bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stabilization of polyamides against degradation caused by heat and light
Authors: Stohler Felix R. 
Published: April 2003

AbstractThe stabilization of polyamides or nylons, considered the oldest engineering plastics, has been the subject of many patents in the last 50 years. Most of these patents refer to attempts to improve the resistance of polyamides against the negative influence of heat and oxygen. Light stability, however, was always of certain interest as well, and more so in recent years when polyamide producers started to search seriously for new fields of application.Some general remarks will be made on how to test the heat stability of this substrate group. The three different types of heat stabilizing systems with their advantages and disadvantages will be discussed briefly. Among these three systems ‐ copper halides, secondary aromatic amines and phenolic antioxidants ‐ the latter will be dealt with in some depth.Some information will cover investigations on stabilization of polyamides in general. Another study will be presented that deals with the behavior of polyamide 6 at various elevated temperatures. The results of an extraction of polyamide 66 with boiling water will be explained including discussion of the consequences.An example will also be given for the heat stabilization of polyamide 12.Some general remarks on testing polyamides under the influence of light lead to several considerations concerning light stabilizer systems for polyamides. Examples will be given for polyamides 6, 66 and 12.A short survey of the status quo with regard to polyamide stabilization and an outlook for the future will conclude this paper.
Cold‐drawing behaviour of naturally aged poly(ethylene terephthalate)
Authors: Avramova Nadka , Fakirov Stoyko 
Published: April 2003

AbstractThe cold‐drawing behavior of naturally aged poly(ethylene terephthalate) (PET) is investigated and an attempt is made to compare the mechanical behavior of unaged commercial PET and material which has been naturally aged for 11 years. Mechanical, viscometric, DSC and IR measurements are applied. The previously observed unusual ability of fresh PET bristles to be cold drawn up to 15:1 is not achieved for the naturally aged material. This fact is related to chemical cross‐linking occuring on the surface of bristles after drawing and thermal treatment. The cross‐linking skin is unsoluble, infusible and uncrystallizable. The naturally aging defeats the ability of PET to respond to external treatments which would otherwise change the internal structure. Such a “stabilization” of material properties is a result of the transformation, during natural aging, of the original physical network into a chemical network consisting of covalent bonds.
Heat stabilization of segmented copoly(ether ester)s
Authors: Zeilstra Job J. 
Published: April 2003

AbstractOxidative degradation of segmented copoly(ether ester)s can be suppressed by interference of the following basic processes:a. degradative radical chain reactions. Effective inhibition is possible by means of primary antioxidants.b. initiation of the radical chain reactions by means of hydroperoxides formed. Such initiation reactions can be suppressed by inactivation of the hydroperoxides with the aid of secondary antioxidants.c. polyester segmental chain scission by formic acid formed during oxidative degradation of the polyether segments. By scavenging the formic acid, or its precursor formaldehyde, this serious process can be restricted.Combined addition of stabilizers, simultaneously influencing the basic processes a., b. and c. can lead to synergism. Examples of the activity of the different stabilizers are given.
The photooxidative gelation of cis‐1,4‐ polybutadiene in solution
Authors: Jovanović Dragiša 
Published: April 2003

AbstractIrradiation of dilute solution of cis‐1,4‐polybutadiene in carbon tetrachloride with UV light in the presence of air causes fast formation of white precipitate—insoluble gel. It has been shown that carbon tetrachloride was effective photosensitizer for oxidation of cis‐1,4‐polybutadiene. Separated sol and gel fractions were analysed by infrared spectroscopy for better understanding of gelation process and structure of the gel. Three stages were detected in the process of oxidative photogelation of cis‐1,4‐polybutadiene in carbon tetrachloride solution: pre‐gelation(sol‐stage), gelation (sol/gel‐stage) and post‐gelation (gel‐stage). In the first stage intensive photooxidative reactions between cis‐1,4‐polybutadiene, carbon tetrachloride and oxygen take place, giving products with high content of hydroperoxide and bounded chlorine. When hydroperoxide and chlorine content reached critical value, precipitation‐gelation takes place. It is proposed sequence of free radical reactions which involves: photolysis of carbon tetrachloride to free radicals, addition of solvent radicals to the double bonds of rubber followed by combining of resulting radicals with oxigen to chlorinated polymeric peroxy radicals. Initially formed gel is peroxidic in nature, which photolyses to the more stabile ether gel by prolonged irradiation.
Ageing of rubber modified thermoplastics and elastomers
Authors: Bach J. , Braun D. , Müller I. , Wendorff J. H. 
Published: April 2003

