bluuebunny/crossref_metadata_2025 huggingface dataset:
A high reynolds number rotating disk rheometer
Authors: Dickerson James P. , Flesher L. Michael , Hester Roger D.
Published: April 2003

The construction and principles of operation of a rotating disk rheometer are outlined as is its use in the study of polymeric fluid drag reduction. The need for a sensitive measuring system under a wide variation of Reynolds numbers has prompted the development of a computer‐controlled system that allows a systematic measurement of the turbulent fluid frictional difference between dilute polymer solutions. Also, the long‐term drag‐reducing stability of macromolecules in a turbulent flow field can be conveniently measured. Representative data from experimental measurements are presented demonstrating the capabilities of this instrument. © 1994 John Wiley & Sons, Inc.
Analysis of the pullout of single fibers from low‐density polyethylene
Authors: Li Jian‐Xin
Published: April 2003

In the present work, a single‐fiber pullout test was used to study the interface/interphase between various fibers and low‐density polyethylene (LDPE) and between glass fibers and a range of other thermoplastic matrices. For well‐bonded fibers, experimental evidence suggests the involvement of plastic deformation and strain‐hardening prior to debonding and pullout. The interfacial shear strength was determined to be the ultimate shear strength of the matrix and was found to be insensitive to the fiber surface structure. A new theoretical model was developed to predict the relationship between the debonding force and the embedded length. The contribution of friction to the debonding force was found to be insignificant when compared with the contribution of plastic deformation. © 1994 John Wiley & Sons, Inc.
Melting behavior of ultra‐high modulus and molecular weight polyethylene (UHMWPE) fibers
Authors: Hsieh You‐Lo , Ju Jie
Published: April 2003

Superheating and double‐melting endotherms are the characteristic melting behaviors of gel‐spun ultra‐high modulus and molecular weight polyethylene (UHMWPE) fibers in differential thermal analysis (DTA). A mostly orthorhombic structure with very little amorphous content is indicated by wide angle x‐ray scattering (WAXS) data. The melting temperatures are elevated and believed to result from superheating and incomplete chain relaxation in the highly oriented and crystalline structure. The melting behavior of the fibers is shown to be strongly affected by changes in polymorphic transformations and in intercrystalline disordered domains. Compression in the direction perpendicular to fiber axis causes significant increases in the 110 and 200 dimensions of the orthorhombic structure. Such lateral compression increases monoclinic forms and perhaps amorphous content, and decreases the degree of transformation to hexagonal phase. Superheating, which is related to the intercrystalline stress, can be reduced by the presence of interacting solvents such as trichlorbenzene. © 1994 John Wiley & Sons, Inc.
Photooxidative effects on properties and structure of high‐density polyethylene
Authors: Jabarin Saleh A. , Lofgren Elizabeth A.
Published: April 2003

The environmental degradation of high‐density polyethylene (HDPE) has been studied, in addition to that of HDPE blends, containing various concentrations of ethylene carbon monoxide copolymer. Extruded sheets of each material were exposed to natural Arizona sunlight for times up to 6 months. Exposed samples were then analyzed with respect to molecular weight, density, thermal behavior, mechanical properties, and infrared absorption. Additional samples were exposed to laboratory weathering conditions, evaluated in terms of property changes, melted, reformed, and then reevaluated without further weathering exposure. Results indicate that sunlight exposure causes decreased elongation to break, increased embrittlement, decreased molecular weight, and increased crystallinity. Environmental oxidative degradation is elucidated by the measurement of specific infrared bands, sensitive to the formation of carbonyl and vinyl end groups. As environmental degradation causes reductions of molecular weight, polymer chain mobility increases, leading to a higher degree of crystallinity. This increased crystallinity, along with the decreased molecular weight, accounts for the loss of ductility, indicated by a sharp decrease in ultimate elongation. The presence of carbon monoxide copolymer in the blended samples accelerates the process of environmental degradation, however, the degradation mechanisms appear to be similar to those observed for nonblended HDPE. © 1994 John Wiley & Sons, Inc.
Miscible blends of polybenzimidazole and polyaramides with polyvinylpyrrolidone
Authors: Cherdron H. , Haubs M. , Herold F. , Schneller A. , Herrmann‐Schönherr O. , Wagener R.
Published: April 2003

The blend behavior of polybenzimidazole and a series of polyaramides with polyvinylpyrrolidone is presented. Regardless of their chemical structure, all systems showed miscible blends over the composition range investigated. This may offer the opportunity to extend the application range of these basically structural materials into the area of functional polymers. Especially in membranes, the addition of the highly hydrophilic polyvinylpyrrolidone leads to a considerable increase in performance, i.e., in flux and antifouling behavior. © 1994 John Wiley & Sons, Inc.
Comparison of some butadiene‐based impact modifiers for polycarbonate
Authors: Cheng C. , Peduto N. , Hiltner A. , Baer E. , Soskey P. R. , Mylonakis S. G.
Published: April 2003

The relationship of blend morphology to deformation mechanisms and notched Izod impact strength was studied with three butadiene‐based impact modifiers for polycarbonate (PC). The impact modifiers were a linear polybutadiene (PB), a styrene–butadiene–styrene block copolymer (SBS), and a structured latex particle having a PB core and methyl methacrylate/styrene shell (MBS). The particle‐size distribution in the blends was determined from transmission electron micrographs (TEM). Fractographic analysis combined with TEM examination of thin sections from impacted specimens provided insight into the failure mechanisms. Good impact was achieved with PC/MBS blends when cavitation of the core–shell particles relieved triaxiality and enabled the matrix to fracture by the plane stress ductile tearing mode that is characteristic of thin PC. The best impact properties were obtained with PC/SBS blends when the modifier was dispersed as aggregates of small particles. Cavitation at the weak internal boundaries relieved triaxiality, but subsequent coalescence of cavitated particles during ductile drawing of the matrix created critical size voids and the resulting secondary cracks reduced the toughness of the blend. In general, PB did not significantly enhance the impact strength of PC. © 1994 John Wiley & Sons, Inc.
Fabrication of composite hollow fibers for air separation
Authors: Chung Tai‐Shung , Kafchinski E. Ronald , Kohn Rachel S. , Foley Paul , Straff Ritchie S.
Published: April 2003

