bluuebunny/crossref_metadata_2025_split huggingface dataset:
Light scattering studies of aqueous solutions of a new flocculation agent from polyacrylonitrile and dicyandiamide
Authors: Dautzenberg Herbert , Gohlke Ulrich , Rother Gudrun 
Published: April 2003

AbstractThe molecular parameters of the flocculation agent from polyacrylonitrile and dicyandiamide (PAN‐DCD) were determined in dimethylsulfoxide. In acidic and alkaline aqueous solutions (0.1 N) PAN‐DCD is weakly aggregated, additionally a small fraction of polymer exists as highly aggregated particle component. A shift of the pH‐value in direction to the neutral range leads immediately to particle growth, which is finished at pH 3, coming from the acidic range and pH 10, coming from the alkaline one. After the passage of the neutral range disaggregation occurs. Flocculation can also be induced by addition of salt.The structural parameters of the particles were determined by a detailed analysis of the light scattering curves. Results obtained give information about the flocculation mechanism.
Highly dispersed Ni catalysts on carbon from thermal decomposition of cellulose‐hydrous nickel gel membrane
Authors: Ishiyama Jun‐ichi , Shirakawa Tetsuo , Kurokawa Yoichi , Imaizumi Shin 
Published: April 2003

AbstractUltra fine particles were impregnated by using a finely porous cellulose gel membrane. The impregnated gel membrane is a green transparent one and looks like a solid solution. Highly dispersed Ni catalysts on carbon were obtained from thermal decomposition of these gel membranes. The particle size is in the range of several nm to a few ten nm. They show interesting catalytic properties for hydrogenation of olefins such as cyclooctadiene.
Selective ethylene adsorbent composed of copper(I) chloride and polystyrene resin having tertiary amino groups
Authors: Komiyama Makoto , Kurima Kazunori , Hirai Hidefumi 
Published: April 2003

AbstractSelective adsorbent for ethylene is prepared from copper(I) chloride and a macroreticular type polystyrene resin having tertiary amino groups. The adsorbent rapidly adsorbs ethylene at 20°C under 1 atm. The adsorbed ethylene is readily desorbed by subjecting the adsorbent to a reduced pressure (3 mm Hg) at 20°C. The ethylene adsorbing capacity of the adsorbent is 5.5 times as large as the adsorbing capacity for ethane. The present adsorbent exhibits no measurable adsorptions of nitrogen and hydrogen at 20°C under 1 atm, and thus is applicable to selective separation of ethylene from mixtures containing these gases and ethane.
Styrene‐divinylbenzene copolymers. VI. Porosity formation in the presence of toluene‐cyclohexanol mixtures as inert diluents
Authors: Okay Oǧuz 
Published: April 2003

AbstractPorosity formation by suspension copolymerization of styrene‐divinylbenzene (S‐DVB) in toluene‐cyclohexanol mixtures was investigated. The total porosity of the copolymers increases and their volume swelling ratio in toluene decreases as the DVB concentration in the starting monomer mixture increases and the solvating power of the polymerization medium decreases. The volume fraction of the diluent separated out of the network phase, vD, was found to be constant after passing a critical amount of DVB and the diluent. The limiting value of vD is only dependent on the solubility parameter difference of the polymer and the diluent. Thus, if sufficient amounts of DVB and diluent are present during the network formation, the maximum porosity of S‐DVB copolymers can be predicted from the solubility parameters of the components.
Styrene‐divinylbenzene copolymers. VII. Stability of the porous structures formed in toluene — cyclohexanol mixtures
Authors: Okay Oǧuz 
Published: April 2003

AbstractThe pore stability of styrene‐divinylbenzene (S‐DVB) copolymers prepared in toluene‐cyclohexanol mixtures as inert diluents was investigated as a function of the DVB concentration, diluent composition, and dilution. The stability of the porous structures increases with increasing DVB concentration and, to some extent, with increasing dilution. At a fixed degree of equilibrium volume swelling in toluene, the pore stability also increases with increasing with increasing solvating power of the diluent. The density of S‐DVB copolymers increases during the sulfonation reaction with chlorosulfonic acid, but the stability of porosity remains unchanged.
Zero‐shear viscosity of dilute to moderately concentrated solutions of cellulose acetate phthalate
Authors: Sinha Vijay K. , Patel Kirit H. , Trivedi Harikrishna C. 
Published: April 2003

