bluuebunny/crossref_metadata_2025_split huggingface dataset:
Microporous polypropylene hollow fibers with double layers
Authors: Nagō Satoshi , Mizutani Yukio 
Published: April 2003

AbstractMicroporous polypropylene hollow fibers with double layers were prepared by stretching double layered polypropylene microtubes containing polymethylsilsesquioxane fillers: the relatively smaller filler in the inner layer and relatively larger filler in the outer layer. The resultant hollow fibers have a finely interconnected fibrous structure parallel to fiber axis. Their N2 gas permeabilities were measured to estimate the fibrous structure: tortuosity factor, effective porosity, and pore size. © 1995 John Wiley & Sons, Inc.
Graft polymerization of acrylic acid onto starch using potassium permanganate acid (redox system)
Authors: Mostafa Kh. M. 
Published: April 2003

AbstractGraft polymerization of acrylic acid (AA) onto rice starch using postassium permanganate/acid redox system as initiator was investigated. When starch was reacted with KMnO4 solution, MnO2 was deposited onto starch. The dependence of MnO2 amount deposited was directly related to KMnO4 concentration. Subjecting the MnO2‐containing starch to a solution consisting of monomer (AA) and acid (citric, tartaric, oxalic and hydrochloric acid) formed poly(AA)–starch graft copolymers. The graft yield, expressed as meq COOH/100 g starch, was measured by the amount of MnO2 deposited, AA concentration, material‐to‐liquor ratio, kind and concentration of acid, as well as temperature and duration. Finally, the newly prepared poly(AA)–starch graft copolymers were applied to cotton textiles to determine their suitability as sizing agents. The highest graft yield was obtained with citric acid and the least with hydrochloric acid, with tartaric and oxalic acid in between. The graft yield increased by increasing the concentration of acid to a certain concentration beyond which grafting leveled off. A similar trend was observed when the magnitude of grafting was related to the amount of MnO2 deposited. The graft yield increased by increasing the polymerization temperature from 30° to 50°C. Increasing the temperature to 60°C is accompanied by decreased grafting. On the other hand, fabric samples sized with poly(AA)–starch graft copolymers acquire higher tensile strength, elongation at break, and abrasion resistance than that sized with native rice starch, i.e., poly(AA)–starch graft copolymers serve as good sizing agents for cotton textiles. A tentative mechanism for grafting rice starch with AA using the KMnO4/acid redox system was elucidated. © 1995 John Wiley & Sons, Inc.
Protonation of polyaniline by surface‐functionalized polymer substrates
Authors: Pun M. Y. , Neoh K. G. , Kang E. T. , Loh F. C. , Tan K. L. 
Published: April 2003

AbstractThe protonation of solution‐coated emeraldine (EM) base by sulfonic and carboxylic acid groups on surface‐functionalized low‐density polyethylene (LDPE), high‐density polyethylene (HDPE), polypropylene (PP), poly(ethylene terephthalate) (PET), and polytetrafluoroethylene (PTFE) films were characterized by X‐ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy, and conductivity measurements. Surface functionalizations were achieved by sulfonation (for LDPE, HDPE, PP, and PET), by hydrolysis (for PET), and by near‐UV‐light‐induced surface graft copolymerization with the Na salt of styrene sulfonic acid and acrylic acid (for all substrates). The efficiency of surface functionalization by graft copolymerization is substantially enhanced for substrates pretreated with O3 or Ar plasma. Protonation levels of 50% can be readily achieved for EM coated on sulfonic acid, but not carboxylic acid, functionalized surfaces. The extent of protonation, however, is also dependent on the microstructures of the modified substrate surfaces. In all cases, charge transfer interactions between the EM layer and the functionalized substrates readily result in good adhesion of the electroactive polymer on the polymer substrates to give rise to conductive surface structures. © 1995 John Wiley & Sons, Inc.
Characterization of a glycidyl azide polymer composite propellant: Strain rate effects and relaxation response
Authors: Duncan E. J. S. 
Published: April 2003