By using microporous polyacrylonitrile (PAN) hollow fibers as the substrate, we developed two types of composite fibers for air‐separation. One was a poly(4‐vinyl pyridine) (4‐PVP)/(hexafluoro propane dianhydride)–durene (6FDA)/PAN composite hollow fiber, and the other was a 6FDA–3,5‐diaminobenzonitrile/6FDA–durene/PAN composite hollow fiber. The asymmetric PAN fiber was prepared using dry‐jet wet‐spinning technology, and the deposition of a thin gutter layer of 6FDA–durene on PAN was carried out by prewetting PAN fibers with Fluorinert® before solution coating. The topcoating of a thin layer (200–300 Å) of PVP or 6FDA–3,5‐diaminobenzonitrile on PAN/6FDA–durene fibers was conducted using a conventional solution coating method. The selectivity of 0.7% 4‐PVP/2% 6F–durene/PAN composite fibers for O2/N2 was 5.6 with an O2 permeance of 32.2 × 10−6 cc(STP)/cm2 s cmHg, whereas the selectivity of 0.5% 6FDA–3,5‐diaminobenzonitrile/2% 6F–durene/PAN fibers was 5.1 with an O2 permeance greater than 37.2 × 10−6 cc(STP)/cm2 s cmHg. Both fiber selectivities can be further improved by increasing the thicknesses of the selective layer. © 1994 John Wiley & Sons, Inc.
Classification of nylon 66 impurities using digital image processing
Authors: Brasington Chandis R. , Gadala‐Maria F.
Published: April 2003

Color image processing was used to classify the impurities in nylon 66 that fluoresce when exposed to ultraviolet light. The hue value determined from digitized color images was found to correlate well to the color of the fluorescence as seen by the naked eye. Digital image processing is advantageous over visual observation because it removes the subjectivity from the classification process, and is a relatively simple and inexpensive method compared to other spectroscopic techniques. The hue values of the impurities may provide a quantitative data base that could lead to process improvements. © 1994 John Wiley & Sons, Inc.
Macromolecular systems in heat‐resistant drilling fluids; advantages of gels on linear polymers
Authors: Collette C. , Lafuma F. , Audebert R. , Brouard R.
Published: April 2003

The degradation process of linear water‐soluble vinyl polymers was followed in aqueous medium at temperatures higher than 150°C. We found that, for any chemical structure, thermal oxidative degradation of the longest chains always occurs, leading to moieties of lower molecular weight (20,000–60,000). The behavior of swollen tridimensionnal networks was tested under the same conditions, and it appeared that rheological and fluid loss properties of the system could be maintained in that case for an optimum number of crosslinks. The corresponding gels were used in simple formulations containing some other drilling fluid components. The first results concerning the thermal stability of the latter are very encouraging. © 1994 John Wiley & Sons, Inc.
Monoepoxy polymerization initiated by BF3‐amine complexes in bulk. II. Influence of water and by‐products on polymer formation
Authors: Chabanne Philippe , Tighzert Lan , Pascault Jean‐Pierre
Published: April 2003

The polymerization of a monoepoxy, phenylglycidylether (PGE), initiated by BF3‐4‐methoxyaniline (BF3‐4MA) was studied at 60°C. The polymerization rate was found to be Rp = kp [BF3‐4MA]0.53 [PGE]. The improper fraction of BF3‐4MA shows the complexity of the polymerization mechanism. Moreover, the influence of water, temperature, by‐products formed during the polymerization, on the kinetics of PGE was also examined. Furthermore, two other monoepoxy monomers, glycidylmethacrylate (GMA) and α‐napthylglycidylether (NGE), were studied for the comparison with PGE. Finally, an overall mechanism of the cationic polymerization of epoxy by BF3‐amine complex was proposed. © 1994 John Wiley & Sons, Inc.
Propylene polymerization in slurry catalyzed by titanium trichloride–diethyl aluminum chloride
Authors: Kahraman R. , Erdoğan M. , Bilgiç T. , Savaşçi Ö. T.
Published: April 2003

Propylene is polymerized in a slurry over a TiCl3 · ⅓AlCl3 catalyst with a DEAC cocatalyst, approaching conditions of industrial relevance. The effects of various parameters such as temperature, pressure, cocatalyst‐to‐catalyst ratio, hydrogen concentration, and polymerization time are investigated with particular emphasis on the yield, tacticity, molecular weight, bulk density, and particle size of the resulting polymer. The highest yield and isotactic content are obtained at an Al/Ti ratio of 6, temperature of 70°C, and pressure of 9 kg/cm2g. The polymerization rate is found to be first order up to a monomer concentration of 2.5 mol/L. The overall activation energy of polymerization calculated from an Arrhenius plot is found to be 11.6 kcal/mol. A correlation between MFI and molecular weight is also presented. © 1994 John Wiley & Sons, Inc.
Polymeric phosphonium salts as a novel class of cationic biocides. VII. Synthesis and antibacterial activity of polymeric phosphonium salts and their model compounds containing long alkyl chains
Authors: Kanazawa Akihiko , Ikeda Tomiki , Endo Takeshi
Published: April 2003

