bluuebunny/crossref_metadata_2025_split huggingface dataset:
Gas permeation properties of hexafluoro aromatic polyimides
Authors: Matsumoto Kenji , Xu Ping 
Published: April 2003

AbstractTwo hexafluoro‐substituted aromatic polyimides, 6FDA‐p‐PDA and 6FDA‐4,4′‐ODA, were synthesized. The influence of some synthetic conditions on physical properties and gas permeabilities of the 6FDA polyimide membranes were studied. Gas permeabilities and permselectivities of six different gases for the homogeneous films have been determined at 15–35°C and at pressures up to 10 atm. 6FDA polyimide composite membranes with asymmetric structure were prepared by the solution‐casting method. The membranes showed exceptionally high permeation fluxes and permselectivities. No capability deterioration of asymmetric membrane was observed during 19 days operation with pure gases. © 1993 John Wiley & Sons, Inc.
Cross‐linking structure of keratin. IV. The number of cross‐linkages in low‐sulfur components and the volume fraction of high‐sulfur domains in various α‐keratin fibers
Authors: Arai Kozo , Hirata Taishi , Nishimura Shushi , Hirano Mitsushige , Naito Sachio 
Published: April 2003

AbstractVarious α‐keratin fibers that had been treated with an 11M LiBr solution containing N‐ethylmaleimide showed typical rubberlike elasticity in a solution composed of equal volumes of 8M LiBr and diethylene glycol mono‐n‐butyl ether. Stress—strain relations of the swollen fibers were treated with a two‐phase model: a mechanically stable phase of higher cross‐linked domains and a rubber phase with lower cross‐link density. Stress—strain curves for a variety of keratins (three different human hairs, six different wools, mohair, cashmere, llama, alpaca, angora, and opossum) were analyzed by applying non‐Gaussian chain statistics to the swollen keratin network, including microdomains, which act as reinforcing filler particles in rubber. The phase structures of unswollen domains and swollen rubber were considered to originate from different structural components characteristic of α‐keratin, namely, the high‐sulfur matrix and the low‐sulfur microfibrils being randomized by swelling. It has been suggested that (1) the modulus of swollen fibers increases with increase of the content of disulfide (SS) in keratins, (2) the volume fraction of high‐sulfur domains increases with increase of SS content, and (3) the number of intermolecular cross‐links in the rubber region of low‐sulfur proteins is virtually the same among keratins and reaches about 65–75% of the SS linkages in the corresponding proteins. Some discussion has been made on the SS bonding in situ, namely, SS linkages between the low‐sulfur proteins, between the low‐sulfur and the high‐sulfur proteins, and between the high‐sulfur proteins in keratins. © 1993 John Wiley & Sons, Inc.
Orientation distribution in the noncrystalline regions of biaxially drawn poly(ethylene terephthalate) film: A chain‐intrinsic fluorescence study
Authors: Gohil R. M. , Salem D. R. 
Published: April 2003

AbstractWe have studied development of the in‐plane distribution of “amorphous orientation” during sequential and simultaneous biaxial drawing of poly(ethylene terephthalate) film, using polarized intrinsic fluorescence. The machine direction (MD) draw ratio was always fixed at 3.5, and the transverse direction (TD) draw ratio was varied. The rate of increase in the proportion of TD‐oriented chains with increasing TD draw ratio is almost identical in the sequential and simultaneous processes up to a draw ratio of 2.7. At this point, sequential drawing starts to involve transverse realignment of MD‐oriented chains, which accelerates redistribution of orientation from the MD to the TD. Consequently, in sequential drawing, a “balanced” biaxial orientation distribution is achieved at a TD draw ratio significantly below the MD draw ratio, whereas at the same TD draw ratio in the simultaneous process, MD orientation remains dominant. At equal MD and TD draw ratios, the non‐crystalline chains in sequentially drawn film are predominantly oriented along the TD, but their orientation distribution is isotropic in simultaneously drawn film. High‐temperature annealing at fixed dimensions diminishes the proportion of TD‐oriented chains in films with transverse draw ratios < 2.5. We attribute this to a more highly developed crystallite network in the MD, which constrains orientational relaxation along the MD. A balanced distribution of amorphous orientation is directly responsible for achieving balanced tensile strength and balanced extensibility. © 1993 John Wiley & Sons, Inc.
The effects of γ irradiation on toughening mechanisms in rubber‐modified polymers
Authors: Birkinshaw C. , Buggy M. , Quigley F. 
Published: April 2003

