bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fracture toughness of injection molded glass fiber reinforced polypropylene
Authors: Hashemi S. , Koohgilani M. 
Published: May 2005

AbstractThe fracture behavior of polypropylene reinforced with 30% by weight of short glass fibers was studied using single and double feed plaque moldings. Plaques were injection molded using several gate types and gate positions. Fracture toughness Kc, was calculated at different positions in the plaque moldings using single edge notched tension specimens. Fracture toughness was assessed in the directions parallel and perpendicular to the mold fill direction through measurements of the load to produce complete fracture. Results indicated that the value of fracture toughness is affected by the type of gate as well by size of gate. Position of the specimen also affected fracture toughness. Generally, specimens taken from positions near cavity walls gave higher toughness values than those taken from the center of the moldings. Furthermore, fracture toughness in the transverse direction was consistently higher than in the melt flow direction. Finally, in the case o double feed moldings, a much higher fracture toughness was obtained when the initial crack was perpendicular to the weld line than when it was placed inside the weld line.
Discrete strength levels in modified polypropylene tapes
Authors: Dmitorva D. , Kostov G. , Garova G. 
Published: May 2005

AbstractA statistical study of the strength of unmodified and modified uniaxially drawn polypropylene tapes was carried out. The results show that the curve representing the distribution of strength for unmodified tapes reveals seven discrete levels corresponding to microdefects in the form of microcrazes and submicrocrazes. On introduction of modifying additive, three discrete strength levels were observed, corresponding to submicrocrazes. The strength of the modified polypropylene tape increase approximately twice compared to the strength of the initial material. The polyfunctional effect of the additives as artificial nucleators and regulators of the structure leads to an increase of the degree of crystallinity which in turn restrains the submicrocrazes development into microcrazes. The method used could be applied for objective analysis of the tensile characteristics of polymeric materials.
Radiation crosslinking of polyethylene with electron beam at different temperatures
Authors: Qu Baojun , Rårby Bengt 
Published: May 2005

AbstractThe effect of temperature over the range −196 to 150°C on the crosslinking of polyethylenes irradiated by electron beam has been investigated on the basis of gel content determination and Fourier transform infra‐red (FTIR) spectroscopy. The crosslinking efficiency increases significantly with increasing irradiation does and at elevated irradiation temperature. The crosslinking rates of high density polyethylene (HDPE) and low density polyethylene (LDPE) samples above the melting point (TM) are much higher than those below Tm. The FTIR data give positive evidence: (i) that trans‐vinylene double bonds in cross linked HDPE and LDPE samples increase with increasing irradiation dose temperature (ii) that vinyl double bonds in HDPE decrease rapidly with increasing irradiation dose and temperature, and (iii) vinylidene groups in LDPE decrease slowly with increasing temperature at the lower dose and are almost independent of the irradiation temperature at above room temperature and the higher dose of more than 100 kGy. Gas bubbles are observed in LDPE samples irradiated at 100 and 150°C with high dose (200 to 250 kGy). The size of the bubbles increases gradually at high temperatures.
Water sorption and diffusion in starch/polyolefin blends
Authors: Willett J. L. 
Published: May 2005

AbstractThe kinetics of water sorption by starch filled polyolefins has been investigated using blends of commercial starch masterbatch with low density polyethylene (LDPE), high density PE (HDPE), and copolymers of ethylene with methyl acrylate (EMA), ethyl (EEA), AND n‐butyl acrylate (EBA). Transient state diffusion coefficients (D) of water in the blends were determined using Fickian analysis of the initial stages of the sorption isotherms. Measured D values were several orders of magnitude lower than values reported for either pure starch of LIDPE by various investigators. Resin effects on D were on the order DHDPE < DLDPE ≪ DEBA < DEEA < DEMA. The resin effects diminished as the starch content increased. The lower magnitude of D in the blends relative to pure LDPE was attributed to the sorption of water by the dry starch particles, in a manner similar to dual‐mode sorption in glassy polymers. Copolymer effects were consistent with reduction in crystallinity caused by the comonomers. The dependence of the diffusion coefficient on starch content was not described by mixing models of heterogeneous systems of percolation theory.
Numerical simulation of fluid flow and heat transfer in twin‐screw extruders for non‐Newtonian materials
Authors: Sastrohartono Trihono , Jaluria Yogesh , Karwe Mukund V. 
Published: May 2005