AbstractThe effect of ozone exposure on several polymers is investigated. From the chemical point of view the consequence of ozone attack on several polybutadienes in solution and as solid polymers is studied. Ozonization of polybutadiene solutions causes a strong decay in the intrinsic viscosity. The behavior of solid polymers was investigated by electron paramagnetic resonance. In the second part of the paper the influence of ozone on Solprene 406, a SBS‐elastomer, and a rubber modified polystyrene on the stress strain behavior is studied. In both cases ozone causes a strong increase of the magnitude of stress relaxation. The dependence of the stress relaxation on the deformation, on the ozone concentration, and on the temperature is described.
Influence of tackifier resins storage stability on EVA based hot melt adhesives
Authors: Hinsken Hans 
Published: April 2003

AbstractRosin (colophony) ‐based resins are a major class of tackifying resins for hot melt adhesives (HMA). These resins are very prone to oxidation. Under ambient storage conditions all types oxidize to varying degrees. As a result of this autoxidation process, considerable concentrations of hydroperoxides can accumulate. The properties of the tackifier resin are significantly effected by these hydroperoxides. When the resin is eventually used in EVA HMA production, these hydroperoxides also adversely effect the HMA properties. Autoxidation of the tackifier resin, under ambient storage conditions, can be effectively suppressed by an appropriate antioxidant. The storage stability of the resin can therefore be improved dramatically, minimizing changes in tackifiers properties.
Relative ultimate strain in white pigmented polymers after ageing
Authors: Skledar Štefan 
Published: April 2003

AbstractThree series of pigmented polymeric films of various pigment volume fractions were prepared. The first series of unsupported films was exposed to ultraviolet radiation and the second to demineralized water, the third series of films being unexposed for comparison. The ultimate tensile properties of all three film series were measured according to ASTM D 2370 standard method. The obtained experimental data follow the equation containing a pigment‐polymer interaction parameter based on the Ziegel's concept. In vinyl acetate‐butyl acrylate copolymer system, the ultraviolet radiation causes an increase of relative ultimate strain at lower pigment volume fractions, where the interaction parameter diminishes. On the contrary, water provokes a decrease of relative ultimate strain in this system by magnifying the interaction parameter at low pigment concentration. In ethyl acrylate‐methyl methacrylate copolymer system, neither ultraviolet radiation nor water affect greatly the relative ultimate strain and the interaction parameter. The results obtained prove good resistance to ageing of this copolymer system, where the thickness of immobilized interfacial polymer region represents a logarithmic function of pigment volume fraction. On the other hand, in poly(vinyl acetate) system both ultraviolet radiation and water diminish the interaction parameter at low pigment concentrations, the thickness of immobilized interfacial polymer region being still the logarithmic function of pigment volume fraction in first approximation. It can be concluded that ageing effects on the relative ultimate strain in white pigmented polymers depend not only upon pigments and their concentration but also upon the nature of polymer matrix.
Comparative study of complex mechanisms of various polystyrene degradations and oxidations
Authors: Kovačević Vera , Bravar Mladen , Hace Drago 
Published: April 2003

