bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of accelerated exposure conditions on the photodegradation of BPA polycarbonate/ABS blends
Authors: Pickett James E. , Barren James P. , Oliver Richard J. 
Published: April 2003

AbstractA BPA polycarbonate/ABS blend containing 2% TiO2 was exposed to xenon are irradiation under SAE J 1885 conditions (quartz/borosilicate filters). “CRD” conditions (borosilicate/borosilicate filters), and ASTM D4459–86 conditions (borosilicate/soda lime filters). The results are consistent with the conclusion that polycarbonate dominates the photochemistry of polycarbonate/ABS blends under SAE J1885 and CRD xenon are exposure conditions. Exposure under ASTM D4459–86 conditions produced results similar to CRD conditions with some additional contribution attributable to the ABS component. The “activation spectrum” of PC/ABS blends under CRD conditions closely resembled the sum of the activation spectra of ABS and PC determined under similar conditions. The well‐known change in mechanism that occurs when polycarbonate is exposed to light with wavelengths < 300 nm was manifested by increased rates of yellowing, surface erosion. and loss of gloss under SAE J 1885 conditions. Because of the mechanism change, testing under quartz/borosilicate filtered xenon are exposure cannot be considered to be appropriate for polycarbonate‐containing formulations.
Degradation of ultra high molecular weight polyethylene in vivo
Authors: Costa L. , Luda M. P. , del Prever E. M. Brach 
Published: April 2003

AbstractMechanical and thermal oxidation of UHMWPE used in the preparation of prosthetic implants is studied and the mechanisms of degradation are reported. Oxidation of new and retrieved prosthetic implants are studied by IR microscopy and clear evidence of oxidation in vivo is shown.
The influence of flame retardant structure on UV stabilization approaches in polypropylene
Authors: Gray Robert L. , Lee Robert E. 
Published: April 2003

AbstractUV stabilization of polymer systems containing brominated flame retardants has proven to be a difficult technical challenge. Generation of acidic products during processing or exposure can cause a catastrophic deactivation of the Hindered Amine Light Stabilizer (HALS). An understanding of the mechanism for bromine generation from aliphatic and aromatic based flame retardants has lead to formulation approaches based on flame retardant structure. In formulations containing aromatic brominated flame retardants, combinations of UV absorbèrs and a new class of siloxane HALS provide the highest level of UV stabilization to date. Alternatively, bicomponent fiber spinning technology can also provide outstanding UV resistance at significantly lower levels of stabilizers than that used in the monocomponent formulation approach.
Photoinitiated degradation of polymers by metal salts‐recent developments
Authors: Kaczmarek H. , Rabek J. F. 
Published: April 2003

AbstractThis paper reexamines the role of transition metal salts (mainly CuCl2 and FeCl3) in the photooxidative degradation of polymers. Metal salts belong to external impurities originated in polymers from synthesis, processing, storage, contacts with metal corrosion, etching reactions, etc. Transition metal salts in the presence of water become very reactive species. In such metal chlorides as CuCl2 and FeCl3 UV and/or visible light irradiation causes an electron‐transfer from Cl− to metal cation. The produced chlorine radical can abstract hydrogen atom from a polymer molecule giving polymer alkyl radical. which is easily oxidized in air. This process is accompanied with a chain scission reaction which is responsible for the degradation of a polymer. Mechanisms of these reactions are discussed in detail.
Polymer bound HALS‐expectations and possibilities
Authors: Malik Ján , Ligner Gilbert , Ávár Lajos 
Published: April 2003

AbstractThe work confronts the traditional opinion on the physical aspects of the HALS efficiency with the available experimental reality. The results indicate that the generally accepted importance of additive's migration may need to be reconsidered. Based on the experimental evidence, three empirical requirements for an effective stabiliser are formulated: high solubility, minimal diffusion, high homogeneity of distribution of active species. Chemical grafting of a low molecular stabiliser is suggested to meet the defined empirical requirements. The results achieved with the polymer bound HALS (PBH) prepared by reactive processing technology confirm the expectations. The stabilisation efficiency of PBH significantly outperforms the conventional low molecular and oligomeric stabilisers.
Polymers degradable under environmental conditions through end‐modification of poly(α‐methylstyrene) derivatives
Authors: Nagasaki Yukio , Yamazaki Noriyuki , Kato Masao 
Published: April 2003