AbstractUniaxial tension tests were completed on a developmental GAP/PSAN solid rocket propellant at constant strain rates ranging over three decades and at five different temperatures. An analysis of the maximum stress (strength) and the strain at maximum stress showed that there is a relatively narrow range of temperatures and strain rates that give rise to strains at maximum stress that exceed 18%. The long‐term equilibrium strain capability (strain endurance) appears to be between 10% and 12%. The trend of the strength and initial deformation moduli were log‐linear with the reciprocal of the strain rate across three decades. However, the shifted master curves were log‐curvilinear in form. The relationship between the strength and the initial modulus can be approximated by a power law. A series of stress relaxation tests was completed at a level of 4% strain and at five different temperatures. The initial portion of the shifted master relaxation curve is concave‐up with correspondingly high stresses and moduli. It decays with time approaching a log‐constant slope. Tensile moduli derived from constant strain rate tests were found to be consistently higher in value than the moduli as a function of time determined from relaxation tests, for an equivalent shifted time. Preliminary evidence suggests that the tensile modulus as a function of the reciprocal of shifted strain rate can be equated to the relaxation modulus as a function of shifted time through an adjustment factor. This relationship extends the relaxation modulus results back a further three and one‐half decades of shifted time. © 1995 John Wiley & Sons, Inc.
Surface and interfacial FTIR spectroscopic studies of latexes. IX. The effect of homopolymer and copolymer structures on surfactant mobility in Sty/BA latices
Authors: Niu B.‐J. , Urban Marek W. 
Published: April 2003

AbstractThe effects of homopolymer and copolymer compositions and structures in styrene/n‐butyl acrylate (Sty/BA) latices on sodium dioctyl sulfosuccinate (SDOSS) surfactant mobility and its preferential concentration at the film–air (F–A) and film–substrate (F–S) interfaces were examined using attenuated total reflectance Fourier transform infrared (ATR FTIR) spectroscopy. It appears that the SDOSS concentration at the F–S interface is highest when the Sty/BA feed ratio is 50/50, and the excess of Sty results in migration of SDOSS surfactant to the F–A interface. This behavior is attributed to the increased glass transition temperature and diminished compatibility between surfactant molecules and copolymer latex. This study also shows that the primary factors that influence exudation to either F–A or F–S interfaces are surface tension of the substrate, glass transition temperature, water flux during coalescence, and compatibility between latex components. © 1995 John Wiley & Sons, Inc.
Preparation and characterizations of thermotropic copolyesters of p‐hydroxybenzoic acid, sebacic acid, and hydroquinone
Authors: Hsiue Lin‐Tee , Ma Chen‐Chi M. , Tsai Hong‐Bing 
Published: April 2003

AbstractA series of copolyesters of p‐hydroxybenzoic acid (HBA), sebacic acid and hydroquinone were prepared by melt polycondensation of p‐acetoxybenzoic acid, sebacic acid and p‐phenylene diacetate. The copolyesters were characterized by IR, NMR, DSC, polarized microscopy, and X‐ray diffraction. It was found that the copolyesters exhibited liquid crystallinity when the HBA content was 25–67 mol %. The copolyesters with an HBA content of 25–43 mol % showed a nematic phase and a biphasic range, and the isotropization temperature increased as the HBA content increased. The copolyesters with an HBA content of 54–67 mol % showed a nematic phase up to above 400°C. The liquid crystalline order increased as the HBA content increased due to the increased of the average length of the rigid moieties. © 1995 John Wiley & Sons, Inc.
Synthesis and characterization of fluorinated poly(imide–amide–sulfone)s
Authors: Bruma M. , Mercer F. , Fitch J. , Cassidy P. 
Published: April 2003

AbstractA series of new, fluorinated poly(imide–amide–sulfone)s has been synthesized by solution polycondensation of aromatic diamines containing sulfone groups with diacid chlorides incorporating both imide and hexafluoroisopropylidene units. These polymers are soluble in polar amidic solvents, and their solutions can be cast into colorless, thin, flexible films having good electrical insulating properties and high thermal stability. The dielectric constant value is 3.49–3.68. The decomposition temperature in air is 464–479°C, and the glass transition temperature is in the range 279–359°C. All these characteristics have been discussed and compared with those of related fluorinated poly(imide–amide)s which do not contain sulfone groups and with other imide polymers without hexafluoroisopropylidene units. © 1995 John Wiley & Sons, Inc.
Coexistence of ductile, semiductile, and brittle fractures of elastomer‐modified polycarbonates
Authors: Liu Wen‐Bing , Chang Feng‐Chih 
Published: April 2003

