bluuebunny/crossref_metadata_2025_split huggingface dataset:
High‐temperature and ageing properties of trans‐polyoctenylene‐filled natural rubber vulcanizates and their correlation with network changes
Authors: Chattaraj P. P. , Kalidaha A. K. , Mukhopadhyay R. , Tripathy D. K. 
Published: April 2003

AbstractA systematic study of filled natural rubber (NR) vulcanizates has been carried out to investigate the effect of a crosslinkable processing aid, trans‐polyoctenylene (TOR) on stress‐strain properties at high temperature and after ageing. Three different crosslinking systems, i. e., conventional (CV), semi‐efficient (SEV) and efficient (EV), are included in this study. Retention of 200% modulus and tensile strength (TS) at high temperature as well as after ageing has been found to be better with TOR in the CV system. TGA results of gum polymeric blends showed enhanced stability with addition of TOR in both oxygen and nitrogen atmosphere. Enhanced thermal stability is also exhibited by higher onset and peak temperature while determining the rescan enthalpy of the filled vulcanized sample by means of DSC. FTIR (ATR) spectra however show no polymeric interaction between NR and TOR. The improvement of properties in the CV system has been explained with the help of DSC results and a probable mechanism has been suggested on the changes of network structure.
Poly(oxadiazole‐imide)s containing hexafluoroisopropylidene units
Authors: Hamciuc Corneliu , Schulz Burkhard , Bruma Maria 
Published: April 2003

AbstractA series of new poly(1,3,4‐oxadiazole‐imide)s has been synthesized from various aromatic dihydrazides and diacid chlorides which contain both imide and hexafluoroisopropylene units. The diacid chlorides were reacted with aromatic dihydrazides to prepare poly(hydrazide‐imide)s which were subsequently cyclodehydrated in their solid state to give poly(1,3,4‐oxadiazole‐imide)s. The new polymers were soluble in polar solvents and were stable up to 450‐480°C in nitrogen, as determined by thermogravimetric analysis.
Surface functionalization of polymer networks. Sulfonation of the internal surface of macroporous styrene‐divinylbenzene copolymers
Authors: Struck Michael , Widdecke Hartmut 
Published: April 2003

AbstractSurface functionalization of porous polymer networks was investigated using the sulfonation of macroporous styrene‐divinylbenzene (S‐DVB) copolymers as model reaction. Reaction conditions for the surface sulfonation were studied. Sulfonation with sulfuric acid in the presence of nitromethane was found to be a suitable method. Models and ideas of network structure are developed in order to estimate surface capacities and to show that surface‐sulfonated networks were obtained.
Condensation polymerization of pyrogallol and benzaldehyde
Authors: Erbay E. , Bilgiç T. , Uyanik N. , Savaşçi Ö. T. 
Published: April 2003

AbstractNovolac‐type polycondensation of benzaldehyde (B) and pyrogallol (P) has been carried out at 60°C, 75°C and 90°C and at B/P mole ratios of 1.5 and 3.0 using phosphoric acid as catalyst. The reaction follows a 2nd order rate law. By using GC consumption data of benzaldehyde and pyrogallol, kinetic parameters such as the overall rate constants, activation energies (Ea) and logA values are investigated. The activation energies for 1.5 and 3.0 B/P mole ratios are found as 62.3 kJ mol−1 and 56.4 kJ mol−1, respectively. The molecular weights of the resins determined by measuring intrinsic viscosities (25°C, THF) are in the range of 0.03 to 0.07 dL g−1 at various temperatures and B/P mole ratios.
The effect of surface modification of aluminium hydroxide on the crystallisation behaviour of aluminium hydroxide filled polypropylenes
Authors: Liauw Christopher Mark , Lees Graham Clayton , Hurst Sidney John , Rothon Roger Norman , Dobson Derrick Clifford 
Published: April 2003

