bluuebunny/crossref_metadata_2025_split huggingface dataset:
Use of inverse gas chromatography to quantify interactions in anhydride cured epoxy resins
Authors: Jackson Paul L. , Huglin Malcolm B. , Cervenka Antonin 
Published: April 2003

AbstractPrevious work has shown that the inverse gas chromatography (IGC) method combined with Flory–Huggins and solubility parameter theories could be used to quantify interactions in an amine cured epoxy resin matrix. In the present communication the same procedures have been adopted for an anhydride cured epoxy resin matrix. The solubility parameter at 298 K thereby obtained for the cured resin was 20–6 (MPa)1/2, which lies between the corresponding values of 18.8(MPa)1/2 and 22.5 (MPa)1/2 for the precursors, viz. Epikote 828 (an epoxide resin) and phthalic anhydride, respectively. It was noted that great care must be exercised regarding choice of solvent used for deposition of phthalic anhydride on a glass bead support because of reaction to phthaclic acid. Similar consderations apply to the choice of probes used.
Investigations by inverse gas chromatography relevant to coated glass fibre/epoxy composites
Authors: Jackson Paul L. , Huglin Malcolm B. , Cervenka Antonin 
Published: April 2003

AbstractInverse gas chromatography has been used on two types of coated glass fibre over a range of temperatures. Interaction parameters, χ, extrapolated to 298K yielded values for the solubility parameter, δ, of 20.1 (MPa)1/2 and 23.5(MPa)1/2. After removal by combustion of the coatings, a higher value was yielded for the δ of glass. The findings, in conjunction with values of 19.8(MPa)1/2 and 20–6(MPa)1/2 for an amine cured epoxy resin and phthalic anhydride cured epoxy resin, respectively, provide a useful guide to the appropriate combination of cured resin matrix with coating with respect to optimum interfacial interaction.
Spontaneous current emission in metal‐ferrocene‐doped ethyl cellulose‐metal systems
Authors: Khare P. K. , Chandok R. S. , Dubey Neeraj , Srivastava A. P. 
Published: April 2003

AbstractSpontaneous current emission (SCE) has been studied in sandwiched different electrode configurations [metal(1)–undoped/doped ethyl cellulose (EC)–metal (1)/(2)] as a function of heating rate, film thickness and dopant concentration in the temperature range 40–200°C. The magnitude and direction of current depend on the combination of electrode metals. SCE thermograms for the Al undoped/doped EC–AI system exhibit two well resolved transition at 110 and 160°C in opposite directions to each other. The phenomena related to these transitions are explained in terms of creation of field at the interfaces and field produced in the bulk of the material. No negative direction transition was observed for electrode systems like Ag–Ag, Pb–Pb, Sn–Sn and Au–Au except for a shoulder of a peak around 100°C. When dissimilar electrode systems (i.e. Al–undoped/doped EC–Ag/Pb/Sn) are used, the current rises and then saturates beyond around 160°C.
Morphology and crystallization of poly(ethylene terephthalate)
Authors: Al Raheil Ismail Ahmad M. 
Published: April 2003

AbstractThe melting behaviour and the morphology of poly(ethylene terephthalate) crystallized from the melt are reported. In general, dual or triple melting endotherms are seen, and single endotherms are seen when the samples are crystallized above 215°C for long times. The location of the uppermost endotherm was found to be constant below Tc = 230°C, and above that temperature the location depends on Tc. Therefore, we have shown that samples of PET which are crystallized above Tc = 230°C contain perfect crystals only; below Tc = 230°C, they contain perfect and imperfect crystals. Scanning electron microscopy showed that the perfect crystals are the dominant lamellae in the spherulitic structure, while the imperfect crystals are the subsidiary lamellae in the spherulitic structure, The amorphous regions are located between individual lamellae.
Light scattering study of the swelling process of poly(acrylonitrile‐co‐butene)‐graft‐poly(acrylonitrile‐co‐methylacrylate) film
Authors: Goto A. , Kuwahara N. , Sato H. , Kubota K. 
Published: April 2003

AbstractThe time evolution of the size and density of the swollen domains during the swelling of poly(acrylonitrile‐co‐butene)‐graft‐poly(acrylonitrile‐co‐methylacrylate) film in methanol was studied by light scattering measurements. The observed scattered light intensity was analyzed by the Guinier plot. The time evolution of the mean radius R(t) and number density N(t) of the swollen domains was given by R(t)3 ∼ t0.12 and N(t) ∼ t1.42.
Synthesis and characterisation of two novel cyanosilicones
Authors: Cameron G. G. , Derouiche Y. , Hirabayashi T. , Lazare P. , Reid J. , White I. M. 
Published: April 2003

