bluuebunny/crossref_metadata_2025 huggingface dataset:
Hybrid carbon‐glass fiber vinyl ester resin composites
Authors: Tan Ton That Minh , Nieu Nguyen Huu
Published: April 2003

Hybrid carbon‐glass fiber composites of novolak epoxy‐based vinyl ester resins have been investigated. The chemical resistance, the thermo‐oxidative stability and the mechanical properties such as tensile strength and tensile modulus, as well as flexural strength and flexural modulus, interlaminar shear strength (ILSS) and impact strength have also been estimated. The combination of glass and carbon fibers in the hybrid turns out to be an excellent mix. These composites have good tensile and flexural properties as well as the good chemical resistance of the carbon fibers and the high impact strength of the glass fibers and also the thermo‐oxidative stability of highly aromatic vinyl ester resins based on novolak epoxy.
Crosslinked polymers from resin acids
Authors: Bicu Ioan , Mustata Fanica
Published: April 2003

New polymers were synthesized by addition of epichlorohydrin to the polyamides or poly(amideimide)s derived from the polycondensation of poly(alkylenepolyamide)s with some Diels‐Alder adducts of resin acids. The adducts were prepared by the reaction between resin acids (extracted from rosin) and acrylic acid or maleic anhydride. The obtained polymers, which were investigated by usual physical and chemical methods, are three‐dimensional, thermosetting and fairly thermostable.
Multiblock copolymers consisting of polyester and polyaliphatic blocks
Authors: Fray Mirosława El , Słonecki Jerzy
Published: April 2003

Multiblock‐(AB)n‐copolymers, consisting of hard segments of poly(butylene terephthalate) (PBT) and soft segments of dimerized fatty acid were synthesized and analysed with DSC and DMTA. The polymers were characterized by their limiting viscosity number and melt flow index. The glass transition temperature (Tg) and melting temperature (Tm) increase with decreasing weight fraction of the dimerized fatty acid and with the increase of the crystalline phase content. It was found that the elasticity (ϵ) depends on the content of dimerized fatty acid in the amorphous phase. Tensile properties were described as a function of the degree of polycondensation Pk (molecular weight).
Amphiphilic enzyme membranes, I. Preparation of amphiphilic membranes using poly(HEMA) and poly(HEMA‐co‐st)
Authors: Liu Jui‐Hsiang , Chung Yi‐Chang , Liu Hung‐Tsai
Published: April 2003

Copolymers of 2‐hydroxyethyl methacrylate (HEMA) and styrene (St) with various HEMA contents were synthesized in this investigation. Amphiphilic membranes were fabricated by using one layer of hydrophilic poly(HEMA) and one layer of hydrophobic poly(HEMA‐co‐St) in the presence of a photosensitizer. The oxygen permeability and the water penetration of the amphiphilic membranes with various HEMA contents were estimated. The dependence of the mole fraction of HEMA on hydrophilicity and binding forces on the surface of the amphiphilic membranes were investigated. Characteristics of the amphiphilic membranes on the enzyme immobilization were compared with those of traditional two‐layer systems. The response time, stability and pH dependences of the amphiphilic enzyme membrane were also evaluated.
Aromatic‐aliphatic polysulfides. Products of the polycondensation of 4,4′‐bis(mercaptomethyl)biphenyl with some dihalogen hydrocarbons
Authors: Podkoscielny Wawrzyniec , Tarasiuk Bogdan
Published: April 2003

Polysulfides were synthesized by high‐temperature solution polycondensation of 4,4′‐bis(mercaptomethyl)biphenyl with selected aliphatic and aromatic‐aliphatic dihalogen hydrocarbons. To determine the optimum polycondensation conditions, the influence of the following factors on reduced viscosity and yield were studied: type of organic solvent, type of hydrogen halide (HX) acceptor, concentration of reagents, reaction temperature and reaction time.

