bluuebunny/crossref_metadata_2025 huggingface dataset:
The effect of carbonization conditions on the properties of rayon-based carbon fibres
Authors: Elmest David , de Vanet Ken
Published: August 2002

The effect of carbonization temperature on the properties of prewoven carbon fibre made from a rayon precursor is examined. Bulk composition is contrasted with surface elemental analysis (XPS) which shows that low carbonization temperatures (2300F, 1260C) produce a fibre with up to 15 and 5 at.% of oxygen and sodium respectively on the surface. At higher firing temperatures (up to 3000, 1649 C), the surface O and Na levels are significantly reduced and the measured fibre surface area declines from 50 m2 g-1 to under 5 ml g-'. Atomic force microscopy (AFM) was used to examine the surface detail of fibres at magnifications over 250000 times. AFM micrographs reveal that the fibre surface after carbonization at low temperatures is covered with a crust believed to be the char residue from tars released during the precarbonization stage. Surface analysis by Auger spectroscopy has confirmed the high oxygen and sodium content of the char material. Use of higher carbonization temperatures results in fibre surface properties which are generally regarded as preferable for use in ablative applications.
Preliminary adhesive and composite properties of LARC™-CPI 2, a new semicrystalline polyimide
Authors: Hergenrothert P M , Havens S J
Published: August 2002

In continuation of an effort to develop processable high-performance structural resins for use in aerospace applications, a new polyimide. LARCTM-CPI 2, has been developed. This semicrystalline polyimide was prepared by the reaction of 4.4'-oxydiphthalic anhydride with 1,4-bis(4-aminophenoxy-4'-benzoyl)benzene. In high-molecular-weight form this material has a glass transition temperature of 223 C and a crystalline melt temperature of approximately 350 'C. Controlled-molecular-weight end-capped versions of LARCTM-CPI 2 were used to fabricate adhesive panels and composites that exhibited good mechanical properties at temperatures as high as 200 C.
The development of processable, fully imidized, polyimides for high-temperature applications
Authors: Southcott Mark , Amone Mike , Senger James , Wang Andy , Polio Amy , Sheppard C H
Published: August 2002

Novel end-capped, fully imidized polyimides have been developed as potential high-performance matrix materials for advanced composites. This study describes the synthetic development of norbornene-capped oligomers, subsequent screening of neat resin mechanical and thermo-oxidative properties and, finally, composite property evaluation. It is shown that these soluble reactive oligomers can be prepared reproducibly and give crosslinked networks that have mechanical properties more typical of thermoplastics, as well as good hot/wet and thermo-oxidative stability. Composites were prepared using a cure cycle more characteristic of thermosetting-type polyimides and it was demonstrated that fully imidized polyimides allow low-void-content laminate manufacture via autoclave processing. The evolution of imidization volatiles, which are generated using the more common PMR- and polyamic-acid-type systems, is averted using these reactive oligomers.
The preparation of poly(methylsilsesquioxane) network-polyimide hybrid materials by the sol-gel process and their properties
Authors: Iyoku Yoshitake , Kakimoto Masa-aki , Imai Yoshio
Published: August 2002

Poly(methylsilsesquixoane) network (silicone)-polyimide hybrid materials were successfully prepared by the sol-gel reaction of methyltriethoxysilane (MTES). The ethoxysilyl group in MTES was hydrolyzed and polycondensed in the solution of the polyamic acid, derived from pyromellitic dianhydride and bis(4-aminophenyl)ether, in N,N-dimethyl-acetamide (DMAc). The hybrid films were obtained by casting the reaction mixture, followed by heating up to 300°C. The hybrid materials containing 0-60wt% of silicone afforded flexible films. The films containing less than 7 wt% silicone were yellow and transparent, whereas the films with higher silicone content were yellow and opaque. Silicone particles with a diameter of around 1-10 μm were observed in the fracture surface of the hybrid films by scanning electron microscopy. Although the tensile strength and tensile modulus of the films obtained decreased with increasing silicone content. the value of the elongation at break remained at 60% up to 30% silicone content.
Study of the crosslinking process in fluorinated poly(imide-amide)s containing pendant cyano groups
Authors: Bruma M , Mercer F , Schulz B , Dietel R , Fitch J , Cassidy P
Published: August 2002

Fluorinated poly(imide-amide)s containing pendant cyano groups have been synthesized by solution polycondensation of aromatic diamines which contain cyano groups with diacid chlorides which have both hexafluoroisopropylidene and imnide groups. Thermal crosslinking of these polymers has been attempted in NMP, or by heating the polymer films up to 370-400 'C. The solubility, thermal stability, glass transition temperature and dielectric constant of both linear and crosslinked polymers have been studied.
Synthesis and characterization of poly(coumarin-urethane)s
Authors: Brahmbbatt D I , Jayabalan L , Patel Harshad D
Published: August 2002

Poly(coumarin-urethane)s (PCUs) were prepared by the condensation reaction of 3,3'-dihydroxy-6,6'-methylcnebiscoumarin (DHMBC) with various diisocyanates. All the poly(coumarin-urethane)s were characterized by elemental analysis, IR spectral studies, number average molecular weight determination (by vapour pressure osmometry), viscosity studies and thermogravimetry.
Kinetic studies by FT-NIR of the curing reactions of two glycidyl ether epoxy resins mixed with stoichiometric quantities of 4,4′ - DDS
Authors: Kozielski K A , George G A , St John N A , Billingham N C
Published: August 2002