AbstractHigh‐impact polystyrene (HIPS) and acrylonitrile butadiene styrene (ABS) have been subject to γ irradiation in doses up to 20 and 12.5 Mrad, respectively. During tensile testing, both longitudinal extension and lateral contraction were simultaneously measured, allowing determination of volume strain, and from this to identify the relative contributions of crazing and shear yielding to the tensile deformation process. Both materials show a dose‐related increase in the strain at which crazing commences, though the relative change with dose in HIPS is much greater than in ABS. However, the contribution of crazing to total deformation remains high in HIPS when compared with ABS. Shear yielding is an important deformation process in ABS and the results indicate that this is relatively unaffected by irradiation, whereas the ability to craze is severely limited. The reduced ability to craze observed in both materials is considered to be the result of crosslinking in the rubbery phase. The notched impact strength of ABS is particularly sensitive to irradiation and again reflects the reduced ability to craze observed in the tensile testing. ABS fracture surfaces examined by scanning electron microscopy display reduced ductility in the irradiated material. © 1993 John Wiley & Sons, Inc.
Volatility of additives from polymers. Concentration dependence and crystallinity effects
Authors: Luston̆ J. , Pastus̆áková V. , Vas̆s̆ F. 
Published: April 2003

AbstractThe evaporation of 2‐hydroxy‐4‐methoxybenzophenone (HMB) from polypropylene was studied by an isothermal method at different concentrations of HMB ranging from 0.3 to 1.2 wt %. The evaporation of the additive was correlated according to first‐order kinetics. and rate constants of evaporation were calculated. A linear dependence of the rate constants of volatility on the initial concentration of the additive in the polymer was observed. This result suggests that in the given system, volatility is governed by evaporation from the polymer surface. Volatility of HMB from polypropylene depends on the degree of crystallinity of polypropylene. Samples with different degrees of crystallinity were prepared by quenching of the polymer blends and subsequent annealing at 423K. Isothermal measurements at 383 and 423K yielded higher rate constants for annealed samples than for quenched samples. The rate constant of evaporation at 383K was 20% higher for the annealed sample, whereas at 423K it was 27.5% higher. These results are interpreted on the basis of the concentration changes occurring during annealing. © 1993 John Wiley & Sons, Inc.
Effect of Fe(III) on the polymerization of butyl methacrylate initiated by a charge‐transfer mechanism
Authors: Baruah Shashi D. 
Published: April 2003

AbstractThe effect of the Lewis acid, iron(III) tris(oxalato)ferrate(III) tetrahydrate (Fe‐[Fe(C2O4)3].4H2O) (A) on the polymerization of butyl methacrylate (BuMA) initiated by a charge‐transfer mechanism has been studied in dimethyl sulfoxide (DMSO) at 60°C. 2,4‐dinitrophenylhydrazine (DNPH) was used as a nitrogen donor compound to initiate the polymerization in the presence of carbon tetrabromide (CBr4). Induction periods are observed for the polymerization initiated by DNPH and CBr4. The rate constant at 60°C for the polymerization of BuMA in the presence of A is 1.70×105L/mols−1. The molecular weight of polymers decreases with the increase of [ A ]. A probable reaction mechanism is proposed to explain the observed results. © 1993 John Wiley & Sons, Inc.
Structure‐property relationship of HTPB‐based propellants. I. Effect of hydroxyl value of HTPB resin
Authors: Manjari R. , Joseph V. C. , Pandureng L. P. , Sriram T. 
Published: April 2003

AbstractComposite propellants based on hydroxyl‐terminated polybutadience (HTPB) resin are the most common contemporary solid propellants for launch vehicle and missile applications. A series of HTPB resins, manufactured by free‐radical polymerisation using a peroxide initiator, with varying molecular weights and hydroxyl values, was used in propellant formulation experiments with a view to studying the resin production variables and their influence on the resultant propellant properties. It is seen that HTPB resins with a wide range of hydroxyl values could be effectively utilized in propellant formulations. Also, propellants with higher strain capability and chain flexibility could be produced from lower hydroxyl value resins. © 1993 John Wiley & Sons, Inc.
Effect of imidization temperature on properties of polymide films
Authors: Chen Ker‐Ming , Wang Tsung‐Hsiung , King Jinn‐Shing , Hung Aina 
Published: April 2003