A through examination was carried out only for the polycondensation of dithiol with bis(4‐chloromethylphenyl)methane and 1,6‐dibromohexane chosen as model system. The structures of polysulfides were confirmed by elemental analysis, X‐ray analysis and infrared spectroscopy. The temperature of initial decomposition, the percentage of its mass loss, and the temperature of the fastest decomposition process were determined from the curves of differential and thermogravimetric analysis. Some physicochemical, mechanical and electrical properties were determined.
Modell zur beschreibung der viskoelastischen eigenschaften von synthetischen fasern
Authors: Schulz Jakob , Stalevitsch Arkadij , Eickmeier Achim , Bossmann Adelgund , Schollmeyer Eckhard
Published: April 2003

Zur Beurteilung des viskoelastischen Verhaltens von Synthesefasern sind zeitaufwendige Relaxationsuntersuchungen erforderlich. Um zu schnelleren Aussagen zu gelangen, werden mathematische Modelle benötigt. Charakteristisch für Synthesefasern ist, daß bereits bei sehr kleinen Dehnungen < 1% kein lineares viskoelastisches Verhalten angenommen werden kann. Es wird ein auf der Grundlage der Boltzmann‐Theorie erweitertes Modell vorgestellt, welches das nichtlineare viskoelastische Verhalten von Synthesefasern beschreibt. Unter Anwendung des hier vorgestellten Modells wird das Relaxationsverhalten der Synthesefasern Nomex® und PEEK beschrieben und ein Konzept zur Messung und Auswertung des Ergebnisses vorgestellt.
New aspects of the synthesis of polymercaptals
Authors: Sensfuß Steffi
Published: April 2003

The proton‐catalyzed polycondensation of aromatic aldehydes with aliphatic and aromatic α,ω‐dithiols leads to polymercaptals. The reaction may be carried out in bulk or solution. The bulk polycondensation was catalyzed by hexafluorophosphorous acid (HPF6), formed photochemically by irradiation of the samples containing diaryliodonium salt. The polymers were obtained in high yields but with low molecular weights of Mn 2300–5700 determined by vapour pressure osmometry (VPO). High‐molecular‐weight products of Mn 9100–24000 (VPO) were obtained by solution polycondensation in dichloromethane catalyzed by p‐toluenesulfonic acid. The polymers have been characterized by NMR, VPO, GPC and TGA. Cyclic side products have been isolated and identified. Polyrotaxane structures were found under special conditions.
Thermal behaviour of graft copolymers of sodium alginate
Authors: Shah Samir B. , Patel Chandrakant P. , Trivedi Harikrishna C.
Published: April 2003

The thermal stability of sodium alginate (SA) and its graft copolymers of acrylonitrile (AN), methyl acrylate (MA), ethyl acrylate (EA) and methyl methacrylate (MMA) has been examined in air atmosphere by means of thermogravimetric analysis. The following order of decreasing stability was found from characteristic decomposition temperatures: SA‐g‐PAN > SA‐g‐PMA > SA‐g‐PEA > SA‐g‐PMMA. The overall thermal stability of the different SA graft copolymers was evaluated by comparing their activation energies of thermal degradation; it agreed with the same order of thermal stability.
Plastic zone in front of mode I crack in phenolphthalein polyether ketone
Authors: Han Yanchun , Yang Yuming , Li Binyao , Feng Zhiliu
Published: April 2003

The plastic zone size and crack opening displacement of phenolphthalein polyether ketone (PEK‐C) at various conditions were investigated. Both of them increase with increasing temperature (decreasing strain rate), i.e. yield stress steadily falls. Thus, the mechanism increasing the yield stress leads to increased constraint in the crack tip and a corresponding reduction in the crack opening displacement and the plastic deformation zone. The effect of the plastic deformation on the fracture toughness is also discussed.
Preparation of hydrophilic membranes by grafting acrylic acid onto pre‐irradiated teflon‐FEP films
Authors: Aouadj S. , Chapiro A.
Published: April 2003

Grafting of acrylic acid onto pre‐irradiated poly(tetrafluoroethylene‐hexafluoropropylene) (Teflon‐FEP) films was investigated, and the reaction parameters dose, dose rate, monomer concentration and grafting temperature were examined.

