bluuebunny/crossref_metadata_2025 huggingface dataset:
Studies on antioxidants, 1. Phenolic antioxidants as stabilizers for polypropylene
Authors: Raja A. , Pendyala V. N. S. , Xavier S. F. , Shah A. C. , Nair K. B.
Published: April 2003

A group of phenolic antioxidants was synthesized, characterized and the performance of these antioxidants in polymer processing was tested in the polymer melt by multiple extrusions. The change in melt flow was observed and compared with the change in melt flow by use of commercially available antioxidants. All the antioxidants examined had the same phenolic stabilization moiety but varied in the size of the substituents in the para‐position of the aromatic ring. Increasing length of the side chain considerably influences the behaviour of the antioxidants in the polymer and thus their effectiveness.
Crystallization behavior of polypropylene filled with calcium carbonate of various shape
Authors: Mitsuishi Kazuta , Ueno Satoru , Kameyama Kenro
Published: April 2003

Calcium carbonate of various particle shape (spheric, cubic, needle‐shaped type) and polypropylene (PP) were mixed on a two roll mill and the mixture was pressed into plates. The effect of particle shape on the crystallization behavior of PP/CaCO3 composites, such as crystallization peak temperature (TMAX), crystallized pattern, etc., was investigated with differential scanning calorimetry measurements. The value of TMAX is explained by the total surface area of added CaCO3 particles; TMAX of needle‐shaped series is larger than that of cubic or spheric ones. TMAX of various shaped CaCO3‐filled PP totally depends on the cooling rate and maximum temperature in the non‐isothermal crystallization, respectively.
The utilisation of latex reclaim rubber in natural rubber
Authors: George Reena Susan , Joseph Rani
Published: April 2003

Scrap latex products contain rubber hydrocarbon of very high quality, that is only slightly crosslinked. A novel economic technique for converting such latex waste into a processible material is developed. This paper reports the effect of adding this latex reclaim to natural rubber. It is shown that latex reclaim can replace raw natural rubber up to about 50 wt.‐% without affecting mechanical properties.
Concentration effects of methylalumoxane, zirconocene dichloride and trimethylaluminum in ethylene polymerization
Authors: Rieger Bernhard , Janiak Christoph
Published: April 2003

A quantitative study was carried out on the homogeneous zirconocene dichloride/methylalumoxane/trimethylaluminum (Cp2ZrCl2/MAO/TMA) catalyst system in ethylene polymerization. The effects of variation of the AlMAO/Zr ratio, absolute Zr concentration, and addition of TMA on ethylene polymerization activity and polymer properties were investigated. The polymerization profiles for small AlMAO/Zr ratios and the changes with the Zr concentration are explained with a complexation equilibrium for the active homogeneous complex and with the change to a heterogeneous catalyst upon polymer precipitation. Good polymer productivities can be achieved at AlMAO/Zr < 1000 when working at Zr concentrations between 10−4 and 10−5 mol/l with addition of TMA (AlMAO/AlTMA≈ 1.4).
Cationic polyelectrolytes, XII. PEG‐precursor for water‐soluble cationic polymers with tertiary n‐atoms in the main chain
Authors: Drǎgan Stela , Ghimici Luminiţa
Published: April 2003

Water‐soluble cationic polymers were obtained by polyaddition of poly(ethylene glycol) (PEG) diglycidylethers (M̄n of PEG were 396, 587, 1437 and 3554, resp.) with asymmetrical diamines such as N,N‐dimethyl‐1,3‐diaminopropane and N,N‐diethyl‐1,3‐diaminopropane. The cationic polymer properties depend on the PEG initial molecular weight and on the diamine reactivity too. PEG with M̄n = 396 had the best behaviour in these reactions. The polyelectrolyte feature of cationic polymers was emphasized both in dilute aqueous solutions and in 2M aqueous NaCl solutions. The polyelectrolyte behaviour in 2M aqueous NaCl solution is determined by the PEG chain presence.
Laser‐induced crosslinking of siloxanes: A semi‐empirical molecular orbital study
Authors: Roth Wolfgang , Lorenz Michael , Clark Timothy
Published: April 2003

The semi‐empirical molecular orbital method AM1 has been used as a tool for the prediction of radical intermediates and crosslink structures that may be of importance in the direct laser excitation of siloxanes. Special emphasis was put on configuration interaction (Cl) in order to calculate energies and geometries of excited triplet states as well as potential curves of triplet reactions. Heats of formation of intermediates and reaction enthalpies of monomolecular fragmentation reactions of T1 excited states of 2‐phenyl‐1,1,1,2,3,3,3‐heptamethyltrisiloxane and octamethyltrisiloxane were calculated. In the former case bimolecular reactions were also considered. Dissociation of a methyl group was found to be the most probable monomolecular fragmentation. Consecutive reactions of the silyl radical formed lead to crosslink structures like SiCH2Si and SiC6H4Si. Biphenyl‐ and phenylcyclohexadienyls are the most probable crosslink structures of bimolecular reactions with phenyl exciplexes as intermediates. Experimental evidence is given for these crosslink structures.
Untersuchungen zur reaktion von o‐kresol mit formaldehyd unter verwendung tertiärer amine
Authors: Roatsch Birgit , Reinisch Gerhard , Hinzmann Karin , Samland Birgit , Schirmer Matthias
Published: April 2003

The reaction between o‐cresol and formaldehyde was investigated using various tertiary amines as catalysts. The influence of the reaction parameters basicity, temperature, reaction time and concentration of formaldehyde was discussed. To yield preferentially 2,4‐bis(hydroxymethyl)‐6‐methylphenol the conditions of synthesis were optimized. The formation of bi‐ and polynuclear products cannot be avoided.
Free radical copolymerization of allyloxyphenylsiloxanes with some vinyl monomers
Authors: Matsukawa Kimihiro , Hirano Hiroshi , Inoue Hiroshi
Published: April 2003

