bluuebunny/crossref_metadata_2025_split huggingface dataset:
pH control of the condensation reaction and its effect on the properties of formaldehyde/urea resins
Authors: Szesztay M. , László‐Hedvig Zs. , Takács C. , Gács‐Baitz E. , Nagy P. , Tüdős F. 
Published: April 2003

AbstractThe conditions of the preparation of formaldehyde/urea (F/U) resins have been supervised with the aim to reduce formaldehyde emission by influencing the ratio of methylene/dimethylene‐ether‐bridge linkages in the product.The most crucial point of this task is to keep the pH values of the reacting mixtures on the required level. The effect of formic acid, unevitably present in industrial formaldehyde solutions, was neutralized by applying a new buffer system, containing boric acid and ethylene glycol.
Determination of the substituent pattern of heterogeneously and homogeneously synthesized carboxymethyl cellulose by using high‐performance liquid chromatography
Authors: Heinze Thomas , Erler Ulrich , Nehls Irene , Klemm Dieter 
Published: April 2003

AbstractA rapid and convenient procedure was developed for the determination of the substituent pattern of carboxymethyl cellulose (CMC) by means of high‐performance liquid chromatography. The hydrolysates of CMC are separated on a polystyrene‐based strong cation‐exchange resin into glucose, 2,3,6‐tri‐O‐carboxymethyl glucose and groups of 2‐, 3‐and 6‐mono‐O‐ and 2,3‐, 2,6‐, and 3,6‐di‐O‐carboxymethyl glucoses. By this method the determination of the average degree of substitution as well as the substituent pattern is possible. In this way we found that CMC samples which were synthesized in LiCl/N,N‐dimethylacetamide as a cellulose solvent, contain a significantly higher amount of both tricarboxymethylated and unsubstituted units than those obtained in a slurry of cellulose in isopropanol/water at comparable DS values. The substituent pattern of heterogeneously synthesized CMC is mainly determined by statistics.
Evaluation of poly(butyl acrylate‐co‐ethylene glycol dimethacrylate) sorbents for chromatographic separation of biomolecules
Authors: Bryjak Marek 
Published: April 2003

AbstractCopolymers of butyl acrylate (BA) crosslinked with ethylene glycol dimethacrylate (EGDMA) were evaluated as potential chromatographic packings. It was found that slightly crosslinked copolymers (up to 30 wt.‐% EGDMA) did not provide porous material, while for matrices which exceeded 40 wt.‐% of EGDMA the porous structure remained unchangeable. The increase of crosslinker content mostly affected the surface hydrophobicity. Two methods of measurement of this property were discussed: Sorption of alkyl alcohols and amino acids. Taking the latter for testing, a polymer matrix hydrophobicity index was calculated as the slope of dependence of column capacity vs. amino acid hydrophobicity parameter. The indices were verified against well‐established interaction energies of CH2 groups of alkyl alcohols and polymer surfaces. Some benefits of the use of the hydrophobicity index in evaluation of polymer sorbents were demonstrated.
Infrared study of the catalytic degradation of a commercial epoxy adhesive on metal surfaces
Authors: Hong Shinn‐Gwo 
Published: April 2003

AbstractReflection absorption infrared spectroscopy (RAIR) has been used to investigate the effects of different surface materials (interstitial free steel (IFS), aluminium (2024‐A1) and copper) on the thermo‐oxidative degradation of a commercial two part epoxy adhesive system. The epoxy resin was spin‐coated on polished metal substrates and aged at 125°C for different periods of time. Based on the relative changes in intensities of the amide, ether and alcohol bands during exposure, it was found that the fastest degradation took place on the Cu surface, whereas the slowest happened on the 2024‐Al surface. The accelerated degradation observed on the Cu surface was partly attributed to the preferential adsorption of labile amino and amide groups on the Cu surface.
Cetylpyridinium chloride‐modified poly(ethyleneimine) for the removal and separation of inorganic ions in aqueous solution
Authors: Palmer Valentina , Zhou Rongnong , Geckeler Kurt E. 
Published: April 2003