Various polymeric phosphonium salts containing long alkyl chains (C10C18) and their corresponding model compounds were prepared, which possess the same hydrophobic structure as that of the common disinfectants (quaternary ammonium salts), and their antibacterial activities were evaluated by means of the viable cell counting method against Staphylococcus aureus (Gram‐positive) and Escherichia coli (Gram‐negative). The polymer with the decyl group exhibited a higher activity than that of the corresponding model compound, particularly against the Gram‐positive strain. Furthermore, antibacterial activity of the polymers was found to decrease as the chain length increased. In contrast with the polymers, the antibacterial activity of the corresponding model compounds increased as hydrophobicity of the substituents increased. The antibacterial activity was strongly dependent on the structure, particularly on the length of the alkyl chain. © 1994 John Wiley & Sons, Inc.
Structure–property relationship in copolymers of methacrylic acid esters. I. Thermal behavior
Authors: Agarwal Seema , Choudhary Veena , Varma I. K.
Published: April 2003

This article describes the synthesis and thermal characterization of copolymers of methyl methacrylate (MMA) and alkyl methacrylates. The copolymerization was carried out using different mol fractions (0.05–0.25) of alkyl methacrylates, i.e., octyl methacrylate (OMA)/decyl methacrylate (DMA)/lauryl methacrylate (LMA)/stearyl methacrylate (SMA), in the initial feed at 80°C. The copolymer composition was determined from 1H‐NMR. The thermal stability of the copolymers was investigated by thermogravimetric analysis and pyrolysis gas chromatography. A two/three‐step degradation was observed in the copolymer samples. The monomers were the major product of degradation in most of the copolymers except in SMA/MMA copolymers where the product of side‐group elimination was also observed. An attempt was also made to determine the yield of the monomers during degradation and then to evaluate the copolymer composition. © 1994 John Wiley & Sons, Inc.
Synthesis and water absorbency of the copolymer of acrylamide with anionic monomers
Authors: Yao Ke‐Jun , Zhou Wen‐Jing
Published: April 2003

A series of novel copolymer superabsorbents based on acrylamide, sodium allylsulfonate, sodium acrylate, andN,N′‐methylenebisacrylamide were prepared by copolymerization. The resulting superabsorbents have a fast swelling rate. The experimental results show that absorbency increases to a maximum as the cross‐linking increases, but an excess of cross‐linking leads to a swelling decrease. Their water retention was observed at pressures of 1–10 kg/cm2and temperatures of 60 and 100°C, respectively. The water retention of soil has been enhanced by using the poly(acrylamide–sodium allysulfonate–sodium acrylate) superabsorbent; its use for bean growth was also investigated. © 1994 John Wiley & Sons, Inc.
Cross‐linking poly(ethylene oxide) and poly[oxymethylene‐oligo(oxyethylene)] with ultraviolet radiation
Authors: Sloop Steven E. , Lerner Michael M. , Stephens Thomas S. , Tipton Andrew L. , Paull Deborah G. , Stenger‐Smith John D.
Published: April 2003

Poly(ethylene oxide) (PEO) and poly[oxymethylene‐oligo(oxyethylene)] (PEM) disks are cross‐linked by exposure to 254 nm radiation. The rate of formation of cross‐links is greatly enhanced by the presence of benzophenone, and an average cross‐link density of up to 6 mol % of ethoxy units can be obtained after several hours of irradiation. The highly cross‐linked polymers are insoluble in water or organic solvents and show improved physical properties for handling and the formation of free‐standing films. Scanning calorimetry and polymer swelling are employed to characterize the polymers, and impedance measurements are reported for sodium salt complexes prepared from the cross‐linked polymers. Dynamic modulus measurements show that, upon irradiation, PEO and PEM become cross‐linked, elastomeric solids. © 1994 John Wiley & Sons, Inc.
Hydrolytic degradation of ionically cross‐linked polyphosphazene microspheres
Authors: Andrianov Alexander K. , Payne Lendon G. , Visscher Karyn B. , Allcock Harry R. , Langer Robert
Published: April 2003

The hydrolytic degradation of gel microspheres based on calcium cross‐linked phosphazene polyelectrolytes, poly[di(carboxylatophenoxy)phosphazene] (PCPP) and poly[(carboxylatophenoxy) (glycinato)phosphazene] (PCGPP), was investigated. These microspheres are of importance as carriers in protein and cell encapsulation. Both PCPP and PCGPP ionotropic polyphosphazene hydrogels are degradable in an aqueous environment (pH 7.4, 37°C). The degradation rates can be increased by incorporation of hydrolysis sensitive glycinato groups as the pendant structures in the polymer (PCGPP). Hydrolysis of these polymer hydrogels led to low molecular weight (<1,000 Da) products. The erosion and molecular weight profiles varied also according to the molecular weight of the polyphosphazene constituting the gel beads. Another approach to affect the degradation rates consists of coating microspheres with poly‐L‐lysine. Ionotropic polyphosphazene hydrogels have potential as biodegradable devices for controlled drug delivery systems. © 1994 John Wiley & Sons, Inc.
Solid‐state polymerization vis‐à‐vis fiber formation of step‐growth polymers. I. Results from a study of nylon 66
Authors: Srinivasan Rangarajan , Desai Prashant , Abhiraman A. S. , Knorr Raymond S.
Published: April 2003

