bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermal dissociation of urethanes studied by FTIR spectroscopy
Authors: Joel Detlef , Hauser Andre 
Published: April 2003

AbstractThe thermal dissociation of urethane groups has been studied by FTIR spectroscopy depending on the type of diisocyanate, the structure of the hard segment and the composition of polyurethane. Independent of the composition and the structure, the dissociation started between 150 and 160°C. Consequently, the dissociation sets in at temperatures below the melting temperature of the model hard segments, i.e. already in the solid state. The NCO absorption band reaches its maximum intensity between 180 and 190°C. This result opposes the references in literature suggesting a four‐centre reaction for transurethanization.
Effect of styrene content and ZnO‐stearic acid on the mechanical properties of radiation‐vulcanized styrene‐butadiene rubber (SBR)
Authors: Youssef H. A. , Aziz M. M. Abdel , Yoshii F. , Makuuchi K. , El Miligy A. A. 
Published: April 2003

AbstractThe effect of styrene content on the properties of electron irradiation‐vulcanized SBR loaded with carbon black was pronounced only at low irradiation doses where the crosslinking densities were not so high. At high doses, no effect was observed especially for SBR containing ZnO. It was also observed that ZnO (3 phr) increased the tensile strength of SBR containing 23.5 wt.‐% styrene by 20% at 20 kGy irradiation dose, compared to 5% at higher doses for SBR containing 46 wt.‐% styrene. However, the increase in tensile strength by ZnO for loaded SBR (23.5%) was almost 17% at all irradiation doses. Besides, tear strength, abrasion resistance and elongation at break were remarkably improved. The high efficiency of ZnO toward SBR (23.5%) may be attributed to the higher butadiene content. The behavior of SBR (46%) at 20 kGy was surprising, since both tensile strength and elongation at break were almost maximum.
Interpenetrating polymer networks of polyurethane and furfuryl alcohol, IIa. Processability and properties of pultruded fiber‐reinforced composites
Authors: Ma C.‐C. M. , Goang D. Y. , Han J. L. , Hsieh K. H. 
Published: April 2003

AbstractA feasibility study of pultrusion of fiber‐reinforced polyurethane/furfuryl alcohol (PU/FA) interpenetrating polymer/network IPN composites has been made. From the viscosity study, it was found that the pot life of the PU/FA IPN prepolymers increased with PU content and showed high reactivity at elevated temperature. It was confirmed from the morphological study that the wetting of fibers by the PU/FA IPN resins was improved with PU content. The appearance of the tensile failure surfaces of the pultruded glass fiber‐reinforced PU/FA IPN composites showed “hackle patterns” for PU contents below 15 phr. The mechanical property study shows that the tensile strength of pultruded PU/FA IPN composites is the highest when the PU content is 5 phr. However, the flexural strength, flexural modulus and HDT decreased with PU content. The mechanical properties of various fiber‐reinforced (glass, carbon, and Kevlar 49 aramid fiber) pultruded PU/FA IPN composites increased with fiber volume content.
Rôle des pigments dans une réaction de polymérisation sous lumière UV‐visible
Authors: Catilaz L. , Fouassier J. P. 
Published: April 2003

AbstractCe travail sur le rôe des pigments définit le comportement d'un nouveau systeme photosensible qui permet de polymériser des milieux épais et pigmentés selon un procédé en une seule étape. Les différentes interactions présentes en milieu pigmenté sont décrites de façon qualitative, et la part de l'intensité lumineuse absorbée par un photo‐amorceur dans un systéme pigmenté est evaluée. Les propriétés optiques telles que l'absorption et la réflectance des différentes familles chimiques de pigments sont déterminées, et, en paralléle, les propriétés optiques des différentes sources d'irradiation sont étudiées de manière à répondre au mieux aux fenêtres de transmission des pigments. L'effet photocatalytique de certains pigments est mentionné, ceci afin d'amkliorer la réaction de polymérisation.
Synthesis and curing of millable polyurethanes based on castor oil
Authors: Suresh K. I. , Thachil E. T. 
Published: April 2003

