bluuebunny/crossref_metadata_2025_split huggingface dataset:
Time‐dependent fracture toughness measure for polyethylene
Authors: Strebel J. J. , Moet A. 
Published: April 2003

AbstractBecause of their extraordinary cracking resistance, medium‐density polyethylenes (MDPEs) do not fail in a brittle manner when tested with conventional fracture toughness procedures, but brittle fractures andJ1cvalues can be obtained for these materials by utilizing fatigue loading. However, because brittle fracture in polyethylene is a result of low stresses (energy) applied over long periods of time, and sinceJ1cneglects time,J1cis incapable of differentiating MDPEs on the basis of their fracture resistance. Thus, the power to fracture method, which incorporates both energy and time, has been developed. During increments of crack growth, the product of the potential energy and the number of elapsed cycles is used to calculate the power to fracture. Within limits that assure a similar failure mechanism, the power to fracture for a particular resin is constant despite varied fatigue conditions. The power to fracture is capable of differentiating between resins on the basis of their brittle cracking resistance. © 1994 John Wiley & Sons, Inc.
Wood‐induced catalytic activation of PF adhesives autopolymerization vs. PF/wood covalent bonding
Authors: Pizzi A. , Mtsweni B. , Parsons W. 
Published: April 2003

AbstractThe reaction of polycondensation of phenol‐formaldehyde (PF) resins in the presence of wood was confirmed to have a lower energy of activation than of the PF resin alone. Under the low temperature and short curing times characteristic of the application of PF resins as thermosetting wood adhesives DSC, TGA, chemical kinetics, and IR of PF resins and relevant model compounds were carried out. These indicated that two effects appear to be present when a PF resin cures on a wood surface, both induced by the polymeric constituents of the substrate, namely carbohydrates and lignin. These appear to be (1) the catalytic activation of the resin self‐condensation induced particularly by carbohydrates such as crystalline and amorphous cellulose and hemicelluloses and (2) the formation of resin/substrate covalent bonding, particularly in the case of lignin. The first appears to be, by far, the major cause of the lowering of the activation energy of PF resins curing. The contribution of the second has been found to be very small and often negligble under the conditions pertaining to thermosetting wood adhesives applications. Molecular mechanics results appear to indicate that the marked catalytic activation of PF resins autocondensation and curing appears to be induced by the strong set of PF adhesive/substrate secondary forces interactions which appear to weaken bonds which, by cleavage, lead to PF resins autocondensation. © 1994 John Wiley & Sons, Inc.
Aspects of surface characterization of polyurethane adhesives
Authors: Ulkem I. , Schreiber H. P. 
Published: April 2003

AbstractThe performances of adhesives is strongly dependent on the contributions to overall surface energies from dispersion and nondispersion forces. In this work, surface energies have been studied for polyurethanes representing the categories of aliphatic and aromatic polyethers and aliphatic polyesters. The surface energies of the polymers were measured by static and dynamic contact angle methods. In addition to determining the energy values for polymers as received, evaluations were also made on the polymers following modification by an aminopropyl silance (APS), present at concentrations ranging from 0.1 to 20 wt %. The dispersion surface energies of the three polymers were roughly equal; however, the nondispersive surface energies strongly differentiated among them. Organic liquids were used for calculations of energy parameters from static contact angles. Data for water failed to follow theoretical expectations and were used instead to compute a work of adhesion parameter for the polymer/water interface. This correlated with nondispersion surface energies of the polyurethanes. Somewhat different values of the nondispersion surface energy were obtained from static and dynamic contact angles, an effect attributed to the tendency of polyurethanes to restructure when their surfaces were in prolonged contact with water during dynamic analysis. This behavior may be important to the type of adhesive bond formed by the polymers and to variations in bond characterstics with time. The use of APS was found to influence both static and dynamic contact angle values, with primary changes occuring in nondispersion contributions. The effects of APS addition were fully developed at concentrations of 1 wt % or less, raising doubts about the efficiency of using this additive at higher concentrations. © 1994 John Wiley & Sons, Inc.
Kinetic study of pyrrole polymerization with iron (III) chloride in water
Authors: Planche M. F. , Thiéblemont J. C. , Mazars N. , Bidan G. 
Published: April 2003