AbstractTwo new cyanosilicones, poly[(dicyanopropyl)dimethylsiloxane] A and poly[(dicyanopentyl)dimethylsiloxane] B, have been synthesised by reaction of the corresponding disilanols with phosgene generated in situ from triphosgene. Both polymers show glass‐to‐rubber transitions at about 250K and crystalline melting points at about 310K. Polymers A and B undergo thermal decomposition at 410 and 550K respectively.
Some of the dielectric properties of starch
Authors: Moteleb M. M. Abdel 
Published: April 2003

AbstractThe dielectric constant and dielectric loss were determined for solid starch free of and contaminated with sodium chloride over a frequency range of 0.1–10 000 kc/s at temeperatures from 10 to 60°C. The results are compared with those of cellulosic fibers. At high frequency both starch and cellulosic fibres exhibit a dielectric dispersion and loss peak. The chain flexibility of starch has a decided effect on the locationof the peak. The low frequency absorption appears only when starch is contaminated with sodium chloride, which modifies the dielectric properties of the starch sample.
Dynamic mechanical properties of isotactic PMMA
Authors: Katime Issa , Calleja Ricardo Diaz 
Published: April 2003

AbstractThe aim of this paper is a comparison of the dynamic mechanical behaviour of amorphous and partially crystallised isotactic PMMA. Parameters are proposed that affect the different relaxations that appear in the dynamic mechanical isochronal spectra. It has been found that the temperature of the maximum of the loss tangent, as well as the activation energy, is higher for the totally amorphous polymer. The beta‐relaxation appears clearly in the case of the completely amorphous polymer, with an activation energy of 105kJ/mol; this relaxation cannot be found for the semicrystalline polymer.
Polymerization of methyl methacrylate with metal acetylacetonates and triethylaluminum catalysts
Authors: Endo Kiyoshi , Inukai Akihiro , Otsu Takayuki 
Published: April 2003

AbstractPolymerization of methyl methacrylate (MMA) with metal acetylacetonates, especially vanadium (III) acetylacetonate [V(acac)3], in combination with AIEt3 was studied. V(acac)3–AIEt3 catalyst could initiate the polymerization of MMA, although other Mt(acac)xs are also effective. It was found that the polymerization of MMA with V(acac)3–AIEt3 catalyst proceeded through a coordination mechanism, from the results of copolymerization with styrene and polymerization in the presence of radical inhibitors. The resulting polymers were found to form stereocomplexes in acetone. Based on these results, it is concluded that multi‐active sites in the polymerization of MMA with V(acac)3–AIEt3 catalyst were produced.
Polymerization of allylthiourea by constant current electrolysis
Authors: Özkan Hülya , Usanmaz Ali , Önal M. Ahmet 
Published: April 2003

AbstractAllylthiourea was polymerized by constant current electroinitiation in acetonitrile using tetrabutylammonium fluoroborate as supporting electrolyte. The polymer obtained was insoluble in common organic solvents. FTIR studies showed that polymerization propagates by addition through the C=C double bond. The cyclic voltammogram of the monomer gave two irreversible oxidation peaks at + 1.3V and + 2.4V versus Ag°/Ag+ reference electrode at 25°C. Polymerization at room temperature gave a limiting conversion of about 10% for 2mA current and 30% for 5mA current, in acetonitrile. Higher initial rates were obtained when dichloroethane was used as solvent.
Transient currents in poly(vinyl alcohol)–poly(vinyl pyrrolidone) polymer blend films
Authors: Narayana K. Lakshmi , Dasaradhudu Y. , Rao V. V. R. Narasimha 
Published: April 2003

AbstractTransient currents (charging and discharging currents) in poly(vinyl alcohol) (PVA)–poly(vinyl pyrrolidone) (PVP) polymer blend films were measured over the temperature range 30–150°C at field strengths of 2.32–23.2 × 106 Vm−1. Polymer films were prepared by the isothermal immersion technique. Activation energies were evaluated from quasi‐steady‐state currents. A single relaxation peak was observed both from isochronal currents and low frequency dielectric relaxation. Activation energies evaluated from these two methods are found to be in fairly good agreement. The polarization is considered to be due to space charge origin along with some contribution from dipolar groups. The maximum loss was observed in Sample I (PVA: PVP = 25:75), suggesting maximum heterogeneity in this blend ratio.
Immobilization of urease and estimation of effective diffusion coefficients of urea in HEMA and VP copolymer matrices
Authors: Demircioǧlu Hüsniye , Beyenal Haluk , Tanyolaç Abdurrahaman , Hasirci Nesrin 
Published: April 2003