AbstractA new simplified approach has been proposed for the numerical simulation of the thermal transport in corotating, tangential, and self‐wiping twin‐screw extruders. It is assumed that the flow domain in a twin‐screw extruder can be divided into (i) the translation region (T‐region), which represents a flow similar to that in a single‐screw channel and (ii) the intermeshing region (I‐region), which is located between the two screws. The two regions are simulated separately and then coupled for each screw section to model the overall transport in tangential and self‐wiping twin‐screw extruders. A finite difference method is employed for the developing flow and temperature fields in the T‐region, in order to minimize the computing effort, while a finite element method is employed for determining the interchannel flow mixing and the thermal transport in the I‐region. Results are obtained in terms of temperature, velocity, and pressure variations along the screw channels and mixing between the two screws.
Model filled polymers. XV: The effects of chemical interactions and matrix molecular weight on rheology
Authors: Agarwal Shishir , Salovey Ronald 
Published: May 2005

AbstractIn order to explore the effects of chemical composition on the rheological behavior o filled polymeric systems, we prepared polystyrene (9PS) and poly(methyl methacrylate) (PMMA) particles crosslinked with either ethylene glycol dimethacrylate (EGDMA) or divinyl benzene (DVB), and mixed these particles in a PMMA matrix. PS particles crosslinked with 10% EGDMA are better dispersed in a PMMA matrix, compared to PS particles, crosslinked with 10% DVB, due to the compatibilizing effect of EGDMA. For PMMA particles crosslinked with DVB, particle‐matrix interactions in a PMMA matrix are smaller than in EGDMA‐PMMA filled PMMA. Therefore, particles tend to agglomerate in PMMA composites filled with DVB‐PMMA particles, especially in a low molecular weight matrix. We compared PMMA matrices of molecular weights 35,000 and 75,000. Higher particle‐matrix interaction in the higher molecular weight matrix resulted in lower relative viscosities for DVB‐PS filled systems, due to better dispersion of the particles. Composites filled with EGDMA‐PS particles behave similarly to those filled with DVB‐PS particles. PMMA composites filled with DVB‐PMMA particles have a lower relative viscosity in the higher molecular weight PMMA matrix at low shear rates, due to better dispersion in the higher molecular weight matrix. However at high shear rates, particles are well dispersed in both PMMA matrices and, then, the relative viscosity is higher due to better bonding in the higher molecular weight matrix.
A model for nonlinear creep and physical aging in poly(vinyl chloride)
Authors: Dean G. D. , Tomlins P. E. , Read B. E. 
Published: May 2005

AbstractThe creep behavior of polymers depends on the physical age of the material at the time of stress application. Creep curves shift to longer times for more highly aged material and, in poly(vinyl chloride), (PVC), this can be modeled by an empirical equation in which the magnitude of an effective mean retardation time parameter is dependent upon, and increases with, the age of the polymer. Creep compliances for PVC also depend on the magnitude of the applied stress when this exceeds about 4 MPa. This nonlinear behavior is caused, at short creep times, by a reduction in the value for the retardation time parameter on application of the creep stress. Specimens appear therefore to be initially de‐aged by elevated stresses. Subsequently, this parameter increases with creep time implying that physical aging has been reactivated, but the rate of increase also depends on the stress level. These influences of elevated stresses can be described by an extension of the creep model, and parametric expressions have been derived which relate creep compliance values to time, stress, and the age of the polymer. It is shown how the parameters can be determined from a short series of creep experiments and thus how creep deformations can be calculated over wide ranges of time, stress, and age.
An integral constitutive equation for nonlinear plasto‐viscoelastic behavior of high‐density polyethylene
Authors: Lai J. , Bakker A. 
Published: May 2005