AbstractThe chemical synthesis of polypyrrole in water, with FeCl3 as an oxidant of pyrrole, was investigated. During these experiments in ambient air, a large evaporation of pyrrole was observed. Moreover, a kinetic study of pyrrole disappearance by high‐performance liquid chromatography (HPLC), with various FeCl3 concentrations, proved that the polymerization is first order with respect to the pyrrole and second order with respect to the FeCl3. These kinetics can be explained by the formation of an intermediary FeCl3–pyrrole complex as the first step of the polymerization. The second step, which is rate‐determining, is the pyrrole oxidation by FeCl3, © 1994 John Wiley & Sons, Inc.
Melt viscosity of oligomeric triblock copolymers (type PEP) of ethylene and propylene oxides
Authors: S̆imek L. , Petr̆ik S. , Bohdanecký M. 
Published: April 2003

AbstractMelt viscosity η at 25°C of four oligomeric triblock copolymers consisting of a central block of ethoxamer units and two end blocks of propoxamer units (PEP) (Mn × 10−3 = 1 and 2; mole fraction of ethoxamer units xE = 0.41, 0.57, and 0.74) was analyzed in terms of the theory advanced by Berry and Fox. The structure‐dependent factor F(X) was deduced from the intrinsic viscosity data, and the mean friction factor per friction center ζ was computed from η and F(X). At a fixed molecular weight, it increases with increasing xE. The dependence of ζ versus xE was compared with curves computed from the data for homopolymers. The best agreement was obtained if the following values of the inherent friction factor (log ζ0) were used: −10.25 for poly(ethylene oxide) PEO and −10.65 for PPO. © 1994 John Wiley & Sons, Inc.
Experimental testing of the polymer–filler gel formation theory. Part I
Authors: Karásek L. , Meissner B. 
Published: April 2003

AbstractExperimental data were obtained on the concentration dependence of the fraction of total filler–bound polymer, fraction of polymer in a coherent polymer–filler gel, and fraction of solvent‐dispersed filler particles in compounds of fume silica (Aerosil OX50) with natural rubber (NR) and styrene butadiene rubber (SBR). Predictions of the polymer–filler gel formation theory were tested and a good formal description of the data was obtained. The two adjustable parameters of the theory assume reasonable values. While A0 is a characteristic of the filler interaction with polymer and has similar values in NR and SBR, the functionality f of the theoretically assumed filler particle acting as a polyfunctional crosslinker of polymer chains seems to depend on the polymer as well. Dimensions of the theoretical filler particle calculated from a comparison of experiment with theory are of the same order of magnitude but smaller than those of primary filler particles. © 1994 John Wiley & Sons, Inc.
Mechanical properties and morphology of PP/SEBS/PC blends
Authors: Srinivasan K. R. , Gupta A. K. 
Published: April 2003

AbstractRubber toughening of thermoplastic polymers always decreases the tensile and flexural properties. In this article, an attempt is made to improve the tensile and flexural properties of a rubber‐toughened polymer system viz., polypropylene (PP)/styrene‐ethylene‐butylene‐styrene tri‐block copolymer (SEBS) binary blend by blending a rigid polymer viz., polycarbonate (PC) with this binary system. The PP/SEBS blend with a blending ratio fixed at three levels, namely 95/5, 90/10, and 80/20, was melt mixed with 0–30 wt % PC to generate the various blend compositions studied. This choice of compositions enabled us to show how the mechanical properties varied as a function of (1) PP/SEBS ratio at a constant PC content and (2) PC content at a constant PP/SEBS ratio of the blend. Data on the corresponding binary blends, namely PP/SEBS and PP/PC, are also presented and discussed as reference systems. The data are discussed in detail for the effect of each component of the blend. As regards the morphology, some distinct changes were seen in the middle of composition ranges of the additives, i.e., around 10 to 20% PC level, and 95/5 and 90/10 PP/SEBS ratios. Variation of mechanical properties in the respective composition ranges are found consistent with the variations of blend morphology. Hence, a correlation of morphology and the properties is discussed. Furthermore, the results suggest stronger interfacial interaction between SEBS and PP than that between PC and PP. Scanning electron microscopic studies of appropriately etched impact fractured samples reveal the existence of composite droplets of SEBS and PC embedded in PP matrix, with SEBS forming the outer envelope around PC. © 1994 John Wiley & Sons, Inc.
Effect of aromatic diamine extenders on the morphology and property of RIM polyurethane–urea
Authors: Gao Yun , Xiu Yu‐Ying , Pan Zhao‐Qi , Wang De‐Ning , Hu Chun‐Pu , Ying Sheng‐Kang 
Published: April 2003

