bluuebunny/crossref_metadata_2025 huggingface dataset:
Determination Factors on Surface Glass Transition Temperatures of Polymeric Solids
Authors: Kajiyama Tisato , Kawaguchi Daisuke , Sakai Atsushi , Satomi Noriaki , Tanaka Keiji , Takahara Atsushi
Published: August 2002

The surface molecular motion of monodisperse proton-terminated polystyrene (PS-H), α, ω-diamino-terminated PS ( α, ω-PS(NH2)2) and α, ω-dicarboxy-terminated PS ( α, ω-PS(COOH)2) films was studied by scanning viscoelasticity microscopy in conjunction with lateral force microscopy. The glass transition temperature Tg, at the surface, Tgs was found to be markedly lower than bulk Tg, Tgb, and the number-average molecular weight, Mn, dependence of Tgs more remarkable than that of Tgb. Also, the magnitude of Tgs was strongly dependent on the chain end chemistry. Hence, the activation of surface molecular motion was explained in terms of an excess free volume induced by the preferential surface segregation of chain end groups. The chain end segregation at the film surface was confirmed by dynamic secondary ion mass spectroscopic measurement. However, the Tgs for the PS-H with quasi-infinite Mn was lower than the corresponding Tgb, even though the number density of chain ends was almost negligible. In addition, Tgs for PS films with hydrophilic chain ends, which might be depleted at the film surface, were lower than the bulk values. The apparent activation energy for the surface micro-Brownian motion corresponding to the αa-relaxation process was approximately half of the bulk value. Finally, the depression of Tgs in comparison with Tgs is discussed on the basis of several factors, such as a decreased segment size of molecular motion for the surface αa-relaxation process due to the existence of the free space on the polymer surface and/or a reduced chain entanglement at the surface, in addition to the chain end effect.
Space Environmentally Stable Polyimides and Copolyimides Derived from Bis(3-Aminophenyl)-3,5-Di(Trifluoromethyl)Phenylphosphine Oxide
Authors: Connell John W , Watson Kent A
Published: August 2002

Polyimides with a unique combination of properties including low colour in thin films, atomic oxygen (AO) resistance, ultra-violet (UV) radiation resistance, solubility in organic solvents in the imide form, high glass transition ( Tg) temperatures, and high thermal stability have been prepared and characterized. Polyimides were prepared by reacting a novel aromatic diamine, bis(3-aminophenyl)-3, 5-di(trifluoromethyl)phenylphosphine oxide, with various aromatic dianhydrides in a polar aprotic solvent. Copolymers were prepared by the addition of a second diamine. The solubility of the polymers in the imide form as well as the colour density of thin films was dependent upon the chemical structure of the dianhydride and the additional diamine. Thin films (25–50 μm thick) prepared by solution casting of amide acid or imide solutions exhibited very low colour and high optical transparency as determined by UV/visible spectroscopy. The polymers exhibited Tg values greater than 200 °C depending upon the structure of the dianhydride and temperatures of 5% weight loss ∼500 °C in air as determined by dynamic thermogravimetric analysis (TGA). Thin films coated with silver/inconel were exposed to a high fluence of AO and 1000 equivalent solar hours of UV radiation. The effects of these exposures on optical properties were minor. These space environmentally durable polymers are potentially useful in a variety of applications on spacecraft such as thin film membranes on antennae, second surface mirrors, thermal/optical coatings and multi-layer thermal insulation (MLI) blanket materials. The chemistry, physical and mechanical properties of the polymers as well as their responses to AO and UV exposure will be discussed.
New Polyimides as Precursors for Functionalized Polymers
Authors: Schab-Balcerzak E , Sek D , Grabiec E , Volozhin A , Chamenko T
Published: August 2002

A series of copolymers from 3,3′,4,4′-benzophenonetetracarboxylic di-anhydride and 3,3′,4,4′-biphenyltetracarboxylic dianhydride and two diamines, 4,4′-diaminodiphenylether and 3,5-diaminobenzoic acid, were synthesized. The influence of various ratios of diamines on the properties of polymers were investigated. A preliminary study on the potential of using the carboxylic acid group for substitution was carried out.
A Study of the Oxidation of Two Aromatic Polyimide Fluoropolymers Containing Phenylphosphine Oxide by a Water Plasma and γ-Radiolysis in Air
Authors: Alexander Mark A , Hill David J T , Connell John W , Watson Kent A
Published: August 2002

The oxidation of two fluorinated polyimides containing phenylphosphine oxide units, TOR-RC and TOR-RC ODPA, have been studied at 300 K for treatment by a water plasma and γ-radiolysis in air. The changes in the O 1s/C 1s ratios obtained from x-ray photoelectron spectroscopy (XPS) analysis showed that for exposure to the water plasma the ratio increases at short exposure times and then levels to a constant value. Evidence for the formation of phosphate species was also obtained from the XPS analyses. Similar observations were made for γ-radiolysis of the polymers in air. The polymers containing phenylphosphine oxide were found to be more resistant to oxidation in the water plasma than Kapton®. Radiolysis of the polymers in air to high doses were also accompanied by a red shift in the visible absorption spectra.
Molecular Design of Heat Resistant Polyimides Having Excellent Processability and High Glass Transition Temperature
Authors: Yokota Rikio , Yamamoto Syougo , Yano Shoichiro , Sawaguchi Takashi , Hasegawa Masatoshi , Yamaguchi Hiroaki , Ozawa Hideki , Sato Ryouichi
Published: August 2002

