bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structural characterization of Celgard® microporous membrane precursors: Melt‐extruded polyethylene films
Authors: Chen R. T. , Saw C. K. , Jamieson M. G. , Aversa T. R. , Callahan R. W. 
Published: April 2003

Abstract“Row nucleated lamellar” structures are formed when highly crystalline polymers are melt‐extruded and recrystallized under high stress. Polyethylene (PE) and polypropylene (PP) films with row lamellar structures have been utilized to produce microporous membranes. Birefringence measurements of melt‐extruded PE films show that improved film orientation can be achieved by annealing, extruding at higher speed, and using higher molecular weight polymers. Images from scanning tunneling, atomic force, and field emission scanning electron microscopy (STM, AFM, and FESEM) clearly show the lamellar structures in the melt‐extruded PE and PP films. Microscopy results also show that surface lamellar textures are more pronounced with thicker lamellae and are better aligned along the extrusion direction after annealing. X‐ray diffraction results show that the increase in film orientation can be attributed to increased lamellar perfection and orientation during annealing and also to better crystallite alignment along the machine direction with higher extrusion speed or with higher molecular weight. High‐resolution capabilities of STM, AFM, and FESEM prove to be very effective tools in elucidating lamellar structures in polymeric membrane precursors and can be used as an aid in establishing structure–process–property relationships in making microporous membranes. © 1994 John Wiley & Sons, Inc.
Rigid rod polyamides based on 2,2′,6,6′‐tetrasubstituted biphenyls: Synthesis, characterization, and structures
Authors: He C. , Griffin A. C. , Windle A. H. 
Published: April 2003

AbstractPolyamides based on 4,4′‐diamino‐2,2′,6,6′‐tetrasubstituted biphenyls and phenylterephthalic acid have been synthesized, and the structures and properties of this series of polymer have been studied. It is shown that the polymers have an amorphous structure although some degree of short‐range order is present. This class of polymer, while consisting of comparatively stiff rodlike molecules, demonstrates high solubility and low glass transition temperatures. The behavior is due to the combination of the noncoplanar conformation of the twisted biphenyl and the fact that they have bulky side groups in the 2,2′‐ and 6,6′‐positions that weaken the interchain interactions (like hydrogen bonding and van der Waals forces) and frustrate parallel packing of the polymer chains. © 1994 John Wiley & Sons, Inc.
Kinetics of reaction of C36 dimer acids with diethylenetriamine and triethylenetetramine for reactive polyamides
Authors: Kale Vijay , Vedanayagam H. Sumathi , Subbarao R. , Rao M. Bhagawant 
Published: April 2003

AbstractKinetic studies were carried out on the reaction between C36 dimer acids and diethylenetriamine (DETA) and triethylenetetramine (TETA) in melt phase. The reactions were performed at temperatures in the range of 145°C to 190°C and followed by determination of the acid and amine values of the intermittent products. The polyamidation reactions of C36 dimer acids and DETA and TETA followed overall second‐order kinetics and had activation energies of 14.4 kcal/g mol and 12.3 kcal/g mol, respectively. © 1994 John Wiley & Sons, Inc.
Facilitated permeation of myoglobin through porous membranes: Different permeation behavior through membranes of polyoxyethylene‐ and dextran‐conjugated polyamides prepared by quasi‐living polymerization of a bicyclic lactam
Authors: Hashimoto Kazuhiko , Sugata Tohru , Mashita Atsushi , Okada Masahiko 
Published: April 2003

AbstractIn the ultrafiltration test of a myoglobin solution through porous membranes of the ABA‐type block copolymers composed of polyamide as outer segments and polyoxyethylene (Mn = 1.9–2.0 × 104) as an inner segment, in which the values of weight fraction of the polyamide segments (W) were 0.90, 0.84, 0.82, 0.81, and 0.73, the concentration of the permeate was found to be much higher than that in feed under the pressure difference of 1–2 kg/cm2. Such singularly facilitated permeation was observed also in the test through the dense membranes of the polyamide–polyoxyethylene block copolymer with W of 0.81 and 0.73. On the other hand, neither porous nor dense membranes of the graft copolymer (W = 0.83) having a dextran stock (Mn = 1.8 × 104) and 2.6 pieces of polyamide branches showed similar facilitated permeation, although dextran was soluble in water as well as polyoxyethylene. The apparent interaction of myoglobin with dextran may be stronger than that with polyoxyethylene. © 1994 John Wiley & Sons, Inc.
Generation and structure–property behavior of novel liquid crystalline foams produced via a gas supersaturation technique
Authors: Risch Brian G. , Wan I‐Yuan , McGrath James E. , Wilkes Garth L. 
Published: April 2003