AbstractAn aromatic diamine, CMOMDA, was synthesized and used as a chain extender for reaction injection molding (RIM) polyurethane–urea. The morphology and properties of CMOMDA‐, DETDA‐, and MDA‐extended poly(ether–urethane–urea)s (PEUUs) were measured by IR, DSC, DMS, SEM, and tensile testing apparatus. Well‐matched values of Ch and Xut,b/Ch were necessary for aromatic diamine‐extended PEUU. DSC and SEM showed that the aggregation state of hard segments might undergo some changes with increasing hard‐segment content. © 1994 John Wiley & Sons, Inc.
Kinetics of radical polymerization of N‐vinylpyrrolidone by peroxidiphosphate–Ag+ system
Authors: Gupta K. C. 
Published: April 2003

AbstractThe kinetics of aqueous polymerization of N‐vinylpyrrolidone (N‐VP) was carried out using potassium peroxidiphosphate–Ag+ system under nitrogen atmosphere at 25°C. The rate of polymerization was directly proportional to the concentration of the N‐vinylpyrrolidone and showed a half‐order with respect to the concentration of the peroxidiphosphate (H2P2O) and Ag+ ions. The value of κp/(κt)1/2 was computed and its value found to increase on increasing the temperature of the reaction mixture. The energy of activation (Ea) was found to be 65.8 ± 0.1 kJ mol−1 within the temperature range from 20 to 50°C. Viscometric average molecular weight of polyvinylpyrrolidone was determined by measuring intrinsic viscosity of the polymer samples collected at different kinetic conditions. The effect of various additives was also studied. A suitable mechanism of polymerization has been proposed and a reaction rate law was derived considering experimental results. © 1994 John Wiley & Sons, Inc.
Enrichment of helium by asymmetric hollow‐fiber membrane of cellulose triacetate
Authors: Kumazawa H. , Sada E. , Nakata K. , Kawashima N. , Kataoka S. , Tada K. 
Published: April 2003

AbstractThe permeation behavior of pure He and separation characteristics of He–air mixtures were examined using asymmetric hollow‐fiber‐type membrane modules of cellulose triacetate. The module was operated in a feed‐outside mode. In permeation of pure He, the permeation rate coefficients slightly increased with increasing upstream pressure, and they agreed fairly well with those calculated on the basis of the assumption that the permeate flow inside the fiber is governed by the Hagen‐Poiseuille equation. In the single‐stage hollow‐fiber module used, the molar fraction of He in the permeate stream was increased to 0.99 and 0.999 at the stage cuts of lower than 0.3 when the molar fraction in the feed stream was 0.90 and 0.99, respectively. The molar fractions of He in the permeate stream were numerically evaluated for various combinations of operating conditions in terms of a countercurrent plug flow model. © 1994 John Wiley & Sons, Inc.
Structure and electrical properties of the oriented polyaniline films
Authors: Wan Meixiang , Li Ming , Li Junchao , Liu Zhenxing 
Published: April 2003

AbstractThe structure of oriented polyaniline (PANI) films were characterized by elemental analysis, FTIR, XPS, SEM, and X‐ray diffraction, and their electrical properties were measured as a function of the protonation state, elongation ratio, temperature, and applied pressure. A maximum conductivity at room temperature for oriented PANI films can be achieved up to 500 s/cm with conductivity anisotropy as high as 20 : 1. The temperature dependence of conductivity for both unoriented and oriented films at 77–300 K and applied pressure of 0–11.4 kbar is consistent with the 3‐D variable‐range hopping model; however, the hopping barrier of oriented films is one order magnitude lower than that of unoriented films. The mechanism of enhanced conductivity for oriented PANI films is discussed. © 1994 John Wiley & Sons, Inc.
Structure and properties of polyvinyl alcohol amidoxime chelate fiber
Authors: Lei Rao , Jie Xu , Jun Xu , Ruiyun Zhan 
Published: April 2003

