bluuebunny/crossref_metadata_2025_split huggingface dataset:
Molecular mobility in styrene‐co‐methacrylic acid random copolymers from 100 to 450 K
Authors: Alberola N. , Bergeret A. , Battesti P. , Revillon A. 
Published: April 2003

AbstractMolecular mobility of both the polystyrene homopolymer and a series of styrene‐co‐meth‐acrylic acid copolymers with various amounts of methacrylic acid is analyzed in the tem‐perature range from 100 to 450 K, by high‐resolution dynamic mechanical spectrometry, IR, and differential scanning calorimetry. Isochronal spectrometry exhibits for polystyrene homopolymer two relaxations, the β and α relaxations, with increasing temperature. Styrene‐co‐methacrylic acid copolymers exhibit three mechanical relaxations, the γ, β, and α re‐laxations, from 100 to 450 K. These relaxations could be related to the progressive occurring of motions of the side groups and of the backbone chains when increasing the temperature. This could be due to the progressive breakdown of hydrogen bonds, which could show a somewhat wide range of magnitude. Furthermore, The decreasing of the magnitude of the α relaxation with increasing methacrylic acid content could suggest the presence of a stable network of chemical cross‐links induced by the presence of anydride so that molecular mobility could be partially inhibited above Tg. The remaining of a fluctuation network of hydrogen bonds (labile contacts) above Tg could also emphasize the decrease in molecular mobility. © 1993 John Wiley & Sons, Inc.
Weathering of starch–polyethylene composite films in the marine environment
Authors: Breslin Vincent T. , Li Boen 
Published: April 2003

AbstractPolyethylene and starch–polyethylene composite films were exposed outdoors in the straw‐line of a marsh and in sea water on flow‐through seatables in the laboratory. The deterioration of these films following exposure was measured by determining changes in tensile properties, weight loss, starch loss, and carbonyl content of the sheet plastic films. Low rates of deterioration were observed for control and starch–polyethylene composite films submerged in sea water. In contrast, both starch–polyethylene composite and control polyethylene films rapidly deteriorated during exposure in the strawline of a marsh. Differences in the observed rate of deterioration of the films placed in the exposure sites is attributed primarily to photodegradation of the films placed in the strawline of a marsh. © 1993 John Wiley & Sons, Inc.
Orientation distribution and layerlike morphology in extrusion‐molded sheets of a liquid crystalline copolyester amide
Authors: Kaito Akira , Kyotani Mutsumasa , Nakayama Kazuo 
Published: April 2003

AbstractFracture surface morphology and orientation distribution in the extrusion‐molded sheets of a thermotropic liquid crystalline copolyester amide were investigated by scanning electron microscopy (SEM), wide‐angle X‐ray diffraction (WAXD), and polarized Fourier transform infrared (FTIR) microspectroscopy. The layerlike morphology consisting of two outer layers and a central layer between them was observed on the fracture surface. The microscopic orientation functions in the extrusion‐molded sheets were evaluated from the polarized FTIR microspectra that were measured in the microscopic domain 40 μm wide using a redundantly apertured infrared microscope. The microscopic orientation function in the outer layer was shown to be higher than that in the central layer. The effects of the draw‐down ratio and extrusion temperature on the orientation distribution and the layerlike morphology are discussed. © 1993 John Wiley & Sons, Inc.
Gas transport through integral‐asymmetric membranes: A comparison to isotropic film transport properties
Authors: Pfromm P. H. , Pinnau I. , Koros W. J. 
Published: April 2003

AbstractPressure‐normalized gas fluxes for defect‐free integral‐asymmetric membranes prepared according to a dry/wet phase inversion process were measured as a function of temperature and pressure and compared to measurements on thick isotropic films. Asymmetric membranes were prepared from polysulfone, polycarbonate, and poly(ester carbonate). The activation energies of permeation for O2 and N2 in the range of 25–55°C were higher for the asymmetric polysulfone membranes than for a thick isotropic film. O2/N2 selectivities of the asymmetric membranes are higher than those for isotropic films. The asymmetric membranes did not show the typical dualmode behavior for the CO2 flux as a function of pressure as determined for thick films. Differences in the free volume and its distribution in the ultrathin skin layer of the asymmetric membranes compared to isotropic films may be responsible for these results. © 1993 John Wiley & Sons, Inc.
Change of morphology in high molecular weight polyethylene during die drawing
Authors: Lee Y. W. , Li J. X. 
Published: April 2003

