bluuebunny/crossref_metadata_2025_split huggingface dataset:
Gas permeation in miscible homopolymer‐copolymer blends: II. Tetramethyl bisphenol‐A polycarbonate and a styrene/acrylonitrile copolymer
Authors: Chiou J. S. , Paul D. R. 
Published: April 2003

AbstractGas sorption and transport properties for He, H2, O2, N2, Ar, CH4, and CO2 at 35°C near atmospheric pressure have been obtained for miscible blends of tetramethyl bisphenol‐A polycarbonate (TMPC) and a random copolymer of styrene with acrylonitrile (SAN) containing 9.5% by weight of acrylonitrile. All gas permeability, diffusion, and solubility coefficients obtained are lower than that calculated from the semilogarithmic additivity rule. These results are qualitatively interpreted by ternary solution theory and activated state theory which have been proposed to describe gas sorption and diffusion in miscible blends. The negative deviation of gas permeabilities for the blends from this rule can be explained semiquantitatively by free volume theory which takes volume contraction on mixing into account. The negative deviation increases with gas molecular size which results in larger ideal gas separation factors than that calculated from the additivity rule. For He/CH4 and H2/CH4 pairs, the permselectivities for the blends are higher than that for either pure TMPC or SAN. The deviation from additivity for gas transport properties of TMPC/SAN blends is the opposite of that observed in the first paper of this series for PMMA/SAN blends. This can be attributed to the stronger interactions in TMPC/SAN blends than in PMMA/SAN blends.
The influence of resin characteristics on the high speed melt spinning of isotactic polypropylene. I. Effect of molecular weight and its distribution on structure and mechanical properties of as‐spun filaments
Authors: Lu Fu‐Min , Spruiell Joseph E. 
Published: April 2003

AbstractThe fine structures and tensile mechanical properties were characterized for high speed melt spun filaments prepared from three polypropylenes with melt flow indices in the range 12–300. It was found that spinnability and the resulting structure and properties are affected by both the weight average molecular weight and the polydispersity of the polymer. Higher tenacities, with consequent lower percent elongation to break, could be achieved by spinning the narrow molecular weight distribution polymers at high spinning speeds. This effect was associated with the development of higher birefringence in these samples. Modulus did not correlate with birefringence in the present study, but it was found to be controlled by the nature and level of crystalline order developed in the filaments.
Low pressure CO2 sorption in poly(vinyl cyclohexane‐carboxylate)
Authors: Hirose Takuji , Mizoguchi Keishin , Kamiya Yoshinori 
Published: April 2003

AbstractA gravimetric method was applied to determine the solubility of CO2 in poly(vinyl cyclohexanecarboxylate) below 1 atm. The temperatures were varied from 5 to 85°C, above and below the glass transition temperature. The sorption isotherms were concave to the pressure axis below Tg and they were tentatively analyzed by the dual‐mode sorption model. Above Tg, the isotherms were linear and described by the Henry's law. Below 75°C, the diffusion coefficients of CO2 were also obtained from the half‐time of the sorption process.
Numerical simulation of coextrusion from a circular die
Authors: Mitsoulis E. , Heng F. L. 
Published: April 2003

AbstractA numerical simulation of coextrusion flow in a capillary die has been undertaken for polymer melts used in a previously reported experimental study of coextrusion. Viscosity data are used for PS, HDPE, and LDPE melts. A Newton–Raphson scheme is employed to solve the equations for a fully developed pressure‐driven flow of two concentric layers in a capillary. A finite element method is used to simulate the full flow field behavior, including determination of the interface and free surface of the exiting stream. Double nodes have been used at the interface to ensure continuity of velocities and stresses and to capture the pressure discontinuities. Pressure gradients, extrudate swell, interface swell, and other relevent flow characteristics are presented and compared with the experimental findings. The finite element analysis revealed that satisfactory convergence of the interface location is found for the cases when the less viscous material wets the capillary walls, which is also the preferential configuration in coextrusion. For the opposite configuration, convergence proved either difficult or impossible depending upon the viscosity ratio. Discrepancies were found to exist between the theoretically predicted and experimentally measured pressure gradients.
Structure of skin layer in injection‐molded polypropylene
Authors: Fujiyama Mitsuyoshi , Wakino Tetsuo , Kawasaki Youtoku 
Published: April 2003