This study is directed toward synergistic integration of processing of nylon 66 fibers with solid‐state polymerization. The following two goals are sought through the incorporation of solid‐state polymerization after the initial shaping operation: eliminating some of the processing problems in the production of high molecular weight, high performance industrial fibers and attainment of improved mechanical properties via high molecular weight. Successful solid‐state polymerization has been achieved with as‐spun fibers of nylon 66 and molecular weights up to 280,000 g/mol have been obtained from a starting molecular weight of 40,000 g/mol. It is shown that much of the ductility of the starting fiber can be retained, or even enhanced, with solid‐state polymerization. Simulated drawing experiments using a thermal deformation analysis technique show an increase in the drawing potential of the solid‐state polymerized fiber as compared to the starting material. This has important implications regarding the ultimate properties that can be achieved in fibers of condensation polymers. © 1994 John Wiley & Sons, Inc.
Crystallization and melting behaviors of poly(aryletheretherketone) (PEEK) on origin of double melting peaks
Authors: Bas C. , Battesti P. , Albérola N. D.
Published: April 2003

The crystallization and melting behaviors of poly(aryletheretherketone) (PEEK) films were investigated, using differential scanning calorimetry and metallurgy concepts. The shape of the time–temperature–transformation (TTT) diagram, established for PEEK, results from both nucleation and growth phenomena. The double melting behavior exhibited by isothermally crystallized PEEK samples are discussed through the TTT diagram and the influence of the thermal history in the molten state. The upper melting peak arises first and the lower melting peak is developed later. The location of such a second endotherm is shifted toward the higher temperature with increasing either the crystallization temperature or the annealing time while the location of the upper melting peak seems to be unchanged. The double melting behavior is related to a bimodal distribution in size and/or perfection of lamellae developed in a two‐step crystallization. With increasing temperature and/or annealing time in the molten state, the pattern of the endothermic curves is modified. The observed changes are discussed through two origins: the progressive disappearance of remnants of the former crystals and a thermal degradation leading to a cross‐linking of the polymer. © 1994 John Wiley & Sons, Inc.
Synthesis and characterization of methacrylic acid–ethyl acrylate copolymers
Authors: Bajaj P. , Goyal Meenakshi , Chavan R. B.
Published: April 2003

Copolymerization of methacrylic acid (MAA) and ethyl acrylate (EA) was performed in aqueous medium in the presence of an emulsifier with MAA as the major component (53.7–82.3 mol %). Emulsion stability was studied as a function of concentration and the nature of the emulsifier (ionic or nonionic). Copolymers were characterized using IR and 1H‐NMR spectroscopy. 13C‐NMR spectra of MAA–EA copolymers have been discussed in terms of their triad monomer sequence distributions. Reactivity ratios of the MAA–EA pair were determined using a nonlinear least‐square errors in variables method. Partition of the monomers in aqueous and organic phases was studied using a gas chromatographic technique. A two‐loci polymerization mechanism was proposed on the basis of this partition behavior and the calculated composition of the oligomeric radicals formed in the initial stages of polymerization. © 1994 John Wiley & Sons, Inc.
Thermal stability studies of a polyimide–polytetrafluoroethylene blend and its components
Authors: Davis Charles R. , Zimmerman Jeffrey A.
Published: April 2003

Low‐dielectric constant (ϵr) polymers, such as polytetrafluoroethylene (PTFE), are an important component of advanced electronic products that transit data, since it is this physical property that largely determines a device's performance. For instance, the dielectric constant determines overall signal speed and proximity in that one circuit line can be placed to another, i.e., wiring density, while maintaining desired electrical characteristics. However, due to PTFE's inertness and intractability, significant challenges exist in the successful application of the polymer as an insulation material. One specific example is the lack of available methods to uniformly and controllably generate fine, high‐density features in the neat fluoropolymer. Recently, it was reported that excellent structuring characteristics of PTFE can be achieved by sensitizing the fluoropolymer to excimer laser radiation using small quantities of an aromatic polyimide. An important physical property of the sensitization agent, in addition to interacting strongly with the laser's emitted energy, is suitable thermal stability due to PTFE's high‐temperature processing requirements. Using multiple analysis techniques, the thermal decomposition behavior of PTFE, polyimide sensitizer, and resulting polymer blend have been evaluated. It was determined that the onset of decomposition for all systems is near or greater than 500°C. © 1994 John Wiley & Sons, Inc.
Thermal analysis of poly(vinylidene fluoride) (PVDF) in composites with polypyrrole (PPy)
Authors: Pawde Sunita , Bhat Narendra
Published: April 2003

The melting behavior and dynamic mechanical properties of poly(vinylidene fluoride) (PVDF) in composites with polypyrrole (PPy) have been investigated using DSC/DTA and a Rheovibron viscoelastometer. Composites with varying percentages of PPy (5–50%) were synthesized using a solution‐casting method with FeCl3 as the oxidant. It was observed that the melting point of PVDF increased as the percent of PPy was increased. A plot of tan δ vs. temperature showed the shift of the α relaxation peak to higher temperature. These results, together with our earlier studies on the basis of XRD and IR, indicate molecular interaction, an antiplasticization effect of PPy, and partial phase transformation of PVDF to phase I (β form). © 1994 John Wiley & Sons, Inc.
Modifying acrylic‐based superabsorbents. I. Modification of crosslinker and comonomer nature
Authors: Omidian H. , Hashemi S. A. , Askari F. , Nafisi S.
Published: April 2003