AbstractIn the present paper an effort is made to model the time‐dependent behavior of high‐density polyethylene (HDPE) with a one‐dimensional integral representation. Owing to the plasto‐viscoelastic behavior of the material, we assume that the total strain can be decomposed into a recoverable viscoelastic strain and an irrecoverable plastic strain. The viscoelastic deformation is represented by the Schapery thermodynamic theory. The plastic deformation is assumed to be accumulated during the loading history. An effective time concept is introduced for the plastic deformation, so that the response due to complex loading can be accounted for. The present representation gives a very good prediction of the responses of creep and recovery, two‐step creep, and constant stress rate loading and unloading. It is also applied successfully to describe the process of preconditioning of semicrystalline polymers.
Cure behavior and properties of an epoxy resin modified with a bismaleimide resin
Authors: Kim Dae Su , Han Mi Jeong , Lee Jae Rock 
Published: May 2005

AbstractA bismaleimide (BMI) resin was added to an epoxy system composed of N,N′‐tetraglycidyldiaminodiphenyl methane (TGDDM) and diaminodiphenyl methane (DDM). Cure behavior of the BMI modified epoxy resins was studied by a dynamic differential scanning calorimetry (DSC) method. Dynamic DSC thermograms of the BMI modified epoxy resins indicated unimodal reaction exothermic peaks. The overall heat of reaction per unit mass decreased with BMI composition. The residual heat of reactions of the epoxy blends cured at 180°C for 3 h increased with BMI composition. Thermal stability of the epoxy system improved by incorporating BMI resin. Flexural strength and modulus increased with BMI composition.
Rubber‐modified thermosets cured in heated molds: Experimental study of phase separation profiles
Authors: Fang Dong Pu , Frontini Patricia M. , Riccardi Carmen C. , Williams Roberto J. J. 
Published: May 2005

AbstractAn epoxy‐amine thermosetting polymer, modified by 15 wt% castor oil (CO) or by a commercial rubber (epoxy‐terminated butadiene‐acrylonitrile copolymer, ETBN), was cured in a mold at different heating rates. CO‐modified materials cured at high heating rates exhibited a nonuniform phase separation profile, i.e. a single‐phase transparent core surrounded by opaque layers containing dispersed domains. The resulting structure was explained by simulating conversion vs. temperature trajectories taking place during the cure. Thermal and mechanical properties of uniform and nonuniform materials were compared. These include glass transition temperature, microhardness, yield stress and yield strain in uniaxial compression, and fracture toughness. Some possibilities for further research in this area are discussed.
Step‐growth polymerization of maleic anhydride and 1,2‐propylene glycol
Authors: Jedlovčnik R. , Šebenik A. , Golob J. , Korbar J. 
Published: May 2005

AbstractThe NMR (nuclear magnetic resonance) and GPC (gel permeation chromatography) studies of the polymerization of maleic anhydride and 1,2‐propylen glycol are reported. Assignment of individual groups was made and their concentration dependence on reaction time was established. The first step of the reaction is the formation of monoesters, which, immediately after the temperature increased, reacted to diesters. The reactivity ratio between the primary and the secondary hydroxyl group of 1,2‐propylene glycol was 2.6:1. The concentration of water formed was followed as a function of reaction time by the Karl–Fischer method.
Synthesis of polyamides from active 4,4′‐diacylbis‐2‐aryl‐1,3,4‐oxadiazoline‐5‐thiones and ‐ones and diamines under mild conditions
Authors: Saegusa Yasuo , Nakamura Shigeo , Chau Nguyen , Iwakura Yoshio 
Published: May 2005

AbstractNew active bisamides, 4,4′ ‐diacylbis‐2‐aryl‐1,3,4‐oxadiazoline‐5‐thiones and ‐ones having various electron accepting groups in the oxadiazoline units were synthesized, and their reactivities toward diamines were investigated. The polycondensation reactions of the bisamides derived from 2‐aryl‐1,3,4‐oxadiazoline‐5‐thiones with both aliphatic and aromatic diamines occurred rapidly even at room temperature to form high‐molecular‐weight polyamides in quantitative yields. The reactivities of the bisamides having electron accepting groups such as p‐chloro and p‐nitro groups, particularly p‐nitro groups, toward diamines were much higher than that of the corresponding bisamide having no such group. It was also found that reaction conditions such as solvent, monomer concentration, and temperature had a strong influence on the molecular weight of the resulting polyamides. Aminolysis of several benzoyl derivatives of 2‐aryl‐1,3,4‐oxadiazoline‐5‐thiones and ‐ones was also carried out as a model reaction, and the effect of electron accepting groups on the reactivity of these compounds was discussed.
The solubility of cellulose in liquid ammonia/ammonium thiocyanate solution: The effect of composition and temperature on dissolution and solution properties
Authors: Hudson S. M. , Cuculo J. A. , Wadsworth L. C. 
Published: May 2005