AbstractLinear and star‐branched polyoxybenzoate–polyoxyphenoxybenzoate copolymers (POB‐co‐POPB) at a 65/35 molar ratio were synthesized via melt acidolysis using AB‐type monomers and branching agents. By controlling the molecular weight and topology of these polymers, both melt processability and solid‐state CO2gas absorption behavior were enhanced. POB–POPB copolymers with a molar ratio 65/35 showed a glass transition of 143°C and completion of melting at ca. 300°C. POB–POBP copolymers with a systematically increasing branching agent content showed a systematically decreasing peak intensity in wide‐angle X‐ray diffraction, indicating that increasing branch‐point concentration leads to a decrease in liquid‐crystal ordering. Star‐branched POB–POPB copolymers showed greatly enhanced carbon dioxide gas absorption behavior relative to their linear counterparts. Whereas CO2blown foams of linear POB‐co‐POPB produced by the gas supersaturation technique had a relatively high density and showed highly anisotropic bubble growth, well‐defined, nearly isotropic foams of star‐branched POB‐co‐POPB with a mean cell size from 200 to 400 μ were made using the gas supersaturation technique. Structural features were characterized via scanning electron microscopy, and mechanical properties were determined by indentation testing with a 0.25 in. ball indenter. These LCP foams exhibit relative mechanical properties similar to polystyrene and microcellular polycarbonate foams. A strong inverse relationship was noted between cell size and modulus for liquid crystalline foams with a cell size below 400 μm. © 1994 John Wiley & Sons, Inc.
High‐energy radiation‐resistant vulcanizates. II. EPDM
Authors: Shah Chaitanya S. , Patni Mahendra J. , Pandya Madhav V. 
Published: April 2003

AbstractIn this article, Part II of the series, we report a detail study on stabilization of EPDM vulcanizates in γ‐radiation environment. The special additives (antirads), namely pyrene (Py), brominated acenaphthene (BrAc), poly(acenaphthene sulfide) (PAcSu) and poly(pyrene sulfide) (PPySu) were used for the stabilization studies. The efficiency of these antirads for EPDM had been monitored by the means of electrical resistivity, wide‐angle X‐ray diffraction, and mechanical properties. The stabilization of EPDM to withstand 200 Mrads of γ radiation in air environment is achieved. © 1994 John Wiley & Sons, Inc.
Study of segmented ethylene terephthalate–caprolactone copolymer by differential refractometry and light scattering
Authors: Wu Chi , Ma Dezhu , Luo Xiaolie , Chan Kam Kwong , Woo Ka Fai , So King Lung 
Published: April 2003

AbstractA segmented ethylene terephthalate (ET)–caprolactone (CL) copolymer was characterized by light scattering in chloroform tetrahydrofuran and butanone. The flexibility of the copolymer chain is comparable with that of typical flexible chains, such as polystyrene. In the process of applying the Bushuk–Benoit light scattering theory to the segmented PET–PCL copolymer, we encountered not only the problem of finding three solvents with different refractive index but also the problem of determining the specific refractive index increments for the PET and PCL segments in the copolymer, i.e., νPET and νPCL. In principle, the approximate values of νPET and νPCL can be obtained from the PET and PCL homopolymers, respectively. In reality, it involves many practical problems, e.g., to find three solvents not only for copolymer but also for the PET and PCL homopolymers. In this study, a different method was used to find both νPET and νPCL, wherein the ν values of at least two segmented PET–PCL copolymers with different PET compositions were used. With νPET, νPCL, and ν, we characterized the absolute molecular weight. Further, we show that the composition of an unknown segmented PET–PCL copolymer can be estimated from νPET, νPCL, and ν. © 1994 John Wiley & Sons, Inc.
Acid‐ and alkali‐catalyzed tannin‐based rigid foams
Authors: Meikleham N. E. , Pizzi A. 
Published: April 2003

