bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermal degradation of cellulose‐containing composites during processing
Authors: Sapieha S. , Pupo J. F. , Schreiber H. P. 
Published: April 2003

AbstractThe strength properties of composites made of untreated cellulose fibers and linear low density polyethylene were investigated as a function of processing parameters. Studies have shown that the strength properties of composites increase with processing time and temperature. The increase in strength is accompanied by the appearance of new infrared absorption bands at 1718 and 1735 cm−1. A linear relationship between the absorbance and yield strength of composites indicates that oxidation, possibly directly at interfaces, takes place and enhances adhesion between the cellulose and polyethylene.
Morphology of HDPE/(PEC/PS) blends modified with SEBS copolymers
Authors: Schwarz M. C. , Barlow J. W. , Paul D. R. 
Published: April 2003

AbstractIn this study, immiscible blends of HDPE and an amorphous glassy polymer were compatibilized with styrene‐hydrogenated butadiene block copolymers. The glassy phase consisted of either pure PS or a miscible blend of PS and polyether copolymer (PEC); PEC is similar to poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO). The morphology of these two‐phase mixtures depended on physical characteristics of the components and the method of fabrication. Suitable copolymers increased the degree of dispersion and minimized heterogeneities resulting from the inherent incompatibility of the individual phases. Further reduction in the phase size and increased adhesion between the components of modified blends were achieved by increasing the composition of PEC in the glassy phase. It was concluded that favorable exothermic mixing between PEC and PS endblocks of the copolymers provided an additional driving force for compatibilization. Results from dynamic mechanical thermal analysis suggests that penetration by the copolymers into the homopolymer phases is not complete.
Crosslinking of poly(vinyl chloride) with metal oxides, sulfur, and organo sulfur compounds
Authors: Běhal Miroslav , Ducháček Vratislav 
Published: April 2003

AbstractThe crosslinking of poly(vinyl chloride) in the presence of zinc oxide, magnesium oxide, ethylenethiourea (ETU), tetramethylthiuramdisulfide (TMTD), and sulfur at 160 and 180°C has been studied. The effects of ETU and sulfur on the crosslinking of PVC in the presence of TMTD have been individually studied. It has been found that zinc dimethyldivhiocarbamate (ZnDMDC) is the actual crosslinking agent and heat stabilizer of PVC, formed in the cured polymer mix.
Influence of inertia and viscoelasticity in entry flows through an abrupt annular contraction
Authors: Mitsoulis E. 
Published: April 2003

AbstractA numerical simulation of entry flows in an annular die has been undertaken for Newtonian and power‐law fluids as well as viscoelastic fluids that exhibit normal stresses in shear flow. Experimentally measured normal stress and viscosity data are included in a simple rheological model. The influence of inertia and viscoelasticity are examined separately as functions of the Reynolds (Re) and Weissenberg (Ws) numbers. It is found that inertia decreases the size of the corner vortices in the reservoir corners which tend to increase rapidly with elasticity level in the absence of inertia. The combined effect of inertia and elastic forces is to first increase the vortex size followed by a decrease at higher Re numbers. The numberical simulations are in qualitative agreement with experimental studies available in the literature.
Synthesis, characterization, and curing of o‐and p‐chlorophenol‐furfural resins
Authors: Arora Pravin B. , Patel Vithal S. , Patel Shanti R. 
Published: April 2003

AbstractPolycondensation of furfural, respectively, with o‐ and p‐chlorophenols has been carried out under various reaction conditions. All the resin samples have been characterized by spectral studies, viscometric measurement and by the estimation of the number‐average molecular weight. Thermogravimetric analysis (TGA) of selected resin samples has been carried out. The kinetics of curing reaction of selected resin samples has been investigated by differential scanning calorimetry (DSC). The properties of the glass laminates prepared using each of the two types of resins showed that the latter are much less suitable than phenol‐furfural resin as matrices for the fabrication of laminates.
Effect of vulcanization temperature on the technical properties of NR, SBR, and BR
Authors: Kurian Thomas , George K. E. 
Published: April 2003

AbstractCompounds of natural rubber, styrene‐butadiene rubber, and butadiene rubber are vulcanized at different temperatures and the crosslink density and physical properties of the vulcanizates are compared. It is found that for each compound there is an optimum vulcanization temperature which results in the best compromise of properties for specific applications.
Modification of solute dissolution rate by coprecipitation with certain acrylate–methacrylate copolymers
Authors: Okor R. S. 
Published: April 2003