AbstractPhenomenologically, coexistence of ductile, semiductile, and brittle fractures in an apparently identical impact testing condition for the elastomer‐modified polycarbonates containing a sharper notch and at high test temperatures has been found. At the ductile–brittle transition temperature, approximately 10% of specimens fractured in the semiductile mode with impact strength about the average of the ductile and brittle modes. The fracture surface of this semiductile mode shows ductile tearing flow in the plane‐stress regions near the edges and brittle crack in the plane‐strain central region. This unusual semiductile fracture occurs only on the thicker specimens with a sharper notch where clear plane‐stress and plane‐strain are present. © 1995 John Wiley & Sons, Inc.
Study on copolymer emulsion containing an epoxy group
Authors: Xu Zushun , Lu Guohong , Cheng Shiyuan , Li Jianzong 
Published: April 2003

AbstractMethyl methacrylate, butyl acrylate, acrylic acid, and various amounts of glycidyl methacrylate (GMA) were copolymerized by a semicontinuous seeded emulsion copolymerization to be a four‐component copolymer emulsion; the copolymers were characterized using swelling capacity, transmission electron microscopy (TEM), etc. The effect of glycidyl methacrylate and its content on the properties of emulsion and copolymer films was studied. The self‐crosslinking reaction of the copolymer was investigated by FTIR and DSC. It was found that the swelling capacity of the crosslinked copolymer films decreased with increase of the glycidyl methacrylate content, the morphology showed a core–shell structure, and the copolymer emulsion possessed a self‐crosslinking property. © 1995 John Wiley & Sons, Inc.
Creep behavior of biaxial cold‐rolled polypropylene
Authors: Li J. X. , Cheung W. L. 
Published: April 2003

AbstractPolypropylene was biaxially rolled up to 60% at ambient temperature, and the tensile creep behavior over the temperature range 27 to 60°C was investigated using a dead‐load apparatus. The degrees of crystallinity of the as‐molded and rolled PP were determined using a differential scanning calorimeter (DSC) and density bottle. The DSC showed a slight change in the crystallinity during the early stage of the rolling process, while the density bottle indicated a continuous drop of the density with increasing rolling reduction. The elongation due to rolling was found almost fully recoverable when the samples were thrown into hot silicon oil at 180°C. The effects of cold rolling on creep strain, secondary creep strain rate, and creep activation energy were investigated. Cold rolling led to an increase in the creep strain and secondary creep strain rate. The creep activation energy was found to increase with increasing rolling reduction. Within the secondary creep stage, the creep process in polypropylene is mainly due to the α‐relaxation process and most of the creep strain was recoverable. © 1995 John Wiley & Sons, Inc.
Synthesis and characterization of new aromatic poly(ether ketone)s
Authors: Mercer Frank W. , McKenzie Martin T. , Merlino Gloria , Fone Matilda M. 
Published: April 2003

AbstractA general method for the preparation of aromatic poly(ether ketone)s containing amide, amide‐imide, cyano, oxadiazole, and pyridazine moieties has been developed. Polymerization is based on a ketone‐activated halide displacement from amide‐, amide‐, imide‐, cyano‐, oxadiazole‐, or pyridazine‐containing bis(4‐fluorobenzoyl) moieties by bisphenoxides in a polar aprotic solvent. The bis(4‐fluorobenzoyl) moieties were prepared by reaction of 4‐fluorobenzoyl chloride with diphenoxy monomers containing amide, amide‐imide, cyano, oxadiazole, or pyridazine groups under modified Friedel–Crafts conditions in methylene chloride. All of the polyether ketones prepared were amorphous and exhibited Tgs ranging from 134 to 218°C. In addition, films of the aromatic polyether ketones displayed good thermal stability and flexibility. The dielectric constants of the films were characterized as a function of relative humidity (RH). © 1995 John Wiley & Sons, Inc.
Effects of physical aging and carbon dioxide absorption in bisphenol‐A polycarbonate
Authors: Risch Brian G. , Wilkes Garth L. 
Published: April 2003