AbstractSome mechanical and electrical properties of the BPDA/ODA/PDA polyimide film prepared on mylar followed by various cure schedules have been studied. It has been found by FTIR that the imidization reaches its maximum after a 200°C cure schedule for this polyimide. However, the optimum condition of curing is a 350°C cure schedule. Following this cure schedule, one can obtained a polymide film with good mechanical and electrical properties. © 1993 John Wiley & Sons, Inc.
Structure of poly(vinyl alcohol)‐iodine complex formed in the amorphous phase of poly(vinyl alcohol) films
Authors: Choi Yoon‐So , Miyasaka Keizo 
Published: April 2003

AbstractThe effect of syndiotactivity of poly(vinyl alcohol) (PVA) both on the formation and thermal stability of the complex formed in the amorphous phase of PVA films is investigated, and then a model of the complex is presented. The amount of the complex formed in syndiotacticity‐rich PVA is much larger than that formed in atactic PVA under a given iodine‐soaking condition, and the former complex has a higher thermal stability in the soaking solution than the latter. The complex formed in the amorphous phase is proposed to have such a structure as that in which a linear polyiodine I5− or I5− with a 3.1 A˚ periodicity is enveloped by four PVA segments of syndiotactic configuration with extended conformation. In this model, these four PVA chains participating in a complex are supposed to be fixed by interchain hydrogen bonds. The observed X‐ray meridional intensity curve of iodinated PVA film can be explained by a series of two I5−. © 1993 John Wiley & Sons, Inc.
Gelled membrane composed of dioctyldithiocarbamate substituted on poly(vinylchloride) and di (2‐ethylhexyl) dithiophosphoric acid
Authors: Levin Gideon , Bromberg Lev 
Published: April 2003

AbstractSubstitution of chlorine of poly(vinylchloride) (PVC) by dioctyldithiocarbamate (DODTC) groups results in a modified polymer (MP) with a glass transition temperature of between −43 and 84°C, depending on the degree of substitution. Formation of a gelled membrane composed of MP and di (2‐ethylhexyl) dithiophosphoric acid (DTPA), as both an ion carrier and a solvent, was demonstrated. The gelled membrane can be formed with the weight ratio between (MP) : (DTPA) as low as 1 : 99 or higher. The membrane is capable of selective separation of metal ions. © 1993 John Wiley & Sons, Inc.
The use of ultrasound to initiate ring‐opening polymerization
Authors: Stoessel S. J. 
Published: April 2003

AbstractIt has been discovered that a combination of heat and high‐power ultrasound can be used to initiate ring‐opening polymerization in cyclic bisphenol A polycarbonate oligomers. The polymerization can be conducted with or without the use of added chemical initiators. The use of ultrasound was extended to prepare glass‐filled composites. © 1993 John Wiley & Sons, Inc.
Microphase separation and crystallization of crystalline‐amorphous type block copolymer. I. Effect of solvent
Authors: Ishikawa Satoshi , Sasaki Sintaro , Fukutomi Takashi 
Published: April 2003

AbstractThe formation process of the microphase separation and crystallization of a crystallineamorphous type diblock copolymer [poly(tetrahydrofuran‐b‐isoprene)] in solution were studied by transmission electron microscope and wide‐angle X‐ray diffraction measurements. The morphologies formed from three kinds of solvent systems are discussed in relation to the crystallization of poly(tetrahydrofuran) sequence. © 1993 John Wiley & Sons, Inc.
Photocross‐linking of low‐density polyethylene. II. Structure and morphology
Authors: Qu Bao Jun , Rånby Bengt 
Published: April 2003

AbstractMorphological structure and other properties of polyethylene photocross‐linked in the melt (XLPE) have been studied by wide‐angle X‐ray diffraction (WAXD), differential scanning calorimetry (DSC), density, and swelling measurements. The WAXD measurements show that the crystallinity of polyethylene decreases with increasing gel content in the XLPE samples and that the regularity and the size of crystals are affected by photocross‐linking. DSC data confirm that photocross‐linking occurs preferentially in the amorphous and interfacial regions and causes depression of the melting point and decreases the heat of fusion. The density of XLPE apparently decreases with increasing gel content, which is due to decreased crystallinity and lattice expansion. The cross‐link density determined by the swelling measurements and evaluated using the Flory–Rehner equation correlates well with the changes in crystallinity and melting point. © 1993 John Wiley & Sons, Inc.
Radiation stability of PTFE with different crystallinity
Authors: Zhong Xiaoguang , Yu Li , Zhao Wenwei , Zhang Yuefang , Sun Jiazhen 
Published: April 2003