AbstractThe structure of skin layer in injection‐molded polypropylen which displayed a clear two‐phase structure of skin and core has been studied by means of wide‐angle x‐ray diffraction, small‐angle x‐ray scattering, melting behavior, density, dynamic viscoelasticity, and tensile test. In skin layer, the c‐axis and a*‐axis were highly oriented to the machine direction (MD), and the plane of the lamellar structure of about 160 Å in thickness was in normal to MD. The density was about 0.907 g/cm3, which was nearly the same as that of core layer. Although the majority of crystallites melted in the same temperature range as in that of the core layer, there was about 5.3% higher temperature melting structure (Tm = 182°C). The dynamic tensile modulus E′ in MD decreased more slowly with increasing temperature than that of the core layer and held high modulus in the range of ca. 30°C, just above the temperature at which E′ of the core layer suddenly dropped. E′ in MD was higher than that in TD in the temperature range below 33°C, which was slightly higher than the primary absorption temperature, and the order reversed above 33°C. The tensile yield stress in MD was 1.5 times higher than that of the core layer. The skin layer in MD ruptured just after yielding and did not show necking. The tensile yield stress in TD was about half of that in MD about 0.7 times that of the core layer. The necking stress in TD was about 0.6 times that of the core layer. In general, a polypropylene melt crystallizes under a high shear stress in injection molding. From these facts, it was concluded that the skin layer is composed of so‐called “shishkebab”‐like main skeleton structures, whose axis is parallel to MD, piled epitaxially with a*‐axis‐oriented imperfect lamellar substructure.
Common thermoanalytical characteristics of durable press reactants based on cyclic ureas
Authors: Trask‐Morrell B. J. , Andrews B. A. Kottes 
Published: April 2003

AbstractThermal analyses, including differential scanning calorimetry (DSC), thermogravimetry (TG), and differential thermogravimetry (DTG), were performed on a series of derivatives of cyclic ureas under nitrogen. Such compounds are used extensively for durable press finishing of cotton textiles. Three common features were discovered in 15 compounds analyzed. Two features related to the presence of an oxygen‐containing substituent on the ring carbons or the ring nitrogens. The former substitution was expressed as an exothermic response between 200 and 300°C and the latter as an endotherm between 300 and 400°C. Specific substituent modifications that changed these responses are described. A final feature was identified. The presence of N‐methylol groups was recognized. This represented the first evidence that compounds capable of releasing formaldehyde have a thermoanalytical marker. The amount of residue produced in TG analyses was related to structure and indicated that thermally induced polycondensations were occurring.
Electrical conduction of CuxS‐treated films
Authors: Im Sung Soon , Kang Eun Young 
Published: April 2003

AbstractElectrical conductivity measurements have been made on CuxS‐treated PET and nylon 6 films in the temperature region between 20 and 200°C. CuxS‐treated films have been observed to have two transition temperatures at about 100 and 180°C, respectively. It should be reasonable to consider that the conductivity behavior between 100 and 180°C is attributed to the character of a metastable structure of the cuprous sulfide. Temperature dependence of conductivity of the CuxS‐treated PET and nylon 6 films was investigated and compared with that of original PET and nylon 6 films. The current–voltage characteristics and time dependence of conductivity of samples were investigated. Conduction mechanism of the CuxS‐treated films was not dependent on matrix polymers but dependent on CuxS crystal, and the conduction is mainly electronic.
Polyanhydride microspheres as drug carriers. II. Microencapsulation by solvent removal
Authors: Mathiowitz E. , Saltzman W. M. , Domb A. , Dor Ph. , Langer R. 
Published: April 2003

