bluuebunny/crossref_metadata_2025_split huggingface dataset:
The effect of the processing steps on the oxidative stability of polyethylene tubing crosslinked by irradiation
Authors: Iring M. , Fodor Zs. , Bödy M. , Baranovics P. , Kelen T. , Tüdös F. 
Published: April 2003

AbstractSome chemical and mechanical properties of intermediate products obtained in the production of PE heat shrinkable tubes were studied, seeking correlations between the composition and the properties. Different PE granulates were mixed with antioxidant (amine or phenol derivative), flame retardant agent and, for some samples, with elastomer. The compounds were extruded to tubes, which were then crosslinked by electron beam irradiation and subsequently extended to twice the original diameter.In the course of the production phases, the thermooxidative stability decreased compared to that of compounded granulate. The greatest decrease was caused by the irradiation. The aromatic amine seems to be the more effective antioxidant at similar compositions than the phenol derivative and it shows a better resistance against irradiation. The oxidative stability of the finished shrinkable tubes was not affected by the quality of commercial granulate (initial polyethylene).Mechanical properties changed slightly upon ageing, and the introduction of the elastomer did not alter the tensile strength and elongation at break. The remaining stability of the end‐product was more than enough to bear the stress of shrinking in use, and the good tensile strength of the material did not decrease upon thermal ageing either.During extrusion of the granulated compound no significant change took place in the distribution and molar mass averages. Irradiation produced more than 50% insoluble fraction, and the thermooxidative properties of the crosslinked sample changed significantly compared to the original PE and to the compound prepared from it.
Complexity of the hydrolytic degradation of aliphatic polyesters
Authors: Vert M. , Li S. , Garreau H. , Mauduit J. , Boustta M. , Schwach G. , Engel R. , Coudane J. 
Published: April 2003

AbstractAliphatic polyesters are more or less hydrolytically degradable, depending on their chemical, configurational and morphological structures. Hydrolysis can be either homogeneous or heterogeneous, depending on many structural and environmental factors. The present understanding of this hydrolytic degradation is recalled. The importance of diffusion‐reaction phenomena is discussed on the basis of the behaviors of polyesters derived from α‐hydroxy acids, namely lactic and glycolic acids and attempts are made to extend the understanding to other members of the aliphatic polyester family. The main results of some recent investigations of the effects on poly(lactic acid) polymers of basic additives and of initiators such as stannous octoate and zinc metal, which are now industrially used, are presented.
Reactions and kinetic modelling of silicone‐carbon resins
Authors: Kasehagen Leo J. , Cheng H. N. , Cowan Patrick J. 
Published: April 2003

AbstractThis paper aims to calculate the average properties of ideal non‐linear stepwise polymerization of comonomers containing multiple reacting sites at the B‐stage prior to gelation. A kinetic model is used to simulate the polymerization process taking into account the mass balances of differently substituted species possible. The molecular weights are obtained either by the use of the Miller‐Macosko method or by solving the differential equations for the polymerization of low‐molecular‐weight species. The approach is applied to the Pt‐catalyzed hydrosilation reaction between methyl‐substituted cyclosiloxane and dicyclopentadiene which produces a high‐performance silicone‐carbon. resin. The approach gives the concentrations of various species present at any given time and the molecular weights. Different modes of monomer addition can also be simulated.
Copolymere aus bifunktionellen Vinylmonomeren: Allylmethacrylat mit Methylmethacrylat und Styrol
Authors: Schmidt‐Naake Gudrun , Bulmahn Birgit , Janke Gudrun , Witt Beata 
Published: April 2003

AbstractMonomere mit zwei polymerisierbaren olefinischen Gruppen unterschiedlicher Reaktivität sind interessant für Polyreaktionen. Copolymere des Allymethacrylats (AMA) mit Methylmethacrylat (MMA) und Styrol (St) wurden durch radikalische Polymerisation weitgehend ohne Vernetzung während des Polymerisationsprozesses hergestellt. Diese Copolymeren wurden hinsichtlich ihrer r‐Werte, der Molmassenverteilung und der thermischen Vernetzung in Abhängigkeit von der AMA‐Konzentration untersucht.
Permeability of CO2 through chitosan membrane swollen by water vapor in feed gas
Authors: Ito Akira , Sato Makoto , Anma Tomotoshi 
Published: April 2003