AbstractThis paper presents the results of studies on the synthesis and curing of millable polyurethanes based on castor oil. To facilitate the preparation of millable urethanes, the hydroxy number of castor oil was modified to about two by acetylation. It was then used with tolylene diisocyanate (NCO/OH‐ratios 1:0.9, 1:1 and 1:1.1, resp.) for polyurethane preparation. The dynamic curing of the synthesized polyurethanes was studied in a Brabender Plasticorder using various sulfur vulcanizing systems. The effect of stoichiometric ratio and choice of chain extenders on the dynamic curing behaviour was also studied. An NCO/OH ratio of 0.9 and 1,4‐butanediol (30 wt.‐%) as chain extender were found to favour the formation of a crosslinkable polyurethane. It was observed that a cure system containing sulfur, N‐cyclohexyl‐2‐benzothiazole sulfenamide and mecraptobenzothiazole was a possible choice for the preparation of a sulfur‐crosslinked polyurethane.
Molar mass distribution of polybutadiene synthesized with nickel‐based Ziegler‐Natta catalysts, I
Authors: Schröder K. , Schmitz G. , Lechner M. D. , Gehrke K. 
Published: April 2003

AbstractCis‐1,4‐polybutadiene was produced by polymerization of 1,3‐butadiene using a catalyst system formed by a two‐step formation, Namely (1) BF3 . O(C2H5)2 and Al(C2H5)3, (2) Ni(OOC8H15)2 and Al(C2H5)3 named in‐situ‐catalyst.The molar mass distributions (MMD) of the polybutadienes are investigated by means of size exclusion chromatography (SEC). The MMD's were fitted by a sum of Schulz‐Flory‐Functions (SFF). Changed catalyst formation and polymerization conditions influenced the parameters of the SFF. Changed areas and changed molar mass averages indicate a polymerization with more than one peak maximum and kind of active species and lead to a better understanding of the polymerization.
Molar mass distribution of polybutadiene synthesized with nickel‐based Ziegler‐Natta catalysts, II
Authors: Schröder K. , Schmitz G. , Lechner M. D. , Gehrke K. 
Published: April 2003

AbstractCis‐1,4‐polybutadiene was produced by polymerization of 1,3‐butadiene using a catalyst system containing Ni(OOC8H15)2 and Al(C2H5)3 and the Lewis acids BF3 · O(C2H5)2 or TiCl4. The molar mass distributions (MMD) of the polybutadienes are investigated by means of size exclusion chromatography (SEC). The MMD's were fitted by a sum of Schulz‐Flory‐Functions (SFF). Taking into account that one kind of active species gives one SFF defined by molar mass averages, one comparable active species in both systems and one different were found. This way it was tried to find a relationship between the grown up of the active species depending on components and reactions conditions.
Synthesis of poly(vinyl alcohol) derivatives containing amidoxime groups
Authors: Arranz F. , Sanchez‐Chaves M. , Gallego M. M. 
Published: April 2003

AbstractThe modification reaction of poly(vinyl alcohol) (PVAL) with acrylonitrile in alkaline medium was studied. The structure of the resulting polymers was determined by means of IR, 1H and 13C NMR spectroscopy. The influence of solvent composition, catalyst and temperature was evaluated. 13C NMR spectroscopy was used for the determination of the sequence distribution of cyanoethylated PVAL (considered as a vinyl alcohol (VAL)‐(2‐cyanoethyl) vinyl ether (VCE) copolymer). The 13C NMR spectra of the methylene carbons in the main chain show three split peaks, the intensities of which change with copolymer composition. These peaks can be assigned to the three dyad sequences. The obtained results show that VCE units have an alternating tendency in the copolymer. Nitrile groups in cyanoethylated PVAL were converted to amidoxime groups by reaction with hydroxylamine. The reaction showed second order kinetics. The activation energy was found to be 51.6 kJ/mol. Soluble polymeric chelates between amidoximated PVAL and cupric ions have been prepared. It is noteworthy that not all the amidoxime groups participate in binding cupric ions.
Synthesis and characterization of epoxy resins containing chromium acrylate
Authors: Anand Manjit , Srivastava A. K. 
Published: April 2003