The relationship between the imide structures and morphology are discussed in order to develop heat resistant polyimides having excellent processability and toughness. Addition-type imide oligomers consisting of asymmetric 2,3,3′,4′-biphenyltetracarboxylic dianhydride (a-BPDA) and 3,4′-oxydianiline (3,4′-ODA) and/or 4,4′-oxydianiline (4,4′-ODA) with 4-phenylethynyl phthalic anhydride (PEPA) were synthesized and characterized. The imide oligomers derived from 3,4′-ODA; 4,4′-ODA (50:50) comonomer having molecular weights of 5240 g mol−1 (Oligo-10) and 1340 g mol−1 (Oligo-1.5) showed good solubility in aprotic solvents such as DMAc and NMP, and were successfully cured at 370°C for one hour. The thermal curing process, and thermal and rheological properties of the imide oligomers were investigated by FT-IR, differential scanning calorimetry, thermogravimetric analysis, and dynamic rheometry. It was observed that the melt flow dramatically decreased above the Tg for Oligo-1.5, resulting in a viscosity as low as 200 Poise at 300°C. Whereas, a melt viscosity for Oligo-10 was 20 000 Poise at 365°C. The glass transition temperatures of these cured oligomers were 341°C and 308°C, respectively. In addition to the excellent melt property, the cured oligomers exhibited good thermo-oxidative stability. Furthermore, the cured imide oligomer consisting of a-BPDA and 4,4′-ODA with PEPA (Oligo-4.5) exhibited over 13% flexural elongation and a Tg of 343°C. Their T-300 carbon fibre composites were also well consolidated demonstrating excellent processability and properties. It is concluded that amorphous, aromatic imide structures without any weak linkages such as alkyl and methylene groups are very effective in the molecular design of heat resistant, addition-type polyimides. The excellent properties exhibited in a-BPDA based polyimides demonstrate a promising potential for future aerospace applications.
High-Temperature Polymers for Advanced Microelectronics
Authors: Maier Gerhard , Banerjee Susanta , Haußmann Jörg , Sezi Recai
Published: August 2002

Several series of aromatic polyethers and polybenzoxazoles with high thermal stability and low dielectric constant were prepared and characterized. The polyethers were synthesized by nucleophilic aromatic displacement of fluorine with phenoxides. In order to avoid strongly polar groups such as carbonyl and sulfone, trifluoromethyl groups were used to activate the fluorine for displacement. An additional benefit of the presence of the trifluoromethyl groups is the decreased dielectric constant, which fluorinated materials exhibit. This is attributed to two factors: the strong electronegativity of fluorine, resulting in very low polarizability of the C–F bonds, and the larger radius of a fluorine atom in comparison with a hydrogen atom, resulting in increased free volume.

Trifluoromethyl substituted terphenyl and quadriphenyl poly(arylether)s prepared in this study exhibit decomposition temperatures far in excess of 500°C, even in air, dielectric constants below three, and mechanical properties comparable to engineering plastics such as polycarbonate and high-performance thermoplastics such as PEEK.

Poly(benzoxazole)s were prepared with and without fluorine substituents. Since most of the poly(benzoxazole)s were insoluble, they were prepared via soluble poly(hydroxyamide) precursors, which were converted to the final polymers by thermal treatment. These materials had dielectric constants as low as 2.69 and also decomposition temperatures far above 500°C in air.
New Synthetic Approach to the Preparation of Polyphenyleneethynylenes and Polyheteroaryleneethynylenes
Authors: Rusanov A L , Keshtov M L , Belomoina N M
Published: August 2002

Polyphenyleneethynylenes and polyheteroaryleneethynylenes—polymers with promising electro-optical properties—are usually prepared by the interaction of dihaloaromatic and diethynylaromatic compounds catalysed with transition metal (first of all, Pd) derivatives. Because of the side reactions these procedures often lead to the formation of relatively low molecular weight polymers; inaddition, preparationoforgano-solublepolyphenyleneethynylenes and polyheteroaryleneethynylenes seems to be rather problematic. In the framework of the present investigation we have developed a new synthetic approach to the preparation of polyphenyleneethynylenes and polyheteroaryleneethynylenes. This approach is based on the utilization of acetylene-containing monomers (e.g. bis- α-diketones, bis-cyclopentadienones and diacetylenearylenes) in smoothly-proceeding polymer-forming reactions (the formation of polyphenylquinoxalines and phenylated polyphenylenes). This approach leads to the preparation of high molecular weight polyphenyleneethynylenes and polyphenylquinoxalineethynylenes combining solubility in organic solvents with film-forming properties.
Synthesis and Characterization of Highly Soluble Polyamide-Imides Derived from α,α′-Bis[3,5-Dimethyl-4-(4-Trimellitimidophenoxy)-Phenyl]-1,4-Diisopropylbenzene
Authors: Liaw Der-Jang , Hsu Pei-Nan , Liaw Been-Yang
Published: August 2002

A new diimide-dicarboxylic acid, α,α′-bis[3,5-dimethyl-4-(4-trimellitimidophenoxy)phenyl]-1,4-diisopropylbenzene (BDTPD), was synthesized by the condensation reaction of α,α′-bis[3,5-dimethyl-4-(4-aminophenoxy)phenyl]-1,4-diisopropylbenzene (BDAPD) with trimellitic anhydride in refluxing glacial acetic acid. A series of new polyamide-imide (PAIs) were prepared by direct polycondensation of BDAPD and various aromatic diamines in N-methyl-2-pyrrolidinone (NMP) using triphenyl phosphite and pyridine as condensing agents. The polymers were produced with high yield and moderate to high inherent viscosities of 0.77–1.03 dl g−1. Wide-angle x-ray diffractograms revealed that the polymers were amorphous. All the PAIs exhibited excellent solubility and could be readily dissolved in various solvents such as NMP, N,N-dimethylacetamide (DMAc), N,N-dimethylformamide, dimethyl sulfoxide, pyridine, cyclohexanone, tetrahydrofuran and chloroform at room temperature or upon heating at 70°C. Such PAIs had better solubility than those containing a hexafluoroisopropylidene linkage in the repeating unit of a PAI backbone. These PAIs had glass transition temperatures between 252 and 269°C and 10% weight loss temperatures in the range of 453–482°C and 462–485°C in nitrogen and air atmospheres, respectively. The tough polymer films, obtained by solution casting from DMAc solution, had a tensile strength range of 80–103 MPa and a tensile modulus range of 1.6–2.0 GPa.
Homo- and Co-Polycarbonates and Blends Derived from Diphenolic Acid
Authors: Moore J A , Tannahill T
Published: August 2002