AbstractComposites based on polypropylene (PP) (homopolymer and impact modified copolymer) and surface modified aluminium hydroxide (Al(OH)3) have been studied using differential scanning calorimetry (DSC) and X‐ray diffraction (XRD). Filler surface modifiers used included 2‐dodecen‐1‐yl succinic anhydride (DDSA) as a dispersant and a commercial silane based coupling agent system (BA Chemicals S21). Treatment of the Al(OH)3 with DDSA led to a considerable reduction of the capacity of the filler to nucleate crystallisation in the PP and, in some composites, promoted growth of β‐PP. With the S21 treatment, however, a nucleation effect was still apparent, despite encapsulation of the filler particles with the elastomeric phase in the case of the impact modified PP. DSC and XRD studies indicated that with the untreated filler nucleation was directly associated with the filler surface. However, with the S21 treated filler this was not the case and PP nucleation was random and/or flow induced with no association with the filler surface.
Synthesis of ketonic resins from self‐polymerization of acetone, 1. Action of protic and lewis acids on acetone
Authors: Cataldo Franco 
Published: April 2003

AbstractAcetone can be homopolymerized by a polyaldolic condensation reaction under the action of protic acids (conc. sulfuric acid), superacids (CF3SO3H), or Lewis acids (AlCl3) to give a solid resin. The polymerization kinetics was followed dilatometrically and spectrophotometrically. Several intermediates formed during the early stage of polycondensation were identified by means of electronic spectroscopy and Woodward‐Fieser rules for α,β‐unsaturated ketones.The general structure of the resin obtained was elucidated, knowing the structures of the early condensation products formed from acetone, by using thermodynamical calculations and the vinylogy principle, as well as by elemental analysis, electronic and infrared spectroscopy, 1H‐NMR and 13 C‐NMR spectrometry. The data thus obtained and the theoretical considerations led to a polyenic structure resembling poly(methylacetylene) but with some functional groups like ketonic groups and hydroxy groups present on the main chain or as end groups and with geminal dimethyl groups as end groups.
Adhesive properties of poly(propylene) modified in bulk
Authors: Novák Igor 
Published: April 2003

AbstractIsotactic poly(propylene) (iPP) was modified in bulk by addition of low‐molecular compounds, e.g. maleic anhydride, sodium maleate, fatty acids or their sodium salts and dibutyl phthalate. It was found that the dependence of the mechanical work of adhesion in the system modified iPP‐poly(vinyl acetate) on the concentration of the low‐molecular compound in iPP exhibited a maximum. It was shown that the highest value of the mechanical work of adhesion was reached in iPP containing 5 wt.‐% of maleic anhydride or sodium maleate and 1 or 1.2 wt.‐% of fatty acids or their salts, respectively. It was found that sodium oleate is the most efficient modifier and its addition increased the mechanical work of adhesion by 6.4 times.
Einfluß von haftvermittlern auf das feuchteverhalten naturfaserverstärkter kunststoffe
Authors: Bledzki A. K. , Gassan J. 
Published: April 2003

AbstractDie Feuchtigkeit stellt bei der Verwendung von Naturfasern in faserverstärkten Kunststoffen neben der geringen Faser‐Matrix‐Haftung eines der wesentlichen Problemfelder dar. Durch eine optimale Trocknung vor der Verarbeitung lassen sich bei Jute‐EP‐Verbunden die mechanischen Kennwerte um bis zu ca. 20% steigern.Durch den Einsatz von Haftvermittlern auf Silanbasis läßt sich neben einer Verbesserung der Faser‐Matrix‐Grenzschicht mit daraus resultierender deutlicher Erhöhung der mechanischen Verbundkennwerte auch der Feuchteeinfluß auf diese deutlich minimieren. So konnte die statische Zugfestigkeit durch die Silanisierung der Faseroberflächen unabhängig vom Feuchtegehalt der Verbunde eingestellt werden. Der Feuchteeinfluß auf den Verbund‐E‐Modul sowie auf die Wöhlerkurve konnte durch diese Art der Faserbehandlung auch deutlich reduziert werden.
Study on process parameters in metallocene polymerizations, I. Apparent viscosity and macro‐scale mass transfer
Authors: Lahti Mikko , Koivumäki Jari , Seppälä Jukka V. 
Published: April 2003