Two p‐allyloxyphenyldisiloxane compounds, 1‐(p‐allyloxyphenyl)‐1,1,3,3,3‐pentamethyldisiloxane (mono‐APDS) and 1,3‐bis(p‐allyloxyphenyl)‐1,1,3,3‐tetramethyldisiloxane (bis‐APDS), were synthesized to study their radical copolymerizations with some vinyl monomers (styrene, methyl methacrylate, N‐phenylmaleimide and maleic anhydride). The reactivities of allyl groups in mono‐APDS and bis‐APDS were found to be almost the same in styrene and methyl methacrylate copolymerization, as evidenced by their composition curves, and increase with the electron‐accepting ability of comonomers. In the case of electron‐poor monomers, such as N‐phenylmaleimide and maleic anhydride, the second allyl group of bis‐APDS readily took part in the crosslinking. Differential scanning calorimetry and thermogravimetry revealed that the increase of APDS contents in those copolymers led to lower glass transition temperature (Tg) and higher thermal degradation temperature.
Degradation and stabilization of PVC in blends
Authors: Braun D. , Böhringer B. , Eidam N. , Fischer M. , Kömmerling S.
Published: April 2003

Poly(vinylchloride) (PVC) was mixed with various poly(methacrylate)s, poly(carbonate)s and polymers containing nitrile groups (poly(acrylonitrile), poly(styrene‐co‐acrylonitrile), nitrile rubber, hydrogenated nitrile rubber) and/or C  C double bonds (nitrile rubber, high‐impact poly(styrene)). The thermal stability was measured at 180°C in nitrogen, and the evolved HCl was detected by conductometry.

It is shown that the nature of the ester group and the content of nitrile groups and C ‐ C double bonds are the dominating factors for the thermal stability of poly(vinylchloride) in these blends. An influence of the miscibility of PVC with the various blend components on the thermal stability can not be clearly detected.

Differential scanning calorimetry (DSC) was used as a powerful method to study the stabilizer distribution of heterogeneous PVC/poly(styrene‐co‐acrylonitrile) and PVC/poly(methylacrylate) blends. It is shown that the stabilizer can be solubilized either in the PVC phase (PVC/poly(methylacrylate)) or in both phases of the blends PVC/poly(styrene‐co‐acrylonitrile)).
The biodegradation of polymers: Recent results
Authors: David C. , De Kesel C. , Lefebvre F. , Weiland M.
Published: April 2003

After a general introduction including definition of biodegradability, the recent literature is briefly summarized. The results obtained in our laboratory for various polymers in three different composting units are then presented. They demonstrate that there is an urgent need for a quantitative method to characterize polymer biodegradation. For that purpose, a manometric method which allows the measurement of the oxygen consumed by the growing microorganisms has been developed. It has been tested with various inocula of increasing complexity: one Streptomyces sp., a mixture of three Streptomyces (badius, setonii and viridosporus), a compost extract or sewer sludge, growing in the presence of low molecular weight molecules as sole carbon source. Its performances and limitations are discussed. It is then applied to various polymer systems: polyesters and their constituent units, autoxidized polyethylene (APE) and its model compounds, polyvinyl alcohol (PVAl), starch and cellulose. The biodegradability of these polymers is characterized and their potential use as biodegradable materials for packaging, sanitary and agricultural uses is discussed.
Thermo‐mechanical degradation of polymer blends
Authors: La Mantia Francesco Paolo , Valenza Antonino
Published: April 2003

Polymer blends can undergo, during processing, degradation phenomena because of the presence of both temperature and mechanical stresses. With respect to pure homogeneous polymers, the degradation of polymer blends shows distinct features because of the possible interaction between the different chemical species. These interaction can give rise to both a faster degradation or to the formation of copolymers which act as stabilizing agents. This latter phenomena is particularly important in the processing of condensation polymers
Reaction of hals in polypropylene during light exposure: Part 1‐iso‐octane as reaction model compound ‐
Authors: Neri C. , Malatesta V. , Costanzi S. , Riva R.
Published: April 2003

The photo and thermal reactivity of nitroxyl radicals derived from di‐, (oligo)meric hindered amine light stabilizers (HALS) on iso‐octane, a model compound for polyprophylene, was studied and compared to that of monomeric 2,2,6,6‐tetramethyl‐ piperi‐dine‐N‐oxyl (TEMPO).

The exchange‐interaction among >NO. groups seems to affect only the thermal process.
The bisphenol‐A polycarbonate dual photochemistry
Authors: Rivaton Agnès
Published: April 2003

The photochemical behaviour of Bisphenol‐A polycarbonate (PC) under various types of monochromatic and polychromatic radiations is reported. The PC dual photochemistry observed in the solid state is characterized using both UV and FTIR spectroscopy. At short wavelength, the intrinsic photochemistry, which is associated with the direct photo‐excitation of PC chromophore groups, accounts for the formation of phenylsalicylate, dihydroxybenzophenone, hydroxybiphenyl and hydroxydiphenyl ether groups. The extrinsic photochemistry of PC, related to the excitation of chromophoric defects, is easily observed at long wavelength. This photoinduced oxidation leads to the formation of tertiary hydroperoxides which decompose into alcohols and ketones. The two photochemistries kinetically overlap but their stoichiometry remains independent. PC films can be used therefore to check the relative importance of short and long wavelength radiations emitted by the various sources used in the field of polymer degradation.
Application of chemiluminescence to polymer degradation studies. Thermal oxidation of polyamide 6.
Authors: Matisová‐Rychlá L. , Lánská B. , Rychlý J.
Published: April 2003

Chemiluminescence (CL) technique was used to study the thermal oxidation of polyamide 6 samples with different ratio of terminal basic and acid groups, which perform a distinct effect on kinetics of the isothermal CL – time runs at 120–140°C. The isothermal experiments are complemented by nonisothermal ramp experiments where the CL intensity is monitored against temperature at a programmed rate of temperature increase.