AbstractThe removal and separation of a series of ions by the water‐soluble cetylpyridinium chloride‐modified poly(ethyleneimine) (PEI‐CPC) in conjunction with membrane filtration were investigated. The Liquid‐Phase Polymer‐Based Retention (LPR) method was applied to study the removal of the low‐molecular species at different pH values and at several element concentrations. The study comprises aqueous solutions of the anions chromate and phosphate, and of the cations Cu(II), Zn(II), Co(II), Ni(II), Cr(III), Fe(III), Cd(II), Pb(II) and Sr(II). The results show that a high retention was attained in neutral solutions for both anions and also for most metal ions investigated. PEI‐CPC exhibited good removing abilities for chromate and phosphate ions even at relatively high concentrations of anions (85 and 150 mg · L −1, respectively) and also for most of the metal ions studied. In the case of Cu(II), Ni(II), Cd(II), and Sr(II) ions, selective interactions were observed. The polymer reagent and its interaction products were characterized by IR, UV/VIS spectrometry, and viscometry. In addition, the interaction behaviour was investigated by the retention ability. A good correlation was found between the retention data and the IR and UV/VIS spectra of the interaction products of the polymer reagent with the metal ions.
Effect of addition of cellulose powder on the viscometric behavior of liquid crystalline solutions of ethyl cellulose in m‐cresol
Authors: Suto Shinichi , Murokoshi Katsunobu 
Published: April 2003

AbstractSteady‐state shear viscosity for the liquid crystalline ethyl cellulose solution filled with cellulose powders was determined using a cone‐plate‐type viscometer and the effects of cellulose powder content, powder aspect ratio and temperature on the viscometric behavior and phase transformation were discussed. The addition of powder increased the viscosity and decreased the activation energy (Ea) for flow, but did not affect the phase transformation. The viscosity and Eadepended on the aspect ratio; with greater aspect ratio, the viscosity enhancement was accelerated and Eaas well as the decrease in Eawith powder content increased. The phase transformation did not depend on the aspect ratio, the dependences of viscosity and of Eaon powder content depended on the solution phase; the dependences for the anisotropic phase were smaller than those for the isotropic one. The findings appeared to originate from the alignments of powders and rod‐like molecules.
Oxygen uptake methods as a tool to determine the mechanism of action of hindered amine light stabilizers1
Authors: Gijsman Pieter , Hennekens Jan , Tummers Daan 
Published: April 2003

AbstractThe UV‐degradation of an unstabilized and two HALS stabilized polyethylene (PE) films is described. The degradations are characterized by measuring the oxygen uptake, the formation of CO and CO2, the FT‐IR spectra, the mechanical properties, the stabilizer concentration and the oxygen content of the film.The oxygen uptake of the unstabilized PE film led to the expected changes in the IR spectra and embrittlement of the film, while the oxygen uptake by the HALS stabilized films caused only minor changes. The differences between the results for the unstabilized and the HALS stabilized polymers are explained assuming that the initiation of the photodegradation of PE is due to charge transfer complexes.
Studies on controlled oxidation of low molecular weight polyethylenes
Authors: Munteanu D. , Toma F. 
Published: April 2003

AbstractThe low molecular weight by‐product of a high‐density polyethylene plant (slurry process in hexane, Ti‐based highly active catalysts) was subjected to controlled oxidation by air bubbling into the polymer melt maintained under stirring at constant temperature (130–170°C). Oxidized polyethylene waxes having various oxidation degree, i.e. acid number up to 60 mg.KOH/g and saponification number up to 120 mg.KOH/g have been obtained under different reaction conditions. Oxidation temperature and polymer/air ratio proved to be the main parameters that control the process. Inhibition and catalytic effects have been also studied as well as the dependence of the oxidation process on the like of the starting low molecular weight polyethylene. the results have been used to develop an industrial process for producing oxidized polyethylene waxes with useful properties and applications.
Photo–degradation of high performance polymers and application of a novel technique to degraded polymers
Authors: Narisawa I. , Kuriyama T. 
Published: April 2003

AbstractOutdoor weathering at three locations in Japan has been carried out for new engineering plastics; PPO, PPS, PA and PEI. The degradation results were compared with those exposed in the Sunshine and Xenon Weather simulation machines. The half‐time of these materials, which was the time to give a 50% decrease of some property, strongly depended on a property to be noted. The elongation to break and impact energy, i.e. fracture energy, reflected the degradation process of neat polymers and they were closely related to the condition of a very thing degraded layer. The half‐amount of ultraviolet radiation also depended both on a property and material. The acceleration rate of the weather simulating machines has been obtained by this half‐amount. The loss in mechanical properties of fiber‐filled materials is much smaller than that of neat polymers. The fibers could reduce the embrittlement of the degraded layer. It has been demonstrated that a micro‐cutting technique to measure cutting resistance is a useful method to monitor a continous change in mechanical properties from the surface to the interior of the degraded layer. The effect of stabilizer has been clearly shown by this technique.
The kinetics and mechanism of polyethylene photo‐oxidation
Authors: Cruz‐Pinto J. J. C. , Carvalho M. E. S. , Ferreira J. F. A. 
Published: April 2003

