damping ability was studied in a semicompatible polyurethane/polyethyl methacrylate IPN. At the 70:30 composition, a broad temperature range (> 130°C) of tan δ values greater than 0.3 and a high TA area of 62.1 K resulted. LA was found to increase with increasing PEMA content, but with values well below those expected from applying the linear rule of mixing to LA of the homonetworks. TEM micrographs further elucidated the multiphase morphologies.
Blends of Reactive Diluents with Phenylethynyl-Terminated Arylene Ether Oligomers
Authors: Knudsen R L , Jensen B J
Published: August 2002

A series of blends containing phenylethynyl-terminated arylene ether (PETAE) oligomers and phenylethynyl-containing reactive diluents were prepared and characterized. Most of the blends prepared met the objective of this work which was to further modify the PETAE oligomers in order to improve solvent resistance, increase modulus and adhesive strength, and reduce melt viscosity. The cured blends generally have higher glass transition temperatures and improved mechanical properties compared with the analogous thermoplastic polymers.
Blends of Aromatic Polysulphones and Alkene Terephthalate Polymers: Compatibilization with Polyhydroxyether of Bisphenol-A
Authors: Mascia L , Martin L H
Published: August 2002

An experimental study was carried out to examine the compatibilizing effect of phenoxy resin for blends of aromatic polysulphones and polyalkylene terephthalates. Dynamic mechanical spectra did not reveal relaxation peaks associated with the phenoxy phase, while the relaxation peaks associated with the glass transition temperatures of the polyester and polysulphone phases were closer to each other than for the corresponding individual polymers, confirming that the phenoxy was totally dissolved in the two main polymer phases.

Whereas the blends containing the butylene terephthalate polymers (homopolymer and block copolymer) exhibited a co-continuous two-phase morphology even at high concentrations of polysulphone, those based on polyethylene terephthalate revealed the presence of discrete particles. These two types of morphologies gave rise to large differences in mechanical properties and solvent resistance. The best properties were obtained with the systems characterized by a co-continuous two-phase morphology. Moreover, the systems based on bisphenol A polysulphones showed superior properties to the corresponding systems containing polyethersulphones.
Processing of Thermoplastic Polymers Using Reactive Solvents
Authors: Meijer Han E H , Venderbosch Rob W , Goossens Johannes G P , Lemstra Piet J
Published: August 2002

The use of reactive solvents offers an interesting and flexible route to extend the processing characteristics of thermoplastic polymers beyond their existing limits. This holds for both intractable and tractable polymers. The first mainly applies for amorphous high- T g polymers where processing may be limited due to the high temperatures required which can cause problems related to degradation and where the solvent helps to decrease the processing temperature considerably. A prime example here can be found in the system poly(phenelyne–ether) PPE/epoxy. The second mainly holds for semicrystalline polymers and the attention here is focused on obtaining low viscosities in order to be able to apply alternative processing routes, like pouring or casting, for those polymers which are generally easy to process by more conventional techniques like injection moulding or extrusion. In this paper the model system poly(ethylene) PE/styrene is investigated. In both cases, based on intractable and tractable polymers, the solvent is polymerized after moulding, thus converting into a non-solvent, and becomes, after the concurrent phase separation and phase inversion, an integral and often structural part of the final product. Interestingly, specific morphologies, in terms of the size of the dispersed (previous solvent) phase formed or the position and thickness of in situ formed interlayers when polymerization occurs in the presence of a polar surface, can be obtained which can otherwise extremely difficult, or not at all, be realized. Moreover, flexibility of the choice of the reactive solvent creates tuneable mechanical (and, if requested, other) properties of those phases, varying from glassy, with a T g of typically 200°C, to complete rubbery, with a T g far below room temperature. Of course a disadvantage of the technique is that a polymerization step must occur after the shaping process. Compared to more standard reactive processing techniques, however, clear advantages can exist with respect to the occurrence of early vitrification—yielding a fast demoulding possibility—induced by the reaction induced phase separation, and the fact that the continuous thermoplast phase ultimately determines the main product properties, including the possibility of second-stage deformability and reprocessability.
Synthesis and Physico-Chemical Properties of 2-Morpholino-4,6-Dichloro-S-Triazine with Various Aromatic Diols
Authors: Patel K C , Kaula S N , Patel P S
Published: August 2002

Several homopolycyanurates were synthesized by stirred interfacial polycondensation of 2-morpholino-4,6-dichloro- s-triazine with various aromatic diols such as 1,5- dihydroxynaphthalene,(DHN-1,5),1,7-dihydroxynapthalene(DHN-1,7),2,7-dihydroxynapthalene resorcinol (R), catechol (C), hydroquinone (H) and phenolphthalein (Ph). They were characterized by density, viscosity measurements, IR spectra, solubility tests and thermogravimetric analysis. The polymer had reduced viscosities in the range 0.468 to 0.829 dl g−1 in chromoform at 30 °C. All the polymers were amorphous and soluble in chlorinated solvents. The thermal stability of polycyanurates decreases in the following matter:

PCDHN-1,5 > PCDHN-1,7 > PCPh > PCR ≃ PCDHN-2,7 > PCHQ > PCC.
Sliding Friction Studies of a Poly(Ether Ether Ketone)/Poly(Ether Imide) Blend
Authors: Stuart B H , Briscoe B J
Published: August 2002

The results of a sliding friction study of a blend of poly(ether ether ketone) (PEEK) and poly(ether imide) (PEI) are reported. The frictional behaviour of the blend follows a similar trend to that of the unblended PEEK, but the overall friction is higher in the case of the blend. However, comparison of the data obtained for unblended and blended PEEK shows that there is a reduction in the failure potential of PEEK when PEI is incorporated. That is, the potential for catastrophic thermally induced contact failure in the PEEK/PEI blend investigated is less than that observed for the unblended PEEK.
Influence of the Conformational Parameters on Physical Properties of Some Polyamides Containing Phenylquinoxaline Rings
Authors: Hamciuc C , Hamciuc E , Ronova I A , Bruma M
Published: August 2002

Conformational parameters of some heterocyclic polyamides containing phenyl-substituted quinoxaline rings have been calculated by the Monte Carlo method taking into consideration the hindered rotation produced by the side phenyl groups. Several physical properties such as solubility, glass transition temperature, initial decomposition temperature and dielectric constant have been studied with regard to the rigidity of the chains of these polymers, and their relationships have been shown.
Synthesis, Properties and Potential Applications of Sulpho-Pendent Poly(Arylene Ether Ketone)s
Authors: Venkatasubramanian N , Dean Derrick R , Price Gary E , Arnold Fred E
Published: August 2002

High molecular weight sulpho-pendent poly(arylene ether ketone) homopolymers and copolymers were synthesized with inherent viscosities ranging from 0.94 dl g−1 to 1.20 dl g−1 and glass transition temperatures ( Tgs) in the range 190–200 °C. Their potential use as transparent matrix hosts for second-order NLO chromophores was explored from the point of view of obtaining monodisperse guest–host systems mediated by specific interaction between the sulphonic acid pendant of the polymer host and the basic functionality of the chromophore structure. Homogeneously dispersed, optically clear thin film composites were obtained for aromatic heterocyclic chromophores with electron-rich thienyl, N,N-dialkylamino or N,N-diphenylamino donors and a pyridyl acceptor in their molecular structures.