The relation of parameters such as initial CL intensity, integrated value of CL intensity for both isothermal and nonisothermal experiments and rate constants corresponding to CL – time curves was discussed within the results of other oxidation stability tests as absroption of oxygen, thermogravimetry, etc.
Synthesis and properties of polyunsaturated xylitol carbonate methacrylates
Authors: Zaks Irene N. , Penczek Piotr , Rot Alfred S. , Pernikis Ruta
Published: April 2003

Xylitol carbonate methacrylates were synthesized from 2‐methacryloyloxyethyl chloroformate and xylitol. The composition of the products was investigated by HPLC. Optimum conditions for obtaining the polyfunctional monomer containing 92% penta‐substituted xylitol were determined. Photopolymerization of the monomers was carried out. The polymers show an extremely low birefringence index.
Phase behaviour and bistable effect of a mixture comprising a dye side chain liquid crystalline polymer and a low molecular weight liquid crystal
Authors: Hwang Jenn‐Chiu , Hsiue Ging‐Ho , Jeng Ru Jong
Published: April 2003

Phase behaviour and bistable effect of dye side chain liquid crystalline polymer (dye LCP)/low molecular weight liquid crystal (LC) mixtures have been investigated. The smectic dye LCP was observed to be miscible with the nematic LC over wide ranges of concentration and temperature. The electro‐optical effects of the dye LCP/LC mixtures could be classified into the turbid and the transparent states upon a respective application of electric fields at low and high frequencies. Both transparent and turbid states of the mixture could be maintained stable, despite an electric field having been turned off.
Modified styrene‐isoprene‐styrene block copolymer membranes complexed with cobalt‐containing schiff's bases for oxygen permeation
Authors: Hsiue Ging‐Ho , Hsu Wey‐Leun , Yang Jen‐Ming
Published: April 2003

The grafting of 4‐vinylpyridine (VP) and 1‐vinylimidazole (VIm) onto styrene‐isoprene‐styrene (SIS) triblock copolymer by radiation‐induced graft copolymerization was studied. The effect of grafting degree on gas permeability of membranes made of grafted copolymers was investigated. The complex formation of the modified SIS (SIS‐g‐VP or SIS‐g‐VIm) with cobalt‐containing Schiff's bases (CoS) in chloroform solution was studied. Facilitated transport of molecular oxygen in modified SIS membranes containing CoS as fixed carrier of oxygen, and oxygen permeability in modified SIS membranes due to the oxygen binding ability to CoS was observed. Mechanism of oxygen transport across the SIS‐g‐VP‐CoS and SIS‐g‐VIm‐CoS membrane is discussed.
Eigenschaften von binären mischungen aus polyethylenen hoher dichte mit ultrahoher und normaler molmasse
Authors: Grigorova Marietta , Michailov Marin
Published: April 2003

Untersucht wurden binäre Mischungen von Polyethylenen hoher Dichte rnit normaler und ultrahochmolekularer Molmasse, die auf zweierlei Weise—in Pulverform oder durch Walzen im Schmelzezustand—homogenisiert und bei Temperaturen zwischen 140 und 220°C gepreßt waren.

Es wurde festgestellt, daß die Art der Homogenisierung der Komponenten praktisch keinen Einfluß auf die Eigenschaften bei Preßtemperaturen ≥ 160°C hat. Von besonderem Interesse sind die Eigenschaften der Systeme, in welchen das ultrahochmolekulare Polyethylen die Rolle der Matrixkomponente spielt.
Viscous and elastic behaviour of SEBS triblock copolymer
Authors: Mathew Ivy , George K. E. , Francis D. Joseph
Published: April 2003

The viscous and elastic behaviour of the saturated triblock copolymer polystyrene‐block‐poly(ethylene‐co‐butylene)‐polystyrene (SEBS) was investigated using a capillary viscometer. The viscous behaviour was evaluated from the variation of viscosity with shear and temperature, and the elastic behaviour from the capillary entrance pressure loss, die swell ratio and surface roughness. The melt behaviour was found to result from the two‐phase structure which existed up to a particular shear and/or temperature and thereafter from the single‐phase structure.
Electron beam initiated grafting of methyl methacrylate onto polyethylene: Structure and properties
Authors: Chaki T. K. , Despande R. S. , Majali A. B. , Tikku V. K. , Bhowmick A. K.
Published: April 2003

Polyethylene (PE, 100 parts by weight) was mixed with methyl methacrylate (MMA, up to 5 parts by weight) at 120°C and subsequently exposed to electron radiation of different doses (up to 20 Mrad) to prepare PE/MMA graft copolymers. Successful grafting was verified by IR spectroscopy. Gel formation indicated crosslinking. Grafting increased with increasing MMA concentration and increasing irradiation dose. Crystalline melting temperature and percent crystallinity were lower than those of untreated PE. Tensile strength, elongation at break and dielectric constant of grafted samples were measured and discussed.
Transesterification in blends of poly(butylene terephthalate) and bisphenol‐A‐polycarbonate
Authors: Wings N. , Trafara G.
Published: April 2003

By means of differential calorimetric and X‐ray examinations it was shown that poly(butylene terephthalate) (PBT) and bisphenol‐A‐polycarbonate (PC) are only compatible in the melt if they stay in the melt for a short period of time. During mixing in the melt, transesterification begins and block copolymers are formed. A characteristic glass transition temperature is observed for each individual blend. Butylene terephthalate (BT)‐blocks are crystallizable; however, with an increasing share of bisphenol‐A‐carbonate (BPAC) the specific melting enthalpy of the BT‐blocks decreases. Within copolymers with a high BPAC content, the BPAC segments crystallize considerably faster than in pure PC. By means of diffraction measurements with synchrotron radiation, the mechanism of stress‐induced α‐β‐modification change in pure PBT and in block copolymers with high BT‐contents could be explored.
Reactive blending of thermosets: Molecular, morphological and mechanical analysis
Authors: Martuscelli Ezio , Musto Pellegrino , Ragosta Giuseppe , Scarinzi Gennaro
Published: April 2003