AbstractNovel epoxy resins containing chromium acrylate have been synthesized by reacting chromium acrylate with bisphenol‐A and excess epichlorohydrin. The quantities such as epoxy equivalent weight, hydroxy content, hydrolyzable chlorine content and viscosity have been determined. The resins have been characterized by IR and 1H NMR spectroscopy. The cured resins were evaluated for thermal properties. The curing of resins was carried out with Ciba Geigy HY 850 (aliphatic amine adduct) at 30°C for 24 h. The cured resins have excellent thermal and chemical resistance, in addition to an excellent electrical conductivity. The reaction follows first order kinetics with an activation energy of 47 kJ mol−1 and 34 kJ mol−1 in the presence and absence of chromium acrylate, respectively. The chromium forms a complex with bisphenol‐A, as indicated by spectroscopic studies, which increases epoxidation.
Auswirkungen von Sterilisationsverfahren auf biologisch abbaubare Kunststoffe
Authors: Bledzki Andrzej K. , Gassan Jochen , Heyne Matthias 
Published: April 2003

AbstractFür den Einsatz biologisch abbaubarer Kunststoffe in der pharmazeutischen Industrie und Medizintechnik wurden Produkte verschiedener Hersteller, wie Biopol, Biocellat und Mater‐Bi untersucht. Dabei zeigte vor allem Biopol das notwendige Anforderungsprofil, d.h. die Anwendbarkeit aller Sterilisationsverfahren ohne Festigkeitsbzw. Steifigkeitsverluste sowie Temperatur‐ und Alkoholbeständigkeit. Dagegen wiesen die Werkstoffe Mater‐Bi und Biocellat einige Schwachstellen auf. Bei Mater‐Bi lagen diese bei der Wasserdampfsterilisation sowie bei der geringen thermischen und Medienbeständigkeit. Biocellat versprödet dagegen durch die erhöhte Temperatur bei der Dampfsterilisation, d.h. daß ein Einsatz über 60°C nicht möglich wäre.
Interpenetrating polymer networks based on liquid natural rubber. 1. Synthesis and effect of nco/oh ratio on physical and mechanical properties
Authors: Pillai V. Bhoothalingam , Francis D. Joseph 
Published: April 2003

AbstractInterpenetrating polymer networks (IPNs) of polyurethane based on hydroxyterminated natural rubber with varying NCO/OH ratios and polystyrene were synthesized under different experimental conditions. These IPNs were found to make tough films. The IPNs were characterized by their physical, mechanical and morphological properties like density, Shore‐A hardness, crosslink density, tensile strength and elongation at break. The IPNs exhibited an increasing trend in density, Shore‐A hardness and tensile strength with increasing polystyrene content, while elongation at break decreased with similar variation in polystyrene content. The crosslink density measurements indicated a possible phase inversion process.
Polymers and copolymers based on vinyl tetrazoles, 1. Synthesis of poly(5‐vinyl tetrazole) by polymer‐analogous conversion of polyacrylonitrile
Authors: Gaponik Pavel N. , Ivashkevich Oleg A. , Karavai Vladimir P. , Lesnikovich Anatoly I. , Chernavina Nadejda I. , Sukhanov Gennady T. , Gareev Gegel A. 
Published: April 2003