The properties of materials derived from diphenolic acid (4-(bis(hydroxyphenyl))pentanoic acid, DPA), such as polycarbonate homo- and co-polymers (with bisphenol A, BPA), have been determined. The influence of copolymer composition on the thermal properties of these materials has been determined. Blends of polycarbonates from BPA and from DPA appear to be compatible.
Poly(Azomethine)s with Rotaxane Architecture Containing a Blocking Group in Every Structural Unit: Synthesis and Characterization
Authors: Farcas Aurica , Grigoras Mircea
Published: August 2002

Poly(azomethine)s with rotaxane architecture containing a blocking group in every structural unit of the polymer chain have been synthesized by polycondensation of 3,6-diformyl-9-butyl carbazole with 1,6-hexamethylenediamine/α-or β-cyclodextrin adducts. As compared with the polymers obtained in the absence of cyclodextrins, these polymers are more hygroscopic and soluble in polar solvents such as dimethylformamide and dimethyl sulfoxide. The infrared, proton nuclear magnetic resonance, gel permeation chromatography and differential scanning calorimetry data support the presence of cyclodextrins in every structural unit of the polymer chain.
Effect of Air and Vacuum Storage on the Tensile Properties of X-Ray Exposed Aluminized-FEP
Authors: de Groh Kim K , Gummow Jonathan D
Published: August 2002

Metallized Teflon® FEP (fluorinated ethylene propylene), a common spacecraft thermal control material, which forms the exterior layer of the Hubble Space Telescope (HST) has become embrittled and suffers from extensive cracking. Teflon® samples retrieved during Hubble servicing missions and from the Long Duration Exposure Facility (LDEF) indicate that there may be continued degradation in the tensile properties over time. An investigation has been conducted to evaluate the effect of air and vacuum storage on the mechanical properties of x-ray exposed FEP. Aluminized-FEP (Al-FEP) tensile samples were irradiated with 15.3 kV Cu x-rays and stored in air or under vacuum for various time periods. Tensile data indicate that samples stored in air display larger decreases in their tensile properties than for samples stored under vacuum. Air-stored samples developed a hazy appearance, which corresponded to a roughening of the aluminized surface. Optical property changes were also characterized. These findings indicate that air exposure plays a role in the degradation of irradiated FEP, therefore proper sample handling and storage is necessary with materials retrieved from space.
Atomic Oxygen Durability of Uncoated and Coated High-Frequency Circuit Materials
Authors: Gouzman I , Grossman E , Lempert G , Noter Y , Altshuler Y , Lifshitz Y
Published: August 2002

Different materials were considered for high-frequency circuit applications requiring exposure to low Earth orbit (LEO) space environment. The potential candidates were TMM3 which is a ceramic thermoset polymer composite, and RO4003 which is a glass reinforced hydrocarbon/ceramic laminate, both manufactured by Rogers Corporation (USA). Various constituents of the space environment can affect these materials’ properties. Atomic oxygen is considered the most hazardous component since it may cause degradation of these materials by etching and/or changing the chemical composition. The candidate materials were tested by exposure to different equivalent atomic oxygen (ATOX) fluences of up to 1.9 × 1021 atoms cm−2. The effects of the atomic oxygen exposures were studied by means of scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDS), atomic force microscopy (AFM) and mass loss measurements. Both materials were degraded under ATOX exposure, resulting in intensive mass loss as well as changes in surface morphology and chemistry. In order to protect these materials in the LEO environment several protective coatings were evaluated for TMM3. The protective coatings tested were SiO2, CV1144-0 (a clear silicone coating) and SG120FD (a white silicone paint). SG120FD was found to provide the best protection against ATOX irradiation attack, while CV1144-0 provided a sufficient, though somewhat inferior protection.
Polyimide Composites from ‘Salt-Like’ Solution Precursors
Authors: Cano Roberto J , Hou Tan H , Weiser Erik S , St Clair Terry L
Published: August 2002

Four NASA Langley-developed polyimide matrix resins, LaRC™-IA, LaRC™-IAX, LaRC™-8515 and LaRC™-PETI-5, were produced via a ‘salt-like’ process developed by Unitika Ltd. The salt-like solutions (65% solids in NMP) were prepregged onto Hexcel IM7 carbon fibre using the NASA LaRC™ multipurpose tape machine. Process parameters were determined and composite panels fabricated. The temperature dependent volatile depletion rates, the thermal crystallization behaviour and the resin rheology were characterized. Composite moulding cycles were developed which consistently yielded well consolidated, void-free laminated parts. Composite mechanical properties such as the short beam shear strength; the longitudinal and transverse flexural strength and flexural modulus; the longitudinal compression strength and modulus; and the open hole compression strength and compression after impact strength were measured at room temperature and elevated temperatures. The processing characteristics and the composite mechanical properties of the four intermediate modulus carbon fibre/polyimide matrix composites were compared to existing data on the same polyimide resin systems and IM7 carbon fibre manufactured via poly(amide acid) solutions (30–35% solids in NMP). This work studies the effects of varying the synthetic route on the processing and mechanical properties of the polyimide composites.
Thermosetting Polyimides with Improved Impact Toughness and Excellent Thermal and Thermo-Oxidative Stability
Authors: Xiao T J , Gao S Q , Hu A J , Wang X C , Yang S Y
Published: August 2002