The results show that the degree of grafting depends on the dose (5‐60 kGy), the weight of grafted specimen increased up to 37%. The degree of grafting was found to be independent of the dose rate.

The overall activation energies were calculated to be 28.8 and 81.6 kJ mol‐1 for treatments at above and below 50°C, respectively.

The swelling of grafted films was measured in water, aqueous potassium hydroxide and methanol. The degree of swelling was found to increase with the length of grafted chains.
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

A 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

A 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

Surface 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

Novolac‐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

Composites 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

Acetone 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

Isotactic 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

Die 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

A 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

Part 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

The 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

The 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

The 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

The 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

The 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

Two 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

Das 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

The 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

The 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

The 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

New 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

PTFE (powder or foils) was defluorinated and derivatized in a one‐step process by alkyl‐ and aryllithium in the presence of tetramethylethylenediamine

Systematic 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

The 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.
Electrochemical polymerization of some monomers with schiff's base structure. A voltammetric study
Authors: Simionescu C. I. , Grovu‐Ivanoiu M. , Cianga I. , Grigoras M. , Duca A. , Cocârla I.
Published: April 2003

The electrochemical polymerization of some Schiff's base‐type monomers like pyrrole‐2‐aldehyde azine, N,N′‐di(2‐pyrrolylmethylene)‐1,4‐diaminobenzene

Systematic name: 2,2′‐[1,4‐phenylenebis(nitrilomethylidyne)]dipyrrole.

, and N,N′‐di(2‐pyrrolylmethylene)‐4,4′‐diaminobiphenyl

Systematic name: 2,2′‐[4,4′‐biphenylylenebis(nitrilomethylidyne)]dipyrrole.

proceeds as a precipitating polymerization to the anodic compartment. The voltammetric study of monomers and polymers using Pt electrodes and paste‐carbon electrodes were carried out. The results are in agreement with the MO calculations using the Hückel approximation for evaluating of the reactivity of the monomers.
Synthesis of a new macromonomeric peroxyinitiator having poly(tetrahydrofuran) Units
Authors: Savaskan Sevil , Hazer Baki
Published: April 2003

A new macromonomeric peroxyinitiator (MMPI) was synthesized by the reaction of polytetrahydrofurandiol (p‐THF‐diol), Mw (1000), isophorone diisocyanate, 2,5‐dimethylhexyl‐2,5‐dihydroperoxide and 2‐isocyanatoethyl methacrylate. Homopolymerization of MMPI at 80°C gave crosslinked polytetrahydrofuran (poly‐THF) with swelling ratios in CHCl3 varying between 1.4 and 4.2.

Styrene polymerization initiated by MMPI at 80°C in bulk gave crosslinked poly‐THF‐b‐polystyrene block copolymers. The overall rate constant, k, was found to be 1 · 10−4 (L mol−1)1/2 s−1 by keeping the polymer yield below 15%. Swelling ratios of the crosslinked block copolymers in CHCl3 were between 2.7 and 75 according to the concentration of MMPI and the polymerization time. In case the MMPI concentration was kept constant while the polymerization time was increased, swelling ratios were found between 3.55 and 7.07. Thermogravimetric analysis showed that the crosslinked block copolymers were still containing undecomposed peroxy groups, so they can thermally initiate styrene polymerization in order to obtain multicomponent cross‐linked copolymers.
Coating of carbon‐fiber surface by silicon carbide via sol‐gel mixtures of tetraethyl orthosilicate and phenolic resin
Authors: Tan Ton That Minh , Nieu Nguyen Huu , Tan Phan Minh , Thanh Nguyen Dac
Published: April 2003

The preparation of a SiC coating on a carbon fiber surface using a sol‐gel mixture of tetraethyl orthosilicat (TEOS) and phenolic resin was studied. FTIR and SEM investigations indicated that the SiC coating can be formed by carbothermal reduction of the sol‐gel mixture at 1420°C for 15–20 min in an argon atmosphere. TGA of the coated fiber was also performed, showing that the SiC coating improves the thermooxidative stability of the carbon fiber. With the thickness of the obtained coating of 0.47 μm using a C/Si ratio of 4, this treatment does not affect the carbon fiber strength.
Stereoselective polymerization of butadiene by a new dicationic nickel complex
Authors: Gerbase Annelise Engel , de Souza Roberto Fernando , de Souza Vichi Eduardo Joaquim , da Cunha Fernanda Vieira
Published: April 2003