AbstractThe kinetics of the natural and accelerated photo‐oxidation of low‐denisty polyethylene (LDPE) films have been studied; different geographical locations have been selected for the natural tests, and a range of temperatures used in the accelerated experiments in a specially built temperature‐controlled ultraviolet radiation enclosure. A meaningful correlation between natural and accelerated weathering results was established, by means of an adequate superposition of the effects of UV radiation exposure and temperature. Reasonably detailed and accurate, lumped‐parameter, kinetic models of the photo‐oxidation process have also been developed, to interpret and predict the results of measurements of carbonyl, hydroperoxide and vinyl absorbances as functions of time and temperature; the models predict the general experimental behaviour, and also that both the formation of hydroperoxides and carbonyl Norrish‐I reactions are important initiation steps. More complex models have the potential of interpreting other fine details of the degradation behaviour, namely the generation of other chemical species, and the chain scission and cross‐linking process which are directly related to changes in the mechanical properties.
Current of status of exploitation of radical scavenging stabilizers in advanced polymer stabilization
Authors: Pospíšil Jan 
Published: April 2003

AbstractPrincipal chemical pathways characteristic of active participation of radical scavenging polymer stabilizers (phenols, aromatic, hydroaromatic and hindered aliphatic amines) are outlined. Pathways resulting in a partial depletion or distortion of activity of stabilizers, in formation of polymer discolouring products, or in interactions in bifunctional stabilizers are involved.
Poly(butyleneterephtalate) photolysis and photooxidation : Identification of the ir‐absorbing products
Authors: Rivaton Agnès 
Published: April 2003

AbstractIrradiations (λ≥300 nm) of poly(butyleneterphtalate) films were carried out in both vacum and air. Photoproducts were investigated by FTIR spectroscopy, chemical derivatization reactions and physical treatments. The repartition of photoproducts in the polymer was shown to be heterogeneous. A scheme accounting for the main routes of PBT photolysis was found on the basis of photoproducts identification. Most of oxidation products were analogous to vacum photolysis species; the mechanism of photooxidation proposed implied both pure photolytical processes and a photo‐induced oxidation route.
Polymer degradation by elimination of small molecules
Authors: Šimon Peter 
Published: April 2003

AbstractAn outline of a method of deriving the kinetic equations for polymer degradation by the elimination of low molecular weight compounds is presented. The method is based on the stochastic approach. The main ideas are that the degradation occurs via the zip mechanism and that the initiating step, i.e. the formation of an olefinic site in the polymer chain, takes place at random. Three mechanisms have been investigated in this study: (i) ordinary zip mechanism; (ii) autocatalytic mechanism with immediate zip growth and catalyzed initiation; (iii) autocatalytic mechanism with gradual zip growth. The kinetic equations derived have been used in kinetic studies of the dehydrochlorination of PVC in inert, HCl, and oxidative atmospheres, and of the degradation of polyvinyl esters, polyvinyl bromide and polyvinylidene chloride. Kinetic parameters for the degradation of individual polymers have been obtained.
The transformations of organic polymers during the illumination by 147.0 and 123.6 nm light
Authors: Skurat Vladimir E. , Dorofeev Yurij I. 
Published: April 2003

AbstractThe main features of photolysis of organic polymers by the light 147.0 and 123.6 nm (resonance xenon and krypton lamps respectively) were investigated by methods of anaylsis of gaseous products by mass spectrometry, of analysis of polymer transformation by UV and VUV absorption spectroscopy and of measurement of gel does. The quantum yields of main products were measured for photolysis of polyerthylene, polypropylene, polyisobutylene, polyisoprene, polybutadiene, silicone rubbers, polymethylmetacrylate and some other polymers. The quantum yields of products in the VUV photolysis are compared with radiation yields of these products in the radiolysis by gamma‐rays. The main difference between mechanisms of VUV photolysis and radiolysis consists in strong predominance of processes of molecular elimination in VUV photolysis in comparison with free radical processes. In contrast during the radiolysis these processes give approximately equal contributions. This difference is explained by reactions of photo excited singlet states of polymer molecules during photolysis while in the radiolysis the great contribution is given also by excited triplet and ionized states. In experiments with partially deuterated derivatives of polymethylmetacrylate the main channels of formation of formaldehyde, methylformate, methanol and methane were determined.
Photo‐ and radiation‐induced degradation of synthetic polymers: Polymer structure and stability
Authors: Torikai Ayako 
Published: April 2003