AbstractThe permeation and separation of carbon dioxide through a water‐swollen chitosan membrane was studied. A chitosan membrane was swollen by water vapor contained in a feed gas and, thus treated, exhibited a large gas permeability. Carbon dioxide preferentially permeated through the swollen chitosan membrane with a permeability of 2.5·10−8 cm3 (STP) cm(s cm2 cmHg)−1 and a CO2/N2 separation factor of 70 at room temperature. This separation performance for CO2 resulted from the basic properties of the chitosan amino groups. The membrane preparation conditions, such as acetic acid concentration of the casting solution, affected the membrane permeation rate. The effect of the operation temperature was also measured. To increase the separation performance of the membrane, several methods of membrane treatment and operation were evaluated.
Preparation and characterization of copolymers from methyl methacrylate and cardanyl methacrylate
Authors: Agarwal Seema , Choudhary Veena , Varma I. K. 
Published: April 2003

AbstractCopolymers of methyl methacrylate (MMA) and cardanyl methacrylate (CMA) were synthesized, characterized and their physico‐mechanical properties were investigated. The benzoyl peroxide‐initiated copolymerization was carried out by using different mole fractions of CMA (0.02–0.10) in the initial feed at 80°C. Structural characterization of copolymers was done using FTIR and 1H NMR spectroscopic techniques. The thermal stability of the copolymers was evaluated using dynamic thermogravimetry. Incorporation of CMA in the MMA backbone leads to an improvement in thermal stability.
Preparation and properties of composites of kevlar‐nomex copolymer and boehmite
Authors: Ahmad Z. , Sarwar M. I. , Krug H. , Schmidt H. 
Published: April 2003

AbstractA new organic‐inorganic hybrid material was prepared by incorporating boehmite into a Kevlar‐Nomex copolymer via a sol‐gel process. Poly(phenylene‐terephthalamide) chains having aminophenyltrimethoxysilane end groups were prepared by reacting a mixture of m‐and p‐phenylenediamine with terephthaloyl chloride, followed by end‐capping with aminophenyltrimethoxysilane. The hydrolysis of the alkoxy groups of an aluminium sec‐butoxide solution in butanol was carried out in the polymer matrix, thus creating an inorganic network structure combined chemically with the aramid chains. Hybrid materials containing different proportions of boehmite in aramid were thus produced and films were cast by solvent evaporation technique. These films with up to 15 wt.‐% of boehmite were yellow and transparent, whereas the films with 20 wt.‐% or more contents of boehmite were opaque. Mechanical properties of these films were analyzed. The values of tensile strength, initial modulus, toughness and maximum strain at rupture were initially found to increase and then decrease with further addition of boehmite. The tensile modulus of the hybrid material was found to be in the range of 3.0–4.5 GPa at 25°C. These ceramers were found to withstand maximum tensile stress of the order of 252 MPa, and the thermal decomposition temperature was around 450°C. The storage modulus as measured using DMTA was in the range of 7.6–18.9 GPa. The tan δ peak which in general became broader with increasing boehmite content showed a shoulder for composites containing large amounts of boehmite. The position of the peaks shifted towards high temperature with the increase in the inorganic contents showing hindrance in motion with increasing boehmite contents.
Crystallization behavior of poly(propylene)/polyamide 1010 blends using poly(propylene)‐graft‐glycidyl methacrylate as compatibilizer
Authors: Zhang Xiaomin , Li Gang , Li Jingshu , Yin Jinghua 
Published: April 2003

AbstractPolyamide 1010/poly(propylene) (PA1010/PP) blends were investigated with and without the addition of poly(propylene)‐graft‐glycidyl methacrylate (PP‐g‐GMA). The effect of the compatibilizer on the thermal properties and crystallization behavior was determined by differential scanning calorimetry and wide‐angle X‐ray diffraction. From the results it is found that the crystallization of PA 1010 is significantly affected by the presence of PP‐g‐GMA. PP/PA 1010 (75/25) blends containing higher amounts of PP‐g‐GMA show concurrent crystallization at the crystallization temperature of PP. Isothermal crystallization kinetics also were performed in order to investigate the influence of the compatibilized process on the nucleation and growth mechanism. In the PP/PA 1010 (25/75) blends, concurrent crystallization behavior was not observed, even though the amount of PP‐g‐GMA was high.
Carbon fibre oxidation, textural and surface changes
Authors: Ibarra L. , Paños D. 
Published: April 2003