AbstractA heat balance reaction calorimeter was used to obtain information about the most informative process parameters in polymerizations carried out with Et[Ind]2ZrCl2‐methylaluminoxane catalyst. The viscosity of the reaction mixture was found to increase dramatically during the homopolymerization of ethylene, but it could be controlled through appropriate selection of the reaction mixture medium. The mass transfer between the gas and liquid phases was the rate‐determining step for the polymerization when the reaction mixture‐based Reynolds number was below 2.500. The limited mass transfer between the gas and liquid phases was caused by the intensive activity of the metallocene catalyst and the increased viscosity of the reaction mixture.
Study on process parameters in metallocene polymerizations, II. Heat transfer and copolymer composition
Authors: Lahti Mikko , Koivumäki Jari , Seppälä Jukka V. 
Published: April 2003

AbstractPart I of this series about the determination of the typical process parameters in Et[Ind]2ZrCl2‐methylaluminoxane‐catalyzed polymerizations carried out with a heat balance reaction calorimeter described how viscosity and macro‐scale mass transfer characteristics changed during the polymerization. Part II looks at the heat transfer properties and the copolymer compositions. The dimensionless Nusselt equation was used to calculate the reaction‐side heat transfer coefficient during the polymerization. The properties of the reaction mixture changed continuously during the polymerization, which means that the dimensionless Nusselt equation needs to be modified to properly express the heat transfer properties. The copolymer compositions were estimated by combining the calorimetric method with the semibatch ethylene polymerization method. Results gathered in this way were reliable when the amount of comonomer in the copolymer exceeded 5 mol‐%.
A nitrocellulose‐modified UV‐curable acrylated urethane prepolymer
Authors: Yildiz Emel , Güçlü Hande , Kuyulu Abdülkadir , Kuyulu Abdülkadir , Yildirim Hüseyin , Güngör Attila 
Published: April 2003

AbstractThe effects of varying nitrocellulose concentrations on mechanical properties of polymeric films prepared from UV‐curable acrylated urethane prepolymer were investigated. The acrylated urethane prepolymer was synthesized from isophorone diisocyanate (IPDI) and poly(propylene glycol monomethacrylate) (PPGMMA). Isobornyl acrylate (IBoA) and N‐vinyl pyrrolidinone (NVP) were used as reactive diluents with the purpose of reducing the viscosity of the prepolymer as well as acting as solvent for nitrocellulose. An increase in nitrocellulose content caused an increase both in tensile strength and elongation values of polymeric films.
Polymerization of acrylamide in single‐phase in‐verse dispersion systems at high volume fractions of dispersed phase
Authors: Barton Jaroslav , Stillhammerova Martina , Lezovic Martin 
Published: April 2003

AbstractThe preparation of single‐phase inverse microemulsions of toluene/sodium bis(2‐ethylhexyl)sulfosuccinate (AOT)/water/acrylamide (AAm) is described and their properties prior to polymerization (macro and microviscosity as a function of volume fraction Φaw of the dispersed aqueous (water + acrylamide) phase, of the [to‐luene]/[AOT] molar ratio and of the acrylamide/water mass ratio) were studied.The polymerization of acrylamide in dispersion systems was initiated by the oilsoluble initiator dibenzoyl peroxide at 60°C. The polymerization rate of acrylamide for a given [toluene]/[AOT] molar ratio and AAm/water mass ratio monotonically decreases beyond a Φaw value of 20%. The polymer particle size in polymerized systems as well as the molecular mass of polymer in the polymer particles increase on increasing the acrylamide concentration in the aqueous phase and/or the Φaw values of the dispersion system. On increasing the surfactant AOT concentration both polymer particle size and polymer molecular mass decrease for a given set of other relevant parameters of the dispersion system (i.e. [toluene]/[AOT] and AAm/water ratios). The polymerized inverse dispersion system can be converted to an oil‐in‐water dispersion by addition of water.
Polymerization of acrylamide in inverse microemulsion in the presence of mixtures of oleophilic and hydrophilic surfactants
Authors: Barton Jaroslav , Stillhammerova Martina 
Published: April 2003