AbstractAcid‐ and alkali‐catalyzed polyflavonoid tannin‐based rigid foams were prepared. These foams have comparable physical and mechanical properties to the synthetic phenolic rigid foam used as a comparative standard. The fluid polymer phase was based on a mimosa tannin‐formaldehyde resin with a minor addition of a fortifier resin. Expansion of the fluid phase was brought about by a physical blowing agent, whereas dimensional stabilization was achieved through cross‐linking at the desired density. In the case of the acid‐catalyzed foam, a heat‐generating agent in the form of furfuryl alcohol was employed. The polymer composition of tannin–formaldehyde/urea–formaldehyde systems as a function of pH was predicted from the respective gel times and rate constants, i.e., above pH 7, the copolymer proportion will tend to 100% and, that at pH 3.4, the polymer blend proportion will tend to a maximum. © 1994 John Wiley & Sons, Inc.
An analytic approach in kinetic modeling of Ziegler–Natta polymerization of butadiene
Authors: Lee Tai‐Yong , Nitirahardjo Singgih , Lee Sunggyu 
Published: April 2003

AbstractA kinetic modeling study was conducted for the Ziegler–Natta polymerization of butadiene with cobalt octoate/DEAC/water catalyst. The model equations for the single and dual active site models were analytically solved, and the closed‐form expressions for conversion and both number and weight average molecular weights were obtained. The expressions for conversion and number average molecular weight are identical for both models. Also, the expressions of weight average molecular weight are similar for both models, but the expression for the dual active site model includes an additional scalar parameter. The parameter can be regarded as a “correction factor of weight average molecular weight,” which reflects the effect of dual active sites on the polydispersity. Using the expressions, a simple and noniterative kinetic modeling algorithm was established, and the parameter estimates were obtained. The estimated value of the correction factor ranges from 1.2 to 1.5 depending on the experimental data. The modeling results indicate the validity of the dual active site model. © 1994 John Wiley & Sons, Inc.
Influence of substrate material and ion bombardment on plasma‐deposited fluorocarbon thin films
Authors: O'Keefe M. J. , Rigsbee J. M. 
Published: April 2003

AbstractThe influence of substrate material and ion bombardment on fluorocarbon thin films deposited using a C2F6 glow discharge in an rf, parallel plate reactor was investigated. Monitoring of the plasma process by optical emission spectroscopy indicated that the dominant species in the glow discharge was CF2. Studies of bulk polytetrafluoroethylene (PTFE) and plasma‐polymerized fluorocarbon thin‐film samples in an XPS system demonstrated that the formation of non‐CF2 species can be induced by ion bombardment of CF2 molecules. Characterization of the deposited fluorocarbon films by XPS found that the F/C ratio and CFx distribution (0 < x < 3) in the films were dependent on processing conditions. Fluorocarbon films deposited simultaneously onto Al, glass, steel, and PTFE substrates using a C2F6 plasma and a graphite sputter target had measurably different F/C ratios, with the F/C ratio of the films deposited onto the Al substrates consistently lower than the F/C ratios of the films deposited onto the other substrates. When a C2F6 plasma was used without a graphite target, the F/C ratio in the film was constant, but the CFx distribution was different for each of the substrate materials. Analysis of the plasma‐polymerized films by TEM revealed that localized growth of fluorocarbon particles occurred during the initial stages of deposition, consistent with an activated growth mechanism. Differences in the F/C ratio for films deposited onto the various substrate materials were attributed to the interaction of the fluorocarbon plasma with the exposed surface of the substrate prior to complete coverage by the polymeric film. © 1994 John Wiley & Sons, Inc.
Sorption equilibria and diffusion coefficients of ethanol and water in the PVA membranes containing cyclodextrin
Authors: Yamasaki Akihiro , Mizoguchi Kensaku 
Published: April 2003

AbstractEffects of cyclodextrin (CD) on the pervaporation characteristics for water/ethanol through the PVA/CD membranes (PVA membranes containing β‐CD oligomer) have been investigated in terms of sorption equilibria and diffusion coefficients based on the sorption–diffusion theory. The increase in water selectivity through the pervaporation by CD was due mainly to the changes in the diffusion coefficients by CD, which depended on the feed composition and the cross‐linking time. The water selectivity through the sorption equilibria was not increased by the addition of CD, and the ethanol‐sorption amount was increased by CD. These effects of CD were interpreted by the inclusion strength in the CD cavity and the cross‐linking density of the PVA phase. © 1994 John Wiley & Sons, Inc.
Graft copolymerization of acrylic acid onto caesarweed fibers by cerric ion–toluene redox pair
Authors: Eromosele Ighodalo Clement 
Published: April 2003