AbstractThe zero‐shear viscosities of dilute to moderately concentrated cellulose acetate phthalate solutions in DMF were measured at different temperatures and the viscosity data were analyzed in terms of Martin's and Fedor's relationships. The [η] values obtained due to the relationships of Martin and Fedor were found to be in very good agreement. The viscosity‐concentration data were also generalized in terms of reduced variables. The temperature dependence of viscosities was expressed by the Frenkel‐Eiring equation and the free energy of activation (ΔGv), heat of activation (ΔHv), and entropy of activation (ΔSv) of the viscous flow of polymer solutions were calculated. It has been observed that the activation energy for viscous flow increases and the activation entropy decreases with concentration of polymer solutions.
Copolymerization of acrylonitrile with maleamic acid derivatives and with carboxyphenylmaleimide
Authors: Elsabee Maher Z. , Mikhael Michael G. , Sabaa Magdy W. , Yassin Ahmady A. 
Published: April 2003

AbstractAcrylonitrile was copolymerized with two N‐arylmaleamic acids and with N‐3‐carboxyphenylmaleimide in dimethylformamide (DMF) using azobisisobutyronitrile as initiator. The reactivity ratios and the Q‐e parameters of these monomers were estimated, and the resulting copolymers were characterized by viscosity measurements and thermal analysis. Thermogravimetry and differential thermal analysis data showed an improvement in the thermal behaviour of the investigated copolymers compared with that of poly(acrylonitrile). Mechanisms illustrating the role of both the acidic group and the maleimide ring in the nitrile oligomerization were proposed. The produced copolymers showed an excellent affinity towards basic dyes and better color fastness towards UV light.
Cyclodehydration of bismaleamic acids
Authors: Varma I. K. , Tiwari Ranjana 
Published: April 2003

AbstractThe paper describes thermal and chemical cyclodehydration studies of bismaleamic acids prepared by reacting 4,4′‐diaminodiphenyl methane (DADPM), 4,4′‐diaminodiphenyl ether (DADPE), and 3,3′‐diaminodiphenyl sulfone (DDS) with maleic anhydride and 3,3′,4,4′‐benzophenone tetracarboxylic acid dianhydride. Thermal cyclisation was carried out by heating the bismaleamic acids at 120 – 140°C for 1 – 4 h. Chemical cyclisation was carried out by treating the bismaleamic acids with NaOAc/Ac2O to give bismaleimides BTM, BTE, and BTS, respectively. The products of thermal and chemical cyclisation were characterized by determination of acid number. Percentage conversion of bismaleamic acid to imide was found to be higher at higher temperatures for the same duration of thermal treatment. Elemental analysis and acid number indicated incomplete cyclisation of bismaleamic acid on thermal treatment. IR spectra of samples confirmed the disappearance of amide groups on cyclodehydration. In DSC traces of bismaleamic acids a broad endothermic peak due to imidization reaction was observed. Thermogravimetric analysis of uncured and isothermally cured samples was carried out in nitrogen atmosphere. Improvement in thermal stability was observed on curing.
Studies on aqueous polymerization of acrylonitrile. Peroxodisulfate‐thiourea redox system
Authors: Misra M. , Mohanty A. K. , Singh B. C. 
Published: April 2003

AbstractAn investigation on kinetics of aqueous polymerization of acrylonitrile (AN) initiated by peroxodisulfate‐thiourea redox system has been carried out in the temperature range of 40° to 50°C. The concentration effect of thiourea, monomer, peroxodisulfate on polymerization rate and percentage of conversion has been studied. The effect of some inorganic salts and different organic solvents on polymerization rate has also been investigated. The isolated polymer has been characterized by IR spectra. A suitable kinetic scheme has been proposed and appropriate rate expressions have been derived and explained in the light of experimental findings.
Shape‐memory pore structure in porous crosslinked polystyrenes
Authors: Takeda Kunihiko , Akiyama Minoru , Yamamizu Takafumi 
Published: April 2003

AbstractPorosity of porous crosslinked polystyrenes was examined by the pressurized‐mercury intrusion method. Various aftertreatments of those polymers revealed interesting results of behaviors of “fixed pores”, whichS indicates pores measurable by this method: (1) fixed pores were found to diminish or vanish by swelling them with ethylene dichloride (EDC) as a good solvent or by heating them above the glass transition temperature (Tg), but (2) those pores were observed to reappear after the polymers treated above were swollen again with EDC, followed by replacing EDC with methanol as a poor solvent. This implies that the fixed‐pore structure has been memorized like a shape‐memory alloy.
Solvent/nonsolvent solubility and polarity parameters in fractional separation of oligomers 2. Styrene‐acrylic acid copolymers
Authors: Spychaj Tadeusz , Hamielec Archie E. 
Published: April 2003