AbstractTo induce degradabilities in polymers in response to environmental conditions, the end‐modification reactions of poly(α‐methylstyrene) derivatives were carried out. When diphenylphosphine chloride was used as a modifier for the living end of para‐substituted PMS, the coupling efficiency was ca. 50%. 2‐Phenylallyl halide derivatives such as 2‐phenylallyl bromide, 2‐(4‐tolyl)allyl bromide, and α‐trifluoromethylstyrene were found to be suitable end‐modification agents. For example, ω‐2‐phenylallyl PMS was prepared with almost quantitative functionality by the reaction of the living PMS with 2‐phenylallyl bromide. In a similar way, ω‐3,3‐difluoro‐2‐phenylallyl and ω‐2‐(4‐tolyl)allyl PMS derivatives were synthesized. Based on thermogravimetric analysis, onset of the degradation temperature of the end‐modified PMS derivatives decreased in the following order: ω‐hydrogen‐ > ω‐3,3‐difluoro‐2‐phenylallyl‐ > ω‐2‐phenylallyl‐ > ω‐2‐(4‐tolyl)allyl‐PMS. Actually, the onset temperature of ω‐2‐(4‐tolyl)allyl‐PMS derivatives was 50°C lower than that of ω‐H‐PMS derivatives. These results indicate that the active species is produced effectively at the end unsaturated bond, which initiates the depolymerization of the polymer at rather low temperatures. Ionic degradation of these polymers was also investigated using butyllithium as an anionic initiator and methanesulfonic acid as a cationic initiator. Tendencies similar to the thermal degradation were observed. Therefore, it is concluded that a 2‐phenylallyl substituent at the end of the PMS chain induces effective degradation through several mechanisms such as radical, anionic and cationic depolymerization reactions.
Thermal degradation of polystyrene in different environments
Authors: McNeill I. C. 
Published: April 2003

AbstractSeveral aspects of the thermal degradation of polystyrene are highlighted in this communication. The factors involved in determining the ratio of volatile to tar fraction products in the degradation of the pure polymer are examined, leading to the conclusion that the initial melt viscosity plays an important role in determining the balance between intra‐ and intermolecular transfer. The effect on the degradation of polystyrene of the presence of a second polymer is discussed. For polystyrene‐polybutadiene and polystyrene‐polyisoprene blends, stabilisation is observed, which is attributed to radical scavenging. The thermal degradation behaviour of polystyrene in the presence of oxygen has been investigated, with and without an antioxidant additive. Products have been characterised for oxidative conditions and the kinetics of degradation have been studied.
Chemiluminescence in thermal oxidation of ABS
Authors: Parikh Sunil S. , Zlatkevich Lev 
Published: April 2003

AbstractTwo concepts in the chemiluminescence research‐the heterogeneous model and the kinetic approach‐are discussed. The analysis of published data obtained by a highly sensitive photon‐counting system reveals the contradictory nature of the heterogeneous model and proves its inconsistency. On the other hand, the kinetic approach has been successfully applied to evaluation of thermal oxidation in a variety of systems, ABS compositions in particular. Emulsion grade ABS were found to be essentially less stable than ionic mass polymerization products. Among the antioxidants studied, Santonox R is clearly more efficient than Irganox 1076. In emulsion grades the superiority of Santonox R to Irganox 1076 is reflected primarily in larger induction period, while in ionic resin it is mostly due to smaller oxidation rate constant values. The introduction of UV stabilizers by themselves has no influence on durability in either ionic or emulsion resins. Similarly to systems without UV stabilizers, Santonox R is more efficient than Irganox 1076 in mixtures with UV stabilizers as well. The comparative study of various ABS‐coloring agent compositions by chemiluminescence and DSC reveals much greater sensitivity of the former. While DSC lets one make only a trivial conclusion that the introduction of an antioxidant improves stability, chemiluminescence shows the differences in durability as large as 3 to 4 times for the samples DSC fails to distinguish. In addition, chemiluminescence furnishes a significant insight on the factors affecting stability. The DSC thermal oxidative stability data can be related to resistance to oxidation during processing, whereas the chemiluminescence results are expected to be useful in predicting materials' lifetime at service temperatures.
Polyelectrolytes with various charge densities: Synthesis and characterization of diallyldimethylammonium chloride‐acrylamide copolymers
Authors: Brand Fabien , Dautzenberg Herbert , Jaeger Werner , Hahn Mathias 
Published: April 2003