AbstractInteraction of polyacrylonitrile with sodium azide and ammonium chloride leading to the formation of poly(5‐vinyl tetrazole) has been studied in detail. The reaction is found to proceed to high conversion extents (up to 94–94.5%) and allows to obtain polymeric products with a wide range of poly(5‐vinyl‐tetrazole) content. Comparative studies of the structures and properties of the obtained polymers and 5‐vinyl tetrazole homopolymer as well as copolymers of 5‐vinyl tetrazole with acrylonitrile have been carried out using IR, 13C NMR and complex thermal analysis data.
Polymers and copolymers based on vinyl tetrazoles, 2. Alkylation of poly(5‐vinyl tetrazole)
Authors: Gaponik Pavel N. , Ivashkevich Oleg A. , Chernavina Nadejda I. , Lesnikovich Anatoly I. , Sukhanov Gennady T. , Gareev Gegel A. 
Published: April 2003

AbstractAlkylation of poly(5‐vinyl tetrazole) with dimethyl sulfate and tert‐butyl alcohol as well as with alkyl halides RHal (RCH3, C2H5, CH2CHCH2, n‐C4H9, t‐C4H9) has been studied under various conditions in order to develop a new method of synthesis of tetrazole‐containing polymers having a complex of valuable properties. The kinetic study of the process and comparison of isomeric compositions and spectroscopic characteristics (IR, 1H NMR and 13C NMR) of poly(N‐alkyl‐5‐vinyl tetrazole)s synthesized by alkylation of poly(5‐vinyl tetrazole) and of those prepared by (co)polymerization of the corresponding vinyl tetrazoles have been carried out. The alkylation is found to proceed to high conversion extents (up to 99.8%) and enables to obtain a wide variety of polymeric products having the composition, structure and properties very similar to those of homo‐ and copolymers.
Determination of 1‐butene distribution in LLDPE by DSC analysis after thermal fractionated crystallization
Authors: Balbontin Giulio , Camurati Isabella , Dall'Occo Tiziano , Finotti Anita , Franzese Rocco , Vecellio Giancarlo 
Published: April 2003

AbstractThe chemical composition distribution (CCD) of LLDPE (1‐butene comonomer) has been studied by thermal analysis. After an opportune thermal treatment of the polymers, thermal fractionated crystallization (TFC), the melting endotherms have been subdivided in areas with fixed temperature ranges. The distribution of the endotherms in different areas gave a semiquantitative idea of the CCD.The comparison with thermal rising elution fractionation and 13C NMR data of the whole polymers and fractions showed fairly good correlations. An approximate evaluation of the average ethylene sequence length was also obtained.
The influence of inert component composition on the porous structure of glycidyl methacrylate/ethylene glycol dimethacrylate copolymers
Authors: Jovanović Slobodan M. , Nastasović Aleksandra , Jovanović Nadežda N. , Jeremić Katarina , Savić Zorica 
Published: April 2003

AbstractThe influence of the content of inert component in monomer phase on the parameters of porous structure (specific pore volume, Vs, specific surface area, Ss, total porosity, P, pore size distribution and pore diameter dp) of the copolymers of glycidyl methacrylate, GMA, and ethylene glycol dimethacrylate, EGDMA, obtained by suspension polymerization has been studied. The content of standard inert component (cyclohexanol/dodecanol) was changed by substituting dodecanol with one of the aliphatic alcohols with 4, 8, 10, 14 or 16 C‐atoms and by varying the ratio of aliphatic alcohol in inert component.The results obtained showed that it was possible by changing type and ratio of aliphatic alcohol in inert component to influence the parameters of pore structure of poly(GMA‐co‐EGDMA) copolymers significantly and that by using tetradecanol or hexadecanol it was possible to obtain these copolymers with pore diameters larger than 200 nm.
Separation of liquid mixtures by using polymer membranes, V. Water‐alcohol separation by pervaporation through poly(vinyl alcohol)‐graft‐poly(styrene‐co‐maleic anhydride) membranes
Authors: Chiang Wen‐Yen , Hsiao Chao‐Yi 
Published: April 2003