AbstractThe preparation of single‐phase toluene/sodium bis(2‐ethylhexyl)sulfosuccinate(AOT)/water/acrylamide/sodium dodecyl sulfate(SDS) inverse microemulsions is described and their properties prior to polymerization (macroviscosity as a function of volume fraction Φaw of the dispersed aqueous (water + acrylamide(AAm) + SDS) phase, and of SDS/AAm mass ratio) are studied. At 20°C three viscosity maxima are observed. At 50°C all three peaks remain, the viscosity of the first and third peak, respectively, is lowered to 5–8 mPa· s while the second, most prominent peak still marks the level of ca. 250 mPa· s. The polymerization of acrylamide in dispersion systems is initiated by water‐soluble ammonium peroxodisulfate (APS) and oilsoluble dibenzoyl peroxide (DBP) at 60°C. The polymerization rate of acrylamide for a given [toluene]/[AOT] molar ratio and AAm/water mass ratio monotonically decreases for Φaw values greater than 20%. The polyacrylamide viscosity molecular mass increases up to a Φaw value of ca. 30%, irrespective of the nature of initiator. For Φaw values over 30% the viscosity molecular mass of polyacrylamide seems to level off with some sings of shallow minimum close to Φaw of 50%.
Polymerization of lactams, 87. Block copolymers of poly(ϵ‐caprolactam) and polybutadiene prepared by anionic polymerization. Part I: Preparation and properties
Authors: Nováková Václava , Sobotík Roman , Matěnová Jana , Roda Jan 
Published: April 2003

AbstractThe effect of the polymerization conditions on the properties of poly(ϵ‐caprolactam)‐polybutadiene block copolymers prepared by polymerization casting through anionic polymerization of ϵ‐caprolactam initiated with potassium salt of ϵ‐caprolactam in the presence of α,ω‐dihydroxy‐polybutadiene and isocyanates or their blocked derivatives as functionalizing agents was investigated.The influence of the content of telechelic polybutadiene, its molecular weight, type of diisocyanate, and polymerization temperature on the fundamental mechanical properties of the prepared materials and on the polymerization rate was evaluated.
Photoactive epichlorohydrin, 2. Photoinitiated free‐radical and promoted cationic polymerization by using polyepichlorohydrin with benzoin terminal groups
Authors: Hepuzer Yesim , Yagci Yusuf , Biedron Tadeusz , Kubisa Przemyslaw 
Published: April 2003

AbstractThe photoinitiated free‐radical polymerization of methyl methacrylate (MMA) and the radical‐promoted cationic polymerization of cyclohexene oxide (CHO) in the presence of low‐molecular‐weight polyepichlorohydrin terminated with groups containing benzoin derivatives were studied. Benzoin‐terminated polyepichlorohydrin was prepared by Activated Monomer (AM) polymerization. Upon photolysis. polymer‐bound alkoxy benzyl radicals were generated, initiating the radical polymerization of MMA. In the case of radical‐promoted cationic polymerization of CHO, the cationic initiating species were formed by the oxidation of photochemically generated polymeric radicals by N‐ethoxy‐2‐methylpyridinium hexafluorophosphate.
Preparation and properties of aramids based on naphthalenedicarboxylic acid and their molecular composites with amorphous nylon
Authors: Wang Cheng‐Huan , Chen Leo‐Wang 
Published: April 2003