AbstractComparative investigations of the polymeric residues remained after degrading polystyrene by heat or by UV irradiation reveal numerous profound changes of the structural and molecular parameters of the polymer when subjecting it to either of these main types of degradation.The polymeric residues of the commercial and of the prepared polystyrene samples were investigated in view of the following characteristics: discolouration, IR, UV and 13C NMR spectra, DSC‐analysis, GPC‐elution curves and X‐ray patterns.The results show pronounced heterogeneity of the degradative reactions occuring in the framework of the thermal and photochemical degradation of polystyrene, including the existence of crosslinking processes and producing thus very inhomogeneous polymeric material.The presumption of the existence of different mechanism paths occuring in various polystyrene structural fractions was confirmed and further promoted, especially from the standpoint that the lower‐molecular fractions of the polymer should behave more sensitively against the degradative attacks.Many‐sided meanings of the informations obtained by analysing degraded polystyrene samples allow to postulate the present degradative mechanism by comparing among them various types of de gradative processes.The gained informations about the locations and ranges of absorption bands in UV, IR and 13C NMR spectra, as well as the complementary evidence from other determinations enabled the claim that polystyrene thermo‐oxidative degradation would preferentially take place in the way to produce acetophenone structures near the chain ends. In the initial degradation periods this would be related with substantial lowering of the molecular mass.The photo‐oxidative degradation mechanisms cause the build‐up ketone and aldehyde structures and ring‐opening reactions concurrent with chain crosslinking reactions.Comparing long‐wave and short‐wave UV irradiations of polystyrene does not only show the existence of inequal induction times, but additionally the presence of two sets of similar reactions leading to the production of many oxidized structures.The investigations would show that oxidative polystyrene degradation is a very complex phenomenon in which the prefered courses of chemical reactions are in the relations to the initial reaction steps, namely they do depend on structures formed in the early stages of the thermal and photo‐degradative processes.
Studies on the thermal stability of poly/vinyl chloride/ and vinyl chloride ‐ carbon monoxide copolymers
Authors: Orbán Sylvia 
Published: April 2003

AbstractThermal stability of vinyl chloride/carbon monoxide copolymers synthetized in the presence of different proportions of carbon monoxide was studied in nitrogen, oxygen or air stream at 180°C. Dehydrochlorination rate increases proportionally to the incorporated carbonyl content. Effect of air and oxygen on acceleration of the decomposition is higher for PVC samples of regular structure than for the vinyl chloride/carbon monoxide copolymers. In the infra‐red spectra recorded after the thermal oxidative decomposition, a broad absorption band appears between 1600 and 1800 cm−1. Two peaks show the most emphasized increase: one at 1720 to 1730 cm−1 assigned to the carbonyl group and another at about 1770 cm−1 of unidentified origin. Additional oxidation products from the polyene yield a “shoulder” in the spectrum between 1600 and 1690 cm−1.
Ageing and recycling of plastic crates
Authors: Vink P. , Rotteveel R. T. , Wisse J. D. M. 
Published: April 2003

AbstractPlastic crates will deteriorate and ultimately fail due to brittle fracture if, either during use or storage, they are exposed to sunlight. The time to failure depends on the UV stability of the polymer used, but in particular also on the conditions of use, such as time of exposure, height of the stack during stocking, rate of circulation and manner of transportation.Because of differences in the conditions of use, the time to failure of creates of the same batch will be different. The decrease of the size of a particular batch in time can be described by a Weibull‐function, an empirical, statistical function. Knowledge of this function for a batch provides the possibility to predict reliably the number of crates to be rejected in forthcoming years.The UV stability of recycled, degraded high density polyethylene (HDPE) create material appears to be hardly dependent on the degree of degradation, although it is lower than the UV stability of the type of HDPE originally used for production of the creates. The UV stability can, however, be markedly enhanced by the addition of a proper stabiliser system.The tensile impact strength and the meltindex of recycled HDPE depend also hardly on the degree of degradation and are, in general, sufficient for crate material.It is concluded that recycling of degraded crates, even of embrittled crates, and reuse of the material for the production of new crates, is worthwile to be considered.
Die dimensionen der kristallinen bereiche in fasern aus regeneratcellulose
Authors: Lenz Jürgen , Schurz Josef , Wrentschur Erich , Geymayer Wolfgang 
Published: April 2003

AbstractDie Dimensionen der kristallinen Bereiche von Regeneratcellulosefasern wurden mittels Transmissionselektronenmikroskopie, Röntgenkleinwinkelstreuung und Röntgenweitwinkeldiffraktion bestimmt. In befriedigender Übereinstimmung wurden nach allen drei Methoden folgende Abmessungen gefunden: Länge: 120–140 Å, Breite: 80–100 Å, Dicke: 30–40 Å. Die breite Ebene der blättchenförmigen Kristallite verläuft parallel zur 101‐Netzebene, die schmale Kantenebene parallel zur 101‐Netzebene. Die Kristallite bilden Ketten mit einer Länge von 1500 bis 5500 Å, die teilweise zu Clustern mit einem Durchmesser von 300 bis 600 Å gebündelt sind, teilweise durch Zonen geringerer Dichte voneinander getrennt sind. Die Abstände zwischen den kristallinen Bereichen betragen in Längs‐ und Querrichtung 20 bis 40 Å.
Porous bead aliphatic‐aromatic methacrylate copolymers V. Grafting of acrylic monomers onto MMA‐DMN copolymers
Authors: Wójcik Anna B. 
Published: April 2003