AbstractA new method to prepare polyanhydride microspheres, namely via solvent removal, is presented. Polyanhydrides composed of the following diacids were used: sebacic acid (SA), bis(p‐carboxy‐phenoxy) propane (CPP), and dodecanedioic acid (DD). Polymers were characterized by infrared (IR) spectroscopy, X‐ray diffraction, viscosity, differential scanning calorimetry (DSC), and scanning electron microscopy (SEM). Drug release was affected by polymer composition, physical properties of the microspheres, and type of drug. The potential for injectable microspheres (size range 1–300 μm) made of copolymer (CPP‐SA 50:50), as biodegradable polymer carriers for the controlled release of insulin in treating diabetes mellitus, was assessed. Both 5% and 10% w/w insulin‐loaded microspheres were prepared. The 10% loaded microspheres produced the best clinical response, demonstrating five days of urine glucose control and four days of serum glucose control in diabetic rats.
The microstructure of stabilized fibers
Authors: Ko Tse‐Hao , Ting Hsing‐Yie , Lin Chung‐Hua , Chen Jia‐Chyuan 
Published: April 2003

AbstractThe morphology and microstructure of a stabilized fiber, nonburning fiber, has been investigated under optical and electron microscopes, and a model for the structure of the stabilized fiber is presented. Skin‐core morphology was found in the cross section of the stabilized fiber. The proposed model is consistent with the lamellar‐plate‐like structure, measuring about 400–700 Å in thickness, 500–4000 Å in breadth and 0.1–0.5 μ m in length along the fiber axis, which is composed of microfibrils. The structure has some circumferential distribution in the outer zone, while the inner zone has a radical distribution. Evidence for the lamellar‐plate structure, including two chemical structures and having two different crystalline phases, which are the original AN units and the ladder polymer, were obtained from electron microscopy, wide‐angle X‐ray, and electron diffraction analyses.
Highly sensitive self‐developing soft X‐ray resists of silicon‐containing aldehyde copolymers and sensitive novolac‐based composite resists containing aldehyde copolymer
Authors: Nate Kazuo , Inoue Takashi , Yokono Hitoshi , Hatada Koichi 
Published: April 2003

AbstractCopolymers of aliphatic aldehydes containing a trimethylsilyl group were prepared at −78°C in toluene using diethylaluminum diphenylamide as an initiator. The copolymer depolymerized into monomeric aldehydes on exposure to soft X‐rays. When the copolymer was used as a soft X‐ray resist, almost complete development was accomplished by exposure alone. No development step was required. The soft X‐ray sensitivity of poly(3‐trimethylsilylpropanal‐co‐propanal) was 50 mJ/cm2 at the film thickness of 1.0 μm. A composite resist system consisting of a novolac resin and an aldehyde copolymer containing trimethylsilyl groups has also been developed and used as an alkaline‐developable positive electron‐beam and soft X‐ray resist.
Rhodium (1) catalyst supported on polyethylene hollow fibers: Preparation and hydrogenation studies
Authors: Butler Jacqueline S. , Gordon Bernard , Harrison Ian R. 
Published: April 2003

AbstractIn recent years polymers have been utilized as binding sites for transition metal catalysts (e.g. crosslinked polystyrene beads). However, general problems exist with the above system. The rate of reaction depends on the presence of solvents that adequately swell the polystyrene bead in order to allow access to the catalyst sites. Differences in polarity and reactant size can inhibit diffusion into the bead. Recently a new system has been developed where the catalyst is bound to polyethylene single crystal surfaces, this has solved the above problems. However, polyethylene single crystals are small and plate‐like causing a new problem, when trying to filter the separate product the crystals cause clogging of the filtering system and limit the reactions to batch process. This paper describes the use of fine microporous polyethylene hollow fibers as the supporting polymer. This gives the advantages of the single crystal support, plus allows for the use of a fixed‐bed flow reaction system.
Laser marking of microporous films
Authors: Kuder James E. , Taskier Henry T. , Hamer E. Geoffrey 
Published: April 2003

AbstractThe potential for microporous films as optical recording media is explored in this report. Irradiation of metallized films of microporous polypropylene and polyethylene with a HeNe laser produced marks having high contrast and which could be read without the aid of polarizing optics. The novel marking process involves melting, collapse of the microporous structure, and thinning of the film as the built‐in strain relaxes.
Modeling of diffusion‐controlled free‐radical polymerization reactions
Authors: Achilias D. , Kiparissides C. 
Published: April 2003