AbstractDeformed high molecular weight polyethylene (HMWPE) rod, produced by die drawing at 115°C, was cleaved longitudinally at liquid nitrogen temperature and the cleaved surface was etched using a permanganic etching technique. A series of etched surfaces of HMWPE sections with different draw ratios (from 1 to 13) were analyzed employing scanning electron microscopy (SEM). The change of crystalline structure in HMWPE during die drawing was observed. In undrawn HMWPE. the spherulites were made up of sheaflike lamellae and scattered within the amorphous phase. During die drawing in the first instance, the microscopically inhomogeneous deformation occurred and the spherulites aligned along the drawing direction. At a draw ratio of about 7, local melting occurred, the spherulites disintegrated, and the sheaflike lamellae oriented, followed by straininduced recrystallization and the growth of the lamellae. Finally, at a draw ratio of about 12, the plastic deformation of the lamellae occurred and microfibrils were formed. © 1993 John Wiley & Sons, Inc.
Microporous polypropylene sheets containing CaCO3 filler
Authors: Nakamura Shunichi , Kaneko Shingo , Mizutani Yukio 
Published: April 2003

AbstractBiaxial stretching of polypropylene sheets containing CaCO3 filler results in microporous sheets, that feel soft and dry. Their properties depend on filler content, particle size of the filler, and stretching degree etc. We have studied the dependency of some properties of the microporous polypropylene sheets on stretching degree. It is elucidated that mechanical properties are controllable by adjusting stretching degrees in machine and transverse directions. © 1993 John Wiley & Sons, Inc.
Kinetics of polyester fiber alkaline hydrolysis: Effect of temperature and cationic surfactants
Authors: Grancarić A. M. , Kallay N. 
Published: April 2003

AbstractThe surface kinetic model was applied to the interpretation of the dissolution of poly (ethylene terephthalate) fibers in alkaline medium. The model assumes first‐order kinetics with respect to surface area and concentration of OH−ions. The dependency of the rate constant of dissolution on temperature was treated by the Arrhenius equation. The addition of a cationic surfactant resulted in an increase in both activation energy and preexponential factor. © 1993 John Wiley & Sons, Inc.
Dynamic mechanical properties of short carbon fiber‐filled styrene–isoprene–styrene block copolymer
Authors: Roy D. , Bhowmick A. K. , De S. K. 
Published: April 2003

AbstractThe mechanical and dynamic mechanical properties of short carbon fiber‐filled styrene–isoprene–styrene (S–I–S) block thermoplastic elastomeric composite have been studied. Brabender mixing followed by milling of the fiber–rubber compositions caused about a 30‐fold decrease in the fiber aspect ratio and random fiber orientation. Although low‐strain moduli increased on fiber incorporation, tensile and tear properties dropped and anisotropy in mechanical properties was not observed. Tan δ values at the Tg region decreased on filler incorporation, but at room temperature, the tan δ values increased with filler loading. The variation of storage moduli and tan δ values with frequency followed a pattern similar to the variation of these properties with filler incorporation. © 1993 John Wiley & Sons, Inc.
Improved mechanical properties of NR/EPDM and NR/ butyl blends by precuring EPDM and butyl
Authors: Suma N. , Joseph Rani , George K. E. 
Published: April 2003

AbstractEthylene‐propylene‐diene rubber (EPDM) and isobutylene‐isoprene rubber (IIR) were compounded, precured to a low degree, and then were blended with natural rubber (NR). The compounding ingredients for NR were then added and the final curing was done. NR/EPDM and NR/IIR blends, prepared using this method, were found to possess much improved mechanical properties as compared to their conventional counterparts. The optimum precuring crosslink density that has to be given to the EPDM and IIR phases has been determined. © 1993 John Wiley & Sons, Inc.
The elastic modulus of filled polymer composites
Authors: He Dayong , Jiang Bingzheng 
Published: April 2003

AbstractThe elastic modulus of polyepichlorohydrin (PECH) filled with glass beads and wollastonite was studied. It was found that the elastic modulus of the composites depends not only on the volume fraction of the fillers but also on their size. Percolation theory was used to explain the experimental results. © 1993 John Wiley & Sons, Inc.
The chelating properties of chitosan fibers
Authors: Qin Yimin 
Published: April 2003