The crosslinking reactions of 4,4'-diaminodiphenyl sulphone with stoichiometric quantities of multifunctional epoxy resins were monitored using Fourier transform near infrared (FT-N1R) spectrophotometry. Manipulation of the pectral data enabled the concentrations of reactive groups throughout isothermal cure to be profiled. A kinetic model which included catalytic and diffusion-controlled reactions was developed to fit the data. Two glycidyl ether resins (Shell 1153 and Tactix 742) were chosen for this study to give an overview of this approach to commercial systems.
Water sorption in thin films of high-temperature polyimides: the effect of imidization history
Authors: Ree M , Han H , Gryte C C
Published: August 2002

PMDA-ODA and BPDA-PDA polyimides in 10-50 Atrn thick films were prepared from the respective poly(amic acid) precursor by thermal imidization for 1-10 h at various temperatures over 230-400C. Their water sorption behaviours were studied in detail by gravimetry. Water sorption in both PMDA-ODA and BPDA-PDA followed a nearly Fickian process in spite of the morphological heterogeneity due to the ordered and less ordered phases. Water clustering or plasticization was very weakly evident on the water uptake versus humidity plots. Water sorption in both polyimides was highly dependent upon imidization history. Both diffusion coefficient and water uptake are decreasing functions of imidization temperature and time. This resulted mainly from the enhancement of overall crystallinity by high-temperature imidization because of their high-rT nature. The diffusion coefficient and water uptake were (1.0-3.0) x 10-9 cm2 s-1 and 0.4-4.5 wt% for PMDA-ODA and (0.9-3.0)x 10-cm2s-' and 0. I2-2.40wt%, depending on humidity,/iihidization history and film thickness. The differences between the water sorptions of the p'olyimides are interpreted by considering the differences in their morphologies and chemical affinities to water.
Preparation of aromatic polyamides from newly separated optically pure phenylindanedicarboxylic acid and their application to enantioseparation
Authors: Morikawa Atsushi , Kakimoto Masa-Aki , Imai Yoshio
Published: August 2002

An optically pure isomer of 1,l,3.-trimethyl-3-phenylindane-4',5-dicarboxylic acid (PIDA) was obtained by introduction of racemric PIDA to a diester of the optically pure alcohol. D-(-)-pantolactone, followed by hydrolysis of the separated stereoisomer of the diester. Optically active aromatic polyamides (aramids) were synthesized by the reaction of the optically pure PIDA with various aromatic diamines. The specific rotations of these aramids ranged from + 284 to +4416. The aramids were soluble in organic solvents such as N,N-dimethylacetamide, pyridine and m-cresol. These materials had glass transition temperatures over 290 'C, and did not decompose below 380 C. The solubility and thermal behaviour were almost the same as those of the racemic aramids. The optically active aramids were examined as a stationary phase for chromatographic enantioseparation. When the aramid derived from p-phenylenediamine was used for this purpose, the stereoisomers of l-phenylethylamine could be easily separated.
Polyimides based on 2,2',6,6'-tetramethylbenzidine
Authors: Chuang Kathy C
Published: August 2002

Thermoplastic and addition curing polyimides based on non-coplanar 2,2',6,6'-tetrarnethylbenzidine (TMBZ) were prepared and investigated. The TMBZ based thermoplastic polyimides displayed high Tg values, enhanced solubility and excellent thermal stability. These high-mnolecular-weight polyimides could be either cast into optically transparent thin films or spun into fibres. The addition curing polyimides based on TMBZ exhibited higher Tg values than the corresponding PMR-1I type polyimides, due to the increased rotational barrier created by the substituents on the biphenyl moiety. However, the methyl substituents on the TMBZ inherently lowered the thermo-oxidative stability of TMBZ based polyimides, relative to the corresponding PMR-II type polyimides.
Chemiluminescence measurement of gel times for amine-cured epoxy resins
Authors: Kozielski K A , Billingham N C , George G A , Greenfield D C L , Barton J M
Published: August 2002

The cross-linking reactions of 4,4'-diaminodiphenyl sulphone (DDS) with stoichiometric quantities of glycidyl ether- or tetraglycidyl amine-based epoxy resins were monitored using chemiluminescence (CL) and rheometry. It was found that, when a sample was cured isothermally in air, the CL profile increased to a maximum, then decreased again. The maximum was found to correspond well with the gel time (tgel), as measured by rheometry. This observation is discussed in relation to the chemical reactions occurring within the material and the physical state of the matrix. The effect of impurities in DDS on the gel time of these epoxy resins is reported.
Copolyimides containing internal acetylene units as a high-performance polyimide molecular composite
Authors: Takeichi Tsutomu , Miyaguchi Noriko , Yokota Rikio
Published: August 2002

Random and block copolyimides made of biphenyltetracarboxylic dianhydride (BPDA) and 3,3'-diaminodiphenylacetylene (intA), p-phenylenediamine (PDA), and 4,4'-oxydianiline (ODA) were prepared. Random copolyimides were prepared by adding BPDA into an N-methylpyrrolidone (NMP) solution of diamine mixtures, followed by thermal imidization. The ratio of PDA and intA or ODA was 7:3. Block copolyimides were prepared by the reaction of amine-terminated BPDA/PDA units and anhydride-terminated BPDA/intA (or ODA) units. The ratio of PDA and intA or ODA was also set at 7:3. For the polyimides containing internal acetylene units, exotherms appeared on DSC measurements starting from 320C, which shows that crosslinking is occurring. Cold-drawing of polyamide acid films gave polyimide films with a higher modulus. High-temperature treatment to induce crossblinking did not lower the high modulus afforded by the cold-drawing. Crosslinking afforded a higher Tr, and a higher modulus at higher temperatures. Laminate processing was performed at 400C with a pressure of 100kgcm"2. The copolyimides containing internal acetylene units gave laminate films whose interfaces are strongly bonded through the crosslinking reaction. It was confirmed that the laminate films maintained the high modulus afforded by crosslinking.
Elastic modulus of the crystalline regions of thermoplastic polyimide
Authors: Nakamae Katsuhiko , Nishino Takashi , Miki Norihiko
Published: August 2002