AbstractThe present paper introduces a new fundamental approach to the modeling of diffusion‐controlled free‐radical polymerization reactions. Our analysis follows the original work of Chiu, Carratt, and Soong (CCS), according to which the termination and propagation rate constants are expressed in terms of both a purely reaction‐limited term and a diffusion‐limited one. The contribution of the latter term to the apparent rate constants is described in terms of the polymer and monomer effective diffusion coefficients and an effective reaction radius. It is shown that all parameters appearing in the original CCS model can be calculated from first principles using available data on the physical and transport properties of a particular monomer–polymer binary system. The generalized free volume theory of Vrentas and Duda and the theory of excess chain end mobility are invoked for the calculation of the effective diffusion coefficients and the reaction radius, respectively. The approach followed in this study is general and needs only the specification of one unknown parameter with a clear physical meaning. All other parameters can be readily calculated from available data. The ability of the new model to predict molecular weight developments and monomer conversion in diffusion‐controlled reactions is demonstrated by application of the proposed model equations to the bulk polymerization of MMA.
The effect of steric hindrance on physical properties in an amine‐cured epoxy
Authors: Duffy James V. , Lee Gilbert F. 
Published: April 2003

AbstractA pair of aliphatic amines were synthesized in order to study the effect steric hindrance has on the physical properties of an amine‐cured epoxy resin. The hindered amine (TMSiDA) has NH2 groups that are obstructed by the presence of adjacent methyl groups while the unhindered amine (SiDA) does not contain any NH2 steric hindrance. DGEBA cured with TMSiDA is less dense, absorbs less moisture, and has a higher Tg than does SiDA/DGEBA. Torsional pendulum results show that TMSiDA/DGEBA has a slightly higher rubbery modulus and a secondary transition at a lower temperature than DGEBA cured with SiDA. Activation energies for the secondary transition were determined for TMSiDA/DGEBA and SiDA/DGEBA and are 19 and 14 kcal/mol, respectively.
Photovoltaic effect based on wet poly(vinyl alcohol)/merocyanine dye junction
Authors: Uehara Kaku , Takagishi Kenji , Tanaka Makoto 
Published: April 2003

AbstractThe sandwich cell, Au/wet poly(vinyl alcohol) (PVA)/merocyanine (MD)/Au, based on the PVA/MD junction exhibited photovoltaic and rectifying effects. Forward dark current from the MD/Au electrode to the counter PVA/Au electrode through the cell was observed. The Au/MD electrode showed a positive photovoltage with respect to the PVA/Au electrode regardless of the direction of the incident light. It was suggested that a heterojunction barrier similar to the Schottky type formed at polymer/dye interface was responsible for the photo charge separation.
Mechanical properties of HDPE/(PEC/PS)/SEBS blends
Authors: Schwarz M. C. , Barlow J. W. , Paul D. R. 
Published: April 2003

AbstractVarious amounts of a styrene‐butadiene‐based triblock copolymer (SEBS) was used to compatibilize immiscible blends of high density polyethylene (HDPE) and an amorphous glassy phase consisting of either pure polystyrene (PS) or a miscible blend of PS and a polyether copolymer (PEC). PEC is structurally similar to poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO). Mechanical properties were determined for blends fabricated by injection and compression molding. The inherently brittle two‐phase HDPE/(PEC/PS) blends show significant increases in ductility and impact strength resulting from addition of SEBS. These improvements coincide with a slight loss in modulus and yield strength. If the amount of HDPE and SEBS is held constant, impact strength and ductility increase with the amount of PEC in the glassy phase. These trends evidently result from the added ductility of glassy phases containing PEC and perhaps from better interfacial adhesion in blends after adding SEBS. The latter stems from the thermodynamic miscibility between PEC and PS endblocks of SEBS which provide an enthalpic driving force for compatibilization. Differences between the properties of compression and injection‐molded blends can be attributed to the degree of crystallinity and orientation induced during molding.
Solvent penetration and photoresist dissolution: A fluorescence quenching and interferometry study
Authors: Limm William , Stanton Deirdre , Dimnik Gerald P. , Winnik Mitchell A. , Smith Barton A. 
Published: April 2003