AbstractThermal and mechanical behavior of bisphenol‐A polycarbonate was studied as a function of thermal history and absorbed mass fraction of CO2. Physical aging at 120°C for one week produced dramatic changes in both the thermal and mechanical behavior. Gas absorption studies indicated that although initial diffusion was somewhat retarded in the aged samples, both aged and unaged polycarbonate samples showed identical equilibrium absorbed gas values at 6500 K Pa and identical gas desorption behavior. Absorbed CO2 was shown to dramatically reduce the glass transition of polycarbonate indicating that CO2 plasticizes polycarbonate. Additionally, samples which had been aged and absorbed a mass fraction of 0.07–0.10 of CO2 showed thermal and mechanical behavior identical to that of a glass quenched from above Tg with identical absorbed mass fraction. Once the absorbed gas was desorbed, the thermal and mechanical properties were similar to those of a glass freshly quenched from above Tg. This study demonstrates that sufficient CO2 gas absorption followed by desorption reverses physical aging in polycarbonate. © 1995 John Wiley & Sons, Inc.
Graft copolymerization of polyacrylonitrile (PAN) onto nylon 6/nylon 66 and simultaneous homopolymerization: A comparative study. II
Authors: Gopalan A. , Vasudevan T. , Manisankar P. , Paruthimalkalaignan G. , Ramasubramanian A. , Hariharan S. S. 
Published: April 2003

AbstractThe kinetics of graft copolymerization of polyacrylonitrile (PAN) onto nylon 6/nylon 66 and the simultaneous homopolymerization initiated by potassium peroxomonosulfate (PMS)–ascorbic acid (H2A) redox systems were studied separately. Various kinetics parameters were evaluated and analyzed to have a comparison among the systems. The occurrence of simultaneous homopolymerization was evident through rate parameters. When the backbone was changed, the following order was observed for grafting efficiency: polyester (PET) > nylon 6 ≳ nylon 66. © 1995 John Wiley & Sons, Inc.
Influence of molecular structure on the degradation mechanism of degradable polymers: In vitro degradation of poly(trimethylene carbonate), poly(trimethylene carbonate‐co‐caprolactone), and poly(adipic anhydride)
Authors: Albertsson Ann‐Christine , Eklund Maria 
Published: April 2003

AbstractRelationships between molecular structure and the degradation mechanism of degradable polymers are of special interest for temporary medical applications. The in vitro degradation study of three aliphatic polymers—poly(trimethylene carbonate) (PTMC), poly(trimethylene carbonate‐co‐caprolactone) (PTMC‐PCL), and poly(adipic anhydride) (PAA)—revealed that these polymers exhibit degradation times from several years (PTMC) to 1 day (PAA). PTMC degraded unexpectedly slow, accompanied by very small changes in weight loss, molecular weight (SEC), and in morphology (DSC, SEM). The degradation was independent of initial molecular weight, ionic strength of the water solution, temperature, and shaking motions. The copolymer PTMC‐PCL showed a higher degradation rate compared to PTMC, with preferential degradation of amorphous parts leading to an increase in % crystallinity. The surprisingly rapid degradation of PAA showed characteristics typical for a surface‐like eroding system in contrast to PTMC and PTMC‐PCL. The degradation products corresponded to the repeating unit of the polymers. The hydrolysis rate increases in the order carbonate, ester, anhydride, and by combining different molecular structures we achieve specific degradation behavior. A change in hydrolysis rate of the labile bond is predicted by altering the electronegativity of groups near the carbonyl‐oxygen region. © 1995 John Wiley & Sons, Inc.
Generalization of kinetics in the reaction of isocyanates and polyols for modeling a process‐yielding linear polyurethane, 1
Authors: Król Piotr 
Published: April 2003

AbstractA general kinetic reaction network has been suggested for the gradual chian growth polyaddition process for the synthesis of linear chain polyurethane. Based on the results from the kinetic investigation of the reactions of model aromatic/aliphatic isocyanates and alcohols and hydroxyethers, some methods were set forth to provide rate‐constant values for the reactions included in this network. Model equations were derived from the collision theory, giving dependencies of reaction rate constant values on the molecular weights of the reacting substances. It was found that it was the structure of the reactants that had the most significant effect on the rate of carbamate‐yielding reactions; the effects derived from temperature, catalyst, and size of reacting molecules follow. © 1995 John Wiley & Sons, Inc.
Rheological characterization of 4,4′‐bis (diethylamino)benzophenone‐functionalized polybutadienes with low and medium vinyl content
Authors: Alcántar Norma A. , Salinas María Del R. , Herrera Rafael , Manero Octavio 
Published: April 2003