AbstractEnzyme urease was immobilized in copolymer matrices of 2‐hydroxyethyl methacrylate (HEMA) and N‐vinyl pyrrolidone (VP). The activities of immobilized urease stored in phosphate buffer solution of pH 7.0 at 4°C were examined periodically for up to 90 days. For the matrices of higher VP/HEMA mole ratio in the structure, a higher volume increase and enhanced apparent activity were observed, while HEMA polymer alone proved to have the most stable matrix for prolonged activity. No appreciable amount of enzyme leakage was experienced for any of the matrices prepared. The effective diffusion coefficients of urea through these polymer matrices were calculated with a ‘diffusion and reaction’ model and the highest effective diffusion coefficient was found with pure HEMA matrix, possibly due to its laminated structure.
Electrical conductivity in iodine‐doped ethyl cellulose
Authors: Khare P. K. , Keller J. M. , Gaur M. S. , Singh Ranjeet , Datt S. C. 
Published: April 2003

AbstractThe electrical conductivity of solution‐grown ethyl cellulose (EC) films, 5–30 μm thick, has been studied in the sandwich configuration (metal–EC–metal) as a function of iodine concentration from 0.5 to 5.0 wt% ratio. The studies were conducted in the temperature range 333–383 K, while the field was varied over the range (3.0–5.5) × 104V/cm. Aluminium was used as the lower electrode, while the upper electrode was of Al, Ag, Cu, Au or Sn. Certain transient effects such as a large burst of current immediately after the application of field were observed. An attempt was made to identify the nature of the current by comparing the observed dependence on electric field, electrode material and temperature with the respective characteristic features of the existing theories of electrical conduction. The results show that the electrical conduction follows Ohm's law at lower fields, while at higher fields, space‐charge limited current (SCLC) was observed. It was also found that Richardson–Schottky emission was responsible, to some extent, for the transport of charge carriers in the polymer. The conductivity of the films increased on doping with iodine. The dopant molecules are considered to act as additional trapping centes and provide links between the polymer molecules in the amorphous region, thus resulting in the formation of charge transfer complexes.
Synthesis and characterization of cryogenic adhesives based on epoxy‐modified polyurethane resin systems
Authors: Ma Chen‐Chi M. , Hsia Hung‐Chung , Chen Der‐Shyang , Li Ye‐Shiu , Li Ming‐Shiu 
Published: April 2003

AbstractPolyurethane adhesives containing the polyether backbone exhibit a good joint strength in cryogenic environments. In practice, many of the commercially available polyurethane adhesive systems contain free or chemically blocked isocyanates which have some limitations. This study presents the synthesis and characterization of a modified polyurethane type adhesive. Glycidol was used to convert the isocyanate‐terminated polyurethane prepolymer to glycidylterminated polyurethane prepolymer. A series of glycidyl‐terminated polyurethanes, based on polyoxypropylene glycol (PPG) soft segments having different molecular weights, were synthesized and their adhesive properties on aluminium were evaluated. The effect of the soft segment length on adhesion was examined.The adhesive properties at room temperature and cryogenic temperature are in line with the phenomenon observed in dynamical mechanical analysis (DMA) and in the phase separation behavior of the polyurethanes. Differential scaning calorimetry (DSC) was used to assess the phase separation content. An improvement in the adhesive strengths at room temperature is achieved by adding epoxy resins to the glycidyl‐terminated polyurethane resins.
Polyether and polyester polyol based glycidyl‐terminated polyurethane modified epoxy resins: Mechanical properties and morphology
Authors: Li Ye‐Shiu , Li Ming‐Shiu , Ma Chen‐Chi M. , Hsia Hung‐Chung , Chen Der‐Shyang 
Published: April 2003

AbstractA glycidyl‐terminated polyurethane prepolymer was synthesized and used to enhance the properties of epoxy resins. Some properties of glycidyl‐terminated PU/epoxy with polyether based (PPG) and polyester based (PBA) glycidyl‐terminated PU were investigated in this research. The polyether based glycidyl‐terminated PU(PPG) modified epoxy resin proved to be superior to conventional epoxy resins in improved impact strength and fracture energy, but not tensile strength, tensile modulus, flexural strength and flexural modulus. On the other hand, the polyester based glycidyl‐terminated PU(PBA) modified epoxy resin had increased mechanical properties while showing slight variation of impact strength and fracture energy. Different mechanisms for this behaviour are advanced in this paper.
Study of polystyrene–polyethylene IPN system by the spin probe method
Authors: Tiňo J. , Borsig E. , Hloušková Z. , Fiedlerová A. 
Published: April 2003