AbstractIn this work, the effects of radiation on polytetrafluoroethylene (PTFE) samples with different crystallinity were studied. Using Suwa's equation for calculating the number‐average molecular weight of PTFE, the radiation‐induced reduction in molecular weight was followed and the G values of scission of PTFE were also obtained on the basis of the changes in molecular weight. The G (scission) for as‐polymerized PTFE was 2.15 ± 0.01, whereas for sintered sample, which has a relative low crystallinity, G (scission) = 6.0 ± 0.14. © 1993 John Wiley & Sons, Inc.
The effect of plasma‐deposited siloxane coatings on the barrier properties of HDPE
Authors: Morra M. , Occhiello E. , Garbassi F. 
Published: April 2003

AbstractThin polymeric films were deposited from siloxane plasma on the surface of polyethylene. The surface composition of the films was measured by X‐ray photoelectron spectroscopy (XPS) and the permeability to O2 by an analytic gas permeability fractometer. No significant improvement of barrier to O2 was observed with 200 nm‐thick coatings. When the siloxane layer was subjected to a further O2 plasma treatment, a threefold decrease of permeability to oxygen was recorded. Results are discussed on the light of the effect of the O2 plasma on the siloxane backbone. © 1993 John Wiley & Sons, Inc.
The mass loss mechanisms of polymers in a radio frequency induced atomic oxygen environment
Authors: Whitaker A. F. , Jang B. Z. 
Published: April 2003

AbstractThe effects of atomic oxygen on several classes of polymers were investigated. Particular attention was directed to the determination of erosion or mass loss mechanisms in relation to the physical and chemical structures of polymers. Nineteen polymeric materials were exposed to a thermal atomic oxygen environment at fluxes of 1022 atoms/m2−sec. Bulk material temperatures were maintained at 10, 45, and 75°C During exposure. Mass loss rate, which was characteristic of the type of polymer, was proportional to the exposure area and was linear in time for most polymers except for Mylar, which produced a shielding high temperature ash. The mass loss rate for the atomic oxygen degradation of polymers was related to the bond strength of the polymer structure and to the shielding effect of pendant structures. This degradation process was strongly dependent on polymer temperature. Activation energies ranged from 1 to 48 KJ / mole and were found to be related to gaseous diffusion in polymers. Frequency factors were proportional to activation energies. Activation energies were found to increase with increased mol wt and crosslinking. An equation was developed relating exposure area, atomic oxygen flux, frequency factor, and activation energy to the rate of polymer mass loss. © 1993 John Wiley & Sons, Inc.
A new modification method of exploded lignin for the preparation of a carbon fiber precursor
Authors: Sudo K. , Shimizu K. , Nakashima N. , Yokoyama A. 
Published: April 2003

AbstractA lignin‐pitch for carbon fiber was prepared in a high yield from exploded lignin on phenolysis followed by heat treatment under a vacuum. The lignin‐pitch had an excellent spinnability in the melt state to form a fine filament. The green fibers were easily made infusible when heated in air at a relatively high heating rate (15‐60°C/h). The lignin‐based carbon fiber was produced in 43.7% of yield based on a starting material. The tensile strength was more than 400 MPa, indicating that the lignin‐based carbon fiber is classified into a general purpose grade. © 1993 John Wiley & Sons, Inc.
Ionomer studies of polyethylene–acrylic acid copolymer. I. Fiber preparation and properties
Authors: Broughton Roy M. , Hall David M. 
Published: April 2003

AbstractTwo EAA (Ethylene/acrylic acid) copolymers from Dow Chemical Company have been studied. Primacor resin (5980), having a mol wt of about 30,000 and an acrylic acid content of 19.2%, was converted into 10 and 20 denier per filament fibers to create a high surface area. Cold drawing and use of a fiber lubricant helped prevent sticking and blocking during spinning. The fiber was optimally swollen in a 0.5 N caustic at 55°C to produce an ion exchange fiber. Primacor resin (5980) in pellet form was reacted with alkali and was subsequently hammermilled into an ion exchange porous particulate. Physical and chemical properties, such as thermal properties, swelling, cation exchange activity and selectivity, tensile and elongation properties, among others, were determined on the fiber before and after conversion to specific metal (cationic) forms. The swollen fibers appeared to have more cation binding capacity than hammermilled pellets. The EAA polymers were colored by some metal cations. Some metal cations could be preferentially removed from solutions of mixed cations. Most fibers were weak, even after exchanging with multivalent ions, and did not have a precise melting point. Fiber tension and solution pH during the cationic exchange had an effect on the cation uptake, as well as on the physical properties obtained. © 1993 John Wiley & Sons, Inc.
Synthesis of polyester pigment binders containing dimethyl 2,2‐dimethyl‐4‐methylene glutarate
Authors: Lin J. C. , Carlson G. M. , Abbey K. J. , Trumbo D. L. 
Published: April 2003