AbstractTwo naphthalene‐aromatic polyamides were prepared from 2,6‐naphthalenedicarboxylic acid and various aromatic diamines by a modified Higashi phosphorylation reaction. The first polymer, poly(4,4′‐diaminobenzanilide‐2,6‐naphthalamide)** (DBNA), was synthesized by the reaction of 2,6‐naphthalenedicarboxylic acid with 4,4′‐diaminobenzanilide. The second polymer, 50/50 copoly(1,4‐phenylene/1,4‐bis(4′‐phenoxy)benzene‐2,6‐naphthalamide)*** (PBNA), is a copolymer synthesized using an equimolar ratio of 1,4‐phenylene diamine and 1,4‐bis(4′‐aminophenoxy)benzene. These two polymers have inherent viscosities of 4.17 and 2.32 dL g‐1, respectively, and dissolve in N‐methyl‐2‐pyrrolidone (NMP)containing LiCl. Highstrength films were obtained by casting from these polymer solutions. Blends of DBNA/amorphous nylon and of PBNA/amorphous nylon were prepared by rapidly precipitating the ternary NMP solution into deionized water, and hot‐pressing to films at 185°C. The compatibility, morphology, and mechanical properties were investigated by dynamic mechanical analysis (DMA), scanning electron microscopy (SEM), and tensile tests. The results revealed that both DBNA and PBNA were partially compatible with amorphous nylon. DBNA formed microfibrils in the amorphous nylon matrix, and its mechanical properties, tensile strength and modulus, improved with increasing DBNA content. PBNA had no reinforcing effect, perhaps because it did not form microfibrils in the amorphous nylon matrix.
Einfluß der temperatur auf die zähigkeit, die bruchflächenmorphologie und das molekulare relaxationsverhalten von polycarbonat
Authors: Grellmann Wolfgang , Lach Ralf 
Published: April 2003

AbstractDas Zähigkeitsverhalten von Polycarbonat wird bei dynamischer Beanspruchung mittels instrumentierter Kerbschlagbiegeprüfung bestimmt. In Abhängigkeit von der Temperatur wird elastisches, elastisch‐plastisches Werkstoffverhalten mit überwiegend instabilem Rißwachstum und elastisch‐plastisches Werkstoffverhalten mit dominanten Anteilen an stabilem Rißwachstum beobachtet. Mit der energiebestimmten bruchmechanischen Kenngröße „J‐Integral”︁ wird eine Auswertemethode zur Verfügung gestellt, die eine Bewertung der Temperaturabhängigkeit in einem weiten Temperaturbereich erlaubt. Die J‐Integral‐Werte zeigen ein kraftdeterminiertes lokales Maximum bei ‐60°C und ein globales Maximum bei 60°C, das mit einem spannungsinduzierten Scherfließprozeß in Beziehung steht. Der Schnittpunkt der Spur der ß‐Relaxation mit der Bruchfrequenz im Arrhenius‐Diagramm ergibt sich zu einer Temperatur von ‐60°C bei einer Frequenz von 300 Hz. Daraus ist zu ersehen, daß die Zähigkeitserhöhung bei ‐60°C durch die ß‐Relaxation stimuliert wird. Im gewählten Temperaturbereich war es möglich, die quantitative Größe ausgewählter Bruchflächenphänomene mittels lichtmikroskopischer Untersuchungen zu ermitteln und in Beziehung zum Werkstoffverhalten zu setzen.
Synthesis of tetrahydrofuran‐styrene and tetrahydrofuran‐methyl methacrylate block copolymers via poly(tetrahydrofuran) with azo groups
Authors: Çakmak İsmail , Ayas Alipasa 
Published: April 2003

AbstractThe cationic polymerization of tetrahydrofuran (THF) initiated by 4,4′‐azobis(4‐cyanopentanoyl chloride) (ACPC) and SnCI4 is described. Poly(THF) samples possessing azo gorups in the main chain thus obtained were used as initiator in the polymerization of styrene (S) and methyl methacrylate (MMA) at 70°C to yield PTHF‐PS‐PTHF and PTHF‐PMMA block copolymers. Characterization of the block copolymers was carried out by fractional precipitation, spectroscopic methods and viscosity measurements.
Copolymerisation of ethylene and vinyl acetate under high pressure with a peroxide/triethylaluminium system
Authors: Luft Gerhard , Jabbari Majid , Dorn Maximilian 
Published: April 2003