A number of different approaches were used to enhance the toughness of tri‐ and tetrafunctional epoxies and of unsaturated polyester resins. In the case of epoxies, tough, thermally stable, engineering thermoplastics, namely a bisphenol‐A polycarbonate and a thermoplastic poly(ether imide) (Ultem 1000) were employed as modifiers. For unsaturated polyesters a different approach was adopted: two commercial liquid rubbers were chemically modified to enhance their reactivity towards the matrix functionalities. In particular, a hydroxy‐terminated polybutadiene and an aminoterminated butadiene‐acrylonitrile copolymer were transformed into isocyanate‐terminated and maleimide‐terminated rubbers, respectively. A further system which is described in the present contribution is aimed at mitigating another deficiency of the polyester matrix, namely its rapidly decreasing rigidity at temperatures above room temperature. In this case, a thermosetting bismaleimide was incorporated into the resin as a co‐reactive second component.
Recycling of egyptian bagasse pith wastes in the synthesis of cationic resins
Authors: Metwally M. S. , Metwally N. E. , Samy T. M.
Published: April 2003

A series of sulfonated cationic resins have been prepared and characterized from Egyptian bagasse pith wastes (as a source of cheaper and renewable material) with m‐cresol and paraformaldehyde as a crosslinking agent. Reaction conditions for the preparation are presented and properties of the synthesized sulfonated bagasse pith‐m‐cresol‐formaldehyde resins are described and compared with resin not containing bagasse pith. The synthesized resins are stable in water, dilute mineral acids (1 M), organic solvents, and to thermal treatment. The resins having a cation exchange capacity up to 2.91 meq g‐1 of dry resin, are being introduced as new exchangers. The synthesized resins are used in the study of the possible separation of some bivalent cations.
Laser‐induced surface grafting of 2‐hydroxyethyl methacrylate and N‐vinyl‐2‐pyrrolidone onto ethylene‐propylene rubber as biocompatible material
Authors: Mirzadeh H. , Katbab A. A. , Khorasani M. T. , Burford R. P.
Published: April 2003

Attempts have been made to provide hydrophilic sites onto the surface of ethylene‐propylene rubber (EPR) by grafting 2‐hydroxyethyl methacrylate (HEMA) and N‐vinylpyrrolidone (NVP) onto the surface of this elastomer using CO2‐pulsed laser as excitation source. The effect of benzophenone (BZP) and azoisobutyronitrile (AIBN) as photosensitizer upon the graft level has been evaluated. CO2‐pulsed laser grafting of HEMA and NVP was found to be dependent upon the wavelength, repetition rate, and fluence of laser. Hydrophilicity of EPR increased upon grafting HEMA and NVP with CO2‐pulsed laser. Surface characterization has been carried out using attenuated total reflectance infrared spectroscopy (ATR‐IR), scanning electron microscopy (SEM) and energy dispersive X‐ray analysis (EDXA). IR‐laser grafting of these monomers is not possible unless the system is irradiated by pulses with the wavelength corresponding to the either maximum absorption of monomer or sensitizer accessible to the laser equipment gain. As the absorption of EPR at these wavelengths is quite low, it is believed that depending upon the wavelength, either photosensitizer and/or monomer molecules are excited through an infrared multiphoton excitation (IRMPE) process above the dissociation energy leading to the decomposition of the excited molecules. Addition of a multifunctional acrylate (MFA) such as 1,1,1‐trimethylolpropane‐trimethacrylate (TMPTA) to the grafting system enhanced the graft yield. Poly(HEMA) grafted onto the surface of EPR by CO2 pulsed laser tends to form a fractal type of morphology. The shape and size of fractals depends upon both laser parameters and HEMA concentration. EDXA analysis showed the presence of ungrafted (hydrophobic areas) as well as hydrophilic sites (fractals) on the surface of modified samples. Finally, the bulk mechanical properties of EPR after being laser‐grafted with HEMA or NVP did not change, as shown by DMTA.
Emulsion polymerization of butyl acrylate, 3. Effect of initiator type and temperature
Authors: Potisk Pavol , Capek Ignác
Published: April 2003

The emulsion polymerizations of butyl acrylate initiated by water‐soluble (ammonium peroxodisulfate, AP) and oil‐soluble (dibenzoyl peroxide, DBP) radical initiators were investigated. Polymerizations were found to be faster with AP. The size of polymer particles formed and the molecular weights decreased with increasing temperature and increased with conversion. The number of particles was constant in the conversion range from ca. 30 to 100%. The overall activation energy (E0) was found to be ca. 50–60 kJ · mol‐1 which is nearly half of that of the bulk polymerization. The activation energy of the AP‐initiated polymerization was found to be independent of conversion while that for the DBP‐initiated polymerization decreased with conversion, and the decrease was more pronounced beyond 60% conversion. This behavior was discussed in terms of the emulsion and bulk polymerizations and variations of the activation energy for termination with viscosity of the reaction media.
Färben in überkritischem CO2: Bestimmung von Einflußgrößen auf das strukturelle Verhalten von Polyethylenterephthalat‐Fasermaterial
Authors: Knittel Dierk , Saus Wolfgang , Hoger Susanne , Schollmeyer Eckhard
Published: April 2003