AbstractChitosan fibers were treated with aqueous solutions of CuSO4 and ZnSO4 for different periods of time to prepare samples containing different levels of metal‐ion contents. The effect of metal ions on the tensile properties of chitosan fibers was studied. It was found that after chelation of metal ions the chitosan fibers gained substantial increases in both dry and wet strengths. The metal ions were readily removed from the chitosan fibers by treatment with an aqueous EDTA solution. The effect of the degree of acetylation on the chelating ability of the chitosan fibers was also studied. It was found that after acetylation the chitosan fibers lost the chelating ability due to the conversion of primary amine groups to acetamide groups. © 1993 John Wiley & Sons, Inc.
Synthesis of phosphorus‐, zinc‐, and chlorine‐containing poly(ethylene terephthalate)
Authors: Troev K. , Kisiova Ts. , Grozeva At. , Borisov G. 
Published: April 2003

AbstractPhosphorus‐, zinc‐, and chlorine‐containing oligomer was used as a comonomer including ionic bonds in its molecules in the synthesis of poly(ethylene terephthalate). Phosphorus‐, zinc‐, and chlorine‐containing poly(ethylene terephthalate) including ionic bonds in its main polymer chain was synthesized. With a content of 0.6% P and 1.25% Zn and 0.1% Cl, the resin has the following characteristics: ηrel= 1.407; COOH 39.90 mg equiv KOH/g 10−6; and mp 255.8°C. The modifier acts as a thermostabilizer. © 1993 John Wiley & Sons, Inc.
Effects of a polymeric additive in a biomedical poly(ether urethaneurea)
Authors: Freij‐Larsson Christina , Kober Maria , Wesslén Bengt , Willquist Eva , Tengvall Pentti 
Published: April 2003

AbstractThe biomedical poly(ether urethaneurea) Biomer has previously been shown to contain a standard antioxidant and a polymethacrylate additive with surface active properties. In the present communication, the latter additive has been shown to influence the morphology, mechanical properties, and surface chemistry of a poly(ether urethaneurea) with a composition similar to Biomer. It was shown that the in vitro blood compatibility of the poly(ether urethaneurea) was improved and that adsorption of fibrinogen from blood plasma decreased significantly due to the presence of the surface active polymethacrylate additive. © 1993 John Wiley & Sons, Inc.
Fibril formation in in situ composites of a thermotropic liquid crystalline polymer in a thermoplastic matrix
Authors: Crevecoeur G. , Groeninckx G. 
Published: April 2003

AbstractBlends of a thermotropic liquid crystalline polymer, Vectra B950, and a matrix of poly (phenylene ether) and a polystyrene were extruded through a capillary designed to yield a converging flow with a constant elongational rate of strain. Fibril formation of the Vectra phase, initially dispersed as spherical droplets, was studied as a function of strain rate and blend composition. It was found that for blends with low Vectra contents, i.e., small Vectra particles, or below a minimum strain rate, no fibril formation takes place. These phenomena could be explained by the balance between interfacial tension and shear stress in the flow field. The critical conditions for fibril formation, estimated from these experiments, are comparable to the literature data. Furthermore, the elongational viscosity of the blends was calculated from the pressure gradient over the capillary. The elongational viscosity was found to decrease with Vectra content, to observe power‐law behavior, and to be three orders of magnitude larger than the shear viscosity of the blends. © 1993 John Wiley & Sons, Inc.
Statistical estimation of diffusion coefficients under finite bath, surface barrier conditions
Authors: Etters J. N. 
Published: April 2003

AbstractWhen surface‐barrier effects are not taken into account, computation of diffusion coefficients from data obtained under finite bath conditions can lead to error. A technique is given by which the most probable diffusion coefficient and the most probable dimensionless surface barrier parameter simultaneously can be estimated for diffusant uptake by solid polymeric cylinders. © 1993 John Wiley & Sons, Inc.
Processing effects on optical anisotropy in spin‐coated polyimide films
Authors: Lin Linda , Bidstrup Sue Ann 
Published: April 2003