AbstractThe present study was carried out to examine the effectiveness of an addition of triethylaluminium to tert‐butyl perpivalate which is frequently used in industrial applications for initiating the copolymerisation of ethylene with vinyl acetate. For this purpose, polymerisation tests were carried out in the laboratory on a continuous basis at 1900 bar and 150°C. Vinyl acetate was added in concentrations of up to 36 wt.‐% in the feed to the reactor. The organic peroxide concentration was 50 mole ppm; the concentration of organoaluminium alkyl was varied within the range of 0–75 mole ppm.The effects observed, namely an increase in the conversion and a decrease in the peroxide consumption were more marked than with the homopolymerisation of ethylene. This is attributable to the increased rate of chain growth in addition to the increased amount of radicals available.The properties of the copolymers obtained are changed only moderately by aluminium alkyl. Apart from a decrease in density and an increase in the melting point, a decrease in the polydispersity was observed.
Effect of EPDM admixture and mixing conditions on the morphology and mechanical properties of LDPE/PP blends
Authors: Fortelný Ivan , Kruliš Zdeněk , Michálková Dana , Horák Zdeněk 
Published: April 2003

AbstractThe effects of EPDM admixture, mixing conditions and additional stabilization on the phase structure and impact strength of low‐density polyethylene/isotactic polypropylene (LDPE/PP) blends were studied. It was proved that EPDM is localized at the interface between LDPE and PP phases. The admixture of 5% EPDM substantially increases impact strength of LDPE/PP blends at all the compositions. Higher intensity and longer time of mixing have a positive effect on the impact strength of the studied blends. For the blends with higher content of polypropylene it is necessary to prevent their degradation by additional stabilization.
New azomethine‐urethanic compounds
Authors: Simionescu C. I. , Filip D. , Ciobanu C. , Stoleriu A. 
Published: April 2003

AbstractNew azomethine‐urethanic compounds were synthesized, starting from 2,2′‐[methylenebis(nitrilomethylidyne)]diphenol and phenylisocyanate for the model compound and tolylene‐2,4‐diisocyanate for the polymer. The products were characterized by elemental analysis, IR and NMR spectroscopy as well as thermogravimetry, DSC and viscosimetry. Through heating, these compounds suffer chemical modification, both addition and condensation reactions being possible. Thermogravimetric studies have evidenced the formation of thermostable products, possibly due to hexahydrotriazinic structures resulted from the thermal treatment.
Simultaneous fluorine elimination and alkylation of poly(tetrafluoroethylene)
Authors: Hlavatý Jaromír , Kavan Ladislav , Bastl Zdeněk 
Published: April 2003

AbstractPTFE (powder or foils) was defluorinated and derivatized in a one‐step process by alkyl‐ and aryllithium in the presence of tetramethylethylenediamineSystematic name: 1,2‐Bis‐[dimethylamino]ethane.
(TMEDA) as a catalyst. As evidenced by infrared (IR) spectroscopy, X‐ray photoelectron spectroscopy (XPS) and elemental analysis the C4H9‐, C8H17‐, C12H25‐ or phenyl groups were attached to a partly defluorinated macromolecular chain. Analogous reactions with dilithioaryl or dilithioalkyl agents presumably lead to crosslinking of the polymeric chains through alkyl or aryl groups. When the PTFE powder is treated with more concentrated RLi (>3 mol L−1) at temperatures >150°C, the defluorination is almost quantitative even in the absence of the catalyst. The TMEDA‐catalyzed reaction proceeds via elimination and nucleophilic addition. On the other hand, more concentrated RLi in the absence of the catalyst seems to react via a radical mechanism.
Surface treatment of an epoxy resin by CO2 laser irradiation
Authors: Hartwig Andreas , Vitr Gilbert , Dieckhoff Stefan , Hennemann Otto‐Dietrich 
Published: April 2003

AbstractThe influence of CO2 laser radiation on the surface properties of a lamination resin (temperature resistant up to 120°C) which is used for carbon fibre‐reinforced plastics (CFRP) is examined. It is shown by XPS and infrared spectroscopy that the hydroxy groups of the resin are eliminated by the laser radiation. Using a carbon dioxide atmosphere, also deeper parts of the resin are influenced compared to the treatment in air. The reproducibility of the bond strength is higher for the laser‐treated samples than for untreated samples if a room temperature‐curing adhesive is used, but the bond strength itself is lower. Laser treatment shows no influence at all if a hot‐curing adhesive is used.