AbstractPolyvinyl alcohol amidoxime (PVAAO) chelate fiber prepared in our laboratory is a good adsorbent. Comparing with other adsorbents, it has many advantages, such as higher hydrophilicity, better adsorbability and easier synthesis. In this work, the synthesis course, structure and properties of PVAAO fiber have been studied by the means of FT‐IR, SEM, ESR, and TG. The structural changes of the fiber associated with adsorbed copper ions have also been investigated using ESR, FT‐IR, and XPS. In addition, chelating mechanisms of the fiber‐adsorbing copper ions have been discussed. © 1994 John Wiley & Sons, Inc.
Effect of corona modification on the mechanical properties of polypropylene/cellulose composites
Authors: Belgacem M. N. , Bataille P. , Sapieha S. 
Published: April 2003

AbstractThe effect of various corona treatment conditions on the mechanical properties of cellulose fibers/polypropylene composites was studied. The cellulose fibers and polypropylene were modified using a wide range of corona treatment levels and concentrations of oxygen. The treatment level of the fibers was evaluated using the electrical conductance of their aqueous suspensions. The mechanical properties of composites obtained from different combinations of treated or untreated cellulose fibers and polypropylene were characterized by tensile stress–strain measurements; they improved substantially when either the cellulose fibers alone or both components were treated, although composites made from untreated cellulose fibers and treated polypropylene showed a relatively small improvement. The results obtained indicate that dispersive forces are mostly responsible for the enhanced adhesion. The relationship between the electrical conductance of the fibers, the mechanical properties, and the mechanism of improved adhesion is discussed. © 1994 John Wiley & Sons, Inc.
Catalysts for the preparation of polybenzimidazoles
Authors: Choe Eui‐Won 
Published: April 2003

AbstractThe single‐stage preparation of poly[2,2′‐(m‐phenylene)‐5,5′‐bibenzimidazole] (PBI), from 3,3′,4,4′‐tetraaminobiphenyl (TAB) with isophthalic acid (IPA) in the presence of a catalyst, was explored and developed. The effects of a variety of catalysts on the polymerization of TAB with IPA and/or diphenyl isophthalate were screened and evaluated. Many organo phosphorus and silicon compounds catalyzed the PBI condensation reactions, increased the molecular weight, and improved the quality of PBI polymers. Fiber and reverse osmosis membrane properties of PBI prepared from TAB and IPA were comparable to those for commercial standard PBI prepared from TAB and diphenyl isophthalate. © 1994 John Wiley & Sons, Inc.
Impact modification of engineering thermoplastics
Authors: Kanai Hiroyuki , Sullivan Vince , Auerbach Andrew 
Published: April 2003

AbstractImpact modification was studied for a variety of engineering thermoplastics to determine if notched Izod data obtained at various temperatures and modifier concentrations could be correlated with particle size or surface‐to‐surface interparticle distance of the modifier. Elastomers evaluated were characteristic of those used in commercial blend systems for those polymers, and both functionalized and nonfunctionalized materials were studied. For the single matrix polymer/elastomer‐modified blend systems studied [poly(phenylene sulfide) (PPS), polyoxymethylene (POM), poly(butylene terephthalate) (PBT)], elastomer interparticle distance provides a better correlation to brittle–tough transition temperature than does particle size, as predicted by the Wu model. In POM, the dispersion morphology of the samples used was not adequate to achieve the critical interparticle distance required for supertoughening at room temperature. In this study, the critical interparticle distance has been shown to depend on the degree of crystallinity (PPS) and the modulus of the impact modifier relative to the matrix (PBT). Actual adhesion of the polymer to the matrix (variation of functionality levels) was not found to have a strong influence (PBT). In POM, the increase in impact at the brittle–tough transition was dependent on the molecular weight of the base resin. This is examined with respect to the ratio of the molecular weight (Mn) to the entanglement molecular weight (Me), which determines the critical molecular weight necessary to achieve useful physical properties. In polyester (PET)/polycarbonate (PC)/elastomer blends, the molecular weight of the primary matrix resin (PET) determined impact properties within the molecular weight range of the resin studied. This was again related to the Mn/Me ratio for PET and PC. © 1994 John Wiley & Sons, Inc.
A thermally stimulated current/relaxation map analysis of the relaxation processes in aromatic polyester, liquid crystal polymer film
Authors: Collins George , Long Barbara 
Published: April 2003