The new dicationic nickel complex [dppfNi(MeCN)4][BF4]2 (dppf = 1,1′‐bis(diphenylphosphino)ferrocene) in the presence of diethylaluminium chloride (AIEt2CI) exhibited high activity on the 1,3‐butadiene polymerization. Reaction time, temperature and aluminium/nickel molar ratio were optimized in order to achieve maximum activity and selectivity. Conversions higher than 90% were obtained in contrast to other nickel‐based systems using phosphine ligands, the resulting polybutadiene showed high cis‐1,4 (<80%) content and only small amount of 1,2‐units (2%). All polymers presented low molecular weights (Mw > 11 800).
Initiation of polymerization with substituted ethanes, 16. End‐reactive methacrylate oligomers as precursors of block copolymers
Authors: Braun Dietrich , Steinhauer‐Beißer Susanne
Published: April 2003

End‐reactive methacrylate oligomers, obtained by free‐radical polymerization of methyl, n‐butyl and tert‐butyl methacrylate with tetraphenylsuccinonitrile as initiator were used as free‐radical macroinitiators for the polymerization of styrene to prepare block copolymers. It could be shown by gel‐permeation chromatography coupled with FTIR spectroscopy that the oligomers are incorporated as segments in the block copolymers.

The tert‐butyl ester groups of tert‐butyl methacrylate‐styrene block copolymers were hydrolysed and neutralized to yield amphiphilic polymers which were characterized by thermogravimetry and dynamic mechanical thermal analysis. The existence of an extended rubbery plateau proved that triblock ionomers had been obtained, due to termination by combination of growing styrene block radicals.
Structural changes in poly(methyl methacrylate) during deep‐etch X‐ray synchrotron radiation lithography. Part III: Mode of action of the developer
Authors: Schmalz Olaf , Hess Michael , Kosfeld Robert
Published: April 2003

The structural changes in poly(methyl methacrylate) (PMMA) caused by radiochemical reactions are predominantly governed by a decrease in molar mass and a splitting of side chains. It can be shown that the removal of the irradiated parts of PMMA is not a pure physical dissolving, but that there is a chemical reaction proceeding, the products of which are well soluble in polar solvents. This special type of reaction restricts this process on the irradiated areas and hence explains the high selectivity of the developing of the lithographic structures. Knowledge of these mechanisms leads to the prediction that isotactic PMMA shows an increased selectivity of the developing agent. Further improvements and optimizations of etching and developing are therefore possible.
Untersuchungen zur synthese von poly(butadien‐co‐propylenoxid) mit einem ziegler‐natta‐titankatalysatorsystem
Authors: Kaulbach Ralph , Gebauer Ulrich , Mähner Christian , Lechner Manfred D. , Gehrke Klaus
Published: April 2003

Für die Copolymerisation von 1,3‐Butadien mit Propylenoxid wurde nach dem Vergleich der drei Katalysatorsysteme Nd(Oct)3/Al2Cl3ET3/Al(i‐But)3, Ni(Oct)2/ BF3OEt2/AlEt3 und Al(i‐But)3/I2/TiCl4 das Titankatalysatorsystem eingesetzt. Neben dem Einfluß der Monomerzusammensetzung auf den Umsatz, die Microstruktur, die Copolymerzusammensetzung, die Molmassen sowie die Molmassenverteilungen wurden auch die Polymerisationszeit und das Aluminium/Titan‐Verhältnis untersucht. Die Copolymerisationsparameter wurden nach Kelen‐Tüdős zu rButadien = 0,9 und rPropylenoxid = 3,9 bestimmt. Der Copolymernachweis erfolgte über 13C‐NMR‐Spektroskopie und Extraktionsuntersuchungen in Verbindung mit 1H‐NMR‐Spektroskopie.
Synthesis of flexible polyarylates by interfacial polycondensation. Part II: Incorporation of 4,4′‐thiodiphenol
Authors: Chen Tsu‐Hwei , Wang Ding‐Chang , Chiu Wen‐Yen , Chen Leo‐Wang
Published: April 2003