AbstractThe effects of spinning speed, substrate material, and thermal treatment on the optical anisotropy of spin‐coated polyimide films have been examined using the Metricon 2010 Prism Coupler to measure the birefringence. A decrease in the molecular orientation, as determined by birefringence, with increasing film thickness has been attributed to a stress gradient in the thickness of the film and the presence of air‐polymer‐substrate interfaces. The extent of the thickness dependence is a function of the polymer chain rigidity associated with the polyimide chemistry. The birefringence of the polymer film is also influenced by the substrate material due to the coefficient of thermal expansion mismatch between the film and the substrate. In addition, as a result of potential interdiffusion of solvent molecules and polymer segments between multiple layers of film, the birefringence in polyimide films obtained from multiple coatings of polyamic acid depends on the thermal treatment between the individual coatings. The birefringence of PMDA/ODA polyimide film derived from polyamic acid solution increases as the imidization temperature is increased to 400°C. For preimidized polyimide, the birefringence initially increases upon solvent removal, but decreases above 200°C, possibly indicating the occurrence of thermal cross‐linking. © 1993 John Wiley & Sons, Inc.
The effect of o‐phenyl phenol on the dyeing of an acrylic fiber with basic dyes
Authors: Kim J. P. , Burkinshaw S. M. 
Published: April 2003

AbstractThe equilibrium uptake of o‐phenyl phenol onto Courtelle S at 98°C was found to follow a Nernst adsorption mechanism, indicating that uptake arises by virtue of hydrophobic interaction as well as ion–dipole, dipole–dipole, and dipole‐induced dipole forces operating between the fiber and the nonionic carrier. Differential scanning calorimetry was used to demonstrate the plasticizing action of the carrier on Courtelle S yarn. A linear relationship was obtained between the extent of plasticization, as measured by reduction in Tg of the fiber, and concentration of carrier applied to the fiber with the maximum extent of plasticization, showing a close correspondence to the aqueous solubility of o‐phenyl phenol at 98°C, the temperature at which the fiber was treated with the carrier. The relationship between the extent of enhancement of uptake of C. I. Basic Green 4 and C. I. Basic Red 13 onto Courtelle S yarn at 98°C and concentration of the carrier in the dyebath was also examined: The concentration of o‐phenyl phenol that gave maximum enhancement of dye uptake coincided with the aqueous solubility of the carrier at 98°C. © 1993 John Wiley & Sons, Inc.
Novel cellulose derivatives. I. Liquid crystal phase formation in tri‐O‐α‐naphthylmethyl cellulose solutions
Authors: Davé Vipul , Frazier Charles E. , Glasser Wolfgang G. 
Published: April 2003

AbstractTri‐O‐α‐naphthylmethyl cellulose was prepared by homogeneous phase reaction using SO2–diethylamine (DEA)–dimethyl sulfoxide (DMSO) as the solvent system. Observations made by dynamic mechanical spectrometry and by cross‐polarized optical microscopy revealed liquid crystalline behavior for the concentrated solutions of tri‐O‐α‐naphthylmethyl cellulose in dimethylacetamide (DMAc). Experimental and calculated (predicted) critical volume fraction of the derivative, Vcp, did not show agreement. It is determined that Vcp is affected by bulky substituents on the cellulose backbone to some extent. © 1993 John Wiley & Sons, Inc.
Structure development during dynamic vulcanization of hydrogenated nitrile rubber/nylon blends
Authors: Bhowmick Anil K. , Inoue Takashi 
Published: April 2003

AbstractThe factors that influence the morphology and the interfacial parameters during dynamic vulcanization of hydrogenated nitrile rubber/nylon blends are examined. The particle size of the dispersed phase (R̄) and the correlation distance (ξ) of a 50 : 50 blend decreased with increasing mixing time at 250°C, attained a minimum value, and then increased. The increase in the number of particles with time (dn/dt) may be expressed as (dn/dt) = k'nm, where n is the number of dispersed particles at time t, and m and k' are constants. R̄ and ξ gradually increased as the mixing temperature was increased from 250 to 300°C at a constant mixing time of 10 min. The particle size increased also with the increasing gel fraction of the rubber. At a constant mixing time of 10 min at 250°C, the particles were larger when the addition of the cross‐linker was delayed. These observations can be explained with the help of a hypothetical model, similar to that proposed by Wu, considering the breaking down of rubber particles, coagulation and coalescence of droplets, and droplet rupture in a matrix of nylon. On vulcanization, the thickness of the interface (λ) reduced from 62 to 48 nm. The interaction parameter and interfacial tension, as estimated from λ, for a bilayer specimen vulcanized in situ, at 250°C were 2.8 × 10–3 and 0.24 mN/m, respectively. The high value of λ for the dissimilar polymer pair may be due to polymer‐polymer graft formation at high temperature. © 1993 John Wiley & Sons, Inc.
Semicontinuous emulsion copolymerization to obtain styrene–methyl acrylate copolymers with predetermined chemical composition distributions
Authors: Schoonbrood Harold A. S. , Thijssen Henk A. , Brouns Harry M. G. , Peters Matt , German Anton L. 
Published: April 2003