AbstractThe effect of polymer density, processing conditions (quenching of annealing), degree of crystallinity, size of crystallite and mobility of polymer chains on the photo‐and radiation‐induced degradation and the polymer stability have been studied by UV, FTIR spectroscopic, viscosity and mechanical property measurements. Four kinds of annealed or quenched polyethylene (PE) films varying densities were used to the studies. Polystyrene (PSt) films were used to investigate the effect of chain mobility on polymer degradation. The following results were obtained.

In linear low density (LLD) PE, greater amounts of crosslinking (irradiated in vacuum) and chain scission (irradiated in air) were noticed than in mediun density (MD) PE and high density (HD) PE samples.
Polyene formation is favored in the case of the irradiation in vacuum for LLDPE.
Polymer stability evaluated by mechanical property such as elongation at break (%) is superior in LLDPE to MDPE and HDPE for annealed and quenched samples.
Segmental motion of polymer chain also affects the polymer stability
Structure and some properties of methacrylonitrile/divinylbenzene macroporous copolymers
Authors: Kolarz Bożena N. , Trochimczuk Andrzej W. , Wojaczyńska Maria , Drewniak Marta 
Published: April 2003

AbstractCopolymers of methacrylonitrile (MAN) and divinylbenzene (DVB) of different crosslinking degree between 6–50 wt.‐% DVB were obtained by suspension polymerization of monomers in the presence of a diluent (1 : 1, v/v), i.e. a mixture of toluene with tetradecane (9 : 1, v/v). Porosity of the copolymers (MAN/DVB) has been found to fall in the range 48–57.3%. Specific surface area of the copolymers increased in the range of mesopores with the increasing crosslinking degree. Sorption properties of the copolymers towards aqueous phenol solution are similar to those of acrylonitrile‐DVB copolymers. MAN/DVB copolymers display rather poor thermal stability (low residue) what indicates that thermally initiated cyclization of nitrile groups can not take place and the influence of depolymerization may be significant.
Aryl ether‐ketone segmented polypyromellitimides
Authors: Biçak Niyazi , Koza Güneş 
Published: April 2003

AbstractAromatic ether‐ketone segments have been incorporated into polyimide backbone to impart the well‐known thermoplastic properties of polyether ketones. For this purpose three aromatic diamines containing ether and ketone connecting groups between aromatic rings have been prepared and polymerized with pyromellitic dianhydride to yield polyimides. The thermal behavior of the polyimide cast films has been investigated.
Polymers with acyloxime ester in the main chain: Synthesis, characterization and initiator properties of an azo‐containing ester initiator
Authors: Onen Aysen , Denizligil Selcuk , Yagci Yusuf 
Published: April 2003

AbstractFor application as initiator, a new polymeric azo‐acyloxime ester (AOE) was synthesized by condensation of 4,4′‐azobis(4‐cyanopentanoic acid chloride) (ACPC) with 1‐(4‐hydroxyphenyl)‐1,2‐propanedione‐2‐oxime (HPO). The initiator structure was confirmed by IR and NMR spectroscopy. The kinetics of the free‐radical polymerization of styrene initiated by AOE was investigated and the kinetic parameters evaluated. The initiation of polymerization of styrene by means of AOE yields polymers with photoactive acyloxime groups in the main chain.
Behaviour of a silica filler surface‐modified with boron‐amine groups
Authors: Elvira M. Rosario , Macias Antonio , Oteo Jose Luis , Royo Joaquin , Rubio Juan 
Published: April 2003

AbstractThe behaviour of silica fillers modified with primary boron‐amine groups has been studied under different reaction conditions. The filler with the best reinforcing properties was used to compare two different vulcanization systems: an efficient vulcanization system, EV, which is the recommended ISO Standards method to study the reinforcing behaviour of new silicas, and a conventional vulcanization system.The results indicate that the best properties are obtained with silica treated for 3 h at 500°C, reaction conditions which fix most of the primary boron‐amine groups. Using the EV system, the properties of this modified silica are similar to those of silane‐modified silica, and in some cases better than those obtained with a conventional vulcanization system. In all cases, the boron‐amination treatment significantly improves the behaviour of precipitated silica as a reinforcing filler.
Study of the mechanism of the antioxidant action of ethoxyquin
Authors: Taimr Luděk 
Published: April 2003