AbstractThe synthesis of defined polyelectrolyte models by radical copolymerization of diallyldimethylammonium chloride (DADMAC, M1) and acrylamide (AAM, M2) in aqueous solution is impeded by a large difference of the reactivity ratios (r1 ≪ r2) leading to a strong conversion dependence of the copolymer composition. For the synthesis of normally distributed polyelectrolytes of the same molecular weight with various charge densities, a general algorithm based on a feeded polymerization with dosage of the more reactive monomer was therefore developed.Various copolymer compositions predictable by the Mayo‐Lewis equation and determined by chloride potentiometry were obtained. The sequence lengths distributions investigated by 13C NMR spectroscopy followed a Markov statistic of first order. The 13C NMR spectroscopy is shown as alternative method to gravimetry in determining reactivity ratios. The partial specific volumes and the refractive index increments of the copolymers correspond to the additivity principle. Further molecular and dynamic parameters are determined by membrane osmometry, static and dynamic light scattering, analytical ultracentrifugation, gel permeation chromatography, and viscometry. Monomodal molecular weight distributions, small polydispersities only for copolymers with high content of DADMAC are obtained at given comonomer and initiator concentration. The number‐average molecular weight is almost constant for a broad copolymer composition range.Rg‐M and [η]‐M relations could be established for practical use at high ionic strength, despite the various chemical compositions. Some indications for a higher stiffness of copolymers with high contents of DADMAC despite the shielding of the electrostatic interactions are, however, given. At low ionic strength the electrostatic interactions prevail. Their influence with increasing charge density is stronger on the Huggins constants (intermolecular interactions) than their effect on the intrinsic viscosities (intramolecular interactions).
Mechanical properties of poly(propylene) filled with calcium carbonate of various shape
Authors: Mitsuishi Kazuta 
Published: April 2003

AbstractCalcium carbonate of various particle shape (CaCO3, sphere, cube, needle) treated with alkyl dihydrogen phosphate ester (APEN, CnH2n+1OPO(OH)2, n = 1, 4, 8, 10, 12) and poly(propylene) (PP) were mixed on a two roll mill. The effect of carbon number of APEN on the mechanical properties (tensile elongation, tensile strength, impact strength, yield stress) and adhesion between PP matrix and various CaCO3 particles and the effect of CaCO3 shape on the storage modulus of elongated PP/CaCO3 has been investigated.The tensile elongation, impact strength and adhesion of PP‐CaCO3 interface increased with carbon number of APEN (n ≦ 10) for needle and cube type, but the dependence of tensile properties on APEN carbon number is not clearly recognized for the sphere type.The relative storage moduli of elongated PP/CaCO3, E/E E – modulus of elongated PP/CaCO3 (untreated); E – modulus of elongated PP matrix could sufficiently be described with a modified Halpin‐Tsai equation, which contains the factors of (i) polymer matrix orientation, (ii) particle effect (content, modulus, aspect ratio), and (iii) void volume at polymer‐filler particle interface.
New preparation method of poly(amide‐imide)s using direct polycondensation with thionyl chloride and their characterization
Authors: Hong Young‐Taik , Jin Moon Young , Suh Dong Hack , Lee Jae‐Heung , Choi Kil‐Yeong 
Published: April 2003

AbstractA study for the development of a new, economical manufacturing process for high‐molecular‐weight poly(amide‐imide) (PAI) was performed via direct polycondensation of trimellitic acid anhydride (TMA) or diimide diacids (DIDAs) with aromatic diamines using an equimolar amount of thionyl chloride in NMP at relatively low temperatures. The polyamidation of DIDAs and diamines for head‐to‐head polymers (H‐PAIs) was sensitive to the reaction temperature and proceeded very quickly, 1 h was sufficient to complete the reaction. The highest value of inherent viscosity, ηinh, of 72 mL g−1 was obtained by polymerization at room temperature. Also several randomly sequenced polymers (R‐PAIs) were prepared by polycondensation from TMA and diamines, followed by imidization with various methods, such as using TPP as a co‐condensing agent, azeotropic dehydration of polyamic acid (PAA) and solid‐state imidization from PAA. Solid state imidization from polyamic acids at 235°C gave satisfactory results with an inherent viscosity 58–85 mL g−1. Solvent content, imidization temperature and time were major controlling factors for the degree of imidization as well as for the molecular weight. Both H‐PAI and R‐PAI showed good mechanical properties with tensile strength of 118–131 MPa and Tg ranged between 263–299°C depending on the nature of monomers. The melt viscosity of the PAIs ranged between 7.4 · 103 and 4.5 · 103 Pa s for H‐PAI and R‐PAI respectively. These values are comparable to that of conventional PAI, Torlon® 4000T of 5.6 · 103 Pa s.
Study on the kinetics of interfacial polycondensation for polyarylate
Authors: Wang Chung‐Yu , Wang Ding‐Chang , Chiu Wen‐Yen , Chen Leo‐Wang 
Published: April 2003