AbstractCoprecipitates containing certain cationic acrylate‐methacrylate copolymers and paracetamol (polar solute) have been prepared by evaporating to dryness an ethanolic solution of both components; their friability (i.e., degree of crumbling to dust under impact stress) and dissolution characteristics were evaluated. Friability decreased with increase in the polymer content of the coprecipitates; this effect was more marked in the polymer system containing the higher cation content. Dissolution rates also decreased with increase in polymer content, but this time the effect was slightly more pronounced in the polymer system with the lower cation content. It is thought that the polymer cationic groups interacted with polar groups of the solute to increase coherence of the particle; on the other hand, the cationic groups confer hydrophilic character and at certain concentrations, > 5% they may promote swelling in aqueous fluids and hence weaken bonding forces in the solute‐polymer particle with a tendency to reduce the polymer effect on dissolution rate.
Crystallinity changes during PVC processing
Authors: Obande O. P. , Gilbert M. 
Published: April 2003

AbstractThermal analysis, solvent sorption, density measurement, and X‐ray diffraction techniques were used to investigate structural changes in a variety of PVC compounds which were extruded or compression‐molded at temperatures in the range 150–220°C. In all cases processing at lower temperatures in this range resulted in a disappearance of primary crystallinity and a concomitant development of secondary crystallinity, of lower order. In many cases processing above 190–200°C caused a small increase in crystallinity. It is believed that this is more ordered secondary crystallinity, which is therefore detectable by X‐ray diffraction and also capable of influencing density and solvent sorption behavior. The observed structural behavior depends on shear as well as temperature. Primary crystallinity is higher in compression moldings, which have experienced lower shear levels, and the increase in crystallinity at higher temperatures is also greater. Equilibrium solvent sorption depends on the presence of primary and ordered secondary crystallinity. Diffusion is, however, unaffected as it occurs through amorphous and disordered crystalline regions only.
Radical copolymerization of ethylene and 2‐phenyl‐3‐vinyloxirane
Authors: Endo Takeshi , Suga Katsufumi , Orikasa Yuichi , Kojima Shinji 
Published: April 2003

AbstractThe radical copolymerization of ethylene and 2‐phenyl‐3‐vinyloxirane was carried out under high pressure to obtain the corresponding copolymers. The structure of the obtained copolymers was discussed by the data of infrared and nuclear magnetic resonance.
Mean field calculations of the dynamic mechanical properties of two‐phase elastomer blends: Included particles in a matrix phase
Authors: Mazich K. A. , Plummer H. K. , Samus M. A. , Killgoar P. C. 
Published: April 2003

AbstractMean field theories developed by Kerner and van der Poel were applied to several binary elastomer blends. Calculations were compared with experimental small strain dynamic mechanical properties of the blends. Although the blends exhibit a wide range of detailed structures, the theories were able to model blenas with well‐defined included particles embedded in a matrix phase. Blends with a continuous morphology were not properly modeled with the Kerner or van der Poel theories.
Determination of the density dispersion of suspension poly(vinyl chloride) by the method of kinetic density curves
Authors: Ševčík Stanislav , Kolínský Miloslav 
Published: April 2003

AbstractA new method has been developed for the evaluation and comparison of quality of various types of poly(vinyl chloride) (PVC) powder with respect to their density homogeneity. The method consists in the determination of the dependence of the volume of a specifically heavier fraction of PVC powder on the density or concentration of testing aqueous NaNO3 solutions after a chosen time of contact between the powder and the testing solutions. Compared with the method of determination of density distribution using densitometric titration, the new method simplifies and extends possibilities of comparison of polymers and improves the density characterization.
Accurate molecular weight distribution of polymers using thermal field‐flow fractionation with deconvolution to remove system dispersion
Authors: Schimpf Martin E. , Williams P. Stephen , Giddings J. Calvin 
Published: April 2003