AbstractStyrene‐acrylic acid (St‐AA) low molecular weight copolymers (M̄w < 15,000) synthesized at high temperatures (230 – 300°C) in a continuous stirred tank reactor were fractionally precipitated in solvent/nonsolvent systems. Fractional precipitation experiments were done in the system methanol‐dichloromethane/hexane to remove residual monomers and the lowest molecular weight oligomers (1st step). Solubility limits of St‐AA copolymers as a function of copolymer composition were determined using the same solvent/nonsolvent system in the 2nd step of precipitation tests (cloud point base). GPC on Styragel‐type columns, low‐angle laser light scattering (LALLS), and volumetric titration of carboxylic groups were applied for copolymer characterization. Two solvent‐derived parameters the total solubility parameter δT and the polarity index P′ are used to determine the solubility diagrams of St‐AA low molecular weight copolymers.
A novel method for vinyl grafting onto cotton fabric using ceric‐cellulose thiocarbonate redox system
Authors: Hebeish A. , El‐Sisi F. , Hafiz S. A. Abdel 
Published: April 2003

AbstractTreatment of cotton fabric with carbon disulphide in presence of NaOH resulted in cellulose thiocarbonate. The latter formed a complex when treated with ceric ammonium nitrate (CAN). After being thoroughly washed, the CeIV cellulose thiocarbonate was capable of initiating vinyl graft polymerization onto cotton fabric without homopolymer formation. The graft yield obtained with methyl methacrylate was found to increase by increasing CAN from zero to 50 mmol/l at temperatures from 60 to 80°C. Grafting was greatly favoured at pH 2; alkaline pH offset grafting. Incorporation of up to 7% of methanol, ethanol, or isopropanol in the aqueous polymerization medium enhanced grafting significantly with the certainty that the highest graft yield was obtained with isopropanol; using higher alcohol percentages decreased grafting. The rate of grafting showed an initial fast rate followed by a slower rate; 60 minutes reaction time proved appropriate for grafting irrespective of the condition used. In addition to methyl methacrylate the ability of CeIV‐cellulose thiocarbonate to induce grafting of acrylonitrile and acrylamide was also examined. The rate of grafting followed the order methyl methacrylate > acrylonitrile > acrylamide.
Interface distribution functions of diluted polymer systems containing core fibrils
Authors: Schöller Thomas , Fiedel Heinz‐Werner , Wenig Werner 
Published: April 2003

AbstractInterface distribution functions have been evaluated from the equatorial small angle x‐ray scattering of blends of isotactic polypropylene and poly(1‐butene) crystallized in the shear field of the oriented melt. The samples contain core fibrils which represent a diluted system with respect to their distance statistics. It is shown, that interface distribution functions can be calculated from only two interfaces (diffuse phase boundaries between fibrils and amourphous phase). The calculated thicknesses agree well with values determined from other methods.
Saponification kinetic study of mica‐acrylonitrile graft copolymers
Authors: Prasad M. P. , George Anne , Radhakrishnan Ganga , Rao K. Panduranga 
Published: April 2003

AbstractKinetics of alkaline hydrolysis of mica‐acrylonitrile graft copolymers was studied. The dependence of alkali concentration and the time of hydrolysis on the degree of saponification was determined. Chemical and spectroscopical techniques were used to determine the mechanism of hydrolysis.
Pigmented and transparent, highly impact‐resistant PVC for outdoor use
Authors: Hepp Dieter 
Published: April 2003

AbstractBased on the high standard of quality of EVA‐modified PVC, Hüls has developed an impact‐modified acrylate‐base PVC which can be processed over a wider range, thus meeting the high demands made with regard to processability.The excellent light stability and resistance to weathering of this material, with its technological properties being retained at the same time, were achieved in white and brown pigmentation within a wide range of stabilizations. This is supported by comprehensive findings from open‐air weathering stations located in various climate zones as well as by findings obtained from Weather‐Ometer and QUV testing.One phenomenon which has been observed in connection with white‐pigmented PVC, but which has been accorded little attention in the technical literature, is the discolouring of weathered samples when stored in a dark room. This phenomenon, which can also be simulated in a Weather‐Ometer, has an impact on the evaluation of PVC materials for out door usage and of ten leads to false conclusions.In addition to this pigmented, impact‐resistant PVC Hüls has also developed a highly transparent, impact‐resistant PVC for out door use which is also acrylate‐modified. Here the selection of stabilizers and of the graft copolymer is limited from the beginning due to the high demands made with regard to the technological properties of the final product, i.e. light stability and resistance to weathering, high transparency as well as impact resistance. Despite this, Hüls has been successful in developing an impact‐modified graft polymer which, when suitably compounded, meets the exacting requirements made by the market.
Der einfluß der luftfeuchte bei der verfärbung von PVC während der bewitterung und bei der anschließenden dunkellagerung
Authors: Trubiroha Peter 
Published: April 2003