This article is devoted to the synthesis, characterization, and modification of acrylic‐based superabsorbents which are synthesized by carrying out the well‐known process of inverse suspension polymerization. The dispersion is stabilized by using a mixture of micromolecular and macromolecular stabilizers. High swelling and appropriate absorption kinetics are obtained, provided that parameters (including initial monomer and crosslinker concentration, range of neutralization degree, initiating and stabilizing system, monomer addition rate, temperature and nature of the organic phase) are being considered. Modifications of crosslinker and comonomer nature and their effects on absorbency characteristics (capacity and rate) of the above‐mentioned superabsorbents are graphically presented. Finally, diffusion behavior of superabsorbents is briefly discussed. © 1994 John Wiley & Sons, Inc.
Preparation and properties of polymide foams
Authors: Kashiwame Josho , Ashida Keneyoshi
Published: April 2003

Catalysts for the raction of aromatic isocyanates with aromatic anhydrides to form imides were investigated using a model reaction. Alkali metal acetylacetone chelate compounds exhibited good catalytic efficiency and selectivity in dimethyl sulfoxide (DMSO). These catalysts were used for the preparation of polymide foams. The resulting foams exhibited excellent fire resistance and thermal stability. © 1994 John Wiley & Sons, Inc.
Segmented block copolyetheramides based on nylon 6 and polyoxypropylene. I. Synthesis and characterization
Authors: Yu Yeong Chool , Jo Won Ho
Published: April 2003

Various segmented block copolyetheramides based on nylon 6 and polyoxypropylene (POP) were synthesized by melt polymerization of caprolactam (CPL) and polyoxypropylene diamines (POPD) as a function of the size and content of POPD. As the content of POPD in the feed increased, the IR absorption band at 1110 cm−1 increased. The 1H‐NMR analysis indicated that peaks characteristic of methylene groups in POP unit appeared at 1.2, 3.6, and 3.8 ppm. The compositions of the hard and soft segments in the block copolymer were determined from the NMR data. The POP content in copolymer was higher than that in the feed due to the removal of unreacted CPL by water extraction. The average block lengths of the hard and soft segments were calculated from molecular weights and copolymer compositions. © 1994 John Wiley & Sons, Inc.
Morphological changes in segmented polyurethane elastomers by varying the NCO/OH ratio
Authors: Spathis G. , Niaounakis M. , Kontou E. , Apekis L. , Pissis P. , Christodoulides C.
Published: April 2003

The morphological changes induced to segmented polyurethane elastomers by varying the NCO/OH ratio during the second step of polymerization, while keeping constant the total hard‐segment content (∼ 30%), were studied by means of fourier transform infared spectroscopy (FTIR), differential scanning calorimetry (DSC), and the thermally stimulated depolarization current method (TSDC). The DSC results gave evidence for the existence of phase separation in thermoplastic polyurethanes, whereas the elastomerc ones appeared to form a more homogeneous network. The FTIR results gave additional evidence regarding phase separation be detecting the sterength of the hydrogen bonds. Moreover, an attempt was made to assess the relative contribution made to the hydrogen bonding in such systems by the two potential acceptors: ester and urethane carbonyls. The TSDC results gave a relaxation mechnism that is due to interfacial (Maxwell–Wagner–Sillars) polarization, providing evidence of the existence of an interfacial phase. The introduced secondary chemical cross‐links was found to affect mainly the irregularly packed hard domains and to form a more homegeneous network at higher values of the NCO/OH ratio. © 1994 John Wiley & Sons, Inc.
Chelating resins supporting dithiocarbamate and methylthiourea groups in adsorption of heavy metal ions
Authors: Lezzi A. , Cobianco S.
Published: April 2003

Two different sulfur atom containing functional groups were introduced into poly(styrene‐g‐ethylene glycols), PSR‐ET (13) OH, consisting of a cross‐linked polystyrene backbone grafted with linear poly(ethylene glycol) chains. Reaction of an amino derivative of the polymeric substrate with carbon disulfide and methylisothiocyanate produced new chelating resins of dithiocarbamate type, PSR‐ET (13) CS2Na, and methylthiourea type, PSR‐ET (13) TU, respectively. The adsorption behavior of these resins was studied toward Hg(II), Cd(II), Cu(II), and Pb(II) ions in different experimental conditions. The order of metal adsorption for dithiocarbamate‐supported resins was Hg(II) > Pb(II) ≫ Cd(II) > Cu(II) and for methylthiourea‐supported resins was Hg(II) ≫ Cu(II) > Cd(II) ≫ Pb(II). Different regeneration methods were performed with the dithiocarbamate and methylthiourea resins; the former was regenerated by complete mineralization of the metal complexes, the latter by treatment with a solution of 6 N HCl and 10% of thiourea. © 1994 John Wiley & Sons, Inc.
Polymer morphology of CO2‐blown rigid polyurethane foams: Its fractal nature
Authors: Grünbauer H. J. M. , Folmer J. C. W.
Published: April 2003

Small‐angle x‐ray scatting (SAXES) and transmission electron microscopy (TEM) have been applied to study polymer morphologies of CO2,‐blown rigid polyurethane foam samples of varying isocyanate index. The results are consistent with an irregular (meso) phase segregated structure with phase boundaries showing fractal symmetry. Phase segregation persists, througtout the index range, althougt the interfacial surfaces tends to smooothen with increasing isocyanate index to evetually results in a significant degree of energetic ‘sharing’ across the4 phase boundary. The latter can satisfactorily be explained by a free volume double layer (PVDL) model. Mechanistically. Fractal symmetry was attributed to the competition between crossliking and phase segregation tendencies in rigid PU foam polymers. The resulting frozen‐in morphology represents an early stage of the development towards a more regular spinodal phase segregation, as occurring in polyuethane foam systems of lower crosslink density (e.g. flexible foams). © 1994 John Wiley & Sons, Inc.
Step‐growth polymerization of unsaturated aldehydes with aliphatic amines
Authors: Šebenik Anton
Published: April 2003