AbstractThe graft copolymerization of acrylic acid onto caesarweed fibers in aqueous media by cerric ion–toluene redox pair has been investigated. The percentage graft increased and then decreased with cerric ion concentration ranging from 8.3 to 100.0 × 10−3 M with a peak value of 17%. The effects of toluene, substituted toluenes, acids, and acrylic acid were examined. The percentage graft increased and then decreased with toluene concentration with an optimum value of 53% at 18.0 × 10−4 M toluene. Under identical reaction conditions, the percentage graft after 30 min for the graft polymerization initiated by substituted toluenes are in the order of p‐toluene sulfonic acid > toluene > p‐Xylene ≃ o‐toluidine. Low concentrations of acetic acid were favorable to the graft polymerization. The percentage graft increased linearly with acrylic acid concentration reaching a value of 53% at 1.39 M acrylic acid. The presence of neutral salts had nominal effects on the percentage graft. The effect of temperature was investigated between 20 and 60°C. The percentage graft increased with temperature up to 40°C but showed a negative temperature dependence beyond 40°C. The calculated activation energy was 6.2 kcal mol−1. Characterization of the physical properties of the grafted fibers was also conducted. © 1994 John Wiley & Sons, Inc.
Determination of microphase structure and scale and scale of mixing in poly‐ε‐caprolactone (PCL)/poly(vinyl chloride) (PVC) blend by high‐resolution solid‐state 13C‐NMR spectroscopy with magic angle spinning and cross polarization
Authors: Kwak S.‐Y. 
Published: April 2003

AbstractHigh‐resolution solid‐state, pulsed Fourier‐transform (FT) 13C‐nuclear magnetic resonance (NMR) spectroscopy with magic angle spinning (MAS) and cross polarization (CP) was applied to a mechanical blend of poly‐ε‐caprolactone (PCL) and poly(vinyl chloride) (PVC) with 50/50 weight ratio (%) whose composition results in very complex morphology and phase structure in the solid state. Proton spin‐lattice relaxation times, T1(1H) and T1ρ(1H), were used as a probe to determine the microphase structure, the degree of homogeneity in terms of the domain size, and the state of mixing of the blend. In particular, T1ρ(1H) was shown to be able to distinguish the separated domains at a level of a few nanometers; the scale of mixing was evaluated from the approximation based on spin‐diffusion phenomenon to be ∼ 4.7 nm below which two polymers were partially mixed and above which they were homogeneously mixed. Treatment of the T1ρ(1H) data with two exponential decay functions resulted in a resolution of individual T1ρ(1H) into rigid and mobile components, from which more detailed information on the phase structure and state of mixing were obtained. © 1994 John Wiley & Sons, Inc.
Use of titanate coupling agents in kevlar–phenolic composites
Authors: Menon Nalini , Blum Frank D. , Dharani L. R. 
Published: April 2003

AbstractSurface modification of Kevlar fibers with titanate coupling agents for improved adhesion of the fiber and resin in Kevla–phenolic composites has been attempted to explore the possibility of enhancement in adhesion and bulk properties of composites for friction materials. Titanate coupling agents were used and flexural properties of the Kevlar–fiber reinforced composites determined. A study of different amounts of the coupling agents at the fiber–matrix interface suggested that 2% by weight of fiber was the optimum amount, in terms of improvement in flexural properties. The composite samples with the coupling agents showed an increase in flexural strength over the untreated samples, with the maximum increase of about 18% over the control. Water‐absorption studies were conducted on Kevlar–phenolic composites treated with organotitanates to detemine the effectiveness of these coupling agents in improving resistance to moisture attack. The treated Kevlar–phenolic composite samples exhibited greater resistance to moisture‐ingress over the untreated samples. The control samples showed a decrease of 17% in flexural strength. The largest decrease in strength was 14% for the treated samples containing coupling agent tetrakis (2‐ethylhexyl) titanate (TYZOR TOT). Recovery in strength on reconditioning was also greater for treated samples over control. A recovery in strength of about 94% was seen for some treated samples. © 1994 John Wiley & Sons, Inc.
Graft‐copolymerization of glycidyl methacrylate onto cotton cellulose
Authors: Shukla S. R. , Athalye A. R. 
Published: April 2003

AbstractGlycidyl methacrylate was graft‐copolymerized onto cotton cellolose using both photo‐and chemical‐initiation techniques using different initiators. The photoinitiators used were uranyl nitrate, ceric ammonium nitrate, and benzoin ethyl ether, whereas the chemical initiators used were ceric ammonium nitrate and potassium persulfate. Optimization of various parameters of grafting, viz., time, temperature, initiator, and monomer concentrations, was carried out. Ceric ammonium nitrate gave the maximum and almost identical values of graft add‐on, by both grafting techniques, at equivalent cocentration of the monomer. Use of optimized conditions of ceric ammonium nitrate‐photoinitiated grafting for sodium hydroxide‐swollen substrate as well as for grafting baths incorporating acids enhanced the graft level. © 1994 John Wiley & Sons, Inc.
Carbonization of polyimide films: Effect of cold‐drawing and chemical structure
Authors: Takeichi Tsutomu , Takenoshita Hidehiro , Ogura Satoshi , Inagaki Michio 
Published: April 2003