AbstractFor the synthesis of polyarylate by interfacial polycondensation of bisphenol A with terephthaloyl/isophthaloyl dichloride, the kinetic mechanism was studied through the detection of the concentration of bisphenolate in the aqueous phase by UV spectrometry. The mechanism consists of three steps: 1. the transportation of bisphenolate in the aqueous phase, 2. the transfer of bisphenolate through the interface followed by its transportation in the organic phase, 3. the reaction of bisphenolate with the phthaloylic dichloride in the organic phase. The reaction of bisphenolate with the phthaloylic dichloride in the organic phase is the rate‐determining step. The influence of the concentration in either the aqueous phase or the organic phase and of the quantity of the phase transfer agent on interfacial polycondensation were studied.
Modifizierung von Faseroberflächen durch die permanente Fixierung supramolekularer Komponenten, Teil 1: Grundlagen
Authors: Denter Ulrike , Buschmann Hans‐Jürgen , Knittel Dierk , Schollmeyer Eckhard 
Published: April 2003

AbstractEin neues Konzept zur Modifizierung von Faseroberflächen durch permanente Fixierung supramolekularer Verbindungen wird vorgestellt, und das Prinzip der selektiven Komplexierung wird erklärt. Als für die Behandlung grundsätzlich geeignete Liganden werden insbesondere Cyclodextrine, Azakronenether, Calixarene, Cyclotriveratrylene und Fullerene hinsichtlich ihrer chemischen Struktur sowie ihrer komplexierenden Eigenschaften beschrieben. Einige erreichbare Oberflächeneffekte werden hervorgehoben.
Modifizierung von Faseroberflächen durch die permanente Fixierung supramolekularer Komponenten, Teil 2: Cyclodextrine
Authors: Denter Ulrike , Buschmann Hans‐Jürgen , Knittel Dierk , Schollmeyer Eckhard 
Published: April 2003

AbstractMit herkömmlichen Verfahrenstechniken der Textilveredlung werden ausgewählte Cyclodextrinderivat über geeignete funktionelle Gruppen permanent auf verschiedenen Fasermaterialien fixiert. Einige der durch die Oberflächenmodifizierung beeinflußten Eigenschaften der Polymeren werden im einzelnen diskutiert. Insbensondere kann für mehrere Liganden gezeigt werden, daß die verankerten molekularen Hohlräume nicht die Fähigkeit verlieren, hydrophobe organische Verbindungen zu komplexieren. Somit lassen sich durch den Einschluß spezifischer Wirksubstanzen spezielle funktionelle Eigenschaften erzielen.
Oxidative polymerization of acrylamide in the presence of L‐threonine
Authors: Özeroǧlu Cemal , Güney Orhan , Mustafaev Mamed I. 
Published: April 2003

AbstractL‐threonine/Ce(IV) salts and L‐threonine/KMnO4 initiator systems were used for the polymerization of acrylamide, resulting water‐soluble poly(acrylamide) which contains hydroxy amino acid end groups. The dependence of polymerization yields and molecular weights of the polymers on the mole ratio of acrylamide (AA)/L‐threonine (Thr), the polymerization time, the temperature and the concentration of sulfuric acid was investigated. The decrease in the mole ratio of acrylamide to L‐threonine resulted in a decrease in the molecular weight of poly(acrylamide) which contains L‐threonine end groups. The maximum yield has been obtained at the mole ratio of nAA/nThr = 250, further decrease in the mole ratio of acrylamide to L‐threonine resulted in a decrease in the yield of acrylamide polymer. With an increasing sulfuric acid concentration, the polymerization yield decreases. Ce(IV) and Mn(IV) reduced to Ce(III) and Mn(II), respectively, in the polymerization reaction. The amounts of polymer‐bound Ce(III) and Mn(II) were determined. The composition of the polymerization products was investigated.
Celluloseether als Trennschichten hydrophiler Polymermembranen
Authors: Schmidt Matthias , Peinemann Klaus‐Viktor , Paul Dieter , Rödicker Herbert 
Published: April 2003