The step‐growth polymerization of unsaturated aldehydes (acrolein, crotonaldehyde, cinnamaldehyde) and aliphatic amines (butylamine, ethylenediamine, triethylenetetramine, diethylenetriamine, hexamethylenediamine) took place intensively in the temperature range between 50 and 90°C. The rates of individual reactions depended on the type of individual aldehydes and amines. The quantity of individual unreacted monomers was mostly under 1%. The average molecular weights of oligomers were between 290 and 710. The individual resins consisted of oligomers with free OH, NH, CHN, and CHCH groups, which are further able to cross‐link the resins with three blocked isocyanate to insoluble, elastic film with high adhesion to glass and metal substratum. © 1994 John Wiley & Sons, Inc.
Polymerization initiation by N‐p‐tolylglycine: Free‐radical reactions studied by pulse and steady‐state radiolysis
Authors: Al‐Sheikhly Mohamad , Farahani Mahnaz , Bowen R. L.
Published: April 2003

The extensive use of N‐p‐tolylglycine (NTG) and analogous compounds in adhesive bonding technologies requires a better understanding of their role in initiating free‐radical polymerization. The fast oxidation and reduction reactions of NTG proceed via the formation of various free radicals and radical cation and anion intermediates. These intermediates were identified and their reactivity with oxygen, to produce the corresponding peroxyl radicals, was measured. Hydroxyl radicals (ȮH) were used to initiate oxidation reactions of NTG, while the reduction reactions were initiated with hydrated electrons (e). OH radicals react with NTG predominately by addition to the aromatic ring followed by OHÞ elimination to produce NTG+· radical cations. In the presence of oxygen, the OH–NTG• adduct also reacts with oxygen to produce peroxyl radicals. The reaction of NTG with e forms the radical anion, which subsequently protonates on the aromatic ring to produce cyclohexadienyl radicals, or undergoes an amine elimination to yield an acetic acid free radical and 4‐methylaniline. Hydroperoxyl radicals (HO) abstract hydrogen from the α position of NTG to form the corresponding alkyl free radical. © 1994 John Wiley & Sons, Inc.

This article is a US Government work and, as such, is in the public domain in the United States of America.
Rheology of polycarbonate/poly(butylene terephthalate) blends containing a core‐shell modifier and high‐molecular‐weight acrylic polymers: Extrusion blow‐moldable resins
Authors: Memon Nazir A.
Published: April 2003

Several different polymer modifications are currently used to produce commercial plastic materials, especially engineering resins, that have significantly improved melt strength. However, these modifications rarely produce materials that can be formed into very large parts. This study shows that the melt strength of engineering resins can be enhanced by rubber particles having grafted shells that are compatible with the resin. The melt strength of the engineering resin can be further improved by the incorporation of compatible highmolecular‐weight polymers. The melt strength improvements thus obtained facilitate the formation of very large parts requiring 8–10 ft long parisons. The effects of shear rate on complex viscosity indicate that the extent of interaction between the polycarbonate matrix and the core‐shell impact modifier decreases with increasing shear rate. Therefore, the impact strength of the part molded from a matrix modified with a core‐shell rubber may depend on the process history. Dynamic mechanical measurements may provide a means to evaluate the interaction between the matrix and a core‐shell modifier in an actual blend. © 1994 John Wiley & Sons, Inc.
Bromination and gas permeability of poly(1‐trimethylsilyl‐1‐propyne) membrane
Authors: Nagai K. , Higuchi A. , Nakagawa T.
Published: April 2003

The bromination of poly(1‐trimethylsilyl‐1‐propyne) (PMSP) was carried out by immersing a PMSP membrane in bromine water at 25°C. The bromine mainly reacted at the carbon–carbon double bonds in the backbone chain, and carbon–carbon single bonds were produced, which was determined from the infrared (IR) and ultravilet (UV)–visible analyses. The glass transition temperature of the PMSP is above 350°C, but a new endothermic peak appeared between 50 and 80°C in the differential scanning calorimetry (DSC) curves of all brominated PMSPs. The permeability for 12 gases in the PMSP membrane and its brominated membranes was investigated between 30 and 90°C below 1 atm. With increasing bromine content in the membrane, the permeability coefficient for all gases decreased together with the diffusion coefficient, and the ideal separation factor for the industrially important gas pairs increased at 30°C. A distinct change in slopes at near the endothermic temperature determined by the DSC analysis was observed in Arrhenius plots of the permeability coefficients in all brominated PMSP membranes. © 1994 John Wiley & Sons, Inc.
Synthesis of poly(2,6‐dimethyl‐1,4‐phenylene ether) catalyzed by copper–diamine system
Authors: Li Kuo‐Tseng
Published: April 2003

Oxidative polymerization of 2,6‐dimethylphenol to poly(2,6‐dimethyl‐1,4‐phenylene ether) (PPE) was studied in a high‐pressure batch reactor using a copper‐diamine catalyst. In the presence of air, the effect of monomer sources, catalyst formulation (copper salts, ligands, surfactant), and reaction conditions (air flow rate and pressure, temperature, agitation, monomer and catalyst concentrations) on the catalyst performance was investigated. The sensitivity of PPE molecular weight and the sensitivity of polymerization rates to these factors were found to be quite different, indicating that little correlation existed between the PPE molecular weight and the 2,6‐DMP polymerization rates. Mechanical test showed that the PPE produced with the copper–diamine catalyst had modulus significantly higher than that produced with the copper–dibutylamine catalyst system. © 1994 John Wiley & Sons, Inc.
Studies on the preparation and properties of conductive polymers. VII. Use of two‐stage method to prepare Ag–Hg alloy on polymer films
Authors: Chang Liang‐Tau , Yen Chih‐Chao
Published: April 2003