The elastic modulus El of the crystalline regions in the direction parallel to the chain axis was measured for poly[3,3',4,4'-(dioxy biphenyl) diphenylene pyromellite imnide] (New-TPI) by x-ray diffraction. An El value of 55 GPa was obtained for New-TPI. This small El value was considered to be due to the coexistence of both ether bonds and mn-phenylene linkages which are introduced to improve the processability. The elastic moduli Et of the crystalline regions in the direction perpendicular to the chain axis were 3.2-3.5 GPa. These small E, values indicate that any special interaction hardly acts for New-TPI.
Effects of catalysts on the model reactions of several maleimide resin systems (III): allyl-modified maleimniide
Authors: Enoki Takashi , Takeda Toshiro , Ishii Keiichiro
Published: August 2002

A detailed investigation on the effects of catalysts on the curing reactions of the allyl-modified maleimide resin system was carried out by using model reactions. Various products and various degrees of polymerization of N-phenylmaleimide are obtained by changing catalysts (no catalyst, imidazole catalyst, radical catalyst and triphenyl phosphine). The products are identified by NMR spectroscopy. These results suggest that the choice of catalyst could control the crosslinking densities and structures of various maleimnide resins; those factors also relate to the physical and mechanical properties. These results would be useful in maleimide chemistry and its application.
Synthesis and properties of fluorinated poly(ester-imide)s
Authors: Bruma M , Sava I , Mercer F , Negulescu I , Daly W , Fitch J , Cassidy P
Published: August 2002

A series of new, fluorinated poly(ester-imides)s has been synthesized by solution condensation, in a high-boiling-point solvent, of dihydroxy compounds containing imide and hexafluoroisopropylidene units with diacid chlorides containing preformed ester groups. Solutions of these polymers in NMP or in a mixture of trifluoroacetic acid with chloroform were cast into colourless, thin, flexible films having a low dielectric constant. These polymers show high thermal stability, with the initial decomposition temperature being over 400cC. The glass transition temperature is in the range 215-272C for fully aromatic structures and is about 170 TC for those polymers containing some ethylene groups along with aromatic ones. All these characteristics are discussed and compared with those of related poly(esterimide)s which do not contain 6F groups.
Water-developable photoresists employing onium salt photoinitiators
Authors: Davidson Keith , Hadley Philip C
Published: August 2002

Aromatic onium salts are known compounds with well understood photoactivity. Their use as acid-generating species has, in the last few years, improved the performance of photoresists, particularly for microelectronics applications. There has, however, been little research dedicated to the use of these photoinitators in aqueousrdevelopable resists. This work investigates the feasibility of employing onium salts in the formulation of resists suitable for aqueous development. The ability of the onium salts to photoinitiate the cationic polymerization or cross-linking of epoxide residues was exploited using water-soluble or water-dispersible copolymers containing glycidyl methacrylate (GMA). The comonomers included N-vinyl pyrrolidinone (NVP), NN-dimethylacrylamide (DMAc) and 2-hydroxyethyI methacrylate (HEMA). Various copolymers were prepared by radical copolymerization to low conversion, typically in chloroform. Several onium salts were prepared by literature methods and their efficiency examined using a model copolymer. The photoacid generator (PAG) that performed best was then used in the examination of the aqueous systems.
High-Performance Thermoset–Thermoset Polymer Blends: A Review of the Chemistry of Cyanate Ester–Bismaleimide Blends
Authors: Hamerton Ian
Published: August 2002

Various blends of a commercial bismaleimide (BMI) mixture, a cyanate ester (CE) and a co-monomer with allyl and cyanate pendant groups were formulated and cured. Differential scanning calorimetry (DSC) data were used to monitor the cure of neat resins, while dynamic mechanical thermal analysis (DMTA) was used to assess cure by the measurement of glass transition temperatures ( Tg). It is suggested that following cyclotrimerization of the CE component, the co-reaction between allyl CE and BMI occurs via an ‘ene’/Diels–Alder mechanism (to form linked interpenetrating networks, LIPNs) as evidenced by 13C nuclear magnetic resonance (NMR) spectroscopy. DMTA reveals that, unlike the commercial CE/BMI blends, the cured LIPNs may display a single Tg value which may exceed 350°C depending on the co-monomers used.
Self-Reinforcing Polymer Blends Containing a Liquid Crystalline Polymer: Processing, Microstructure and Properties
Authors: Lekakou C , Dickinson C E
Published: August 2002