AbstractThermally stimulated current (TSC) and relaxation map analysis (RMA) have been applied to the examination of dynamics of thermally induced relaxation processes in highly oriented, wholly aromatic, polyester liquid crystalline polymer films. Films of two compositions were examined. A primary distinction in composition was the difference in level of 6‐hydroxy‐2‐napthoic acid. Following an analysis protocol developed by Sauer et al., it was found that values of activation enthalpy were well above the zero entropy value at temperatures well below the Sauer “Tg.” This indicates a high level of cooperativity in rotational relaxation processes even at low temperatures. Cooperative rotational relaxation domains were postulated to account for this behavior. The persistence of cooperativity above the Sauer “Tg.” is evidence that these materials did not undergo a conventional glass transition at any temperature in the range–80 to 200°C. The behavior of these materials as a model system of “loosely bundled rods” was examined using a modified Barker–Crine analysis. This type of model behavior seemed to fall off at relatively low temperatures. The occurrence of rotational processes at high temperatures with little or no loss in orientation suggests that polymer chains are physically constrained to maintain their relative positions. © 1994 John Wiley & Sons, Inc.
Thermosetting cure diagrams: Calculation and application
Authors: Simon S. L. , Gillham J. K. 
Published: April 2003

AbstractThe time–temperature–transformation (TTT) isothermal cure diagram and the continuous‐heating‐transformation (CHT) cure diagram are calculated from a reaction model for a high‐Tg epoxy/amine system that has been developed to describe both epoxy/amine and etherification reactions in kinetically and diffusion‐controlled reaction regimes. The cure diagrams are applied to various processing operations. The optimization of processing and of material properties by exploiting gelation and/or vitrification during cure is discussed. © 1994 John Wiley & Sons, Inc.
Characterization of polyamide 6 made by reactive extrusion. I. Synthesis and characterization of properties
Authors: Hornsby P. R. , Tung J. F. , Tarverdi K. 
Published: April 2003

AbstractThe anionic polymerisation of ε‐caprolactam in a corotating, intermeshing twin‐screw extruder is discussed in terms of the materials formulation, extruder screw profile, and processing parameters such as temperature and screw speed. Using a variety of analytical characterization techniques, it is demonstrated that molecular mass, residual monomer content, and mechanical properties of the polyamide 6 are very sensitive to the reactive processing conditions employed. © 1994 John Wiley & Sons, Inc.
Studies on semiinterpenetrating polymer networks based on poly(vinyl chloride‐co‐vinyl acetate) and poly(alkyl methacrylates)
Authors: Mathew Annakutty , Deb P. C. 
Published: April 2003

AbstractA number of semi‐interpenetrating polymer networks (IPNs) based on linear poly(vinyl chloride‐co‐vinyl acetate) and poly(alkyl methacrylates) were synthesized. The semi‐IPNs were found to be transparent, high strength materials. The IPNs show only one glass‐transition temperature and it is dependent on the composition as studied by differential scanning calorimetry and dynamic mechanical analysis. These IPNs are also characterized by high tan δ values. The tensile strength of the IPNs were found to be higher compared to the starting polymers. In order to compare the properties of these IPNs with the corresponding homopolymers and blends, the latter were synthesized and the properties were studied. © 1994 John Wiley & Sons, Inc.
Modification of isotactic polypropylene by a cold plasma or an electron beam and grafting of the acrylic acid onto these activated polymers
Authors: Poncin‐Epaillard Fabienne , Chevet Bruno , Brosse Jean‐Claude 
Published: April 2003

AbstractSurface grafting of polymeric materials, such as films and fibers, may improve their reactive surface properties. Polypropylene active sites that should initiate a surface postgrafting can be formed by either nitrogen cold plasma or an electron‐beam irradiation. The plasmamodified polymer surface is cross‐linked and functionalized with primary amino groups and with oxidized groups, and it is almost not degraded. Electron‐beam‐modified polypropylene is also functionalized through an aging reaction, emphasized by a high radical concentration. In both cases, active surface films are susceptible to react with monomers in a postgrafting reaction. The grafting yield and rate of acrylic acid were shown to be dependent on the formed amino group concentration: The hydrophilic character of the modified polypropylene surface enhances the acrylic acid approach. The electron‐beam treatment leads also to a reactive surface that can initiate a grafting reaction. But its yield and rate are dependent on the radical concentration: radicals formed during the irradiation. © 1994 John Wiley & Sons, Inc.