AbstractThermal field‐flow fractionation (ThFFF) is an elution process that separates polymeric materials by molecular weight. Elution profiles thus provide approximations to the molecular weight distributions of polymers. The accuracy of such approximate distributions is expected to be improved by accounting for the effect on the elution profile of band‐broadening processes in the FFF system. Fortunately this intrinsic band broadening, referred to as system dispersion, is theoretically well‐defined in ThFFF. In this article we present an algorithm that corrects ThFFF elution profiles by removing system dispersion. The program is applied to ThFFF fractograms of standard polymers having both narrow and broad molecular weight distributions. The increased accuracy obtained by accounting for system dispersion is demonstrated. For the narrow standard, deconvolution shows that the polydispersity (weight/number‐average mol. wt.) is only 1.004. For the broad standard, NBS 706, the molecular weight distribution and parameters obtained agree well with previously published results. Application to a simulated fractogram resulting from mixing five narrow standards helps define the conditions under which accurate molecular weight information can be recovered.
A scanning electron microscopic study on the morphology of beech wood (Fagus crenata) copolymerized with acrolein using the xanthate method of grafting
Authors: Hirabayashi Yasuhiko 
Published: April 2003

AbstractPowdered beech wood (Fagus crenata) copolymerized with acrolein by using the xanthate method of grafting is examined in a scanning electron microscope. Homopolymer was observed as spherical‐shaped particules deposited on the surface of cell walls. Coral‐ and spongelike shaped graft polyacrolein made its appearance after the removal of the homopolymer by the extraction with the pyridine–water mixture. Wrinkles which were observed in the noncopolymerized sample were interpreted as a result of the formation of voids by dissolving the oxidatively degraded cell wall materials in the pyridine–water and the subsequent collapse of the voids and shrinkage of the cell walls on drying. The wrinkle formation was minimized in the case of the copolymerized samples because of the restriction of the shrinkage of the cell wall by the presence of graft polymer in the cell wall.
Mixing study of L shape mixheads in reaction injection molding
Authors: Molnar John A. , Lee L. James 
Published: April 2003

AbstractThe effect of mixhead geometry on the impingement mixing in the reaction injection molding (RIM) process is largely unknown. In this study, high speed photographs are used to show the flow patterns produced by L shape mixheads. The mixing quality of the conventional I and various L shape mixheads is quantified by an emulsion test. The adiabatic temperature rise of a polyurethane/urea system is followed to further characterize the mixing produced by I and L shape mixheads. The results show that L shape mixheads give a better mixing quality than the I shape mixhead, especially at lower Reynolds numbers. In addition, the L shape mixheads can provide a more laminar flow from the mixhead, which is important for mold filling.
CO gas sensor devices plasma‐polymerized from tetramethyltin
Authors: Inagaki N. , Tasaka S. , Mase T. 
Published: April 2003

AbstractThin films plasma‐polymerized from tetramethyltin was applied for CO gas sensor device. The films formed from tetramethyltin contains alkyl chains with organic tin moieties, and pyrolysis of them at 350–500°C yields carbonized films with SnO2 moieties. The electrical resistance for the films pyrolized at 350–500°C decreases in exposing to CO gas. The sensitivity, the ratio of the electrical resistance between in air and in CO atmosphere, is enhanced by catalytic actions of palladium chloride, specially in operation at low temperatures below 50°C. The gas sensitivity between CO and other gases such as ethanol, methane, and propane gases is good. The possible determination of CO gas concentration by the sensor device is in ranges from 10 to 1000 ppm.
Solubility parameters of amine‐crosslinked aromatic epoxies
Authors: Bellenger V. , Morel E. , Verdu J. 
Published: April 2003

AbstractFor six epoxide–amine systems, based on mixtures of two different aromatic epoxides with four various aromatic amines, the solubility parameters δ were determined by calculation, by using several literature sources and molar additive laws, and experimentally from equilibrium concentrations of 25 solvents, by using bidimensional solubility maps. δ values ranging from 20 to 27 MPa1/2 were found. Their variations with the epoxide and amine structure were discussed. The crosslink density was found to have a neglectable effect on the solvent absorption compared to interaction parameters.
MMA/TPX homograft membrane for oxygen enrichment
Authors: Lai J. Y. , Shieh J. J. , Shyu S. S. 
Published: April 2003