AbstractIn this article a mechnical spectroscopic study of a series of low (≃8%) and medium (≃ 70%) vinyl‐content polybutadiences, some of them functionalized with 4,4′‐bis(diethylamino)‐benzophenone, is presented. Characterization of polymers with well‐known structure by small‐amplitude oscillatory shear flow enabled investigation of the effect of the vinyl content and functional groups on the rheological behavior of the samples in the linear viscoelastic region. The Doi–Edwards viscolastic model, without any adjustable parameter, proved to be adequate to describe the relationship between the macro/micro structure of the polymers and their viscoelastic properties. Results indicate that the vinyl content and functional groups modify the rheological behavior extensively. © 1995 John Wiley & Sons, Inc.
Effects of catalyst on sequence distribution and transparency of poly(tetramethylene terephthalate)–poly(tetramethylene ether) segmented copolymers
Authors: Shi Youheng , Wu Meiyan 
Published: April 2003

AbstractPolyether‐polyester segmented copolymer based on hard segments of tetramethylene terephthalate (PBT) and soft segments of poly(tetramethylene ether glycol) (PTMG) was synthesized by four kinds of catalyst: tetrabutyl titanate and magnesium acetate (Ti‐Mg); tetrabutyl titanate and triethanolamine; tetra(isopropyl) titanate; and isopropoxy(triethanolaminato) titanate, respectively. Their segment sequence distributions were analyzed by 13C‐NMR, based on different chemical shifts of aromatic quaternary carbons in the three different triad sequences. The effects of catalyst on sequence distribution and transparency were investigated. It was found that the copolymer has lower probability of B‐T‐B when Ti‐Mg was used as catalysts, and results in higher transparency. © 1995 John Wiley & Sons, Inc.
On‐line conversion monitoring through ultrasound propagation velocity measurements in emulsion polymerization
Authors: Canegallo S. , Apostolo M. , Storti G. , Morbidelli M. 
Published: April 2003

AbstractAn on‐line sensor for estimating conversion from measurements of ultrasound propagation velocity in emulsion polymerizations has been developed. The sensor does not require a sampling circuit, because it can be directly plugged in the reacting mixture. The performance of the sensor has been tested by comparison with off‐line gravimetric measurements of conversion under various operating conditions. These include the homopolymerization of methyl methacrylate and vinyl acetate, with different values of the monomer to water ratio and the initial concentrations of emulsifier and initiator. The results obtained using either an empirical calibration curve or a suitable a priori model indicate excellent reliability of the sensor with somewhat lower accuracy at low conversion values, i.e., when monomer droplets are present. © 1995 John Wiley & Sons, Inc.
NEW‐TPI thermoplastic polyimide: Structure and relaxation using SAXS and TSDC
Authors: Lu Sharon Xin , Cebe Peggy , Capel Malcolm 
Published: April 2003

AbstractThe thermoplastic polyimide RegulusTM NEW‐TPI has been studied using small‐angle X‐ray scattering (SAXS) and thermally stimulated depolarization current (TSDC). SAXS was used to study the development of lamellar structure during isothermal or nonisothermal crystallization. The one‐dimensional electron‐density correlation function was used to determine structural parameters. The long period, lamellar thickness, and amorphous layer thickness increase as crystallization temperature increases from 300 to 360°C. By combining melting‐point data with SAXS results, we report the side and fold surface free energies of NEW‐TPI crystals, which are 29 ± 3 and 41 ± 3 erg/cm2, respectively. Real‐time SAXS was carried during nonisothermal cold‐crystallization at 5°C/min. The long period decreases, while lamellar thickness, linear crystallinity, and interphase thickness increase, with increasing temperature. These changes are explained by a crystal‐insertion model. TSDC was used as a more sensitive probe of the amorphous phase structure below 300°C. Both semicrystalline and amorphous NEW‐TPI exhibit complex TSDC behavior. Above the glass transition, amorphous NEW‐TPI has a strong TSDC peak attributed to short‐range‐ordered structures, which may serve as nucleation sites for subsequent crystallization. This peak was not seen in semicrystalline material. At the glass transition, both amorphous and semicrystalline NEW‐TPI have a strong TSDC peak. In the semicrystalline polymer, relaxation of the amorphous dipoles is slightly restricted by the crystals, which results in a smaller relaxation peak and a shift to higher temperature. Below Tg, another TSDC peak occurs which is not due to dipolar relaxation. This peak is attributed to the combined effects of space charge, electrode type, ionizable species, and interfacial charges. © 1995 John Wiley & Sons, Inc.