Blends of nylon-6,6 with a thermotropic liquid crystalline polymer (VECTRA) were processed by injection moulding. Tensile testing was carried out on specimens of blend compositions in the range of 20 to 30% VECTRA where specimens with 25% VECTRA presented the best Young’s modulus and strength. The fracture surfaces were examined in SEM and showed a skin/core morphology. The skin contained highly oriented fibrillar domains of VECTRA, the size and texture of which changed with blend composition. VECTRA displayed the best reinforcing properties when its fibrillar domains in the skin region were arranged into thick bundles of detectable fibrils. This marked the VECTRA concentration above which the VECTRA fibrils started coalescing into thicker fibres of smaller aspect ratio which reduced the reinforcing properties of VECTRA.
Functionalized Poly-Imide–Amides: Molten State Reaction Mechanisms and Kinetics
Authors: Grenier-Loustalot Marie-Florence , Trillaud Marc , Grenier Philippe
Published: August 2002

Molten state polymerization reaction mechanisms and kinetics of telechelic polyimide–amides (PIA) were investigated. We conducted a basic study of the reactions of these functionalized systems as a function of the chemical structure of the polymer. Since reaction products very rapidly became insoluble, the study was carried out on model compounds characteristic of reactive chain ends. The data obtained were applied to the study of industrial prepolymers. Different model compounds were synthesized and studied in the temperature range of 100 to 300 °C using such physicochemical methods as HPLC, 1H and 13C NMR (liquid and solid), FTIR and DSC. We were thus able to determine a number of precise parameters characteristic of the different reactions occurring (isomerization, crosslinking, co-reactions and side reactions).

The results were applied to the study of 1500 molecular weight prepolymers and preimpregnated carbon fibres.
Preparation and Characterization of Some Novel Bismaleimide Monomers and Polymers Based on Diaminobisimides
Authors: Dao B , Hawthorne D G , Hodgkin J H , Jackson M B , Morton T C
Published: August 2002

New bismaleimide monomers, based on pure diaminobismides (DABIs) have been synthesized. In a number of cases the bismaleimide of the 2:1 (amine/anhydride) DABI adduct has been isolated as a pure compound, but where the starting DABI consisted of a mix of imide oligomers of the diamine and dianhydride (2:1, 3:2 and higher) the corresponding bismaleimide product was found also to have a similar composition ratio. This has been confirmed in one example by separation of the oligomer mix and characterization of the components. The utility of the various bismaleimides as monomers in composite matrices has been assessed by cocuring with the common coreactant, 3,3′-diallylbisphenol A. The physical properties and thermal stability of neat resin samples and laminates are reported as well as some mechanical properties.
Propargylic and Chromene Terminated Prepolymers. 3. Study of Homopolymerization and the Effect of the Chromene Content on Reaction Kinetics
Authors: Grenier-Loustalot M F , Sanglar C
Published: August 2002

We have chemically synthesized CTR (chromene terminated resin) prepolymers in order to more specifically study the homopolymerization reaction of chromene. Physicochemical data were used to show the value of working with dichromene prepolymers instead of propargylic monomers. In particular, the homopolymerization reaction is less exothermic than the thermally induced ring formation. So, when the homopolymerization reaction is predominant, the processability of the final thermoset material will be easier. Besides, the rate constant of the homopolymerization reaction is higher than that measured for dipropargylic monomers. This explains the interest in overcoming β stage formation which is the kinetically rate limiting step. On the other end, the presence of residual propargylic functions in dichromene prepolymers after synthesis has no considerable effect on reaction temperature or advancement of reaction.
Design, Preparation and Characterization of Thermotropic Liquid Crystal Polyamides
Authors: Alder P , Dolden J G
Published: August 2002

There are few examples of thermotropic polyamides reported in the literature due to the strong tendency for hydrogen bonding between polymer chains. The vast majority of reported liquid crystalline (LC) polyamides are aromatic, highly crystalline and consequently infusible— and can only exhibit LC behaviour in solution (lyotropic behaviour). In this paper, the authors set out to synthesize novel amorphous wholly aromatic and semi-aromatic thermotropic polyamides. As crystalline aromatic polyamides are normally infusible, it was necessary to ensure that the target polyamides were amorphous with a definable softening point below their temperature of decomposition. The ‘Symmetry Index’ approach first developed by Dolden was used to ensure that the chosen monomer compositions were able to produce amorphous polyamides. Aharoni has reported that three amide linked aromatic rings is the minimum unit size needed to obtain mesogenic polyamides. Building on this principle, a new empirical predictive technique called the ‘Mesogenic Index’ is introduced and combined with the Symmetry Index to predict polyamides which are both amorphous and thermotropic. This approach was validated by the preparation of a whole new series of thermotropic amorphous polyamides which were based on 3,3′-dimethoxy benzidine, and the acid chlorides of terephthalic, isophthalic and adipic acids. Furthermore, this led on to the preparation of two more series of amorphous polyamides, believed by the authors to be the first wholly aromatic thermotropic polyamides to be reported, based on 3,3′-dimethoxy and 3,3′-dimethyl benzidine in conjunction with a variety of aromatic and cyclic diacids.
Fluorinated Poly(Phenylquinoxaline–Imide–Amide)S
Authors: Hamciuc C , Hamciuc E , Mercer F W , Belomoina N M , Bruma M
Published: August 2002

Poly(phenylquinoxaline–imide–amide)s have been synthesized by solution polycondensation of aromatic diamines containing preformed phenylquinoxaline rings with a diacid chloride incorporating preformed imide rings and hexafluoroisopropylidene (6F) groups. These polymers do not decompose up to 400 °C and have glass transition temperatures in the range of 284–308 °C. They are soluble in polar amidic solvents, such as N-methyl-pyrrolidone, and in less polar solvents such as pyridine and tetrahydrofuran, and give flexible films by casting from solutions.
Polyphosphazene Toughened PMR-type Thermosets
Authors: Abu-Shanab O L , Chang C P , Soucek M D
Published: August 2002