AbstractThis work reports on the variations in specific surface, porosity, surface functionality and dimension of commercial carbon fibre subjected to oxidative treatment with nitric acid. Scanning electron microscopy (SEM) observation did not reveal any topographic changes on the fibres, although crypton adsorption evidences increases in specific surface and microporosity.Oxidative treatment has an effect on fibre length, although it also slightly reduces the fibre diameter and the fibre strength, as measured in terms of the elastic modulus.Functional analysis by means of volumetric measurements and X‐ray photoelectron spectroscopy (XPS) reveals an increase in the overall fibre surface acidity through carboxy group increase. Prolonged treatment gradually removes hydroxy groups from the fibre surface.
Mechanical properties‐structure relationships of crosslinked blends based on LDPE/HDPE waste
Authors: Viksne Armanda , Malers Laimonis , Bledzki Andrzej K. 
Published: April 2003

AbstractLow‐density polyethylene (LDPE) waste was blended with high‐density polyethylene (HDPE) waste of different degrees of degradation. Structural, mechanical and rheological properties of these blends were investigated. It was found that 2 wt.‐% of dicumyl peroxide improves simultaneously the tensile strength and elongation at break without serious decrease of the melt elasticity of separate PE wastes and their binary blends in comparison with unmodified PE. It was shown by DSC analyses that modification of the blends leads to better compatibility between LDPE and HDPE.
Polymerization of butadiene and isoprene with the NdCl3 · 3TBP‐TIBA catalyst system
Authors: Iovu Horia , Hubca Gheorghe , Simionescu Eugenia , Badea Elena Gabriela , Dimonie Mihai 
Published: April 2003

AbstractThe isoprene and butadiene polymerization processes with the NdCl3 · 3TBP‐TIBA catalyst system (TBP: tributylphosphate, TIBA: triisobutylaluminium) are studied in detail using an original and very accurate experimental technique. The influences of the initial monomer concentration, the polymerization temperature and the catalyst and cocatalyst concentrations on the conversion, the average molar masses, the polydispersity and the microstructure of the polymers are discussed and explained considering the allylic complexes formed between the neodymium atom and the last monomer unit in the macromolecular chain. A first‐order reaction with respect to the monomer was obtained. The calculated value of the activation energy (25.58 kJ mol−1) is lower than for classical Ziegler‐Natta catalysts, thus demonstrating the higher catalytic activity of the NdCl3 · 3TBP‐TIBA catalyst system used. Two types of active centers are possible, as confirmed by GPC data. One of them, which includes aluminium, is more stable and favors the transformation from “anti” allylic units to “syn” allylic units. Thus, the 1,4‐cis unit content of the prepared polymers is mainly determined by the TIBA concentration. The catalyst does not react by transfer reactions as TIBA does. The obtained conversions are always higher for butadiene than for isoprene due to a higher tendency of the former to complexate with the neodymium atom and forming allylic complexes.
Polymerization and characterization of ethylene/propylene and ethylene/1‐octene copolymers produced with bridged Zr‐ and Hf‐based metallocenes
Authors: Starck Paul , Lehtinen Christel , Löfgren Barbro 
Published: April 2003

AbstractEthylene/propylene (E/P) and ethylene/1‐octene (E/O) copolymers were polymerized with two bridged metallocene catalyst systems, Et(Ind)2ZrCl2/MAO and Et(Ind)2HfCl2/MAO, respectively. The copolymers produced and some commercial reference copolymers were characterized by DSC, SEC, DMA and 13C NMR.The Hf‐catalysed E/P polymerizations showed much lower activities than the corresponding Zr‐catalysed polymerizations but gave polymers with high molar mass. The Hf‐based copolymers also showed two melting peaks which may be indicative of several active sites of the catalyst. A comparison of E/P copolymers, containing about 20 mol‐% propylene and produced with Zr, Hf and homogeneous V‐catalysts, respectively, indicated that the Hf and V‐catalysts gave material more similar to each other.The E/O copolymers produced with Zr‐catalysts gave very low molar masses and the reactivity ratios, calculated from the NMR data, indicated that the Hf‐catalyst has a slightly higher reactivity for 1‐octene and the Zr‐catalyst some better reactivity for ethylene. Segregation fractionation studies by DSC indicated that a lower 1‐octene feed gives more heterogeneous copolymers and the DMA measurements reveal the existence of a linear correlation between the 1‐octene content and the intensity of the tan δmax peak.
A study on the structure and properties of polymeric sulfur
Authors: Cataldo Franco 
Published: April 2003