AbstractThe spin probe method has been used to study the structure and molecular mobility of PS–PE IPN with various ratios of PS:PE. The dependence of the correlation times of motion of the spin probe and the linwidths of the EPR spectra on the composition of the IPN system and its thermal processing has been studied. The results imply that rotation correlation time of the probe is highest at the ratio PS:PE 1.5:0.5 and lowest at the ratio 0.75:1.25. The value of τ decreases with decreasing content of PS. At the transition from the ratio PS:PE 1.25:0.75 to 1:1 τ decreases sharply to a value close to the correlation time of PE. In the temperature range 173–373 K there are two domains which differ in molecular mobility. At temperatures above Tm of PE, heterogeneity is observed for samples with ratio of PE 1 or 0.75. Annealing at 473 K makes the samples homogeneous, which means that mixing of the chains of both polymers is observed in the interpenetrating regions.
Plastic zone radius of crosslinked bismaleimide resins
Authors: Pritchard Geoffrey , Swan Martin , Rose R. G. 
Published: April 2003

AbstractThere appear to be very few literature estimates of the size or the shape of the plastic zone in polybismaleimides, whether calculated or observed experimentally. Bismaleimides are characteristically much more brittle on a macroscopic scale than other thermosetting resins and might be expected to have exceptionally small plastic zone radii. In this paper, experimental investigations are described, which conclude that the plastic zone must be much smaller in bismaleimides than in epoxies, even after rubber toughening, and before the network is fully developed by postcure. No direct observation of the zone radius could be made, but model calculations were carried out using Irwin, Dugdale, Tresca and von Mises expressions. The estimated zone radii declined with cure time, and became more or less negligible for all except the highest rubber concentrations after postcure. Plane stress models gave higher radii than plane strain ones. The very small calculated plastic zones of bismaleimides were consistent with the low observed ratio of tensile to compressive strength. This ratio implies marked resistance to yielding compared with that to crack propagation, and suggests a morphology consisting of exxtensive regions of continuous, rigid crosslinked structures, with minimum scope for shear.
Partial specific volume of poly(D‐β‐hydroxybutyrate) in chloroaliphatic solvents
Authors: Bakoš Dušan , Ortega Francisco , Hernández‐Fuentes Irmina 
Published: April 2003

AbstractPartial specific volumes, v02, of poly(D‐β‐hydroxybutyrate), PHB, were determined by density measurements in several chloroaliphatic hydrocarbons. We observed that v02 of PHB in tetrachloroethane is influenced only very little by temperature. This can be generalized for the group of solvents used. The experimental results are comapred with the data obtained theoretically using the concept of additivity of group contributions.
Study of transient currents in discharging mode in pure and iodine doped ethyl cellulose films
Authors: Khare P. K. , Chandok R. S. 
Published: April 2003

AbstractA study of transient currents in discharging mode in vacuum aluminized pure and iodine doped ethyl cellulose (EC) films, approximately 20 μm in thickness, measured at various temperatures (303–353K) and applied fields (2.0 × 104−4.5 × 104 V/cm) is described. The order of current has been found to increase considerably with increase in poling temperature, field and iodine mixing. The currents have been found to show I ∝︁ t−n (i.e. Curie–Von Schweidler law) time dependence with different slopes in the short and long time regions. The conductivity of the films is increased on doping with iodine. The dopant molecules are considered to act as additional trapping centres and provide a link between the polymer molecules in the amorphous region, thus resulting in the formation of a charge transfer complex. The results of the experiments and the mechanisms involved are discussed on the basis of available theories.
Polymerization of 1,3‐butadiene with MgCl2‐supported cobalt catalysts activated by ordinary alkylaluminums
Authors: Takeuchi Masaki , Shiono Takeshi , Soga Kazuo 
Published: April 2003