Two new polyphosphazenes, poly(4-maleimidophenoxy/phenoxy)phosphazene and poly(4-phthalimidophenoxy/phenoxy)phosphazene, were prepared and used to toughen a PMR polyimide designated LaRCTMRP46. These toughened polyimides were evaluated as thin films with a 0–40 wt% range of polyphosphazene to polyimide. The structure–property relationships of these inorganic/organic polymeric matrices were studied and evaluated in terms of fracture toughness, thermo-oxidative stability, and thermal, mechanical, and tensile properties. The hybrid systems revealed an increase in fracture toughness up to 20 wt% polyphosphazene load without any substantial loss in tensile properties. With 5 wt% poly(4-phthalimidophenoxy/phenoxy)phosphazene loading, the fracture toughness of the semi-interpenetrating network was increased by 124%. When 10 wt% poly(4- maleimidophenoxy/phenoxy)phosphazene loading was used, the fracture toughness of the grafted copolymer was improved by 217%. In addition, substantial enhancement in thermo-oxidative stability was also observed.
Propargylic-Terminated Prepolymers. 5. Mechanistic and Kinetic Studies of the Polymerization Reaction of Compounds with an Imide Group meta to the Propargylic Function
Authors: Grenier–Loustalot Marie–Florence , Sanglar Corinne
Published: August 2002

We have synthesized two functionalized prepolymers with an imide group meta to the propargylic function in their central skeleton. Based on data obtained by a variety of solid and liquid state physicochemical techniques, we show that meta substitution modifies the reaction path and leads to the formation of two chromenes, α and β. In addition, the reaction kinetics and thermal stability of the final system are affected by the presence of an imide group in the structure of the propargylic prepolymer.
LaRC ™-SI: A Soluble Aromatic Polyimide
Authors: Bryant Robert G
Published: August 2002

LaRC™-SI (NASA Langley Research Center-Soluble poly Imide) is a wholly aromatic, high-performance thermoplastic with a unique combination of physical, mechanical and adhesive properties. LaRC™-SI is synthesized from equimolar amounts of the dianhydrides 4, 4′-oxydiphthalic anhydride (ODPA) and 3, 3′, 4, 4′-biphenyltetracarboxylic dianhydride (BPDA); 3, 4′-oxydianiline (3, 4′-ODA) and phthalic anhydride (PA) as an endcapping reagent. The most unique property of LaRC™-SI is its initial solubility in conventional high-boiling aprotic solvents. However, when exposed to temperatures above its softening point of 250 °C it becomes insoluble yet retains its melt processability. This allows LaRC™-SI to be solution processed as both a polyamic acid and a polyimide. In addition to this solubility characteristic and high softening point, LaRC™-SI is extremely tough and fracture resistant with G1c and K1c values of 4.6 kJ m−2 and 4.4 MN m−3/2 respectively. As a melt extruded film, LaRC™-SI has been used as a hot melt adhesive to bond titanium and aluminium with lap shear strengths for titanium and cleavage strengths for aluminium exceeding 43 MPa and 16.9 MPa respectively at 23 °C.
Preparation and Stress Relaxation Properties of Thermoplastic Polysiloxane-Block-Polyimides
Authors: Furukawa Nobuyuki , Yamada Yasuharu , Kimurak Yoshiharu
Published: August 2002

Three series of thermoplastic polysiloxane- block-polyimides were prepared from 3, 3′, 4, 4′-benzophenonetetracarboxylic dianhydride, aromatic diamines with four phenylene rings and diamine-terminated polydimethylsiloxane ( Mw D 1240). The tensile modulus of their films was lowered and the coefficient of thermal expansion was increased with increasing polysiloxane composition. The copolyimides showed a good adherence onto silicon wafer even without adhesion promoter added. The adherence was maintained even after exposure to an environment of 23 °C and 78% RH for 72 h. The residual stress in the interface between the copolyimide coating and the silicon wafer was lowered according to the tensile modulus of coating materials, so the introduction of polysiloxane into aromatic polyimides can afford excellent adhesion and stress relaxation properties despite mismatching in thermal expansion between polymer and substrate.
LC Polyimides 29. Non-Crystalline Cholesteric Copoly(Ester-Imide)s Derived from Adipic Acid and Isosorbide
Authors: Kricheldorf Hans R , Krawinkel Thorsten
Published: August 2002

Numerous cholesteric copoly(ester-imide)s were prepared from mixtures of isosorbide and tert.-buthylhydroquinone (or other diphenols), on the one hand, and mixtures of adipoylchloride and N-(4-chlorocarbonylphenyl) trimellitimide chloride on the other. When the molar ratio of isosorbide/diphenol was varied, Grandjean textures were only observed for low concentrations of isosorbide (5/95 or 10/90). In the case of adipoylchloride/imide dichloride molar ratios of 30/70–50/50 favoured the formation of Grandjean textures. Most copoly(esterimide)s were non-crystalline with glass transition temperatures ( Tgs) between 90 and 190 °C. In several cases the Grandjean textures were frozen in by cooling below Tg. Such copoly(esterimide)s may be useful as pigments. All copoly(ester-imide)s containing methylhydroquinone were semicrystalline with melting temperatures in the range of 240–270 °C.
LC Polyimides 30. Non-Crystalline Cholesteric Poly(Ester-Imide)s Based on Isosorbide and 1, 6-Bis(4-Carboxyphenoxy)Hexane
Authors: Kricheldorf Hans R , Krawinkel Thorsten
Published: August 2002