Polymer metal chelate films were prepared by silver nitrate mixed with polymers containing functional groups such as poly(vinyl alcohol) (PVA) by using two‐stage method to prepare Ag–Hg alloy on polymer films. In the first stage, polymer silver chelate was treated with doping agents. In the second stage, these treated films were further treated with Hg metal. After the two stage treatment, films with good electrical conductivity can be obtained. © 1994 John Wiley & Sons, Inc.
Size‐exclusion calibration curves from light‐scattering detection: Application to poly(ethylene terephthalate)
Authors: Mourey T. H. , Balke S. T.
Published: April 2003

A simple method is proposed for using a size‐exclusion chromatograph equipped with both concentration and light‐scattering detectors to calibrate other chromatographs having only concentration detectors. The method is developed and demonstrated for poly(ethylene terephthalate) in methylene chloride/dichloroacetic acid. It is shown that, in addition to circumventing the need for a light‐scattering instrument on other chromatographs to be used for the analysis of PET, precision and accuracy of results are improved over those obtainable with light‐scattering detection. The method uses averaging of the light‐scattering detector data to establish a correlation between the molecular weight of the polymer of interest and the molecular weight of polystyrene at each retention volume. This correlation can then be used for other instruments employing the same mobile phase and only a concentration detector. Although the method assumes the validity of the universal calibration curve, the actual curve is not required, nor are Mark–Houwink constants or intrinsic viscosities. © 1994 John Wiley & Sons, Inc.
Chemical modification of polypyrrole. II. Thermal stability, dielectric, and conductivity characteristics of polypyrrole substituted with phthalic and pyromellitic dianhydride
Authors: Biswas Mukul , Roy Anindita
Published: April 2003

Polypyrrole (PPY) was electrophilically polycondensed with phthalic anhydride (PA) and pyromellitic dianhydride (PMDA). PPY–PA and PPY–PMDA polycondensates were evaluated in regard to their thermal stability and dielectric and conductivity behavior. The overall thermal stability is in the order PPY < PPY–PA < PPY–PMDA, which may be rationalized in terms of intra‐ and intermolecularly cross‐linked structures of the polycondensates. IR spectral analyses of PPY–PA and PPY–PMDA subjected to heating at 300, 400, 500, and 550°C, respectively, were conducted to understand some of the structural changes in the polymer matrices. Both PPY–PA and PPY–PMDA exhibit high dielectric constants (200 and 125) at low frequency (103 Hz), which fall monotonically with increasing frequency, suggesting the possibility of interfacial polarization. The conductivity values of PPY–PA and PPY–PMDA are in the range 10−3–10−4 ohm−1 cm−1, which are conspicuously lower than that for unmodified PPY (2.5). This is due to the adverse effect of incresing temperature on the PPY chain stability, whereby structural conjugation and eventually conductivity will be affected. © 1994 John Wiley & Sons, Inc.
Study of some polyurethane elastomers using electrical methods
Authors: Murthy S. S. N. , Sobhanadri J.
Published: April 2003

A study of some poly ether/ester urethanes has been carried out using electrical methods, viz. dielectric spectroscopy (400–105 Hz), dc conductivity, and dc step‐response techniques. X‐ray diffraction and thermal analysis also are used for characterization of the samples. The studies indicate a hard‐segment glass transition Tgh around 318–322 K in addition to a soft‐segment glass transition around 233–270 K. The breakage of hydrogen bonding mainly starts above Tgh. The studies also show a hard‐segment melting around 1.5–1.8 Tgh, but do not reveal any soft‐segment melting except in the case of the polyetherurethane sample. © 1994 John Wiley & Sons, Inc.
Poly(3‐hydroxybutyrate)‐co‐(3‐hydroxyvalerate)/Poly‐L‐lactide blends: Thermal and mechanical properties
Authors: Iannace S. , Ambrosio L. , Huang S. J. , Nicolais L.
Published: April 2003

Blends of poly(3‐hydroxybutyrate)–poly(3‐hydroxyvalerate) (PHBV) and poly(L‐lactides) (PLLA) have been prepared by solvent casting. Compatibility, thermal behavior, morphology, and mechanical properties of systems with various compositions were studied using differential scanning calorimetry (DSC), dynamic mechanical measurement, tensile tests, scanning electron microscopy (SEM), and wide‐angle X ray (WAXS). Glass transition temperature of solvent cast materials, detected by dynamic mechanical analysis (DMA), showed partial molecular interactions between PHBV and PLLA. Crystallinity of the PLLA phase slightly decreased with increasing amount of PHBV, confirming the partial dispersion of PLLA in the PHBV phase. Mechanical properties were analyzed with theoretical models able to predict the behavior of heterogeneous systems. Phase separation was confirmed by SEM observations. © 1994 John Wiley & Sons, Inc.
Polyolefin–wood filler composite. I. Performance of m‐phenylene bismaleimide‐modified wood fiber in polypropylene composite
Authors: Sain M. M. , Kokta B. V.
Published: April 2003