AbstractPolyimides of various chemical structures were prepared from pyromellitic dianhydride (PMDA), biphenyltetracarboxylic dianhydride (BPDA), oxydianiline (ODA), and p‐phenylenediamine (PDA). The cold‐drawn polyimide films were prepared and carbonized. The electrical conductivity of the carbonized films enhanced linearly with the draw ratio. The effect of cold‐drawing on the electrical conductivity is more remarkable with the rigid polyimides such as PMDA/PDA and BPDA/PDA than the flexible polyimides such as PMDA/ODA and BPDA/ODA. The tendency is well in accord with the effect of cold drawing on the improvement of modulus of polyimides. With the rigid polyimides, the higher alignment of polymer chain is supposed to be achieved by the cold‐drawing. © 1994 John Wiley & Sons, Inc.
Effect of zone annealing on LARC‐CPI thermoplastic polyimide
Authors: Teverovsky Justyna B. , Rich David C. , Aihara Yoshihiko , Cebe Peggy 
Published: April 2003

AbstractMechanical properties and structure were studied for undrawn and zone‐drawn films of LARC‐CPI thermoplastic polyimide. The dynamic modulus of undrawn glassy material ranged from about 1.8 to 4.3 GPa, depending upon the degree of crystallinity. After zone drawing to draw ratio of 3.6–4.0, the dynamic glassy modulus was increased to a maximum of 9.5 GPa. The highest moduli were attained in samples that were multiply zone‐drawn. The maximum‐achievable draw ratio increased with the maximum drawing temperature, but the semicrystalline nature of the starting material limited the ultimate drawability. For the first time, highly oriented crystalline films were obtained for X‐ray diffraction and preliminary crystal structure analysis. The crystal lattice was fit to the orthorhombic crystal system, and the results indicate that the lattice parameters are a = 8.0 ± 0.2 Å, b = 5.9 ± 0.2 Å, and c = 36.5 ± 0.3 Å. The value of the c‐axis lattice parameter is very close to the fully extended chain length of the monomer repeat unit. © 1994 John Wiley & Sons, Inc.
Preparation and application of porous silk fibroin materials
Authors: Tsukada Masuhiro , Freddi Giuliano , Minoura Norihiko , Allara Giulia 
Published: April 2003

AbstractThis article deals with the preparation and morphological characterization of porous materials obtained by freezing and lyophilizing silk fibroin solutions. When an aqueous silk solution is frozen at different temperatures (−18, −45, and −80°C), the average pore size decreases with lowering of the freezing temperature. Silk fibroin aggregates obtained in these conditions exhibit a sheetlike structure. By lowering the pH from neutrality to 4.01 and 2.65, the morphology of the solid phase changes from a sheet to a fiber structure. The average pore size is smaller at pH 4.01 than is the former value corresponding to the isoelectric point of silk fibroin. The addition of different amounts of methanol to the silk solution results in a sharp fall of the average pore size and hardens the material, as a consequence of the high packing density of the fibroin molecules. Silk fibroin aggregates prepared in these conditions exhibit a typical fibrous structure. A drug‐delivery system was prepared by incorporating acetylsalicyclic acid into a porous silk fibroin carrier, and the kinetics of the drug release was studied. © 1994 John Wiley & Sons, Inc.
Surface characteristics of polymer/small molecule blends
Authors: Champagne France , Li J.‐F. , Schreiber H. P. , Dipaola‐Baranyi G. 
Published: April 2003

AbstractInverse gas chromatographic data have been obtained for polystyrene, polycarbonate, and two substituted amines used as additives in the polymers. Surface energies have been determined and evaluations made of acid/base interaction parameters and Flory–Huggins χ values for the surface bounded interphase. It was shown that acid/base considerations are implicated in the miscibility of these polymer/additive systems. Surface energy analyses showed that surface and bulk compositions in blends differed whether or not the blend components were miscible. Composition differences were the result of thermodynamic drives to minimize surface free energy. © 1994 John Wiley & Sons, Inc.