AbstractGraft copolymerization of styrene‐maleic anhydride copolymer (ST‐co‐MA) onto poly(vinyl alcohol) (PVA) was carried out by a condensation‐coupling reaction through esterification. The ST‐co‐MA copolymer was obtained by the copolymerization of MA and ST in dimethyl sulfoxide (DMSO), using azoisobutyronitrile as initiator. The structure of the reaction products was confirmed by infrared analysis. The dependence of composition, viscosity and yield of the graft terpolymers on the concentration of the reactants are presented in detail. Mechanical properties of membranes with different compositions were measured over a wide range of composition. It was found that water was permeated through the membranes preferentially in all ranges of feed compositions. The permeation decreased and the selectivity increased with increasing ethanol concentration in the feed and with increasing PVA content in the membrane. The effect of the molecular size of the permeating species on both permeation and separation is also discussed.
Synthesis and biological activity of chlorine‐containing polyketones
Authors: Patel J. N. , Patel R. K. , Ray R. M. , Patel R. M. 
Published: April 2003

AbstractChlorine‐containing polyketones of low molecular weight were synthesized from anisole, chloroacetyl chloride and dichloroalkanes, i. e. dichloromethane and 1,2‐dichloroethane, by the Friedel‐Crafts reaction using carbon disulfide as solvent. The resins were characterized by IR spectra and vapour pressure osmometry. The thermal properties were studied by thermogravimetry and differential scanning calorimetry. The characteristics of the decomposition reactions were evaluated by the Broido and Doyle methods. All the resins were tested for their microbial activity against bacteria, fungi and yeast. The results show that most of the resin can be used as biocides.
Study of some flocculating processes with cationic polyelectrolytes
Authors: Lupaşcu Tudor , Dranca Ion , Sandu Maria , Drăgan Stela , Ghimici Luminiţa 
Published: April 2003

AbstractThe flocculating efficiency of two cationic polyelectrolytes with quaternary ammonium salt groups in the main chain, with different branching degrees, on a bentonitic clay suspension, in comparison with polyacrylamide (PAM) was followed. The cationic polymer with a smaller branching degree operated similar to PAM. In both cases a purification of 100% was achieved. When the cationic polymer with a higher branching degree was used, a stabilization effect on the suspension was observed. The flocculating activity of the mixtures of the cationic polymer and polyacrylamide was also studied.
MgCl2·6H2O‐based titanium catalyst for propylene polymerization: Effect of polymerization parameters
Authors: Gupta Virendra Kumar , Satish Sheo , Bhardwaj Ishwar Singh 
Published: April 2003

AbstractA supported titanium catalyst was prepared by using MgCl2·6H2O as a precursor for generating an active support. The performance of such catalyst was evaluated for propylene polymerization in conjunction with triethylaluminium as cocatalyst and dimethoxydiphenylsilane as an external Lewis base. The efficiency of the catalyst system is dependent on the polymerization parameters such as time, temperature and monomer pressure. The variation in the concentration of hydrogen used as a chain transfer agent alters the performance of the catalyst system and molecular weight characteristics of polypropylene. The morphology of polymer particles is of globular type and is not affected by the variation in the melt flow characteristics of the polymer.
Hydrolytic stability and mechanical properties of poly(ester urethanes)
Authors: Pegoretti Alessandro , Kolarik Jan , Penati Amabile 
Published: April 2003

AbstractThe effect of hydrolysis time at 70°C on molar mass and mechanical properties of commercial poly(ester urethanes), i.e., Estanes 54600, 54610, and 54650, was analyzed. Kinetics of hydrolysis is plausibly described in terms of a first‐order reaction with an average induction period of about 7 days. The resulting reduction of molar mass brought about a significant decrease in ultimate properties, particularly in stress at break and tensile energy to break, while elastic properties were affected much less. A quantitative correlation between relative changes in tensile strength and molar mass was attempted. Hydrolysis resistance of Estanes decreasing in the succession 54650 > 54600 > 54610 was related to their chemical composition.
Viscosity behaviour of multivalent metal ion‐containing carboxymethyl cellulose solutions
Authors: Heinze Thomas , Heinze Ute , Klemm Dieter 
Published: April 2003