AbstractThe structure of insoluble sulfur prepared by quenching sulfur vapours, a polymeric sulfur allotrope used as non‐blooming vulcanizing agent in the rubber industry, has been studied by X‐ray diffraction of powders. The diffraction pattern has been compared with previous data taken on stretched plastic sulfur and fibrous sulfur prepared at very high pressures (30–60 kbar).The superstructures of stretched plastic sulfur and fibrous sulfur are shown to be similar to each other but different from that of insoluble sulfur used in the rubber industry. The FT‐IR spectrum of insoluble sulfur has been reported in comparison with that of rhombic sulfur, showing that this technique is very useful for qualitative analysis of sulfur allotropes. The thermal behaviour of insoluble sulfur was studied by DSC and the heat of fusion and the melting point were determined in comparison with rhombic and monoclinic sulfur.
Textures of thermotropic liquid‐crystalline copolymers containing either 2,7‐, 1,5‐ or 1,4‐naphthalenediol or vanillic acid units
Authors: Li Xin‐Gui , Huang Mei‐Rong 
Published: April 2003

AbstractThe melts of the thermotropic liquid‐crystalline copolymers prepared from 2,7‐, 1,5‐ or 1,4‐naphthalenediol (N)/terephthalic acid/4‐hydroxybenzoic acid/poly(ethylene 2,6‐naphthalene dicarboxylate) or vanillic acid (V)/4‐hydroxybenzoic acid/poly(‐ethylene terephthalate) and other five types of 4‐hydroxybenzoic acid/poly(ethylene terephthalate)/comonomer copolymers are turbid and exhibit a thready texture on the basis of visual observation. Strong shear and stir opalescences in the copolymer melts are also observed. The polarized light micrographs of the melts show a marble or threaded schlieren texture which is a typical optical texture of the nematic mesophase. The polarizing microscopy observation indicates that the vanillate unit‐containing copolymer films obtained by drawing the melts are highly oriented and fibrillated. Elliptical light scattering patterns are obtained for the sheared films of the copolymers, suggesting the existence of a preferred orientation of the copolymer chains. The X‐ray fiber diagrams of the extrudates from the 2,7‐N and 1,5‐N, and V units‐containing copolymers, show broad halos centered at 0.436–0.444 nm and diffraction spots centered at 1.2−1.5 nm along the equator that are reminiscent of amorphous polymers with a “frozen” nematic phase, indicative of chain orientation. Additionally, the X‐ray fiber diagram of the V unit‐copolymer film shows strong meridional reflections at spacings 0.208 and 0.328 nm, representing the molecular repeat spacing of the copolymer chains. The X‐ray fiber diagram of 1,4‐N unit‐containing copolymer rods exhibits two diffuse annular rings, the outer at the d‐spacing 0.438 nm and the inner at 1.3 nm, indicating no definite order or amorphous structure.
Simulation of the hydrolytic polymerization of ϵ‐caprolactam with bifunctional regulators
Authors: Tang Zhi‐Lian , Lin Jian , Huang Nan‐Xun , Fantoni R. F. 
Published: April 2003

AbstractA simulation model dealing with the kinetic behavior of the hydrolytic polymerization of ϵ‐caprolactam with bifunctional regulators has been proposed to analyse such characteristic data of the polymerization as the concentrations of caprolactam. endgroups, ϵ‐aminocaproic acid, cyclic dimer, and as well as conversion, number‐ and weight‐average molecular weights, and polydispersity index. The calculated values based upon the model were found to be quite compatible with the observed values. It is found that the presence of more bifunctional acid leads to a lower equilibrium value of polydispersity index, unlike the case of monofunctional acid where the polydispersity index asymptotically reaches a value of 2, regardless of the amount of monofunctional acid initially added.
Radiation‐induced graft polymerization of styrene onto poly(3‐hydroxybutyrate) and its copolymer with 3‐hydroxyvalerate
Authors: Bahari K. , Mitomo H. , Enjoji T. , Hasegawa S. , Yoshii F. , Makuuchi K. 
Published: April 2003