Numerous cholesteric copoly(ester-imide)s were prepared from tert.-butylhydroquinone and isosorbide, on the one hand, and from the acid chlorides of N-(4-carboxyphenyl)trimellitimide and 1, 6-bis(4-carboxyphenoxy)hexane on the other. Two polycondensation methods were applied and compared. The molar ratio of the diols was varied and also the molar ratio of hot dicarboxylic acid chlorides. The copoly(ester-imide)s formed Grandjean textures with a low content (5–10 mol%) of isosorbide and relatively high content of the flexible dicarboxylic acid. The glass transition temperatures ( Tgs) varied in the range of 160–180 °C.
Preparation and Properties of Silicon-Modified Polynaphthalimides
Authors: Yamada Yasuharu , Furukawa Nobuyuki
Published: August 2002

Silicon-modified polynaphthalimides derived from 1,4,5,8-naphthalenetetracar-boxylic dianhydride, 4,4′-dinaphthalic anhydride and bis(1, 8-dicarboxynaphth-4-yl)dimethyl silane dianhydride and several types of aromatic diamines were prepared and their thermal stability was studied. The monomers of 4, 4′-dinaphthalic anhydride and bis(1, 8-dicarboxynaphth-4-yl)dimethyl silane dianhydride were also synthesized from acenaphthene followed by oxidation. Polyimides obtained were brittle because of the low molecular weight and the rigidity of the polymer structure. Therefore, no good thin films were made from the polyimides (the colour of which was dark brown). The imidization of polynaphthalimide occurred in the temperature range of 100–200 °C which is lower by about 50 °C than that of polypyromellitimide. The polyimides having a naphthalimide structure showed higher thermal decomposition temperature than the polyimides having a pyromellitimide structure derived from pyromellitic dianhydride. However, the decomposition temperature of silicon-modified polynaphthalimides decreased with increasing silicon content in the polyimides.
Synthesis, Characterization and Glass-Reinforced Composites of Acetone–Formaldehyde–Phenol Resins
Authors: Patel Hasmukh S , Dixit Bharat C
Published: August 2002

Acetone–formaldehyde (AF) resin having the methylol group (–CH2OH) has been prepared and characterized. The condensation of AF resin with phenol (P) was carried out in the presence of alcoholic alkali catalyst at varying ratios of AF:P, namely 1:1, 1:1.5 and 1:2. The resultant AFP resins were characterized by elemental analysis, IR spectral studies, number average molecular weight ( Mn) estimated by non-aqueous conductometric titration, and thermogravimetry. The curing study of AFP resins with hexamethylene tetramine (HMTA) was monitored by differential scanning calorimetry (DSC) and kinetic parameters were evaluated.

Glass-reinforced composites based on the AFP–HMTA system have also been prepared and characterized.
Structure–Property Relationships in Addition Polyimides. II. Resins from Three-Ring Aromatic Diamines Containing Carbonyl and Methylene Groups
Authors: Delvigs Peter , Klopotek David L , Cavano Paul J
Published: August 2002

The use of flexibilized three-ring aromatic diamine moieties was investigated in an effort to improve the processing characteristics of addition-type polyimide resins. A series of 10 diamines containing carbonyl and methylene bridging groups was synthesized. The diamines were polymerized with the dimethylester 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 the solubility and rheological properties during cure was determined. The effect of diamine structure and formulated molecular weight on the thermo-oxidative stability and glass transition temperature of the polyimides was also investigated. Unidirectional laminates were fabricated from selected resins, using carbon fibre as the reinforcement. Interlaminar shear strength and flexural properties of the laminates were determined. The results indicate that polyimides from some of the diamines containing methylene bridging groups have potential as matrix resins for long-term applications at temperatures up to 300 °C.
Preparation and Properties of Polyisoimides as a Highly Dimensionally Stable Polyimide Precursor with Low Dielectric Constant
Authors: Seino Hiroshi , Haba Osamu , Mochizuki Amane , Yoshioka Masahiro , Ueda Mitsuru
Published: August 2002

Fluorinated polyimides (PIs) with low dielectric constant and high dimensional stability have been developed using polyisoimides (PIIs) as a polyimide precursor. The PIIs were prepared by the ring-opening polyaddition of the dianhydrides pyromellitic dianhydride, biphenyltetracarboxylic dianhydride and 4, 4′-hexafluoropropylidenedi(phthalic anhydride) with the diamines 2, 2′-dimethylbenzidine and 2, 2′-bis(trifluoromethyl)benzidine, followed by treatment with trifluoroacetic anhydride/triethylamine or dicyclohexylcarbodiimide in N;N-dimethylacetamide. The PIIs were soluble in a wide range of solvents including dipolar aprotic solvents, cyclohexanone and tetrahydrofuran at room temperature, and easy to convert to corresponding PIs by high thermal treatment. The resulting PIs showed low dielectric constants of less than 3 at 1 MHz as well as low CTEs. Furthermore, during the isomerization reaction, migration of copper in the PI film was hardly observed.
Temperature Dependence of Absorption Spectra and Optical Parameters for Polyester Films of Dibenzylidene Cyclohexanone
Authors: Osman M A , Othman A A , Abd-Alla M A
Published: August 2002