AbstractDer Einfluß der relativen Luftfeuchte auf die Lichtechtheit und beim Nachdunkeln von weißem PVC und besondere Veränderungen der bestrahlten Oberflächen werden beschrieben. Die Ergebnisse zeigen, daß das Grenzflächenklima an der bestrahlten Probenoberfläche einen entscheidenden Einfluß auf das Alterungsergebnis hat.
Contribution to polyethylene photooxidation
Authors: Gugumus F. 
Published: April 2003

AbstractThe hydroperoxides formed on thermal oxidation of polyethylene have been used to examine their photolysis. The kinetics and mechanisms of the photolytically induced decomposition of these hydroperoxides are considered. The difficulties encountered with the mechanism based on homolysis of the hydroperoxy bond are discussed. New mechanisms of hydroperoxide photolysis based on bimolecular reactions are proposed. They are in agreement with the products found experimentally ‐ mainly ketones and trans‐vinylene groups ‐ and with the kinetics of the product formation. The mechanisms envisaged are easily adapted to polyolefins other than polyethylene and polymers in general.
Natural ageing of high impact two phase styrene‐copolymer‐systems
Authors: Karaenev S. , Nikolova S. , Dobrewa D. , Tschilingirian M. 
Published: April 2003

AbstractDie Aufgabe der hier vorliegenden Arbeit ist es, die atmosphärische Alterung der schlagfesten Zweiphasen‐Styrol‐Copolymere in Abhängigkeit von der Monomerzusammensetzung der Matrix sowie der Art und Menge des Kautschuks zu untersuchen. Zu diesem Zweck wurden BS, ABS, MBS und PS, SAN untersucht, die in der Zusanmensetzung des Monomers der Matrix zveim der Zweiphasensysteae entsprechen (BS und ABS).Aus der Interpretation tier aufgenoi;mienen Daten wurde festgestellt, der eine ßorrelation zwischen den Strukturveränderungen, der Kerbschlagezähigkeit und der ßiegefestigkeit besteht. Die durchgeführten Untersuchungen zeigen den deutlich schwierigen Charakter der Alterungsprozesse der phasenheterogenen Systeme im Vergleich zu den Homopolyneren und homogenen Copolymeren. Die Schlußfolgerungen können zur Vorauswahl des Typs und der Henge des Stabilisators in Abhängigkeit von der Honomer‐ und Phasenzusammensetzung der Systeme herangezogen werden.
Neueste ergebnisse ueber die stabilisierung von polyurethan‐systemen gegen photooxidative einfluesse
Authors: Stohler Felix R. , Berger Kurt 
Published: April 2003

AbstractAfter a few general remarks with regard to degradation of polyurethanes under the influence of light, some new results considering the stabilization of such systems will be treated. Apart from a comparison between aromatic and aliphatic one component systems for textile coating, the main subject of this paper is the light stabilization of integral‐PUR foams as well as the stabilization of thermoplastic polyurethane. New fully liquid systems as light stabilizers for PUR may be of special interest.
Simulation des natürlichen hagelschlags an transparenten kunststoffplatten
Authors: Hennig J. , Lehmann J. , Zaengler G. 
Published: April 2003

AbstractNatural hail impact tests are scarcely available because hailstorms are limited to a small area and cannot be predicted regarding time, place and intensity. Therefore we relied on laboratory tests simulating natural hailstones by polyamide balls (5‐50 mm dia.) whose final velocity could be varied according to meteorological data. So the influence of diameter (weight) and velocity of the artificial hailstones could be taken into consideration independently.The energy of damage or equivalent natural hailstone diameter were determined for 16 mm double skin sheet from PMMA as 0.2 J (14 mm dia.) for star shaped cracks and 2 J (26 mm dia.) for holes. These values do not significantly decrease after 10 years weathering. 10 mm double skin sheets from PC show an extremly high energy of damage of abt. 10 J (38 mm dia.) which decreases to a medium level of 2 J (26 mm dia.) after several years weathering. This decrease is remarkably reduced by weather resistant protective coating.As hailstorms consist to more than 80% of hailstones below 10 mm dia. (0.04 J) the mentioned sheet materials are quite hail resistant also after long weathering periods, but they cannot withstand an extreme hail catastrophe as in Munich July 12, 1984.
Some special aspects of thermal ageing of isotactic polypropylene (measuring method: Isothermal long‐term DTA)
Authors: Steiner G. , Koppelmann J. , Schwarz Th. 
Published: April 2003