AbstractGraft copolymerization of styrene (St) onto poly(3‐hydroxybutyrate) (PHB) and poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (P(HB‐HV)) was carried out using simultaneous irradiation and pre‐irradiation techniques with 60Co γ‐rays. The degree of grafting (Xg) of styrene onto PHB increased with increasing pre‐irradiation dose and grafting temperature while in the graft reaction of the copolymer, Xg was higher at 50°C than at 70°C. This Xg was lower than that in grafting methyl methacrylate (MMA) onto PHB and its copolymer. In the electron spin resonance (ESR) study, the PHB radical formed by irradiation was converted to a propagating radical by introducing St monomer at room temperature (25°C) for grafting. The propagating radical was observed even at 50°C and 70°C, grafting of St onto PHB occurs actively at such temperatures. The decay of the radical concentration during grafting well corresponded to radical consumption in graft polymerization. The molecular weight (M̄n) depended on the grafting conditions and the increase of the grafting temperature induced the formation of reduced M̄n because of early termination. It was confirmed that the increase of Xg in pre‐irradiation of more than 10 kGy was due to the increment of the graft chain.
Synthesis and properties of poly(ether ether ketone)/4,4′‐dihydroxydiphenyl sulfone multiblock copolymers
Authors: Cao Junkui , Su Wencheng , Wang Junzuo , Wu Zhongwen , Shibata Mitsuhiro , Yosomiya Ryutoku 
Published: April 2003

AbstractPoly(ether ether ketone) (PEEK)/4,4′‐dihydroxydiphenyl sulfone (DHDPS) multiblock copolymers with a content of the diphenoxysulfone (DPOS) moiety between 4.9 and 36.6wt.‐% were synthesized by the reaction of DHDPS and fluorine‐terminated PEEK oligomers. The number‐average molecular weight of PEEK oligomers (Mn) was varied from 470 to 4900. The effect of the compositional variation on the properties was investigated. Microphase separation was not observed. The copolymers formed a homogeneous system having good compatibility. The copolymers whose DPOS contents are not exceeding 23.1 wt.‐% (Mn of PEEK segment ≥ 865) have crystalline structure.From the measurements of wide‐ and small‐angle X‐ray scatterings it was revealed that the crystal structure of the copolymers is rhombic, equal to PEEK, and the distribution of the thickness of the crystalline and amorphous regions is very broad. The degree of crystallinity and the melting point of the copolymers decreased and the glass transition temperature (Tg) gradually rose with the increase of the DPOS content (or the decrease of Mn of the PEEK segment).
Products of polycondensation of 4,4′‐biphenyldithiol with some hydrocarbon dihalides
Authors: Tarasiuk Bogdan , Podkoscielny Wawrzyniec , Majewski Władysław 
Published: April 2003

AbstractPolysulfides were synthesized with high yield by high‐temperature solution polycondensation of 4,4′‐biphenyldithiol with selected aliphatic and aromatic‐aliphatic hydrocarbon dihalides. To determine the optimum polycondensation conditions, the influence of the following factors on reduced viscosity and yield was studied: type of organic solvent, type of hydrogen halide acceptor, concentration of reagents, reaction temperature, and reaction time. A thorough examination was carried out only for the polycondensation of dithiol with bis(4‐chloromethylphenyl)methane chosen as model system. The structures of the polysulfides were confirmed by elemental analysis, X‐ray analysis, and infrared spectroscopy. The temperature of initial decomposition, the percentage of mass loss, and the temperature of the fastest decomposition, process were determined from curves of differential thermal and thermogravimetric analysis. Some physicochemical, mechanical and electrical properties were determined. The highest thermal and chemical resistance has been found for the polysulfide obtained from 4,4′‐biphenyldithiol and 4,4′‐bis(chloromethyl)biphenyl, probably because of the predominantly aromatic structure.
Carbamoylethylation of moghat mucilage
Authors: Ragheb A. A. , Rahman A. A. Abdel , Hebeish A. 
Published: April 2003

AbstractMucilage isolated from the grinded roots of Glossostemon bruguieri (Desf.) (moghat) was subjected to carbamoylethylation, which involved the reaction of the moghat mucilage with acrylamide along with sodium hydroxide as a catalyst. The reaction was found to depend on the acrylamide concentration as well as on temperature. While the extent of carbamoylethylation increases by increasing acrylamide concentration from 20 to 100 g/100 g mucilage, it decreases by raising the reaction temperature from 25°C to 75°C. The carbamoylethylated moghat mucilage exhibits non‐Newtonian pseudoplastic behaviour irrespective of the extent of carbamoylethylation. On the other hand, increasing the extent of carbamoylethylation is accompanied by an enhancement in the apparent viscosity. This was evidenced by the direct relation of the apparent viscosity with the increase in acrylamide concentration and its inverse relation with the temperature. A 72 h storage of the pastes under investigation causes a considerable decrement in apparent viscosity only when the extent of carbamoylethylation is low. Higher extents of carbamoylethylation stabilised the molecular structure of the moghat mucilage.