Thermoset polyimides were prepared by thermally curing B-staged endcapped polyimide resins that were obtained by thermally baking PMR polyimide matrix resins. The polyimide matrix resins were prepared by incorporating flexible ether-bridged aromatic segments [–Ar–O–Ar–] into PMR polyimide backbone to improve their processability and impact toughness. Experimental results indicated that the B-staged polyimide resins possessed adjustable and easily controllable thermal processability which ensure that thermoset polyimides are produced with improved impact strength and high glass transition temperature compared with PMR-15. Thermal and thermo-oxidative stability as well as hygrothermal resistance of the thermoset polyimides were also systemically investigated.
Addition Polyimides from Non-Mutagenic Diamines
Authors: Delvigs Peter , Klopotek David L , Hardy-Green DeNise
Published: August 2002

Studies were conducted to find an acceptable non-mutagenic diamine to replace 4,4′-methylenedianiline (MDA), a suspect carcinogen, which is currently being used in PMR-15 polyimide applications. Several diamines containing fluorine and trifluoromethyl substituent groups were synthesized. The diamines were polymerized with the dimethyl ester of 3,3′,4,4′ -benzophenonetetracarboxylic acid (BTDE), using the monomethyl ester of nadic acid (NE) as an endcap. The effect of diamine structure on rheological properties, glass transition temperature, and thermo-oxidative stability was investigated. Unidirectional laminates were fabricated from selected resins, using carbon fibre as the reinforcement. The results indicate that some of the diamines containing trifluoromethyl groups are non-mutagenic, and have potential to replace MDA in PMR polyimides for long-term applications at temperatures up to 300 °C.
Synthesis and Characterization of 2-Hydroxy-4-methoxyacetophenone-Thiourea-Trioxane Polymers
Authors: Pancholi Hemendra B. , Patel Mohan M.
Published: August 2002

Polymers were synthesized by the condensation of 2-hydroxy-4-meth-oxyacetophenone with thiourea and trioxane in the presence of 2 M HCI or H2S04 as a catalyst and varying molar proportions of reactants. The polymers were characterized by elemental analyses and IR spectral studies. The number average molecular weights of polymers were determined by vapour pressure osmometry and non-aqueous conductometrc titrations in pyridine. Viscosity measurements were carried out in DMF. A study of the thermal properties of the polymers has also been carried out.
Bis[3-(2-Propenylphenoxy)phthalimides]-a New Family of Comonomers for Bismaleimides
Authors: Stenzenberger H. D. , Konig P.
Published: August 2002

A series of new bis[3-(2-propenylphenoxy)phthalimides] has been synthesized from bis(3-nitrophthalimides) and o-propenylphenol-sodium involving a nucleophilic nitrodisplacement reaction. The chemical structures lre confirmed using 'H-NMR spectroscopy and show evidence of two stereo isomeric structures for the propenyl group (E:Z ratio 10:1). The new bis(propenylphenoxy)phthalimides copolymerize with bismaleimide as shown via differential scanning calorimetry analysis and provide temperature resistant polymeric networks.
Functional Poly(N-phenylmaleimide) as a Cation Exchanger—II
Authors: Parmar Jayant S. , Patel Chetan G. , Patel Dinesh K.
Published: August 2002

New cation exchangers based on the monomer, 4-(2,5-dioxopyrrolin-l-yl)benzoic acid (DPBA) were prepared, ie. poly(DPBA) and DPBA-divinylbenzene (DVB) copolymer. DPBA-styrene copolymer was prepared by addition polymeriation and DPBA-maleic anydride-styrene terpotymer by polycondensation of p-amino benzoic acid with poly (maleic anhydride-co-styrene). These polymers and copolymers were characterized by elemental analyses, number average molecular weight (M) IR spectral studies, viscosity measurements and thermogravimetry. The polymers exhibited polyelectrolytic behaviour in solution state and, in solid state, they possess good thermal stability. Preliminary results from ion exchange studies by the batch method indicate the possibility of the use of these polymers in the selective separation of several important metal ions.
Synthesis, Characterization and Ion Exchange Properties of 2,4-Dihydroxybenzoic Acid-Urea-Formaldehyde Copolymers
Authors: Patel G. C. , Pancholi H. B. , Patel M. M.
Published: August 2002

Copolymers were synthesized by the condensation of 2,4-dihydroxybenzoic acid woith urea and formaldehyde in the presence of 2 M HCI/HzS04 as a catalyst and varying molar proportions of reactants. The copolymers were characterized by elemental analyses, IR spectral studies, number average molecular weight determination, viscosity measurements and thermogravimetry. Ion exchange properties have been studied employing the batch equilibration method. The copolymer showed a higher selectivity for UO(2+2 and Fe3+ ions than for Cu2+, Ni2+, Co2+ and Zn2+ions.
Synthesis and Biological Activity of Polyketone Resins. Part III: Systems Based on Toluene with Nitrobenzene as Solvent
Authors: Patel N. Z. , Patel J. N. , Ray R. M. , Patel R. M.
Published: August 2002

Polymers were prepared by condensing chloroacetyl chloride/l,2-dichloroethane/dichloromethane with toluene in the presence of anhydrous aluminium chloride in nitrobenzene. The polymer samples were characterized by an IR spectral study, measurement of their number average molecular weight by vapour pressure osmometry, thermnogravimetric analysis and differential scanning calorimetry. All the polymers were tested for their biological activity against bacteria and fungi. The results show that the growth of the organisms tested can be controlled to some extent by the polycondensates.
N-Acryloyl-o-aminobenzoic Acid and Styrene Copolymer-III. Application of Different Methods for Intrinsic Viscosity and Viscosity Constant Determination
Authors: Suthar Bhikhu , Joshi Jayesh
Published: August 2002