AbstractThermo‐oxidative ageing processes were investigated in films (100 μm thick) made from isotactic polypropylene with different antioxidant concentrations between 0% and 0.1% using isothermal long‐term differential thermal analysis (ILDTA). The end of the oven life of polypropylene coincided with the loss of mechanical properties which was confirmed by tensile tests at temperatures far below the crystallite melting range. Already prior to the beginning of autocatalytic decomposition, ILDTA experiments permits conclusions to be drawn on the thermal history of the specimens and statements made regarding the end of thermo‐oxidative stability of the polymer, which is accompanied by a deterioration in the mechanical properties.In consequence of the correlation between oxidation time and antioxidant concentration the local antioxidant concentration in sheets or films can be measured by ILDTA. Thus, investigating the diffusion of an antioxidant in polypropylene using ILDTA is possible.
Carbon fibre reinforced bismaleimide composites, I
Authors: Choudhary V. , Fitzer E. , Heine M. 
Published: April 2003

AbstractThe paper deals with the effect of addition of bis(allylphenyl) type (TM 120) monomer on the properties of unidirectionally carbon fibre reinforced 4,4′ bismaleimidodi‐phenyl methane (BM) – 2,4‐tolylene diamine (A) (1:0.3 molar ratio) (BM‐A) composites. The curing and thermal behaviour of the blends was investigated by using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) in air atmosphere. A marginal decrease in thermal stability was observed with increasing concentration of TM 120. Flexural, interlaminar, and impact strength of the laminates increased in the presence of this monomer. Optimum mechanical properties were observed at ∼ 20 phr of TM 120.
Reaction of some polymers containing carbonyl groups with phenol in the presence of mineral acids
Authors: Akar Ahmet 
Published: April 2003

AbstractThe reaction of polymers containing carbonyl groups such as poly(methyl vinylketone), poly(methyl vinyl ketone‐co‐styrene) and acetylated polystyrene with phenol in the presence of HCI or H2SO4 has been studied in order to produce bisphenol A type structure on the polymer chain. Poly(methyl vinyl ketone) shows intramolecular aldol condensation and acetylated polystyrene results in bisphenol A type structure.
Studies on the electrodeposition of polyimides
Authors: Yang Chin‐Ping , Chen Yahn‐Haur 
Published: April 2003

AbstractThe emulsions of aromatic polyamic acids (PMPE and PBPPM) in DMF and methanol were used to coat uniform films on conductor surfaces by electrodeposition. The deposition yield and quality of the deposited films are dependent on sort of polyamic acid, solvent (DMF), precipitant (MeOH), surfactant (TEA), pH value and solid content. To get maximum deposition yields from PMPE and PBPPM, the best conditions of electrodeposition were required as follows: pH value 5.7 and 5.58, MeOH/DMF weight ratio 3.0 and 2.8, solid content 3.5 and 2.4 wt.‐%. Deposition yield was found to obey Faraday's law of electrolysis, and the higher the equivalent weight of the polyamic acid, the higher the coulombic yield.
Model of double associates for sorption of binary gas mixtures on polymers
Authors: Pyda M. , Jaroniec M. 
Published: April 2003

AbstractA simple model of double associates is used to represent bilayer sorption of binary gas mixtures on a flexible linear chain of a polymer. The isotherm equation derived in terms of this model is a simple product of the isotherm equation describing bilayer adsorption of binary gas mixtures on a homogeneous solid surface and a function reflecting specific features of sorption on polymers.
Thermosetting mechanism of polyethersulfone
Authors: Wu Zhungwen , Jiang Da Zen , Seki Miharu , Yosomiya Ryutoku 
Published: April 2003

AbstractThermosetting mechanism of paint‐use polyethersulfones was studied by utilizing FTIR/PAS and ESCA. As a result, it was confirmed that the oxygen in the air has an effect on the thermosetting mechanism. That is, the polyethersulfone film were baked from the surface, and proceeded according to reaction (4).