Die Beeinflussung von Merkmalen der Polymerstruktur durch Behandlung mit überkritischem CO2 wird anhand von Polyesterfasermaterial untersucht. Das überkritische System verursacht eine Absenkung der Glastemperatur und bewirkt die Ausbildung netzwerkstabilisierender Kristallite in den fehlgeordneten Bereichen des Fasermaterials, die denen entsprechen, die ohne Gegenwart eines überkritischen Fluids erst bei deutlich höheren Behandlungstemperaturen gebildet werden. Die Bedeutung der Polymerstruktur für Fäbung bzw. Imprägnierung von Fasermaterial in überkritischen Systemen wird diskutiert.
Epoxysiloxane resins by the condensation of 3‐glycidyloxypropyltrimethoxysilane with diphenylsilanediol
Authors: Wipfelder Ernst , Höhn Klaus
Published: April 2003

Condensation of 3‐glycidyloxypropyltrimethoxysilane I with diphenylsilanediol II was investigated. Depending on solvent, temperature and catalyst, different products were obtained. Bulk reaction at 120°C using titanium(IV)‐isopropylate as a catalyst provided the transparent resin A. A was characterised by IR, 1H‐ and 13C‐NMR spectroscopy and contained no reactants. GPC and HPLC studies revealed that A consists of trimer and tetramer siloxanes of pertinent diphenylsilane and 3‐glycidyloxypropylmethoxysilane moieties. The proportion of cyclic to linear molecules was evaluated 2:1. Only small amounts of high‐molecular‐weight compounds were observed. The epoxysiloxane product proved to be miscible with various organic solvents and with commercial epoxy resins. Time dependence of viscosity and epoxy content were recorded during ambient storage and monitored by HPLC. Pot‐life was improved by a subsequent thermal procedure.
Synthesis of polypyrrole by electrochemical polymerization using organic anion electrolytes and its application
Authors: An Heishoku , Haga Yutaka , Yuguchi Toshiyuki , Yosomiya Ryutoku
Published: April 2003

The synthesis of polypyrrole from aqueous solutions using various organic anion electrolytes and its electric and mechanical properties and the junction characteristics of sandwich devices were investigated.

As electrolytes the following anions were used: p‐toluenesulfonate (p‐TS‐), benzenesulfonate (BS‐), dodecylbenzenesulfonate (DBS‐), naphthalene‐2‐sulfonate (N‐2‐S‐) and sulfosuccinate (SS‐1); their effect on the conductivities of the polypyrroles decreases in the order DBS‐1 > p‐TS‐1 > N‐2‐S‐1 > BS‐ > SS‐. Higher conductivity and mechanical properties were obtained by drawing of films. With indium, polypyrrole forms rectification contacts, whereas ohmic contacts are formed in junction with Au or Pt. From the analysis of the current‐vs.‐voltage and capacitance‐vs.‐voltage characteristics, it is suggested that a Schottky barrier is formed at the interface between polypyrrole and indium.
Kinetics studies on the free radical polymerization of styrene in the presence of asphalts
Authors: Milczarska Teresa , Szafko Jerzy
Published: April 2003

A study was made of the free radical polymerization of styrene in bulk at 60°C initiated with 2,2′‐azoisobutyronitrile in the presence of the stable free radical 4‐hydroxy‐2,2,6,6‐tetramethyl‐piperidine‐1‐oxyl (TMHPO) and two types of petroleum asphalts D and F. It was found that petroleum asphalts contain compounds effective as polymerization inhibitors and that they also include substances taking part in initiation processes. The differences between the kinetics behaviour of asphalts in comparison with stable free radicals were the subject of the discussion.
Triazine‐based polymers, 1. Synthesis of poly[(2,4‐dichloro‐6‐ethoxy‐s‐triazine)‐alt‐(bisphenol a)]
Authors: Braun D. , Ziser T.
Published: April 2003

Poly[(2,4‐dichloro‐6‐ethoxy‐s‐triazine)‐alt‐(bisphenol A)] (T‐BPA), a polymer with interesting mechanical and thermal properties, was synthesized by phase transfer catalysed interfacial polycondensation. The reaction conditions for the synthesis of T‐BPA were investigated and optimized. The influence of several reaction parameters, such as temperature, reaction time, type and concentration of phase transfer catalyst, concentration of monomers, type of solvent, type of base, salt addition, and molecular weight terminator concentration on the reduced specific viscosity and yield of T‐BPA was investigated. As a result, it is possible to synthesize T‐BPA at reaction conditions being favourable with regard to the costs of energy and equipment.
Preparation and characteristics of amphiphilic membranes by photosensitive poly(vinyl cinnamate)
Authors: Liu Jui‐Hsiang , Chung Yi‐Chan , Lin Ming‐Ter
Published: April 2003

A series of hydrophilic‐hydrophobic poly(vinyl cinnamate) (PVCin) membranes was developed. The poly(vinyl cinnamate)s were synthesized from poly(vinyl alcohol) with various amounts of cinnamoyl chloride in the presence of alkali. The amphiphilic membranes, which can be used instead of the traditional two‐layer membranes in the enzyme electrode, were prepared by using photosensitive poly(vinyl cinnamate) and/or poly(vinyl alcohol) with sensitizers. The properties of photocrosslinking, water permeability and oxygen permeability of the amphiphilic membranes were investigated. The combinations of amphiphilic membranes were examined by scanning electron microscopy (SEM).
Synthesis and characterization of uv‐curable acrylated urethane prepolymers, I. Effects of reactive diluents and relative humidity on physical properties
Authors: Yildiz Emel , Güngör Atilla , Yildirim Hüseyin , Baysal Bahattin M.
Published: April 2003

A UV‐curable acrylated urethane prepolymer was synthesized from tolylene‐2,4‐diisocyanate (TDI), a polyether polyol (Arcol 1131) and endcapped with 2‐hydroxyethyl methacrylate (HEMA) by addition reaction in the presence of dibutyltin dilaurate as catalyst. UV curing was performed with either diethylene glycol diacrylate or thiodiethylene glycol diacrylate as reactive diluent.