A high molecular weight copolymer of N-acryloyl-o-aminobenzoic acid (OAB) and styrene has been prepared by radical polymerization using benzoyl peroxide initiator in dioxane solvent. The copolymer has been fractionated by fractional precipitation and the fractions characterized by viscometry, vapour pressure osmometry and gel permeation chromatography. Mark-Houwink-Kuhn-Sakurada (MHKS) relationships are developed for three different solvents. Both the intrinsic viscosities and the viscosity constants of eight PO-PS fractions were obtained by the Huggins, Kraemer, Martin and Schulz-Blaschke methods in dimethyl formnamide, toluene and tetrahydrofuran solvents. It was concluded that the values obtained by these four methods are in close agreement.
Polyimides based on Poly(4-furanyl-butan-2-one)
Authors: Patel Hasmukh S. , Patel Harshad D.
Published: August 2002

Polyimides were prepared by Diels-Alder (DA) reaction of furfuralacetone (FAC) resin [poly(4-furanyl-butan-2-one)] with various bismaleimides. The DA reaction was carried out in tetrahydrofuran (THF) as solvent as well as in bulk, followed by aromatization of the tetrahydrophthalimide intermediates in the presence of acetic anhydride. All the polyimides were characterized by elemental analysis, IR spectral studies and thermogravimetry. The results show that polyimides based on FAC resin exhibit good thermal stability. Preliminary tests for glass reinforcement of the polyimides indicate that laminates with good mechanical strength can be prepared.
Kinetic Studies on Epoxy Resins Cured with a Novel Polyamine
Authors: Rao R. M. V. G. K. , Padma A. , Patel H. S.
Published: August 2002

Differential scanning calorimeny was used to study the cure kinetics of three epoxy resin systems cured with two hardeners: diaminodiphenylmethane (DDM) and a poly (keto-amine) (PA). The results showved that the curing of the epoxy resins by PA occurs at higher temperatures and the activation energy for PA curing was higher compared with the DDM curing process, showing the er reactivity of PA.
Stabilization of Polystyrene by Oligomeric UV Absorbers
Authors: Ramachandran Susha , Parmar Jayant S.
Published: August 2002

Copolymers were prepared by the condensation reaction of formaldehyde and 2,4-dihydroxy benzophenone, 2-hydroxy-4-methoxy benzophenone and 2-hydroxy-4-butoxy benzophenone. The polystyrene films incorporated with these stabilizers were subjected to UV irradiation and then tested for any change in the carbonyl index, hydroxyl index, tensile strength, elongation at break and evaporation loss to evaluate the efficiency of the new stabilizers.
Ceric-induced Grafting of Acrylonitrile onto Sodium Alginate
Authors: Shah S. B. , Patel C. P. , Trivedi H. C.
Published: August 2002

Acrylonitrile (AN) was grafted onto sodium alginate (SA) using ceric salt as initiator. The optimized reaction conditions affording the maximum percentage of grafting are determined by varying the concentrations of nitric acid, ceric ammonium nitrate, SA and AN, and also temperature and time. The results are discussed and the efficiency of ceric salt is compared with that of Fenton's reagent.
New Polymer Syntheses-I. Synthesis of Linear Unsaturated Polyesters
Authors: Aly Kamal I. , Geies Ahmed A.
Published: August 2002

3,5-Bis(p-hydroxybenylidene)-isopropylpiperidinone (BHIP) and 3,5-divanillylidene-isopropylpiperidinone (DVIP) were used as new starting materials for preparing new unsaturated polyesters. The polyesters were prepared by reacting BHIP or DVIP with adipoyl, sebacoyl, isophthaloyl or terephthaloyl dichlorides utilizing the interfacial polycondensation technique. In addition, the model compounds were synthesized by reacting BHIP or DVIP with benzoyl chloride. The model compounds were characterized by 'H-NMR, IR, and elemental analyses. The polyester samples have been characterized by elemental and spectral analyses. All the synthesized polymers readily dissolved at room temperature in dimethylsulphoxide or concentrated sulphuric acid. The thermal properties of the polymers were evaluated and correlated to their structural units by TGA measurements. X-ray analysis of the polymers showed that all the polyesters are amorphous.
Arylidene Polymers—XXII. Thermogravimetric and Kinetic Analyses of Non-isothermal Decomposition of Organometallic Arylidene Polyester
Authors: Abd El-Wahab Mohamed M. M. , Abd-Alla Mohamed A.
Published: August 2002

Studies of non-isothermal decomposition of certain iodo-organometallic arylidene polyesters and organometallic arylidene polyesters have been performed with TGA measurements at atmospheric pressure. The analysis of the non-isothermal TG and DTG curves of the samples under investigation revealed that their decomposition course proceeds via three stages. The kinetic parameters such as activation energy (E,), preexponential factor (A) and entropy of activation (AS*) for all polymers at different decomposition stages are determinedfrom an appropriate kinetic equation. More particularly, the data showed that the thermal stability of some of the polymers decreases with increasing ring size of arylidene moieties. Furthermore, the effect of absence of iodoand presence of-OCH3 groups upon the thermal properties of polymers was also evaluated.
Interpenetrating Polymer Networks Based on Poly Chromium Acrylate/Poly Acrylonitrile: Synthesis and Properties of Semi IPN-1
Authors: Gupta Nidhi , Srivastava A. K.
Published: August 2002

A series of semi-I tpe interpenetrating polymer networks (IPN) based on poly chromium acrylate and poly acrylonitrile crosslinked with divinyl benzene have been synthesized. Synthetic details, including concentration of poly chromium acriylate (PCrA), acrylonitrile (AN) and divinyl benzene (DVB) and average molecular weight of PCrA were varied and their effect on the crosslink density of the network was studied by swelling experiments. High [PCrAJ and low [AN] increases swelling and thereby average molecular weight between crosslinks (M,). SEM micrographs and glass transition temperature show phase separation at high [PCrA] content.
Preparation of soluble polyimides containing pendent imide groups
Authors: Rusanov A L , Shifrina Z B
Published: August 2002