AbstractMgCl2‐supported CoBr2 catalysts were prepared from mixture of MgCl2 and CoBr2L2 (L = triphenylphosphine or pyridine) in toluene. Polymerization of 1,3‐butadiene was conducted over the catalysts combined with ordinary alkylaluminums as cocatalyst. The CoBr2(PPh3)2/MgCl2 catalyst gave polybutadiene with approximately 80% of 1,2 units, whereas cis‐1,4‐poly‐butadiene was obtained with the CoBr2(C5H5N)2/MgCl2 catalyst.Addition of triphenylphospine to the latter catalyst caused a marked increase in the content of 1,2 units. The content of 1,2 units could be thus controlled in the range from 0 to 80% by changing the amount of triphenylphosphine.On the other hand, the CoBr2(PPh3)2/MgCl2 catalyst with very low content of CoBr2(PPh3)2 hardly displayed any activity. Addition of dimethoxydiphenylsilane to the catalyst gave polybutadiene containing 90 % of 1,2 units with a fairly high activity.
Preparation and thermal characterization of graft copolymer obtained by radiation grafting of individual and binary monomer systems
Authors: Osman Massarat B. S. , Hegazy El Sayed A. , Mostafa Abo El‐Khair B. , Abdel‐Maksoud Afaf M. 
Published: April 2003

AbstractGraft copolymers were obtained by radiation‐induced grafting of vinyl acetate (VAc) and N‐vinylpyrrolidone (NVP) individually and in binary mixture on to polypropylene (PP) films. The effect of some grafting conditions on the grafting yield was determined. The addition of Cu2Cl2 as inhibitor to the reaction medium inhibited the homopolymerization of the comonomer. The grafting process was remarkably enhanced by using dioxan as a diluent compared with other solvents used. The addition of some inorganic salts has a great influence on the individual grafting of both monomers. The gel percent in the graft copolymer was determined; it increased as the grafting yield increased. The swelling behaviour and electrical conductivity for the grafted films slightly increased by grafting. The changes in thermal parameters such as glass transition (Tg), melting (Tm) and recrystallization (Trc) temperatures and heats of melting (ΔHm) and recrystallization (ΔHrc) of the graft copolymers were also followed by differential scanning calorimetry (DSC). These thermal parameters of PP were varied by grafting with VAc and NVP and depend on the graft yield, which reflects the change in its crystalline domains and formation of crosslinks in the graft chains. The heat of recrystallization of the graft copolymer by cooling from the molten state decreases by grafting which is a good indication of crosslink formation, since crosslinking decreases the crystallizability of the polymer matrix.
Synthesis of ultra‐high molecular weight polyacrylonitrile with highly isotactic content (mm > 0.60) using dialkylmagnesium/polyhydric alcohol system as catalyst
Authors: Nakano Yasuhiro , Hisatani Kunio , Kamide Kenji 
Published: April 2003

AbstractAn attempt was made to synthesize a catalyst having high activity for synthesis of highly isotactic polyacrylonitrile (PAN) with high molecular weight by anionic polymerization. The reaction products of di‐n‐hexylmagnesium [(n‐C6H13)2Mg] with alicyclic alcohols such as 1,4‐cyclohexanediol or 1,5‐decalindiol were found to be effective as polymerization catalysts for preparation of PAN samples whose triad isotacticity [the content of mm (m, meso configuration)] is about 0.64 and viscosity‐average molecular weight (Mv) exceeds 1 × 105. The triad tacticities [mm, mr, and rr contents (r, racemo configuration)] of the polymers obtained were analysed by 13C NMR and their Mvs were determined by viscometry in dimethylsulphoxide at 25°C using Kamide et al.'s Mark–Houwink–Sakurada equation.Mv of PAN increased significantly by after‐treatment of the catalysts, prepared from (n‐C6H13)2Mg and alicyclic alcohols, with triethylalyminium (Et3Al). Ultra‐high molecular weight PAN samples ranging in Mv from 2 × 106 to 6 × 106 [(mm) = 0.57–0.66] were obtained in anisole at 135°C by using the above catalyst system. A main role of Et3Al in these catalyst systems is considered to reduce, in advance, OH groups on the catalyst, resulting in a significant suppression of termination reactions of propagating PAN chains during the polymerization.
Mixing of rubber and viscoelasticity—III. Viscoelastic characterization of gum rubber
Authors: Nakajima N. 
Published: April 2003

AbstractThis paper is the third in a series where the author attempts to provide scientific interpretation for mixing of rubber. Each gum rubber exhibits its own characterstic behavior during mixing. In the previous paper, the behavior was identified with viscoelastic properties and failure. This paper describes characterization of gum rubbers based on viscoelastic properties.Methods of describing deformation are discussed with a proposal to use material functions for the present purpose. Non‐linear viscoelasticity is discussed with a proposal to use a particular linearization scheme. The conventional characterization methods are discussed concerning the limitations and shortcomings of dilute solution methods and the Mooney index. The linearization scheme is applied as the characterization method most suitable for gum rubbers. A number of examples are given to demonstrate the effectiveness of this characterization method in relating the results to molecular architecture. Finally, the discussion covers processability of gum rubbers and their molecular structure.