The effects of reactive diluent types, their concentrations and the humidity of environment on mechanical properties of cured films were investigated. Changes in the tensile strength, elongation and Young's modulus values of the cured films upon addition of reactive diluents with different concentrations were related to the effect of the diluent on the crosslinking density of cured films.

The increase of relative humidity from 50 to 95% caused a decrease of tensile strength and Young's modulus values of cured films. It is proposed that the decrease of these physical properties in high relative humidity is due to the formation of hydrogen bonding in polymer chains caused by water molecules.
Preparation and characteristics of immobilized glucose oxidase on membranes of photosensitive polymers
Authors: Liu Jui‐Hsiang , Chung Yi‐Chang
Published: April 2003

A study of the immobilization of glucose oxidase on a poly(vinyl alcohol) (PVAL) membrane in the presence of UV sensitizers was carried out. Enzyme membranes were prepared from PVAL‐diazoresin and PVAL‐sensitizer systems, crosslinked by means of UV irradiation. An effective enzyme electrode was developed by using the immobilized glucose oxidase membrane, and its characteristics were investigated. The effects of the concentration of sensitizers in poly(vinyl alcohol) and UV irradiation time on the degree of insolubility as well as the activity yield of the membrane were examined for the immobilized glucose oxidase using glucose as a substrate. Temperature and pH dependences of the relative activity, stability in repeated use, storage stability and calibration plots of the enzyme membranes were evaluated. The unstability phenomenon, found in the initial use of the immobilized glucose oxidase membrane, which was prepared from PVAL‐sensitizer system, was also investigated.
Plasma treatment of polyethylene ultrafiltration membranes
Authors: Bryjak Marek , Gancarz Irena
Published: April 2003

The effect of plasma treatment of polyethylene ultrafiltration membranes on fouling and cleaning phenomena during filtration of bovine serum albumin solutions is discussed. Air‐plasma of 2.45 GHz raises the membrane surface hydrophilicity from 0 up to 60%. The flux is maintained at 90–99%. Plasma‐treated membranes are easier to clean than untreated polyethylene membranes. Despite that, the plasma‐modified membranes are susceptible to more intensive deposition of albumin.
Temperature/rate dependence of yield and fracture behaviour of phenolphthalein poly(ether ketone)
Authors: Han Yanchun , Yang Yuming , Li Binyao , Feng Zhiliu
Published: April 2003

The rate/temperature dependence of yield stress, tensile modulus and crack opening displacement of phenolphthalein poly(ether ketone) (PEK‐C) has been investigated. The rate/temperature dependence of crack opening displacement and the correlation established between stress intensity factor, KIC, yield stress, and type of crack growth suggest that the extent of crack tip blunting largely governs the relative toughness of PEK‐C and induces transitions in the types of crack growth observed. A quantitative expression is then presented which successfully describes the fracture toughness values over a wide range of temperatures and rates.
Hydroxamic acid esters and oximes as isocyanate blocking agents. Study on thermal dissociation
Authors: Quérat Evelyne , Tighzert Lan , Pascault Jean‐Pierre
Published: April 2003

Blocked isocyanates were prepared and their thermal dissociation into isocyanates and blocking agents was studied. Three blocked versions of 4,4′‐diphenylmethane diisocyanate (4,4′‐MDI) were synthesized. The selected blocking agents were 2‐butanone oxime (methyl ethyl ketoxime, MECO), ethyl acetoacetate oxime (EAO) and benzyl methacrylohydroxamate (BMH), in order to compare their temperature of dissociation (Td). Chemical titration of —NCO groups was tested as suitable technique to follow the unblocking with the temperature. Confirmation of the results by infrared spectroscopy was successful with the hydroxamic ester as blocking agent. Thermodynamic parameters were evaluated for the BMH‐MDI adduct and allowed to predict the free —NCO ratio at high temperatures.

Benzyl methacrylohydroxamate can be used as blocking agent and the blocked system shows lower unblocking temperature than the usual oxime‐blocked isocyanates.
Adsorption of cis‐1,4‐polyisoprene at solid/liquid interface
Authors: Vangani Veena , Rakshit Animesh Kumar
Published: April 2003

The adsorption of cis‐1,4‐polyisoprene on alumina and silica gel was studied at three temperatures. The solvents used were toluene, chlorobenzene and various mixtures of both. The adsorption from the mixtures of the solvents was much less than from either of the pure solvents. The amount of adsorption was an inverse function of temperature. The thermodynamic quantities of adsorption at infinite dilution were obtained by extrapolation and at isosteric conditions. They were computed and discussed for all the systems.
Metal ion binding properties of synthetic vinyl resins
Authors: Rivas B. L. , Maturana H. A. , Pereira E.
Published: April 2003

The synthesis of a water‐insoluble chelating resin was carried out by radical copolymerization of 4‐vinylpyridine and N‐hydroxymethyl acrylamide with subsequent crosslinking. Both the crosslinked reference homopolymers of 4‐vinylpyridine and N‐hydroxymethyl acrylamide were also synthesized. The resins were characterized by elemental analyses and FT‐IR spectroscopy. The ability of these resins to bind copper(II), iron(II), iron(III) and uranyl ions as well as the elution of the metal ions from the loaded resins were studied. For uranyl ions, pH 1 was the optimum sorption pH value for all the resins. Sorption selectivity from the binary mixture Cu(II) + U(VI) was studied at the optimum sorption pH value. Finally, the uranium(VI) sorption isotherms, binding constants, and ΔG°, ΔH° and ΔS° corresponding to the uranium(VI) sorption process were calculated.
Dyes for nonlinear optics prepared from 2‐hydroxyethyl methacrylate. Nonlinear properties of the resulting copolymers
Authors: Monthéard Jean‐Pierre , Chatzopoulos Farroudja , Amine Hassan El , Cachard Alain , Trouillet Alain
Published: April 2003