Polyimides containing imide and (p-phenoxy)imide side groups were obtained by the interaction of new aromatic tetramines, bis[3-amino-4-(p-aminophenoxy)]arylenes, with equimolar amounts of aromatic tetracarboxylic acid dianhydrides and twofold molar amounts of aromatic dicarboxylic acids anhydrides. Structures and properties of the final polyimides depend on the nature of starting monomers and subsequent introduction of monomers to the reaction mixtures. Polyimides thus obtained demonstrate good solubility in organic solvents, high glass transition temperatures and good stability.
Epoxy-modified polyimides: part I
Authors: Patel Hasmukh S , Shah Vipul J
Published: August 2002

The Michael addition reaction of N,N'-l,4-phenylene bis(maleimide) (PBM) with 4,4'-diamino diphenyl methane (DDM) at 1:1, 1: 1.5 and 1:2 molar ratios was carried out in melt at 125-130'C. The resultant polyimide oligomers (PBM-DDM) were characterized by elemental analysis, number of amino and imino groups, IR spectral studies, number average molecular weight, by non-aqueous conductometric titration, and thermogravimetry. These polyimide oligomers were used to cure epoxy resin, namely diglycidyl ether of bisphenol-A, and studied by differential scanning calorimetry (DSC). The unreinforced PBM-DDM epoxy-cured products have also been prepared and characterized. A preliminary study of glass reinforcement based on the PBM-DDM epoxy system has also been established.
Room-temperature kinetics of formation of castor-oil-based polyurethane/poly(methyl methacrylate) interpenetrating polymer networks
Authors: Suthar Bhikhu , Jadav Kanak , Dave Mayank
Published: August 2002

Infrared spectroscopy was used to follow the kinetics of formation of castor-oil-based polyurethane/poly(methyl methacrylate) interpenetrating polymer networks (PU/PMMA IPNs) at room temperature. The synthesis of the individual networks, PU, PMMA and IPNs was studied by measuring the decrease of characteristic absorption peaks of each system.
Synthesis and characterization of aromatic poly(ether ketone amide)s
Authors: Mercer Frank W
Published: August 2002

A general method for the preparation of amide-containing aromatic polyether ketones has been developed. Polymerization is based on a ketone-activated halo displacement in amide-containing bis(4-fluorobenzoyl) moieties by phenoxides. N,N-Bis[4-(4-fluorobenzoyl)-(4-phenoxyphenylJ]terephthalamide and 4-[(4-fiuorobenzoyl)-(4-phenoxyphenylcarbamoyl)]-N-[(4-fluorobenzoyl)-(4-phenoxyphenyl)]phthalimide were prepared by reaction of 4-fluoro-benzoyl chloride with N,N.bis(4-phenoxyphenyl)terephthalamide and 4-(4.phenoxy-phenylcarbamoyl)-N-(4-phenoxyphenyl)phthalimide, respectively, in dichloromethane in the presence of aluminum chloride. Reaction of N,N-bis[4-(4-fluorobenzoyl)-(4-phenoxyphenyl)]-terephthalamide and 4-[(4-fluorobenzoyl(4-phenoxyphenylcarbamoyl)]-N-[(4-fluorobenzoyl)-(4-phenoxyphenyl)]phthalimide with diphenols in an aprotic solvent in the presence of potassium carbonate gave a series of aromatic poly(ether ketone amide)s. Films of the aromatic poly(ether ketone amide)s displayed good thermal stability, flexibility, and T, values ranging from 134 to 186 CC. The dielectric constants of the films were characterized as a function of relative humidity (RH).
Preparation, cure behavior and properties of bismaleinides containing well defined oligo(phenylene sulfide) segments
Authors: Glatz F P , M'ilhauptt R
Published: August 2002

A family of bismaleimides (PPS-BMIs) containing flexible oligo(phenylene sulfide) (PPS) segments was prepared from the corresponding monodisperse diamine-terminated oligo(phenylene sulfide)s (PPS-DAs). PPS-BMIs and PPS-DAs formed eutectic mixtures which melted below 200 C. Upon heating above 200 C, chain advancement via Michaeltype addition of PPS.DA to PPS-BMI followed by cross-linking produced networks containing PPS segments. The influence of the PPS segment length on processing, cure reaction, phase transitions, and thermal stability was investigated.
Electrical, thermal and mechanical properties of polyimide thin films prepared by high-temperature vapor deposition polymerization
Authors: lijima Masayukli , Takahashi Yoshikazu
Published: August 2002

Polyimide thin films were prepared on the whole surface of a substrate using a high-temperature vapor deposition polymerization method (VDP-H). In this method, pyromellitic dianhydride (PMDA) and oxydianiline (ODA), which are monomers of polyimides, are introduced into a process chamber from separate evaporation sources through inlet tubes. As the process chamber was kept at about 200 C, neither monomer could deposit on the substrate. Because the temperature of the substrate was higher than the evaporation temperature of the monomers, only polymerized films were deposited on the substrate. Infrared spectroscopy indicated that the VDP-H films were about 50% imidized. When the film thickness was less than I1 m, a uniform step coverage was observed, and above 2.5 pm a patterned surface was reduced to a planar surface. Film thickness was controlled by changing the amounts of monomers in the evaporation sources. The dielectric constant (E= 3.5), dissipation factor (tan 5 0.002), thermal characteristics (5% weight loss temperature= 551 C), and tensile strength (170 MPa) of the vDP-H films cured for 60 min at 300 C in vacuum were the same as those reported for Kapton® films. The modulus of elasticity (4.0 GPa) was larger than that of Kaptont®, and it was found that the VDP-H films showed less elongation than Kapton®.
Synthesis and Properties of Aromatic Poly(Ether Ketone Pyridazine)s
Authors: Mercer Frank W
Published: August 2002