AbstractUtilizing the factors of degradation and crosslinking of TPX polymer and high O2/N2 selectivity of MMA, the performances of MMA homografted TPX membrane are efficiently improved compared to those of pure TPX membrane. The degradation and crosslinking of TPX polymer solution with or without dissolved oxygen during irradiation were observed and proved in existence by the gas permeability, mechanical, and viscosity change study. High O2/N2 permeability ratio of 7.6 and fairly high oxygen permeability of 28 × 10−10 cm3 cm/cm2 s cm Hg of the membrane which was cast from the degassing polymer solution, with 20% degree of MMA grafting, can be obtained. Also the membrane for high oxygen permeability of 63 × 10−10 cm3 cm/cm2 s cm Hg with an O2/N2 permeability ratio of 4.5, which was cast from the polymer solution with dissolved oxygen, can be obtained under the condition of 60 h irradiation time and about 7% degree of grafting. O2/N2 selectivity of TPX membrane can be improved by homografting method with lower MMA grafting degree than that of heterografting method.
Graft polymerization of polyvinylpyrrolidone onto silica
Authors: Chaimberg Mark , Parnas Richard , Cohen Yoram 
Published: April 2003

AbstractA new technique is reported for the surface grafting of polyvinylpyrrolidone (PVP) to hydroxylated solid surfaces. Free radical graft polymerization of vinylpyrrolidone onto vinylsilane–modified impermeable silica particles was carried out in an aqueous slurry reactor. The graft yield and the monomer conversion were determined by thermogravimetric analysis and UV spectroscopy, respectively. The graft yield was shown to increase by increasing the initial monomer concentration. A comparison of the graft polymerization reaction with the adsorption of polyvinylpyrrolidone onto untreated, vinylsilane‐modified, and PVP‐grafted silica was performed.
Pervaporation separation of water/ethanol mixtures through polysaccharide membranes. I. The effects of salts on the permselectivity of cellulose membrane in pervaporation
Authors: Mochizuki Akira , Sato Yoshio , Ogawara Hisashi , Yamashita Shuzo 
Published: April 2003

AbstractIn the separation of water/alcohol mixtures through cellulose membranes, the addition of trace amounts of specific salts to the feed mixture (10−5−5 × 10−3 mol/kg) caused the marked increase of the separation factor and only the salts composed of a multivalent metal ion and a multivalent counteranion were effective for the increase of the selectivity. For example, when 1.5 × 10−3 mol/kg CoSO4 was added to water/ethanol mixture (35/65 wt/wt), the separation factor was 194 and the permeation rate was 5.14 kg/m2 h. But, in the absence of the salt, the separation factor was only 6.7 and the permeation rate was 5.63 kg/m2 h. We presumed that the increase of the selectivity by the addition of specific salts would be attributed to the contraction of the “holes” produced by the thermal motion of polymer chains and this contraction would be correlated with the conformation change of cellulose molecule.
Molecular orientation in the amorphous fraction of poly(ethylene terephthalate) and polyamide 6 fibers
Authors: Urbańczyk G. W. 
Published: April 2003

AbstractComparison of the Hermans orientation functions of the amorphous fraction of PET and PAG fibers oriented by stretching to various degrees was made. The orientation functions obtained by different methods enable one to draw conclusion about the acceptability of different methods and their correlation with each other.
Influence of the catalyst on the kinetics of a RIM formulation
Authors: Rego J. M. , Pastor M. A. , Campo J. J. , Katime Issa 
Published: April 2003

AbstractThe influence of three different catalysts [triethylendiamine (TD), stannous octoate (SO), and dibutylindilaurate (DBTDL)] and their blends (TD + SO and TD + DBTDL) on the kinetics of a RIM formulation, based on a high functionality polyether–polyol and a polymeric MDI, has been studied using the adiabatic temperature rise method and Fourier transform infrared spectroscopy. The synergism observed in the DBTDL/TD systems is explained by means of complex formation between the amine‐based and metal‐based catalysts. Infrared spectroscopy data support this complex formation. The SO/TD systems do not exhibit synergetic behaviour, being the reaction rate controlled by the metal catalyst which complexes the isocyanate group.
Mechanical behavior of closed cell plastic foams used as cushioning materials
Authors: Miltz J. , Ramon O. , Mizrahi S. 
Published: April 2003