AbstractThe influence of Ca2+‐and Al3+‐ions, respectively, upon the viscosity behaviour (so‐called salt tolerance) of aqueous solutions of sodium carboxymethyl cellulose (CMC) with different degree of polymerization (DP) and, on the other hand, with both different degree of substitution (DS) and distribution of substituents, was investigated. Viscosimetry by means of a rotational rheometer at a shear rate of 500 s‐1 shows that the relative drop in viscosity as a result of addition of the multivalent metal cations is independent of DP (ranging from 160 to 900) of the CMC samples. Homogeneously synthesized CMCs (2) with a higher content of 2,3,6‐tri‐O‐carboxymethyl glucose units in the polymer chain possess a significantly higher salt tolerance than those (1) prepared under heterogeneous reaction conditions at comparable total DS values.
Adhesion properties and phase separation behavior of glycidyl‐terminated polyurethanes
Authors: Hsia Hung‐Chung , Ma Chen‐Chi M. , Chen Der‐Shyang 
Published: April 2003

Abstract2,3‐Epoxy‐1‐propanol has been introduced into isocyanate‐terminated polyurethane to form glycidyl‐terminated polyurethane resins. A series of glycidyl‐terminated polyurethanes based on hydroxyterminated poly(oxypropylene) (poly(oxypropylene) glycol, PPG), toluene diisocyanate (TDI), and 1,4‐butanediol (BD) was synthesized with various PPG soft segment lengths (MW 700, 1000 and 2000) and soft segment concentrations (30, 50 and 70 wt.‐%). The effects of glycidyl‐terminated polyurethane on the adhesion properties and the phase separation were investigated. The adhision properties at liquid nitrogen temperature coincide with the phenomenon observed in the phase separation behavior of polyurethane. Differential scanning calorimetry (DSC) and infrared technique (IR) were used to assess the phase separation content. The enthalpy jump at the glass transition temperature (ΔCp) and the unique spectroscopic features in the NH and CO stretching regions were applied to characterized the phase separation behavior. It was found that the modified resins do not only show superior adhesion at liquid nitrogen temperature but also exhibit some unique properties, e.g., room temperature curing and good storage stability.
Air separation characteristics with liquid crystalline alkyl cellulose blend thin‐film composite membranes
Authors: Li Xin‐Gui , Huang Mei‐Rong 
Published: April 2003

AbstractComposite membranes were made of liquid crystalline triheptyl cellulose (THC)/ethyl cellulose (EC) blends as dense thin films and poly(ether sulfone) (PES) or polysulfone (PSF) as porous support layer. The effects of the composite membrane composition and operating conditions on the air separation characteristics of oxygenenriched air (OEA) permeating through the membranes were studied using a constant pressure‐variable volume method. The flux (OEA) through the membranes decreases slightly and the oxygen concentration in the OEA permeated increases with increasing THC content in the thin film from 4 to 15 wt.‐%. The OEA flux increases significantly with decreasing thin‐film thickness or increasing operating temperature and transmembrane pressure difference. The oxygen concentration in the OEA increases with increasing the thin‐film thickness or the pressure difference but decreases slightly with increasing the operating temperature. There is no regular variation in the air separation properties by changing the support from PES to PSF. In long‐term tests, the air separation properties remained almost constant for as long as 800 h. An OEA flux of 1.0–1.9·10‐3 cm3 (STP)/s·cm2 containing 34.8–39.4 vol.‐% oxygen can be attained at 30–55°C and 0.41–0.49 MPa pressure difference in a single pass through the membranes. The OEA flux is much higher for the thin‐film composite membranes than for the homogeneous dense membranes made of the same materials.