Effect of temperature on the optical absorption spectra and optical parameters is investigated in new synthesized polyester films of poly[oxyiso-phthaloyloxy(2-methoxy- p-phenylene)methylidyne(2-oxo-1, 3-cyclohexanediylidyne)methylidyne(3-methoxy- p-phenylene)] (I) and poly[oxysebacoyloxy-(2-methoxy- p-phenylene) methylidene (2-oxo-1, 3-cyclohexanedi-ylidene)-methy-lidene-(3-methoxy- p-phenylene)] (II). Absorption measurements are carried out in the temperature range 80–370 K and in the photon energy range 1.9–4 eV. The optical absorption spectra of polymers I and II reveal excitonic absorption bands at 80 and 120 K respectively. These bands are associated with n →π* optical transitions along polymer backbone chains. Analysis of optical absorption data indicates that the Tauc equation for indirect optical transitions successfully explains the optical absorption process in polymeric film I, whereas Urbach’s law is more suitable for describing the optical absorption in polymeric film II. Temperature dependence of the optical bandgap, Eoptg, the Tauc slope √B, and the width of Urbach’s tail states ( Ee) exhibits anomalous parabolic behaviour which can be explained in terms of various current theories. Moreover, DSC, x-ray diffraction and morphological studies by TEM are used in the explanation of the experimental results. The values of optical parameters, as well as the temperature coefficient of the optical bandgap for these polymers, are calculated and reported.
The Utility of 2-Naphthol Derivatives As Diels–Alder Based Co-Reactants for Bismaleimides
Authors: Dao B , Hodgkin J H , Morton T C
Published: August 2002

A number of 2-naphthols were found to undergo a Diels–Alder addition reaction with maleimides. This reaction can be used to bring about the cure of bismaleimides. The simplest co-reactant prepared in this work was 7-allyloxy-2-naphthol and satisfactory cures were obtained with appropriate bismaleimides. However, the laminate coupons made using this system had lower thermal stability than those of a comparable system using the commercial co-reactant Matrimid 5292B. The performance of this new chemistry was further tested by incorporating the naphthol/maleimide Diels–Alder addition structure into two other co-reactants. The most successful of these compounds (the diallyl ether of the adduct made from Diels–Alder addition of 2, 7-dihydroxynaphthalene and 4-hydroxyphenylmaleimide) produced cured neat resin samples having Tgs 30 °C higher than those of a comparable system cured with the standard bismaleimide co-reactant (Matrimid B) and had slightly higher tensile strength and modulus than this system. The fact that these laminate coupons had better thermal performance than the system using commercial co-reactant showed that the presence of the Diels–Alder adduct structure in the resin backbone was not detrimental to the normal performance of ene cured bismaleimides. On the other hand the same structure incorporated into phenylethynyl end-capped resins was found to compromise its thermal stability.
Gender, parental and peer influences upon science attitudes and activities
Authors: Breakwell Glynis M. , Beardsell Sue
Published: August 2002

This paper explores the extent to which variance in science attitudes and involvement in science activities may be attributable to gender, parental and peer influences upon 11-14 year olds in the UK. The data presented are derived from a sample of 391 pupils drawn at random, but stratified by age and gender, from Local Education Authority schools (i.e. schools within the state sector where parents make no direct payments for education). A self-completion questionnaire was administered to the pupils in school. Attitudes toward scientific change, involvement in scientific extra-curricular activity, liking and performance in school science subjects, and participation in peer youth culture were indexed, in addition to estimates of the amount of positive regard for science expressed by peers and parents.

Boys had more positive attitudes to science and greater levels of participation in scientific extra-curricular activities. They also reported performing better at school science than girls. A positive attitude to science was strongly positively related to having a father and mother who support science, coming from a lower socio-economic family background, being male, and having scientific peers. Greater involvement in scientific extra-curricular activities was predicted by having a father who supports science, having parents who engage in activities jointly with their children, and having scientific peers.

In terms of predicting participation in science, liking of it and success at it, these data lead to the conclusion that both parental and peer support are influential. Though it does seem that they are relatively more important in predicting variance in attitudes to science in society than as indicators of liking of or performance at school science. The problems involved in estimating whether commonly reported gender effects are mediated through peer or parental support are discussed.
Spotlighting women scientists in the press: tokenism in science journalism
Authors: Shachar Orly
Published: August 2002

Science and its practitioners have been extensively covered in the media, and research has analyzed this coverage. Yet relatively few studies have analyzed news coverage of science and scientists in a social context. This project concerns itself with the question of cultural power in the context of gendered media representation. In this study, I borrow on the concept of social tokenism and argue for its broader application for investigating journalistic discourse. In particular, I address the treatment of female scientists by science journalists as an illustration of the use of tokenistic rhetoric routines in the press. Before examining conceptualization and methodology, I provide a brief review of the portrayal of scientists as anchors in stories involved in the presentation of the scientific enterprise, including the depiction of female scientists in the news media.
Journal writing in practice: From vision to reality
Authors: English Leona M. , Gillen Marie A.
Published: August 2002

This chapter highlights the themes from the previous chapters, identifies the challenges of implementing journal writing, and offers suggestions for further reading.
Women, work, and learning
Authors: Bierema Laura L.
Published: August 2002

Women are disadvantaged when it comes to opportunity and learning. Adult educators can take steps to begin changing women's secondary status in the workplace.
New perspectives on the face in fetal alcohol syndrome: What anthropometry tells us
Authors: Moore Elizabeth S. , Ward Richard E. , Jamison Paul L. , Morris Colleen A. , Bader Patricia I. , Hall Bryan D.
Published: August 2002