AbstractTwo methods for the prediction of force–deformation curves of closed cell plastic foams at any strain rate from a limited number of experiments are described. These methods are based on the “modified Boltzman integral model” and on the “reference model.” Both methods use constitutive equations and experimentally determined parameters. The modified Botlzman integral model uses data obtained in a limited number of stress–relaxation experiments while the reference model uses a very limited number of stress–relaxation and one force–deformation curve data. Both models predict well the force–deformation curves, the reference model providing somewhat better predictions.
Polymerization of isoprene in n‐heptane with triethylaluminum–titanium tetrachloride catalyst. I. Effect of Al/Ti ratio on stereoregularity, conversion, molecular weight, and molecular weight distribution
Authors: Al‐Jarrah Mustafa M. F. , Abdul‐Latif Numan A. , Al‐Madfai Suham H. F. , Apikian Rita L. 
Published: April 2003

AbstractThe influence of the Al/Ti ratio of the heterogeneous Ziegler–Natta catalyst system AlEt3–TiCl4 on the isoprene polymerization in n‐heptane at 30°C in a bench scale reactor was investigated. Each batch run consisted of 50 mL isoprene, 200 mL n‐heptane with 0.45 and 0.5g catalyst. Conversion of isoprene and molecular weights of polyisoprene increased with increasing Al/Ti ratio, reaching their maxima values at 1.0 and 1.2, respectively. Conversion and molecular weights decreased remarkably at a higher ratio of Al/Ti. As this ratio decreases from the value of 1.2 to 0.4, the cis1,4 content in polyisoprene decreased from 97 to 25%. When the ratio of Al/Ti increased from 1.2 to 2.2 the cis‐1,4 structure of polyisoprene decreased from 97 to 85%.
The preparation and properties of acrylic and methacrylic acid grafted cellulose prepared by ceric ion initiation. III. Some physical, mechanical, and ion exchange properties
Authors: Vitta S. B. , Stahel E. P. , Stannett V. T. 
Published: April 2003

AbstractThe first two articles were concerned, (1) with the preparation and, (2) with the water retention properties of the grafted cellulose. This articel presents some physical, mechanical, and ion exchange properties. Bleached sulfite softwood puplp filter paper was the substrate and polyacrylic acid the grafted side chains. The thickness of the paper increased with grafting accompanied by a decreased in area, particularly in the machine direction. The air permeabilities of the grafted papers were essentially unchanged even at high degrees of grafting. The dry tensile strength increased somewhat with grafting but the zero span strength decreased. Wet tensiles increased considerably up to about 50% graft, but then decreased. The wet elongations, however, steadily increased but began to level off at 120% graft. Strength properties were also measured with melamine wet strenghened paper. The ion exchange capacities of the dispersed paper pulp indicated that all the grafted polyacid groups were rapidly utilized.
Pole figure analysis of poly(vinyl chloride) samples: A first approximation
Authors: Guerrero Saul J. 
Published: April 2003

AbstractPole figure analysis has been applied to different types of poly(vinyl chloride) (PVC) samples. Drawn samples of formulations containing increasing amounts of plasticizer show that the presence of plasticizer at concentrations exceeding 20 pph decreases the orientation of the crystalline phase for a given draw ratio. Cast and pressed films of PVC show incipient orientation in the plane of the films. This orientation can be removed to a great extent by immersing the films in diethyl ether. The method is experimentally feasible and the resolution achieved is determined by the automation of the equipment.
A simple one‐step synthesis of unsaturated copolyesters
Authors: Mathias Lon J. , Kusefoglu Selim A. , Kress Albert O. 
Published: April 2003

AbstractCopolyesters containing pendent vinylidine groups were prepared in a one‐step synthesis by reacting either chloro‐ or bromoacetic acid with 2‐(bromomethyl)acrylic acid and triethylamine in diethyl ether. Polymers were characterized by IR, 1H‐ and 13C‐NMR, DSC, and TGA. Copolymer formation supports a mechanism involving a triethylammonium carboxylate salt acting as an active nucleophilic species in a manner analogous to that seen in phase transfer catalysis involving carboxylate anions. Comparison of 13C‐NMR spectra intensities indicates that 2‐(bromomethyl)acrylic acid is much more reactive than the haloacetic acids leading to higher copolymer incorporation than in the monomer feed. Unsaturation in the copolymers provides a site for crosslinking during radical polymerization with an added vinyl monomer, similar to the way unsaturated polyesters function in commercial fiberglass formulations. This was confirmed by polymerization of both styrene and methyl methacrylate in the presence of an unsaturated copolymer giving insoluble semi‐interpenetrating networks. These unsaturated copolymers are the first examples of soluble biodegradable glycolic acid polyesters containing such reactive functionality.