The properties of the composite of polypropylene (PP) and chemithermomechanical pulp reactively treated with bismaleimide‐modified PP or premodified pulp have been investigated. The results were compared with the properties of unmodified composites of PP and pulp. The effect of some flame retardants on the properties of composites was also studied. Premodifications of PP as well as pulp with m‐phenylene bismaleimide provided a positive response with regard to the mechanical properties of the composites. The tensile strength of a 35 wt % pulp‐filled PP composite was found to be much higher than that of the strength of pure PP. On the other hand, tensile strength decreased considerably with increase in the chemithermomechanical pulp content if unmodified PP was used. The occurrence of chemical grafting reactions between PP and bismaleimide as well as between pulp and bismaleimide have been suggested, which can explain the aforementioned difference in mechanical properties among different composites. In situ addition of sodium borate, boric acid, or phenolic resin during processing of the composite decreased the rate of burning of PP. © 1994 John Wiley & Sons, Inc.
Polyurethane–urea anionomer dispersions. I
Authors: Xiao Hong , Xiao Han X. , Frisch Kurt C. , Malwitz Nelson
Published: April 2003

Polyurethane–urea anionomer dispersions with different stoichiometric DMPA/polyol and NCO/OH ratios were preapred from poly(oxypropylene)glycol, toluene diisocyanate (TDI), dimethylolpropionic acid (DMPA), and ethylenediamine (EDA). The dispersion‐cast films were prepared and characterized by mechanical properties, dynamic mechanical analysis (DMA), and differential scanning calorimetry (DSC). Increasing the hard‐segment content by either increasing the DMPA/polyol or the NCO/OH ratios affects the glass transition temperature (Tg) of the soft segments. © 1994 John Wiley & Sons, Inc.
Use of empirical polarity parameters to describe polymer/liquid interactions: Correlation of polymer swelling with solvent polarity in binary and ternary systems
Authors: Jonquières Anne , Roizard Denis , Lochon Pierre
Published: April 2003

Dimroth and Reichardt polarity parameters ET(30) have been used, in a new approach, to quantitatively describe the swelling features due to polymer liquid interactions in binary and ternary systems. With the help of a polyurethaneimide (PUI) synthesized from polytetramethyleneglycol 650, sorption of pure liquids was first examined, and it was shown that a linear relationship between the molar swelling Gm and the ET(30) values well fits the experimental data of each of the two series studied, i. e., aliphatic alcohols and linear ethers: Gm = a+b ET(30). The slope value b, regarded as the sensitivity of the polymer to the liquid polarity, is 3 times higher for the aprotic series. The proposed correlation was further proved valid from the study of published results concerning nine binary systems polymer–liquid, whatever the polarity of the liquids in a given family (alcohols, esters, ketones, hydrocarbons) and the nature of the polymer. Finally, that method was tested on two types of PUI‐alcohol‐ether ternary systems, and it was found for each case that the partial molar swelling due to an homologous set of solvents can also be described by a similar law. © 1994 John Wiley & Sons, Inc.
Influence of ABS type on morphology and mechanical properties of PC/ABS blends
Authors: Lombardo B. S. , Keskkula H. , Paul D. R.
Published: April 2003

The morphology and the mechanical properties of polycarbonate (PC) blends with different acrylonitrile–butadiene–styrene (ABS) materials were investigated. PC/ABS blends based on a mass‐made ABS with 16% rubber and large (0.5–1μm) rubber particles are compared to blends based on an emulsion‐made ABS with 50% rubber and small, monodisperse (0.12 μm) rubber particles over the full range of blend compositions. The blends with the bulk ABS showed excellent impact strength for most compositions, and those containing 50 and 70% PC exhibited ductile to brittle transition temperatures below that of PC. The blends with the emulsion ABS showed excellent toughness in sharp notch Izod impact tests at room temperature and in standard notch Izod impact tests at low temperatures near the Tg of the rubber. By melt blending the various ABS materials with a styrene–acrylonitrile (SAN 25) copolymer, materials with lower rubber concentrations were obtained. These materials were used in blends with PC to make comparisons at constant rubber concentration of 5, 10, and 15%. The results of this investigation show that brittle ABS materials can produce tough PC–ABS blends. It is apparent that small rubber particles toughen PC–ABS blends at lower rubber concentrations and at lower temperatures than is possible with large rubber particles. However, additional work is needed to understand the nature of toughening in these PC–ABS blends with different rubber phase morphologies. It is of particular interest to understand the exceptional ductility of some of the blends at low temperatures. © 1994 John Wiley & Sons, Inc.
Morphology and mechanical properties of biaxially oriented films of polypropylene and HDPE blends
Authors: Kim Woo Nyon , Hong Suk‐In , Choi Jin‐Sung , Lee Kwang‐Ho
Published: April 2003

Biaxially oriented films of blends of high‐density polyethylene (HDPE) with polypropylene (PP) homopolymer and PP copolymers prepared by twin‐screw extrusion and lab‐stretcher have been investigated by scanning electron microscopy (SEM), polarized microscopy, differential‐scanning calorimeter, and universal testing machine. Three different kinds of PP copolymers were used: (i) ethylene–propylene (EP) random copolymer; (ii) ethylene–propylene (EP) block copolymer; (iii) ethylene–propylene–buttylene (EPB) terpolymer. In the SEM study of the morphology of films of HDPE with various PP blends, phase separation is observed between the PP phase and the HDPE phase for all blends and compositions. In all blends, HDPE serves to reduce the average spherulites size, probably acting as a nucleating agent for PP. The reduction of spherulite size appeared most significantly in the blend of EPB terpolymer and HDPE. A large increase of crystallization temperature was found in the blend of EPB terpolymer and HDPE compared with the unblended EPB terpolymer. For the blend of EPB terpolymer and HDPE, the improvement of tensile strength and modulus is observed with an increase of HDPE content, and this can be considered as a result of the role of HDPE in reducing average spherulite size. © 1994 John Wiley & Sons, Inc.