Dyes for nonlinear optics have been synthesized in two steps from 2‐hydroxyethyl methacrylate (HEMA), 4‐carboxybenzaldehyde and various substituted anilines. The obtained dyes (aromatic imine esters of HEMA) have been copolymerized with styrene, the copolymers characterized by DSC as well as IR, 1H NMR and UV‐VIS spectroscopy, and studied for their nonlinear properties. The d31 and d33 nonlinear coefficients proved to be dependent on the dye content of the copolymers and on the nature of electrondonating groups.
Study of the surface properties of ultrathin films of poly(dimethylsiloxane)‐polyamide multiblock copolymers
Authors: Kishida Akio , Furuzono Tsutomu , Ohshige Taka‐aki , Maruyama Ikuro , Matsumoto Takeo , Itoh Haruhiko , Murakami Mikio , Akashi Mitsuru
Published: April 2003

Ultrathin films of poly(dimethylsiloxane)‐polyamide copolymers (PAS) with different silicone contents were prepared by the methods of water casting and spin coating. The surface properties of the films were investigated in detail using contact angle measurements and X‐ray photoelectron spectroscopy (XPS). The water‐cast films were thin enough to be applicable as laminate films for an artificial lung or an air‐separator for oxygen‐enrichted air. Uniform and ultrathin films were obtained by the spin coating method. XPS and contact angle measurements suggested that poly(dimethylsiloxane) segments were condensed at the outermost surface of spin‐coated PAS films. XPS measurements also revealed that the surface properties of PAS were affected by the molding method, especially the solvent evaporation conditions.
Effect of a curing accelerator on the glass transition temperature of non‐stoichiometric epoxy amine networks
Authors: Strehmel Veronika , Deltschewa Kalina , Häusler Karl‐Georg , Schröter Klaus
Published: April 2003

Networks were prepared from Bisphenol A diglycidylether and 4,4′‐diaminodiphenylmethane both in the presence of different amounts of imidazole and in the absence of any accelerator. The ratio of epoxy groups to amino hydrogen was varied: the networks were made with amino hydrogen excess, a stoichiometric ratio of epoxy groups to amino hydrogen, and an epoxy excess.

The resulting networks were investigated by thermomechanical analysis, by torsion pendulum analysis and by uniaxial compression modulus measurements in the rubbery‐plateau zone. Further characterization was done by sol gel analysis of the cured samples.

It was shown that imidazole does not significantly influence the glass transition temperature and the soluble content of the samples of an excess of amino hydrogen was used. In the case of a stoichiometric ratio of epoxy groups to amino hydrogen and in the case of an epoxy excess, imidazole considerably influences the glass transition temperature of the networks. A dependence of the soluble content of the samples on imidazole concentration used for network synthesis was found mainly in epoxy excess systems.
Functionalization of carbon fibres
Authors: Palma Enrique , Ibarra Luis
Published: April 2003

This work reports on a study conducted to achieve carbon fibre functionalization by means of a diazide derivative(p‐(azidosulfonyl)benzoyl azide) in two stages. The first stage comprises surface oxidation of the fibres, which causes an increase of the number of superficial COOH groups. During the second stage the oxidated fibres are brought to react with the diazide derivative via the isocyanate group, obtained by means of the Curtius transposition of the carbonyl azide groups. Fibre oxidation depends on reaction time, following a similar patterns as the one described for carbon black particles. Oxidized fibres functionalization is evidenced both in the progressive decreases in SO2N3 groups in the reagent solution and through differential scanning calorimetry analysis (DSC), which shows an exothermal peak around 190°C due to the decomposition of the azide grafted onto the carbon fibre.

The degree of attainable functionalization is a function of COOH groups concentration, generated during fibre oxidation, and the ratio of the functionalizing agent with regard to the carboxy groups formed.
Zum reaktionsverhalten von resol‐ und novolak‐modellen mit säureanhydriden
Authors: Böschel Dorit , Fedtke Manfred
Published: April 2003

Benzylalkohol und p‐Kresol wurden als Modellverbindungen für Phenolharzvorstufen mit Bernsteinsäureanhydrid, Hexahydrophthalsäureanhydrid und Citraconsäureanhydrid umgesetzt. Das Reaktivitätsverhalten von 2,6‐Dimethylol‐p‐kresol mit den genannten Anhydriden wurde näher untersucht. Es wurde nachgewiesen, daß bei der Umsetzung mit Citraconsäureanhydrid die phenolische Hydroxygruppe erhalten bleibt und der entstandene Ester in zwei Modifikationen vorliegt. Die Carbonsäureanhydride wurden ferner mit höhermolekularen Resol‐ und Novolakmodellen umgesetzt.
Studies on curing characteristics of natural rubber‐, nitrile rubber‐, and silicone rubber‐based filled compounds in the presence of boron compounds
Authors: Maity S. K. , Chakraborty K. K.
Published: April 2003

The influence of four different boron compounds (boron carbide, boron nitride, boron oxide and disodium tetraborate decahydrate) on the curing characteristics of carbon black‐ and silica‐filled conventional natural rubber‐, nitrile rubber‐, and silicone rubber‐compounds has been studied. The curing parameters have illustrated the individual action. Rheographs have been analysed through the application of CoraN's model. The kinetic parameters have revealed the effects of the boron compounds on different stages of cure. The crosslink density has been assessed from swelling for comparison with the related parameters.
Sulfobetaine polyurethane ionomers, 5. Tensile properties of polyether polyurethane ionomer and related compounds with Co2+ and Pb2+
Authors: Diaconu I. , Coman P. , Buruianǎ T.
Published: April 2003