Fetal alcohol syndrome (FAS) refers to the adverse effects to the fetus from prenatal exposure to alcohol. Originally, the diagnosis of FAS was given only to those individuals that were the most severely affected. Since that time, it has become apparent that the effects of prenatal alcohol exposure are broad‐based, and those individuals diagnosed with FAS represent the severe end of the continuum in their phenotypic expression. This study utilized 21 craniofacial anthropometric measurements on 100 prenatally exposed individuals to quantify the elements of the FAS facial phenotype and to extend the quantitative phenotype to individuals who exhibited less severe or incomplete manifestations of prenatal alcohol exposure. © 2002 Wiley‐Liss, Inc.
Synthesis of ultrafine titanium carbonitride powders
Authors: Monteverde Frederic , Medri Valentina , Bellosi Alida
Published: August 2002

Titanium‐carbonitride‐based materials are very hard materials with increasing technical importance. They are mainly used in composites with various metal carbides and/or metallic binders (cermets) for metal cutting operations. These applications call for the synthesis of titanium carbonitride powders with homogeneous chemical composition, as small as possible grain size and narrower grain size distribution. Nowadays on the market, only commercial submicrometric (0.5–2 μm) powders are available. Starting from blends of nanosize commercial TiN or TiO2 powders mixed with different carbon powders (carbon black, active carbon), this study aimed to set up a low‐cost process to synthesize fine and pure TiC1−X N
X powders with an X value close to 0.5. The morphology of the as‐obtained powders and the progress of the reaction were investigated by scanning electron microscopy and ­X‐ray diffraction. The stoichiometric parameter X was estimated on the basis of a TiC1−X N
X Raoultian solid solution together with Vegard's rule. The results are presented and discussed to assess relations between powder characteristics and processing conditions. The most encouraging results were obtained using a mixture TiN + 10 wt%C (carbon black) processed at 1430 °C for 3 h under flowing argon. Regularly shaped particles with limited agglomeration ranged from 100 to 300 nm and an X value close to 0.5 Copyright © 2001 John Wiley & Sons, Ltd.
Synthesis and investigation of properties of silaoxadihydrophenanthrene‐diphenylsiloxane fragments containing block copolymers
Authors: Mukbaniani O. , Samsonia A. , Karchkhadze M. , Khananashvili L.
Published: August 2002

The reaction of heterofunctional condensation of 1,1‐dichloro‐1‐sila‐2‐oxadihydrophenanthrene with dihydroxydiphenylsilane at various ratios of initial compounds in the presence of pyridine is investigated. α,ω‐Dihydroxysilaoxadihydrophenanthrene‐diphenylsiloxane oligomers with various degrees of condensation are obtained. Organosiloxane block copolymers with the regular arrangement of silaoxadihydrophenanthrene‐diphenylsiloxanes fragments in the main linear dimethylsiloxane chain are produced by the reaction of heterofunctional condensation of α,ω‐dihydroxysilaoxadihydrophenanthrene‐diphenylsiloxanes with α,ω‐dichlorodimethylsiloxanes in the presence of anhydrous pyridine, as an acceptor of hydrochloric acid. Thermogravimetry, differential scanning calorimetry, gel permeation chromatography, and wide‐angle X‐ray analysis are carried out on the synthesized block copolymers. The microheterogeneous structure of block copolymers is observed at definite values of the length of the flexible dimethylsiloxane chain by DSC and X‐ray investigation. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 9–16, 2002; DOI 10.1002/app.10045
Studies on isotactic poly(phenyl glycidyl ether)‐modified epoxy resins. I. Physical gels
Authors: Zhang Zheng , Xu Jianjun , Yu Yunzhao
Published: August 2002

Isotactic poly(phenyl glycidyl ether) (i‐PPGE) was prepared using a Teyssie catalyst. The polymer was dissolved in the epoxy resin at approximately 200°C and Gels were formed as the solutions cooled to room temperature. The gels were studied by rheological techniques, differential scanning calorimetry analysis, optical microscopy, and electron microscopy. The existence of a network in the gels was demonstrated by the nonlinear increase of the viscosity with i‐PPGE concentration and by the significant storage modulus. A high isotacticity of the polymer was essential for gel formation. The thermal history of the system showed a great influence on the network structure and on the performance of the gel. The yield stresses of the physical gels increased with the concentration of i‐PPGE. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1214–1222, 2002; DOI 10.1002/app.10444
Viscometric study on the specific interaction between proton‐donating polymers and proton‐accepting polymers
Authors: Qi G. R. , Wang Y. H. , Li X. X. , Peng H. Y. , Yang S. L.
Published: August 2002

The interpolymeric specific interaction between proton‐donating polymers (PDPs) and proton‐accepting polymers (PAPs) was studied by viscometry. The intrinsic viscosities and Schultz‐Blaschke constants were measured for the component polymers as well as for the polymeric mixture systems. The estimation of the extent of interpolymeric interaction was done with a new criterion, β, based on the relationship between the degree of complexation (DA) and the theoretical specific viscosity of the polymeric mixture (ηsp,m,cal). This method shows the interpolymeric interaction predictions to be in agreement with those found by a viscosity‐enhancement factor. According to the β criterion and viscosity enhancement factors, the octyl acrylate unit in the PDP/PAP mixture is found to make a positive contribution to the complexation between PDP and PAP attributed to its solvation and van der Waals force between side chains of the octyl acrylate unit on unlike macromolecular chains. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 415–421, 2002