AbstractLow molecular weight oligomers of dimethyl 2,2‐dimethyl‐4‐methylene glutarate and neo‐pentyl glycol have been synthesized. These oligomers were chain‐extended with select diacids and diols to polyesters that were used as pigment binders in paint formulations. Such paints were shown to possess superior detergent resistance when compared to paints formulated using pigment binders that did not contain dimethyl 2,2‐dimethyl‐4‐methylene glutarate. © 1993 John Wiley & Sons, Inc.
Functional polymers for colloidal applications. IV. Aggregate formation of lipophile‐grafted water‐soluble copolymers in aqueous solutions
Authors: Kuo Ping‐Lin , Hung Min‐Nan 
Published: April 2003

AbstractA water‐soluble styrene–maleic anydride copolymer (SMA) is derivatized with different lipophilic groups, butylamine and dodecylamine, with different degrees of substitution (5, 15, and 30%). These lipophile‐grafted SMAs are water‐soluble, and their solutions are transparent. A plot of I1/I3 as a function of polymer concentrations indicates the extent of aggregate formation. Surface tension methods also verify the existence of aggregates. It is found that the aggregates begin to form at concentrations below that of the polymer transfer to the air–water interface. The plots of I1/I3 as a function of polymer concentrations for SMAs of different molecular weights derivatized with different lipophile with varying degrees of substitution show that the polymers with a higher degree of substitution and lower molecular weights aggregate at lower concentrations. Polymers substituted by butylamine form aggregates at a very high concentration, independent of the degree of sub‐stitution. These phenomena are interpreted in terms of hydrophobic interactions as in micelles formed from surfactants. The higher degree of dodecyl‐substituted SMA solubilizes pyrene at higher concentrations, and these pyrene solubilized solutions show pyrene excimer emission spectra. These emission spectra are used to characterize the relative size and hydrophobicity of aggregates. © 1993 John Wiley & Sons, Inc.
Tensile retraction measurements. V. The effect of carbon black on the cross‐link density of cured rubber
Authors: Hergenrother William L. , Doshak John M. 
Published: April 2003

AbstractTensile retraction measurements have been made on the same SBR filled with 50 phr of 10 different carbon blacks. The slopes and intercepts determined from the plots against λmax were determined in three different elongation ranges. These carbon blacks were chosen to have a variety of different surface areas and structures such that the influence of these features on the slopes and intercepts could be measured. The tensile retraction parameters determined were also evaluated at elevated temperatures and Arrhenius plots were made. The activation energies calculated from these plots showed that the structure and surface area of the carbon blacks had no effect on the process being measured. A series of different molecular weight SBRs were also made by anionic techniques to have 0, 1, and 2 tributyltin end groups. The changes in the constants determined from tensile retraction measurement on these cured filled stocks were explained in terms of the number of loose end groups still present after reaction with the carbon black. © 1993 John Wiley & Sons, Inc.
Gas transport properties of polycarbonate–polyurethane membrance
Authors: Cao N. , Pegoraro M. , Bianchi F. , Di Landro L. , Zanderighi L. 
Published: April 2003

AbstractPolyurethanes (PU) were prepared using polymeric diols, containing polar groups, as OC(O)O(carbonate) groups, carbonate and ether (O) groups, or carbonate and ester groups [C(O)O]. PUs were prepared by the prepolymer two‐step technique using ethyl acetate (EA) as the solvent; the diol was reacted at about +80°C with TDI (ratio 1:2) to give the prepolymer terminated with NCO, which was then cross‐linked with triisopropanolamine (TIPA). The membranes were prepared using a Gardner knife and were characterized by differential thermal analysis (DSC). Most of the polymers prepared from low and medium molecular weight diols were amorphous and elastomeric at the temperature of gas transport measurement (35°C). The permeabilities (P) and the diffusion coefficients (D) of different gases (O2, N2, CO2, CH4, CO) were measured by a modified Lyssy apparatus, the solubility coefficient (S) was also calculated. The water‐vapor transport properties D and S were measured according to ASTM. Diffusivity data follow the Fujita model and the solubility coefficients the regular solution theory, as developed by Prausnitz and Shair. © 1993 John Wiley & Sons, Inc.