A general method for the preparation of pyridazine-containing aromatic poly(ether ketone)s has been developed. Polymerization is based on a ketone-activated nucleophilic halo displacement in pyridazine containing bis(4-fluorobenzoyl) moieties by phenoxides. 3,6-Bis(4-fluorobenzoyl-4'-phenoxy-4"-phenoxy)pyridazine was prepared by reaction of 4-fluorobenzoyl chloride with 3,6-bis(4-phenoxyphenoxy)pyrfdazine in dichloromethane in the presence of aluminum chloride. Reaction 3,6-bis(4-fluorobenzoyl-(4-phenoxy-4phenoxy)pyridazine with diphenols in an aprotic solvent in the presence of potassium carbonate gave a series of aromatic poly(ether ketone pyridazine)s. Films of the aromatic poly(ether ketone pyrdazine)s displayed good thermal stability, flexibility, and T. values ranging from 159 to 198 'C. The dielectric constants of the films were characterized as a function of relative humidity (RH).
Semi-Interpenetrating Networks of Sulfur-Containing Bismaleimides
Authors: Glatz F P , Mdiilhaupt R
Published: August 2002

Microphase-separated semi-interpenetrating polymer networks (semi-n Ns) were obtained by curing 4,4'-bismaleimidodiphenylmethane (BMII), which was advanced in situ with diamine-terminated oligo(phenylene sulfide) (PPS-DA), in the presence of a non-crosslinked linear high-T, aromatic polyether. Poly(thioether amide imide) (PTEAI) containing two phenylene sulfide units, Ultems 1000 poly(ether imide) (PEI) and benzophenone tetracarboxylic acid anhydride/diaminophenylindane polyimnide XU 218$ (PI) were used as non-crosslinked modifiers for the sulfur-containing BMI/PPS-DA resin system, which formed the continuous polymer matrix. Morphological and mechanical properties of the polyether-modified BMI/PPS-DA resin systems were investigated as a function of semi-n?,-compositions and polymer compatibilities. The soluble high-TA P1 gave improved strength and toughness without sacrificing the high T, of the resulting multiphase semi-iPNS.
Studies on bismaleimides and related materials: Part III. Synthesis and characterization of bismaleimiides derived from benzophenone, 1, 2-diphenylethane, 1, 4-diphenylbutane and condensed pyrazines
Authors: Prestont P N , Shaht V K , Simpsont S W , Soutar I , Stewart N J
Published: August 2002

New bismaleimides have been synthesised from diamines derived from benzophenone, 1,2-diphenylethane, 1,4-diphenylbutane, 2, 3-diphenylquinoxaline and 2, 3-diphenylnaphtho[2, 3-b]pyrazine. Cure profiles have been established by both differential scanning calorimetry (Dsc) and dynamic mechanical thermal analysis (DMTA). Cured resins prepared from the bismaleimide monomers were studied by thermal gravimetric analysis (TGA) with all materials exhibiting good thermal and thermo-oxidative stability.
Kinetic studies of the reactions between isocyanates and carboxylic acids
Authors: Xiao Hong , Xiao Han X , Frisch Kurt C , Malwitz Nelson
Published: August 2002

Reaction kinetic studies between isocyanates and carboxylic acids were undertaken to evaluate the kinetic parameters. Various isocyanates (phenyl isocyanate, cyclohexyl isocyanate) and carboxylic acids (acetic acid, n-butyric acid, isobutyric acid, dimethylbutyric acid and benzoic acid) were used to study the kinetics of the reactions at different temperatures and in different solvents. It was found that these reactions followed the rate law of second-order reaction. From the Arrhenius plot, the activation energies of these reactions were computed.
Toughening studies on an ABS/PC blend-modified epoxy resin system
Authors: Natarajan K , Rao R M V G K
Published: August 2002

Studies were carried out on the toughening of a bifunctional epoxy (diglycidyl ether of bisphenol-A) matrix system with an ABS/PC thermoplastic blend. The thermoplastic blend was incorporated into the epoxy matrix by particle dispersion and melt-mix methods. The unmodified and modified epoxy resin systems were cured with a stoichiometric quantity of diamino diphenyl methane (DDM). The cured castings were characterized by measurement of glass transition temperature (Tg) by DsC, evaluation of plane strain fracture toughness (Klc) by three-point bending tests and SEM analysis of non-etched and base/acid etched fracture surfaces. In genera] ABS/PC-modified (15% w/w) epoxy-resin-cured systems showed enhanced fracture toughness without lowering the glass transition temperature. The melt-mix method yielded higher fracture toughness than the particle dispersion method; this conclusion was also supported by scanning electron micrographs.
Adhesive and composite properties of LARCTM-8515 polyimide
Authors: Jensen B J , Hou T H , Wilkinson S P
Published: August 2002

LARCTM-8515 (Langley Research Center-8515) is an aromatic polyimide based on 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) and an 85:15 molar ratio of 3,4'-oxydianiline (3,4'-ODA) and 1,3-bis(3-amnophenoxy)benzene (APB). This material is currently under evaluation as an adhesive and composite matrix resin for use in high-performance aerospace applications. The synthesis and development of the copolymer as well as studies of the effect of molecular weight on properties will be discussed. LARCTM-8515 has been evaluated as an adhesive, and titanium to titanium tensile shear strengths will be presented. Unidirectional prepreg was' made utilizing the Langley multipurpose tape machine. and the thermal and rheological properties and the solvent/volatile depletion rates of the poly(amide acid)/NMP resin system were determined. This information was used to successfully design a moulding cycle for composite preparation. Composite laminates were moulded under 200 psi, which consistently yielded good consolidation quality as measured by C-scan, acid digestion and optical photomicrography. Composite mechanical properties measured included short-beam shear strength and flexural strength and modulus at RT, 93, 150 and 177C. and compression strength (ITRI) and open hole compression (OHC) strength at RT and 177 C (wet).
Synthesis and characterization of poly(arylene ether)s and poly(arylene ether imidazole)s
Authors: McDaniel P R , Orwoll R A , Connell J W
Published: August 2002