AbstractThe dissolution process and some solution properties of cellulose in mixtures of liquid ammonia (NH3) and ammonium thiocyanate (NH4SCN) are discussed. The mole fraction ratio of NH3, NH4SCN, and H2O which dissolve cellulose were determined. The effect of temperature on several solution properties was also examined. The temperature coefficient d In [n]/dT for the limiting viscosity number [n] has a value of −1.58 × 10−2 °C−1. This is considered to be rather large but is, in fact, a common occurrence for almost all cellulose derivatives in solution. The values for the Huggins constant K′ showed no systematic trends with temperature. They did, however, suggest the presence of considerable association of the cellulose in solution. Miscibility results of adding the cellulose solutions to organic liquids are also reported.
Synthesis and characterization of linear high molecular weight poly(amino‐s‐triazine)s
Authors: Wang David Wei , Fisher Michael M. 
Published: May 2005

AbstractA two‐phase polycondensation reaction was used to prepare high molecular weight linear poly‐(amino‐s‐triazine)s from aminodichloro‐s‐triazines and diamines. These polymers contain a high concentration of melamine‐type units in the polymer backbone. Molded specimens exhibited good mechanical properties and resistance to organic solvents. Dimethyl substitution at the exocyclic amino group led to a significant reduction in indentation resistance, strength, and modulus.
Long‐lived polymer radicals. III. Synthesis of block copolymer by the reaction of living poly(N‐methylacrylamide) radical with some vinyl monomers
Authors: Sato Tsuneyuki , Iwaki Takahiko , Mori Shigeki , Otsu Takayuki 
Published: May 2005

AbstractN‐Methylacrylamide (NMAAm) was polymerized quantitatively by using di‐tert‐butyl peroxide as photosensitizer to be, for the most part, incorporated in living poly(NMAAm) radical. The living polymer radical reacted effectively with acrylate monomers to yield block copolymer. Longer alkyl chain of the acrylate monomer caused a decrease in the conversion of the second monomer. Methacrylate monomers, such as methyl methacrylate and cyclohexyl methacrylate, showed relatively low reactivities in comparison with acrylates. Styrene exhibited a much lower conversion. The resulting block copolymers showed different thermochromic behaviors in methyl benzoate from that of poly(NMAAm). This is explained on the basis of the difference between refractive indexes of the block copolymers and poly(NMAAm).
Dehydrofluorination of poly(vinylidene fluoride) in dimethylformamide solution: Synthesis of an operationally soluble semiconducting polymer
Authors: Dias Anthony J. , McCarthy Thomas J. 
Published: May 2005

AbstractThe reaction of poly(vinylidene fluoride) with several different bases in dimethylformamide solution yields dehydrofluorinated products with conjugated polyene structures. The extent of elimination can be controlled by varying the amount of added base. The structural properties of dehydrofluorinated materials depend on the base used. Polymer films cast from DMF solution exhibit electronic conductivity upon iodine doping; the conductivity is also a function of the base used.
Surface modification of polypropylene with CF4, CF3H, CF3Cl, and CF3Br plasmas
Authors: Strobel Mark , Corn Stewart , Lyons Christopher S. , Korba Gary A. 
Published: May 2005

AbstractESCA and contact angle measurements were used to characterize the surfaces of polypropylene and glass substrates exposed to CF4, CF3H, CF3Cl, and CF3Br plasmas. The use of both organic and inorganic substrates allowed clear distinction between treatments which led to plasma polymerization and treatments which caused grafting of functional groups directly to the substrate surfaces. CF4 plasmas were the only treatments studied which fluorinated polypropylene surfaces directly, without the deposition of a thin, plasma‐polymerized film. CF3H polymerized in a plasma, while CF3Cl and CF3Br plasmas caused chlorination and bromination of polypropylene surfaces, respectively. Correlations were made between the active species present in the plasmas and the surface chemistry observed on the treated polypropylene substrates.
Preparation Technology for Fine Particle Measurement
Authors: Polke Reinhard , Schäfer Michael , Scholz Norbert 
Published: May 2005