The toughness of polyarylates was improved by incorporation of 4,4′‐thiodiphenol and bisphenol A, being introduced in the aqueous phase of an interfacial polycondensation reaction. The modified polyarylates possessed slightly lower tensile strength and modulus but much higher Izod impact strength due to the flexibility of the incorporated segments. In addition, the superb thermal properties typical for polyarylates were reserved in the modified polyarylate, thus assuring its broad applicability for those applications where extremely stringent criteria of thermal characteristics are required.
Hydrogels for biomedical use based on 1‐vinyl‐2‐pyrrolidone crosslinked with macromonomers
Authors: Michálek Jiři , Vacík Jiři , Kúdelková Jana , Ježová Naděžda
Published: April 2003

Macromonomers of various chain lengths with an average of three allyl double bonds per chain were prepared by anionic copolymerization of allyl methacrylate with methyl methacrylate. The macromonomers were characterized by gel permeation chromatography and nuclear magnetic resonance. The macromonomers were then copolymerized with 1‐vinyl‐2‐pyrrolidone to form three‐dimensional structures. Their optical, swelling and mechanical properties were studied and the crosslinking efficiency was determined. The copolymer properties are not greatly affected by macromonomer chain lengths up to 40‐mers; above 50‐mers there is a slight decrease in the equilibrium water content and a significant increase in the modulus of elasticity. The crosslinking efficiency depends on the macromonomer chain length; a marked increase was observed for the 50‐mer because of a greater number of methyl‐methyl interactions. Copolymers have favourable strength‐strain properties and a low content of water‐soluble extracts, in which the IR analysis demonstrated the presence of 1‐vinyl‐2‐pyrrolidone homopolymers. In spite of the good results obtained for all the macromonomers described in this work, the 50‐mer seems to be optimal for copolymerization with 1‐vinyl‐2‐pyrrolidone.
Graft polymerization of vinylidene chloride onto cellulose. A method to ascertain the grafting yield
Authors: Casinos Ismael , Gual Cristina
Published: April 2003

The graft polymerization of vinylidene chloride (VDC) onto cellulose initiated by ceric ions is reported. The grafting yield increases with reaction time and then levels off after 6 h. On the other hand, the grafting efficiency decreases rapidly from high initial values at short reaction times and then approaches to a constant value. The mechanism from of grafting is suggested for the present copolymerization. In order to determine both grafting yield and grafting efficiency, the separation of homopolymer and graft polymer is required. Sufficiently high temperatures are needed to dissolve poly(vinylidene chloride) (PVDC) because of its high crystallinity and melting point. Cyclohexanone dissolves the graft copolymer at 120°C bringing about some degradation of cellulose. Degradation is produced by hydrogen chloride formed throughout a slight dehydrochlorination of the synthetic polymer. A method inert for cellulose is suggested to retrieve the homopolymer from the polymerization crude by using a mixture of dry cyclohexanone and 4‐methylpyridine as solvent.
Elastic properties of thermosets in glassy state
Authors: Verdu J. , Tcharkhtchi A.
Published: April 2003

The Young's modulus E and Poisson's ratio v of various thermosets, including 6 amine crosslinked epoxies, one anhydride crosslinked epoxy, one styrene crosslinked polyester and one styrene crosslinked vinylester, were determined from tensile tests in the 220–393 K temperature range and 1.6710−4−1.6710−2 s−1 strain rate range. The bulk (B) and shear (G) modulus were calculated from E and v. Some observations about structure‐property relationships can be derived from these data and their comparison with corresponding ones relative to linear polymers. B appears to depend essentially of the cohesion and packing density and does not depend, practically, of temperature and strain rate. In contrast, G depends sharply of the local molecular mobility, this latter being affected by an antiplasticization mechanism. The Poisson's ratio seems to be systematically higher for thermosets than for linear polymers.
Monte‐carlo modelling of the formation, structure and properties of polymer networks
Authors: Dutton S. , Stepto R. F. T. , Taylor D. J. R.
Published: April 2003