AbstractEs wird die Entwicklung hydrophiler Polymermembranen diskutiert, die nach Beschichtung mit Celluloseethern und anschließender Vernetzung auf den asymmetrischen Trägermembranen interessante Permeations‐ und Trenneigenschaften bei hervorragenden chemischen Stabilitäten, vor allem beim Membrantrennverfahren der Nanofiltration, aufzeigen. Weiterhin werden Aussagen zu den Gastrenneigenschaften der Celluloseetherkompositmembranen getroffen.Erläutert werden die Permeations‐ und Trenndaten der Kompositmembranen in Korrelation zur Vernetzung der Celluloseether anhand verschiedener Einflußgrößen, was qualitative und gegebenenfalls quantitative Aussagen zum Vernetzungsmechanismus der Celluloseetherderivate erlaubt. Dabei stehen die Vernetzungstemperatur, der Einfluß der katalysierenden Wasserstoffionen und bedingt die Vernetzungszeit im Vordergrund. Abgerundet werden die Arbeiten durch Ermittlungen rheologischer Daten, die in Zusammenhang zu den Vernetzungsreaktionen und damit zu membranspezifischen Größen stehen.Infolge der hervorragenden chemischen Stabilität der Celluloseether werden Einsatzmöglichkeiten der Kompositmembranen zur Nanofiltration niedermolekularer Verbindungen aus organisch hochbelasteten Systemen beschrieben.
Etching of a low‐density polyethylene film by fuming nitric acid
Authors: Bag Dibyendu S. , Kumar V. Pradeep , Maiti Sukumar 
Published: April 2003

AbstractLow‐density polyethylene (LDPE) films were treated with fuming nitric acid (FNA). The surface characteristics and also the insertion of polar groups like on the etched LDPE film surface were measured by SEM, IR and XPS analyses, respectively. The mechanical performance of a laminate of the etched film with epoxy resin and also the printability of the etched film surface were tested and compared with the unetched sample. The surface roughening and the presence of polar groups enhance the mechanical strength of the laminate of FNA‐treated film due to mechanical interlocking and chemical interaction. The printability of the treated film surface is also superior to that of the untreated LDPE film surface.
Polyester networks based upon epoxidized and maleinated natural oils
Authors: Warth Holger , Mülhaupt Rolf , Hoffmann Botho , Lawson Sonya 
Published: April 2003

AbstractNovel families of flexible, semiflexible and rigid crosslinked polyesters were prepared from modified natural oils such as soybean, rape‐seed and linseed oil. Maleinated oils were used as anhydride‐functional curing agents of epoxy resins such as bisphenol‐A‐diglycidylether and epoxidized natural oils. A new class of unsaturated polyester resins was based upon maleic anhydride, epoxidized natural oils and styrene. The resulting thermosetting polyesters were reinforced with natural fibers such as hemp and flax fibers. The influence of molecular architectures, curing conditions and formulations on thermal, mechanical and morphological properties were investigated.
X‐ray diffraction of thermotropic liquid‐crystalline copoly(vanillate‐4‐hydroxybenzoate‐ethyleneterephthalate)
Authors: Li Xin‐Gui , Huang Mei‐Rong 
Published: April 2003

AbstractPrecision X‐ray diffractometry was used to study directly the structure of as‐made films and fibers, which were uniaxially extruded from thermotropic liquid‐crystalline nematic melts of copolymers consisting of vanillate (V), 4‐hydroxybenzoate (B) and ethylene terephthalate (E) units with various molar ratios. The addition of a small amount of unit V (at most 5 mol‐%) to the well‐known poly(4‐hydroxybenzoate‐ethylene terephthalate) (B/E) polymer will produce an increase in orientation, but an addition of 15–34 mol‐% of unit V might result in the decrease of the orientation. The X‐ray diffractions of the oriented samples of V/B/E and B/E copolymers show a series of aperiodic intensity maxima on the meridian, which are consistent with that expected for a random sequence of the units. The equatorial scans exhibit single broad peaks centered at 0.437–0.446 nm due to intermolecular scattering. The meridional and equatorial maxima shift in position with the V/B/E ratio of the copolymers. The positions of the meridional maxima are slightly affected by spinning temperature. The linewidth of the most intense maximum at the spacing of 0.207 nm on the meridian was used to determine the correlation length of extended V/B/E copolymer chains. No discrete maxima are observed in both meridional and equatorial small‐angle X‐ray scattering curves.
Heat‐shrinkable films based on polyolefin waste
Authors: Viksne Armanda , Zicans Janìs , Kalkis Valdis , Bledzki Andrzej K. 
Published: April 2003

AbstractPolyethylene wastes (low‐density polyethylene, high‐density polyethylene and their binary blends) were subjected to high‐energy radiation, using a 60Co gamma radiation source. The crosslinked materials thus obtained were processed to heatshrinkable films. Tensile strength could be sharply improved by increasing the dose up to 20 Mrad, simultaneously increasing the elongation at break of the most degraded PE waste. An increase of the degree of compatibility of LDPE and HDPE waste was also observed. All samples examined exhibit a “memory effect” after drawing at 130°C and cooling under tension followed by further heating under relaxed conditions. The value of shrinkage depended on the degree of degradation of the PE waste and on the irradiation dose.