AbstractA study has been carried out of the reaction of 6‐ethoxy‐2,2,4‐trimethyl‐1,2‐dihydroquinoline (ethoxyquin, I) with alkylperoxyls. In the presence of a relatively low concentration of 1‐cyano‐1‐methylethylperoxyl, I reacts to form dimer IV (8‐(6‐ethoxy‐2,2,4‐trimethyl‐1,2‐dihydroquinolin‐1‐yl)‐6‐ethoxy‐2,2,4‐trimethyl‐1,2‐dihydroquinoline) as the main product and quinoline derivative III (2,4‐dimethyl‐6‐ethoxyquinoline), as a side product, i.e., substances formed by the conversion of the aminyl II (6‐ethoxy‐2,2,4‐trimethyl‐1,2‐dihydroquinolin‐1‐yl) alone. Smaller amounts of p‐quinoneimine VI and o‐quinoneimine VIII (2,2,4‐trimethyl‐2,6‐dihydro‐6‐quinolone and 6‐ethoxy‐2,2,4‐trimethyl‐2,8‐dihydro‐8‐quinolone) have been found; these substances are formed by further oxidation of II. In the presence of relatively high concentrations of tert‐butylperoxyls, peroxide IX (6‐tert‐butylperoxy‐6‐ethoxy‐2,2,4‐trimethyl‐2,6‐dihydroquinoline) is formed as the main product. Substance IX thermally decomposes to form VIII, while in the presence of weak acids IX is converted into VI as the main product.Dimer IV is a medium‐strength antioxidant which is gradually converted into 8‐(6‐ethoxy‐2,2,4‐trimethyl‐1,2‐dihydroquinolin‐1‐yl)‐2,2,4‐trimethyl‐6‐quinolone (XI) and 8‐(6‐ethoxy‐3‐hydroxy‐2,2‐dimethyl‐4‐methylene‐1,2,3,4‐tetrahydroquinolin‐1‐yl‐)‐2,2,4‐trimethyl‐2,6‐dihydro‐6‐quinolone) (XII). The methyl group in XI actively participates in the antioxidation process.When formed, nitroxide V (6‐ethoxy‐2,2,4‐trimethyl‐1,2‐dihydroquinolin‐N‐oxyl) acts as an efficient antioxidant which, however, does not participate in the cyclic mechanism that is employed to explain the action of antioxidants of the HALS type.The antioxidant properties were evaluated on the basis of their effect on the course of the autoxidation of squalene.
Antistatic modification of polyester with carboxyterminated poly(oxyethylene)
Authors: Zhao Yao‐Ming , Chen Junwu , Sano Yoshiyuki , Kimura Yoshiharu 
Published: April 2003

AbstractCarboxy‐terminated poly(oxyethylenes) (PEO‐acid) with number‐average molecular weights Mn = 8400, 3300, and 1000 were used for antielectrostatic modification of poly(ethylene terephthalate) (PET). The blend PET fibers containing 2.0 and 5.0 wt.‐% of PEO‐acids were melt‐spun at 285°C with an ordinary extruder and then drawn about 4.5‐fold at 80°C. The processabilities of spinning and drawing were excellent at higher molecular weights of PEO‐acid. The anti‐electrostatic properties of the blend fibers became also improved with increasing molecular weight of PEO‐acid. Since little ester interchange reaction took place between PET and PEO‐acid during meltspinning, the blend fibers could retain almost the same mechanical properties as the original PET fiber.
Preparation and characterization of spinning dopes for dry spinning of continuous alumina green fibers
Authors: Clauss Bernd 
Published: April 2003

AbstractAqueous spinning dopes for dry spinning of alumina green fibers were prepared by using basic aluminium chloride Al2(OH)5Cl · 2.5 H2O and SiO2 sol as inorganic components and poly(vinyl alcohol) (PVA) as polymeric organic component.Certain rheological properties of the mixtures are essential to achieve good spinnability at high spinning speeds. The rheology of the dope is influenced by the molecular weight and the degree of hydrolysis of the PVA, as well as by the composition and the concentration of the mixture. For mixtures without SiO2 best results were obtained at a PVA: Al2O3 mass ratio of 18:82 and an Oxide content of about 27 wt.‐%. The PVA used has an average molecular weight of 70000 and a degree of hydrolysis of 89%.The dopes were spun to continuous green fibers at speeds up to 500 m/min. The structure and the ageing behaviour of concentrated solutions of basic aluminium chloride has been intensively studied.