A new Monte Carlo (MC) algorithm is reported which enables RAfa +RBfb polymerisations to be simulated. It is based on the random reaction of pairs of groups for intermolecular reaction, with intramolecular reaction weighted according to Gaussian statistics and the size of ring structure being formed. The algorithm counts all the ring structures formed and enables polymerisations to be simulated efficiently up to complete reaction. Gel point and modulus results from trifunctional and tetrafunctional polyurethane‐forming polymerisations are modelled, with particular emphasis on the effects on modulus of network defects at complete reaction. More in keeping with experiment, higher reductions in modulus at complete reaction are predicted using the the present algorithm than using Biosym MC software. However, it is shown that quantitative agreement with experiment cannot be obtained unless relationships defining the entropies of various ring structures are elucidated and more accurate modelling of the chain statistics governing the intramolecular reaction forming ring structures of various sizes is used.
Synthesis and properties of epoxy‐episulfide resins
Authors: Bell J. P. , Don Trong‐Ming , Voong Senh , Fernandez A. , Ku W.
Published: April 2003

Standard epoxy resins have good mechanical properties, but their prolonged low temperature curing time limits their potential use in clinical applications as well as in many industrial applications. A fast‐curing epoxy‐episulfide resin has been developed. The gel time of epoxy‐episulfide made from EPON

Trade mark of Shell Chemical Company.

828 ranges from 2 to 10 minutes by changing the ratio of the ingredients. The heat of reaction of this system is low, resulting in low cure shrinkage. Water absorption of the episulfide network is low. The epoxy‐episulfide system cured with polyamide curing agent V‐40 exhibits two transition temperatures, at about 85°C and 130°C, as shown in dynamic mechanical analysis data. In order to solve the long term stability problem of the above episulfides, and also the mixing problem, a lower viscosity resin, Eponex, was used to make Eponex‐sulfide. Eponex‐sulfide systems show promise in that they remain in a stable liquid form without epoxy. The other advantages appear to be retained.
Molecular design of reactive microgels
Authors: Kaczun J. , Funke W.
Published: April 2003

Structure and properties of microgels prepared by emulsion copolymerization depend on the composition and concentration of the monomers at the reaction sites, on the reactivity ratios and on the solubility of the comonomers in water. By separate and joint solubilization of 1,4‐divinyl benzene and various comonomers of different solubility it could be shown, that the diffusion control of the copolymerization rate is favoured by crosslinking, by a high concentration of an oil‐soluble initiator and of the emulsifier and by a low solubility of the comonomer in water.
Designing elastomer network for desired tire performance characteristics
Authors: Futamura Shingo
Published: April 2003

Rubber elasticity is associated with changes in configurational entropy of a long chain. Because the chain cannot change its configuration instantaneously, there is a time delay in deformation to an applied force. This delayed response is the source of viscoelasticity and hysteresis energy loss of elastomer networks. Many tire performance properties are related to the viscoelasticity of tire components. Wet and dry traction of tire is related to the energy loss of the tread material at very high frequencies. On the other hand, rolling resistance of tire is characterized by the energy loss of tread material at relatively low frequencies. The dynamic viscoelastic properties of elastomer network shows characteristic zones on a frequency scale. At very high frequencies the energy loss is controlled by the segmental motions of the polymer chain. At lower frequencies the energy loss is related to the longer range motions of the chain. A series of polymers was synthesized to study the effect of micro‐ and macro‐structure of the polymer on the viscoelastic properties of tread compounds and their tire performance properties. As expected from the theory, the wet traction of the tire was highly correlated to the segmental motions of the chains; namely, the glass transition temperature of the polymer. The energy loss of the compounds at a higher temperature, however, was related to the macrostructure of the polymer chain. Those examples illustrate that the fundamental understanding of the theory of elastomer network allows a tire engineer to obtain the best balance of tire performance characteristics.