Poly(arylene ether)s, poly(arylene ether imidazole)s and poly(arylene ether coimidazole)s are under investigation as part of a structure/property relationship study. The objective of this study is to identify polymers or copolymers with an attractive combination of properties for use as toughening agents for epoxies. The copolymers are being studied as possible toughness modifiers for epoxy resins because of their high glass transition temperatures, their high toughness and the ability of the active hydrogen on the imidazole moiety to react with the oxirane ring of epoxies. Homopolymers and copolymers were characterized by differential scanning calorimetry, thermal gravimetric analysis, thin-film tensile properties and neat resin flexural and toughness properties.
Smectic A structure in main-chain liquid crystalline polymers with two different spacers
Authors: Nakata Yasukazu , Shimizu Kazuya , Watanabe Junji
Published: August 2002

We have prepared a homologous series of polymers, BP-CO4-On (n= 3-15).

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The BP-CO4-On polymers are classified as a new type of main-chain liquid crystalline polymer, characterized by having the mesogenic biphenyl moieties and the two different aliphatic spacers incorporated in a regularly alternate fashion. All the polymers form a smectic A phase. The smectic behaviour and structure have been examined by differential scanning, optical microscopic and x-ray methods, concentrating on how the two spacers, which are different in length and of odd-even nature, are accommodated into a smectic layer structure.
New coordination polymers of glyoxal bis(2-hydroxyanil)
Authors: EI-Shatoury Salah A
Published: August 2002

Coordination polymers of [2,2'-(ethandiylidenedinitrilo) diphenol) have been prepared with the metal ions Cu(II), Ni(1I) and Cr(III). They were characterized by elemental analysis, IR and electronic spectra. The metal content in all polymers was found to be consistent with a 1:1 (metal:ligand) stoichiometry. The thermal behaviour of these coordination polymers has been studied by thermogravimetric and DSC analyses in air up to 500 C. The crystallinity of the formed polymers was determined by x-ray analysis. The morphological structures of these polymers were determined by scanning electron microscopy.
Novel Bismaleimide–Epoxy Resin System: II
Authors: Patel Hasmukh S , Shah Sanket N
Published: August 2002

Novel diamines, namely N, N′-bis[1-(2-methyl-4-aminophenyl)ethanonyl]-1,4- benzenediamine (BMAED 1) and N, N′-bis[1-(4-methyl-3-animophenyl)ethanonyl]-1,4-benzenediamine (BMAED 2), have been prepared and reacted with various bismaleimides (BM) at a BM:diamine ratio of 1:2. The resulting oligoimides have been characterized by elemental analysis, IR spectral studies and the number average molecular weight ( Mn) estimated by non-aqueous conductometric titration and thermogravimetry. Some of the oligomides have been modified by addition (i.e. curing reaction) of epoxy resin, namely the diglycidyl ether of bisphenol-A, and studied by differential scanning calorimetry (DSC). The glass- and carbon-reinforced composites have also been prepared and characterized by their mechanical properties.
Synthesis and Characterization of Coumarin–Trioxane–Urea Copolymers
Authors: Brahmbhatt D I , Hirani B R
Published: August 2002

4-methyl-7-hydroxycoumarin trioxane urea (MHCTU) copolymers were prepared by copolycondensation of 4-methyl-7 hydroxycoumarin (MHC), trioxane (T) and urea (U) in the presence of 2 M HCl/H2SO4 as a catalyst with different molar ratios of reacting monomers. The copolymers were characterized by elemental analysis, IR spectral and TGA studies. The number average molecular weight ( Mn) of all the produced copolymers was determined by non-aqueous titrimetry.
Novel Epoxy Resin—Part 2
Authors: Patel K D
Published: August 2002

A novel epoxy resin, namely diglycidyl ether (DGE) of 2,4-dihydroxyacetophenone (i.e. resacetophenone, RAP) was prepared and characterized. The curing of DGE–RAP by various diamines was studied kinetically by differential scanning calorimetry (DSC). The cured neat products have been characterized by IR spectral studies and thermogravimetric analysis (TGA). The glass-reinforced composites based on such a novel epoxy resin–diamine system have also been prepared and characterized.
On the Oxidative Degradation of Nadic Endcapped Polyimides: I. Effect of Thermocycling on Weight Loss and Crack Formation
Authors: Meador Mary Ann B , Lowell Carl E , Cavano Paul J , Herrera-Fierro Pilar
Published: August 2002

The effects of thermocycle frequency, aging temperature and post-cure conditions on weight loss, microhardness and crack formation of PMR-15 neat resins were investigated. Crack formation was monitored by metallography. The molecular level changes, occurring under the same conditions, were monitored by microscopic FT-IR in reflectance mode on the same samples. FT-IR analysis was carried out in zones 100 μm in diameter, allowing examination of different regions of the aged samples. It was found that weight loss, crack formation and microhardness were highly dependent on aging time and temperature, but not thermocycling frequency. Molecular level changes were also highly correlated to time and temperature of aging. Both the physical effects of aging and the chemical effects were isolated to a thin surface layer. No changes whatsoever to the interiors of the samples were evident by FT-IR, microhardness or microscopy.