Stress‐strain properties of sulfobetaine polyurethane ionomer based on polyether were studied comparatively to the non‐ionic polyurethane and derived compounds with Pb2+ and Co2+. Sulfonation and treatment with H2S improve the tensile properties due to the increased phase segregation and to the semiconducting microphases formed by clustering of metal sulfides, respectively. Complexation with Pb2+ and Co2+ diminishes the tensile properties owing to the partial neutralization of ionic centers.
Novel biodegradable copolyamides based on adipic acid, isophorone diamine and α‐amino acids, 3. Synthesis, study of properties and evaluation of their biodegradability for food packaging applications
Authors: Arvanitoyannis Ioannis , Nikolaou Eleftherios , Yamamoto Noboru
Published: April 2003

Novel biodegradable copolyamides were synthesized by melt polycondensation. Statistical copolymers were produced by the incorporation of α‐amino acids showing a gradual increase in their Tg but a decrease in their tensile strength followed by higher susceptibility to alkali hydrolysis which was confirmed with GPC measurements. The amorphous nature of these novel copolyamides was confirmed with the aid of wide‐angle X‐ray diffraction patterns and differential thermal analysis. FT‐IR spectra of the copolymers confirmed the existence of the amino acid moiety. These novel biodegradable copolyamides are expected to find application either on their own in the fields of food packaging and agriculture (disposable plastics) or as a part of composites, as sutures for fixation of macroscopic implants.
Characterization of thermoplastic poly(ethylene terephthalate)‐glass fibre composites, 2. Mechanical behaviour
Authors: Gauthier Catherine , Chauchard Jacques , Chabert Bernard , Trotignon Jean Pierre
Published: April 2003

The aim of this study was to understand how changes in processing conditions affect the morphology and ultimately mechanical performances of unidirectional poly(ethylene terephthalate) / glass fibre composites. In a previous paper, we have presented the influence of fibres on the crystallization kinetics and on the matrix morphology of poly(ethylene terephthalate) (PET), considering fusion‐crystallization conditions, thermal stability and the addition of nucleating agents in the matrix (talc or sodium benzoate). Based on the results of that crystallization study, various processing conditions were implemented on compression‐moulded plated made from PET‐glass pultruded ribbons. Short‐term (dynamic and static) shear tests and long‐term flexural fatigue tests were performed to characterize the effects of moulding conditions. The mechanical results were analysed considering both processing conditions and microstructural parameters.
Yield behaviour and viscoelastic interpretation by activation volume of phenolphthalein polyether ketone
Authors: Han Yanchun , Yang Yuming , Li Binyao , Feng Zhiliu
Published: April 2003

Phenolphthalein polyether ketone (PEK‐C) exhibits a marked tensile yield behaviour. The yield stress depends on strain rate and the activation volume V could be evaluated from the data of the yield stress. From the creep and stress relaxation behaviour, V could also be evaluated. So the yield behaviour can be interpreted by the viscoelasticity.
Electrokinetic measurements on porous polysulfone membranes
Authors: Schwarz Simona , Jacobasch Hans‐Jörg , Wyszynski Danuta , Staude Eberhard
Published: April 2003

The surface properties of porous ultrafiltration membranes were determined by means of the streaming potential. The membranes were prepared from chemically modified polysulfone through a phase inversion process. The chemical reactions were carried out in such a way that the resulting polysulfone either was fitted out with chloromethyl substituents or with quaternary ammonia groups. Due to this, the surface of the membranes cast from these materials were either neutral or positively charged. In aqueous solution, ion adsorption as well as dissociation can occur at the surface of the membranes. This can be demonstrated by streaming potential measurements at different pH values, but constant ionic strength. From the calculated zeta potential using a recently developed model, evidence can be given on the dissociation constants of acidic and basic functional groups on the surface of the membranes and on the amount of charges within the shear plane adjacent to the membrane. Using solutions which contained surfactants, qualitative information on the amount of charges within the capillaries of the membrane can be obtained. In the range from 20 to 70°C no temperature dependency of the zeta potential could be observed.
Synthesis of block copolymers by using polysilanes
Authors: Yücesan Dilek , Hostoygar Halil , Denizligil Selçuk , Yagci Yusuf
Published: April 2003

Poly(methyl phenyl silane) was used to photoinitiate the polymerization of methyl methacrylate. Poly(methyl methacrylate) (PMMA), obtained this way, contains remaining polysilane chains. Photolysis of this PMMA in the presence of vinyl monomers such as styrene makes it possible to prepare block copolymers. Such PMMA prepolymers were also used to induce the polymerization of cyclohexene oxide through formation of PMMA‐attached silyl radicals and subsequent oxidation to the corresponding ions in the presence of N‐ethoxy‐2‐methylpyridinium hexafluorophosphate resulting in the formation of a block copolymer.
Action of some organophosphonic compounds on a diglycidyl ether‐bisphenol‐A epoxy resin
Authors: Petreus Oana , Popescu Florin N. , Caşcaval Constantin N.
Published: April 2003

The effect of three organophosphonic compounds on the thermooxidative degradation of the uncured diglycidyl ether‐bisphenol‐A epoxy resin was investigated, using infrared spectroscopy, thermogravimetry, differential thermogravimetry, static pyrolysis, pyrolysis‐gas chromatography and elemental analysis. The results obtained indicate that additives with phosphorus and chlorine or nitrogen in molecules exercise an influence upon the degradative process of uncured resin by catalysing its decomposition in the lower temperature region. At the same time, the tested additives promote the formation of highly thermostable and non‐flammable structures in the solid residue.
Grafting of acrylonitrile onto bagasse dissolving pulp with KMnO4/oxalic acid system
Authors: El‐Torky Alaa M. M. , El‐Masry Ahmed M. , El‐Fattah Ali H. Abd
Published: April 2003

Bagasse dissolving pulp was grafted with acrylonitrile by using a KMnO4 oxalic acid redox initiator system. The effects of monomer concentration, reaction time, initiator concentration, acid concentration and reaction temperature were investigated.