AbstractPorous methyl methacrylate‐di(methacryloyloxymethyl)‐naphthalene (DMN) copolymers were subjected to superficial grafting processes with engagement of double bonds present in the polymer structure. Grafting monomers were acrylic and methacrylic acids, acrylonitrile, acrylamide, and glycidyl methacrylate. Grafted copolymers were investigated by elemental analysis, infra‐red measurements, adsorptiondesorption isotherms of nitrogen and scanning electron microscopy. Irrespective of low grafting efficiency, the changes due to grafting with respect to the parent copolymers were easy to observe.
Thermal properties of chlorendic acid based polyester resins
Authors: Bansal R. K. , Ghogare A. B. 
Published: April 2003

AbstractPolyester resins were prepared from chlorendic acid, maleic anhydride, and ethylene‐ and/or propylene‐glycol. The resins were cured at room temperature with two different crosslinking agents including styrene and methyl methacrylate. The thermal behaviour of these polyester resins and their cured products was studied. From the thermogravimetric data it was observed that the polyester resins cured with styrene are thermally more stable than the methyl methacrylate cured products. It was also observed that the polyester resin prepared from propylene glycol is thermally more stable relatively than the ethylene glycol based polyester resin. The activation energies of thermal degradation of the resins and their cured products were calculated. The implications of these results are discussed.
Synthèse de monomères acryliques et méthacryliques derivés de biocides. Etude de leur homo et copolymérisation
Authors: Potin C. , Pleurdeau A. , Bruneau C. M. 
Published: April 2003

AbstractEn vue de la mise au point de biocides macromoléculaires destinés à être utilisés en tant que liants dans des formulations peinture, divers agents biocides, principalement des phénols, ont été transformés en monomères acryliques et méthacryliques. L'aptitude de ces monomères à l'homopolymérisation et à la copolymérisation avec des comonomères classiques (styrène, esters acryliques) a été étudiée par processus radicalaire. Les monomères actifs, leurs homo et copolymères ont été caractérisés par les méthodes habituelles de spectrographie infra‐rouge, RMN1 H et 13C, analyse élémentaire et chromatographie d'exclusion.
Thermal decomposition of petroleum and coal tar pitches by thermogravimetry
Authors: Eder Marek , Włochowicz Andrzej 
Published: April 2003

AbstractThermogravimetry was used to investigate petroleum and coal tar pitches undergoing pyrolysis in an atmosphere of air and nitrogen at three different heating rates.Pyrolysis of pitches in air is a three‐stage process, whereas in nitrogen two stages were found.A kinetic analysis of the thermogravimetric data has been made. The orders and activation energies have been determined for each stage of decomposition using the methods of Kissinger, Freeman, and Hüttinger.
Oligomeric 1,4‐phenyleneterephthalamide. Synthesis by interfacial polycondensation and structural properties
Authors: Cum Giampietro , Gallo Raffaele , Severini Febo , Spadaro Agatino 
Published: April 2003

AbstractThe synthesis of a fully aromatic oligoamide by low temperature interfacial polycondensation between terephthaloyl chloride and 1,4‐phenylenediamine is reported. The reaction product was characterized with respect to its physical properties and chemical structure by infrared, X‐rays, electron spectroscopy for chemical analysis (ESCA), and mass spectroscopic techniques. Elemental and thermal analysis, as well as viscosimetric and titrimetric methods were applied to evaluate the average molecular weight of the oligomer, whose chain length consists mainly of 3 to 4 monomeric units.
Morphology property relationships in poly (2‐methoxy)cyanurate of bisphenol‐C (PMCBC)/polystyrene (PS) blends — dynamic modulus
Authors: Parsania Purshottam H. , Shah Praful P. , Patel Kanti C. , Patel Raman D. 
Published: April 2003

AbstractThe dynamic mechanical, thermal, and morphological properties of poly(2‐methoxy)cyanurate of bisphenol‐C (PMCBC), polystyrene (PS), and their blends have been investigated. Dynamic mechanical data show that there is appreciable adhesion at the PMCBC/PS interface but that the PMCBC/PS blends are incompatible. Morphological and thermal analysis results indicate that the PS appears as inclusions in the PMCBC matrix and as a result of interfacial adhesion contributes substantially to the sample's overall modulus. Theories based on perfect adhesion are found to be applicable to the PMCBC/PS blends.
Permeability of alkali chlorides through charged cellulosic membranes
Authors: Kimura Yuzi , Lim Han‐Jin , Iijima Toshiro 
Published: April 2003