AbstractFour types of emulsion copolymerization processes were applied to produce various styrene–methyl acrylate copolymer latices. (1) Batch emulsion copolymerization. (2) Monomer starved semicontinuous emulsion copolymerization, i.e., a monomer mixture of constant composition was fed to the reactor at a constant rate. Sufficiently low addition rates led to homogeneous copolymers. (3) Optimal addition rate profiles were used to produce homogeneous emulsion copolymers in relatively short times. The profiles were determined in a semiempirical way, and applied to three different copolymer compositions. (4) We made an attempt to determine an addition rate profile to produce a heterogeneous emulsion copolymer with predetermined heterogeneity, i.e., a copolymer of which the chemical composition distribution (CCD) did not consist of one narrow peak, as with homogeneous copolymers, but had a predetermined broadness profile. Strategies (2) and (3) were used to produce homogeneous emulsion copolymers with varying fractions of styrene. Strategy (3) was also used to demonstrate the influence of the monomer ratio on the kinetics. The advantage of this method is that the monomer ratio is constant over the whole conversion range in the latex particles. High performance liquid chromatography (HPLC) was used to determine the homogeneity/heterogeneity of the copolymers produced, and proved to be invaluable in determining the optimal addition rate profile. The final goal will be to study the influence of the chemical composition distribution (CCD) on mechanical properties of these copolymers, as both homopolymers used in this study have quite differentglass transition temperatures; the results will be published later. © 1993 John Wiley & Sons, Inc.
On the chemistry, behavior, and cure acceleration of phenol–formaldehyde resins under very alkaline conditions
Authors: Pizzi A. , Stephanou A. 
Published: April 2003

AbstractThe curing acceleration by organic esters of alkaline phenol‐formaldehyde (PF) resins can be explained by two different mechanisms. In the course of the work, the unexpected curing behavior of PF resins alone, under very alkaline conditions, was observed, which diverged from past assumptions. PF resins curing, which is supposed to be accelerated by the formation of phenate ions, is instead markedly slowed down by increasingly alkaline pHs and accelerates in the presence of esters. The mechanism of ester acceleration of PF resins curing was clarified and the effect of different esters was quantified and was related to the pKa and quantity of the acid forming the ester. A second mechanism, which appeared also to explain the peculiar slowing down at increasing pH of PF resin curing, could not be confirmed; some evidence appeared clearly to deny it. The impossibility of isolating an Na+ phenol ring complex, theorized by other authors and other evidence, indicates that this second mechanism is unlikely to occur. © 1993 John Wiley & Sons, Inc.
Membranes of semicrystalline aliphatic polyamide nylon 4,6: Formation by diffusion‐induced phase separation
Authors: Bulte A. M. W. , Folkers B. , Mulder M. H. V. , Smolders C. A. 
Published: April 2003

AbstractThe preparation of membranes of nylon 4,6 by diffusion‐induced phase separation (DIPS) using formic acid as a solvent and water as a nonsolvent was studied. Nylon 4,6 is a semi‐crystalline polymer; phase separation from a solution can occur by solid–liquid (s–l) de‐mixing as well as by liquid–liquid (l–l) demixing. Upon quenching films of solutions with low polymer concentration (< 17 wt %) in a nonsolvent bath containing water, the morphology of the membranes show a foam‐like structure typical for l–l demixing. When phase separation is induced by water vapor a transition in structure occurs from the cellular type to a morphology typical for s–l phase separated films. At higher polymer concentrations membranes exhibit structures consisting of spheres or smaller crystal‐like units resulting from an s–l phase separation process. The addition of 2 wt % or more of water to polymer solutions with low concentration (up to 15 wt %) resulted in s–l demixing as well. In a DIPS process s–l demixing is kinetically competitive with l–l demixing if nuclei are already present in the starting solutions (heterogeneous nucleation), or if a relatively long time is available for crystal nuclei to be formed. The morphology resulting from s–l demixing is a result of spherulitic crystallization. A certain concentration of nuclei or of precursor particles already present results in a small nucleation density during precipitation and thus large spherulites can be grown; at higher polymer and/or water concentrations the nucleation density increases resulting in an axialitic morphology of the membranes. © 1993 John Wiley & Sons, Inc.