AbstractA novel method, based upon fluorescence quenching measurements, is described for the study of the mechanistic details of solvent penetration into thin polymer films. Here poly(methyl methacrylate) (PMMA) labelled with phenanthrene (Phe) groups was coated as a film (0.8 μm thick) onto quartz disks. Diffusion of solvent (1 : 1 2‐butanone/2‐propanol) into the film was followed by a decrease in Phe fluorescence, while film dissolution was monitored simultaneously by laser interferometry. In the case of PMMA (Mw = 411,000, films annealed at 160°C) both processes occur at approximately the same rate and exhibit non‐Fickian (relaxation‐controlled) diffusion behavior. Correlating the results of these two experiments shows that, once the steady state is reached, the dissolution rate is controlled by the advance of the solvent front into the PMMA film. The “transition layer,” an important dissolution parameter, increases its thickness from 50 to 90 nm during the plasticization stage of solvent penetration and maintains its thickness until the solvent front reaches the quartz substrate.
Improved dispersive mixing through reduction in flow field vorticity
Authors: Roland C. M. , Nguyen M. 
Published: April 2003

AbstractDispersive mixing is most efficiently accomplished with pure straining flow. Vorticity in the flow field inhibits this extending action; accordingly, the presence of shearing flow will decrease the overall effectiveness of dispersive mixing processes. A method to reduce the vorticity by inducing lubricated flow through development of a nonuniform distribution of the components of a polymer blend is described.
Effect of pressure on the precipitation and sol‐phase aqueous polymerization of methyl methacrylate
Authors: Mohanty Baijayantimala , Palit Sunanda K. , Biswas Mukul 
Published: April 2003

AbstractEffect of pressure (atmospheric to 120 kg/cm2) on the K2S2O8–Na2S2O4‐initiated aqueous polymerization of methyl methacrylate has been studied at 25°C. When the concentrations of the redox initiator are so adjusted as to obtain the separating polymer phase as a coarse coagulum, the conversion, rate, and molecular weight of polymerization tend to rise initially with increase of pressure up to a certain value and fall subsequently to a limiting value. However, these parameters fall monotonously with an increase in pressure when the polymer phase separates out as a fine colloid at a lower concentration of the initiator. The initial rise in rate is consistent with an increase in kp and or a decrease in kt under high pressure; the ultimate fall in rate may be due to a decrease in the diffusion of monomer from the aqueous phase to the growing polymer radical site. The fall in the molecular weight with pressure is explained on the basis of enhanced monomer transfer. In the colloidal range the pressure dependence trend is related to the stability of the colloidal phase. The rate is proportional to the square root of the product of K2S2O8–Na2S2O4 and varies linearly as the first power of the monomer concentration as also observed under normal pressure conditions. The MWD values of the polymers are ca. 2.5 and do not change with applied pressure.
Thermal and crystallization behavior of engineering polyblends. I. Glass reinforced polyphenylene sulfide with polyethylene terephthalate
Authors: Shingankuli V. L. , Jog J. P. , Nadkarni V. M. 
Published: April 2003

AbstractThe thermal and crystallization behavior of blends of glass fiber reinforced polyphenylene sulfide (PPS) with polyethylene terephthalate (PET) has been reported. The blends showed two overlapping melting peaks and two separate crystallization peaks. The heat of crystallization of PPS was found to decrease continuously with increasing PET content, whereas the heat of crystallization of PET was found to increase with increasing PPS content. This indicates that the degree of crystallinity of PPS is reduced whereas that of PET is increased as a result of blending. It is interesting to note that the combined heats of fusion of the blends were marginally higher than those calculated by proportional additivity rule in spite of the drop in the heat of crystallization of PPS. The temperature onset of crystallization of PET in the blends shifted to higher temperature whereas there was no significant change in the crystallization temperature of PPS. The increase in the temperature of crystallization of PET indicates enhanced nucleation. The isothermal crystallization studies of the component polymers revealed that both the component polymers crystallized at a relatively faster rate in the blend. The crystallization rate of PPS was found to increase significantly with increasing PET content. A significant increase in the rate of crystallization of PET was also observed in the blends. The acceleration of crystallization rate of PET in the blends was more pronounced as compared to that of PPS. The acceleration in the PET crystallization rate was attributed to the presence of glass fibers and crystallized PPS.