AbstractThe permeation of alkali chlorides through charged cellulosic membranes was investigated. The membranes used were partially carboxymethylated and carboxyethylated cellulose with various degrees of substitution. The permeability coefficients were found to increase in a sequence of LiCl < NaCl < CsCl < KCl. This sequence is explained by considering the partition and the hydration of the ions in these hydrophilic membranes. The dependence of the permeability on the salt concentration was interpreted by means of Teorell‐Meyer‐Sievers (TMS) theory. The effectiveness of the charged groups in the membranes is explained by the counterion binding mechanism.
Coordination polymers. 7. Synthesis and characterization of some polychelates derived from bisphenolic complexes
Authors: Spiratos Mihaela , Airinei Anton , Voiculescu Nicolae 
Published: April 2003

AbstractChelate polyesters and polysiloxanes derived from bisphenolic complexes with some bivalent ions as copper, nickel, cobalt, iron, zinc have been synthesized. The polychelates are studied in terms of spectral, thermal, magnetic, and electrical properties; the probable structures of these polymers have been proposed.
Rheologische eigenschaften von ethoxylierte amine enthaltende polycapronamidschmelzen
Authors: Peev G. , Garvanska R. , Draganova K. 
Published: April 2003

AbstractEs wurde eine rheologische Charakterisierung von Polycapronamidschmelzen vorgenommen, die 2 bis 10 Masse‐% zweistufig ethoxylierte Ethylendiamine und Diethylentriamine mit einer Molmasse von 983 bis 8660 enthielten. Diese Amine sind geeignete Zusatzstoffe zur Gewinnung von Polycapronamidfasern mit dauerhaften antielektrostatischen Eigenschaften.Es wurde festgestellt, daß die Zusatzstoffe die scheinbare Viskosität senken, ohne daß der nichtlineare Charakter des viskosen Fließens wesentlich verändert wird, und daß die Viskosität von Art und Menge der ethoxylierten Verbindungen nicht abhängt.
Investigations of electrokinetic properties of dyed polyamide fibres
Authors: Pfeifer Stanisław , Włochowicz Andrzej 
Published: April 2003

AbstractChanges of the electrokinetic flow intensity Qv and the zeta potential for polyamide fibres colourless and dyed with Polan dyes were analyzed.Essential differences in determined quantities were found for fibres dyed with dyes of different steric structure.
Analytical studies on surface damage of PVC sheets
Authors: Jayabalan M. 
Published: April 2003

AbstractAnalytical studies on surface damage of PVC sheets due to weathering were carried out. PVC sheets which contain embossed and smooth surface which were subjected to cyclic weathering conditions of humidity and temperature were analysed. PVC sheets prepared with di‐2‐ethylhexyl phthalate as plasticizer undergo leaching of plasticizer; the leaching being high in smooth and less in embossed surface. The presence of plasticizer on the surface was detected by Attenuated Total Internal Reflectance Infrared Spectrophotometry (ATIR). The higher the leaching in smooth surface, the higher the surface damage in the embossed surface. The higher damage is ascribed to surface brittleness whereas the lower damage is ascribed to the surface plasticization. The surface damage was assessed by photomicrography.
Photoconductivity properties of zinc oxide encapsulated in polymers
Authors: Haga Yutaka , Inoue Syouzo , Sato Takanori , Yosomiya Ryutoku 
Published: April 2003

AbstractZinc oxide encapsulated in various polymers was studied concerning its effect on photoconductivity. Consequently, zinc oxide encapsulated in polystyrene (C‐St‐ZnO) showed a marked light sensitization effect. Further, the tendency was observed that the light sensitization effect was increased in proportion to an increase of the encapsulation ratio. Furthermore, in the composite films of C‐St‐ZnO and polystyrene, the film in which 5% of polystyrene is blended showed a remarkable light sensitization effect. Some studies were carried out with respect to the light sensitization mechanism of this encapsulated zinc oxide by examining the dark current property and the initial rising rate of the sensitized photocurrent.