AbstractDescribing the disperse state is important for quality assurance, operational safety and the design and modelling of processes, especially in solids technology. Starting materials, intermediates and end products have to be characterized. Apart from representative sampling, preparation greatly influences the results of particle characterization. Very fine particles are normally agglomerated unless a highly dispersed state is stabilized by an additive. For a meaningful measurement, they must be preserved in this state or be definitely dispersed, depending on the type of problem.If the point of interest is the present disperse state with regard to the processing characteristics, e.g. for a filtration, the system should not be changed by the preparation method. If it is necessary to determine the property functions, i. e. the functional relationship between technological and physical properties, it is necessary in general to use a high dispersion energy or a long dispersing time in order to obtain the best achievable dispersion. The finer and more unstable a disperse phase is, the more the correct processing is important for the result. The problems of dispersion in gases and liquids are discussed with some examples.
Detection and Chemical Characterization of Polycyclic Aromatic Hydrocarbon aerosols by means of laser‐induced fluorescence
Authors: Niessner Reinhard , Krupp Andreas 
Published: May 2005

AbstractLaser‐induced and time‐resolved aerosol fluorescence is introduced as an analytical technique for the qualitative and quantitative determination of surface‐bound polycyclic aromatic hydrocarbons (PAHs). The analytical figures of merit are evaluated by studying the fluorescent properties (emission wavelengths and temporal behavior) of PAHs adsorbed on submicrometer NaCl particles. In addition to singly adsorbed PAHs on NaCl particles, a three‐component PAH adsorbate system is characterized. Detection limits are in the range 5 ng/m3 (e. g. for anthanthrene).
Using Sierpinski Fractals to Characterize Changes in the Cytomorphology of hepatopancreatic b‐cells of porcellio scaber latreille (fam: Porcellionidae, crustacea) reared on different diets
Authors: Alikhan M. A. 
Published: May 2005

AbstractSierpinski fractal dimension analysis is used to describe the cytomorphology of hepatopancreatic large B‐cell of a terrestrial isopod, Porcellio scaber Latreille (Fam.: Porcellionidae, Crustacea). Isopods were starved for six weeks, and then re‐fed for two days on diets containing glucose and butter. The cytomorphological changes undergone by hepatopancreatic B‐cells after starvation and re‐feeding periods are characterized by their fractal dimensions. The significance of these findings is discussed.
Sieving Capture of Liquidborne Particles by microporous membrane filtration media
Authors: Grant Donald C. , Liu Benjamin Y. H. 
Published: May 2005

AbstractTest methodology has been developed to measure the particle removal efficiency of microporous membrane filtration media under conditions in which sieving is the dominant particle capture mechanism. The methodology was used to determine the particle capture efficiency of a 0.45 μm membrane filter for removal of submicrometer sized particles from DI water. Particle capture was found to be a strong function of particle diameter, filter media thickness, and filter loading. Particle removal efficiency increased with increasing particle diameter and media thickness. It decreased with increased filter loading when the filters were challenged with the smaller particles used in this study. Removal efficiency initially decreased then subsequently increased during loading with larger particles. Capture was independent of filtration velocity and particle concentration. A sieving model was developed to predict particle capture by the filter media as a function of particle diameter, filter thickness and filter loading. The model was found to accurately predict breakthrough of monodisperse particle suspensions through the media. Particle breakthrough occurred more slowly than predicted when the filters were challenged with a polydisperse particle suspension.
The Work of the British Standards Institution in Particle, surface and pore size characterisation
Authors: Lines Roy W. 
Published: May 2005

AbstractBritish Standards committee GME/29/4 is concerned with “Particle sizing methods other than sieving”. Its work covers not only particle size distribution analysis but also methods of estimation of surface area and pore size distribution, as well as a glossary of terms relevant to those subjects. The current British Standards in the BS 3406 series (particle size analysis) and BS 4359 series (surface area) are reviewed, and a progress report is given on the status of several new and revised Standards which are in preparation.