bluuebunny/crossref_metadata_2025 huggingface dataset:
The preparation and characterization of new polyether ketone‐tetraethylorthosilicate hybrid glasses by the sol‐gel method
Authors: Noell John Lee W. , Wilkes Garth L. , Mohanty Dillip K. , McGrath James E.
Published: April 2003

In recent years, tetraethyl orthosilicate (TEOS) has been used as a precursor in preparing inorganic glasses. The technique, known as the sol‐gel process involves a two step poly(hydrolysis‐condensation)reaction sequence. The work presented here is concerned with the utilization of a suitably functionalized oligomeric “glassy” organic polymeric component in this two step sequence. In particular, an amine terminated amorphous poly(arylene ether) ketone, (PEK), end capped with isocyantonropyl triethoxy silane was used to synthesize a hybrid network with TEOS. Low incorporation of the PEK oligomers into the network caused by early vitrification can be eliminated by carrying out reactions at elevated temperatures. A systematic change in mechanical and physical properties of the hybrid glass has been found with TEOS content and the annealing temperatures. A model for the network has been proposed based on structural and morphological evidence.
Preparation of high‐modulus and high‐strength fibers from high molecualar weight poly(ethylene terephthalate)
Authors: Ito Masayoshi , Takahashi Katsumi , Kanamoto Tetsuo
Published: April 2003

High molecular weight poly(ethylene terephthalate) (PET) was obtained by solid‐state polymerization of solution‐grown crystals of PET that were prepared from commercially available PET. The intrinsic viscosities of the sample before and after the polymerization were 0.67 and 2.41 dL/g, respectively. As‐spun fibers from the high molecular weight material were prepared by a solution spinning method using two kinds of solvents: nitrobenzene (NB) and a mixture of hexafluoro‐2‐propanol and dichloromethane (HD). Both as‐spun fibers could be drawn up to a draw ratio of 12–13 by a two‐stage drawing technique. The highest tensile modulus and strength of 275 g/d (34.4 GPa) and 15 g/d (1.9 GPa), respectively, were obtained for the drawn fibers from the HD system. These values were 15%–20% higher than those achieved for the drawn fibers from the NB system. The difference was explained on the basis of the morphological differences of asspun fibers and the extent of molecular degradation during processing observed between the two series.
Graft copolymerization of collagen with N, N, N′, N′‐tetra (2‐hydroxypropyl) ethylene diamine methacrylate by use of potassium persulfate as an initiator
Authors: Patil D. R. , Smith D. J.
Published: April 2003

Graft copolymerization of collagen with N,N,N′,N′‐tetra (2‐hydroxypropyl) ethylene diamine methacrylate (THPEDM) was carried out in an aqueous medium using potassium persulfate as the radical initiator. Collagen‐g‐poly(THPEDM) was characterized by the percent yield and the copper chloride test. The percentage of grafting was determined as functions of concentration of monomer, concentration initiator, reaction time, and temperature.
Observation technique of polymer micelle by using transmission electron microscope
Authors: Ishikawa Satoshi , Fukutomi Takashi
Published: April 2003

The method, established by Price et al. to observe the polymer micelle, was modified and applied to the region of high polymer concentration. The novelty of our method consists of the preparative method of the specimen for transmission electron microscopy. Polymer solution was diluted and solvent was evaporated rapidly before the micelle was decomposed. As a result, dilution ratio had no effect on the decomposition of polymer micelle, and the original micelle structure was conserved over 10 wt % block copolymer solution if the operations were carried out within 30 min. This time limit related to the concentration of solution.
Thermal degradation of poly(aryl‐ether‐ether‐ketone): Experimental evaluation of crosslinking reactions
Authors: Day M. , Sally D. , Wiles D. M.
Published: April 2003

Poly(aryl‐ether‐ether‐ketone) (PEEK) has been heated at 400°C in both nitrogen and air. The extent of thermal degradation has been monitored by a variety of techniques including: solution viscometry, UV‐visible spectroscopy, 13C high‐resolution cross‐polarization/magic angle spinning nuclear magnetic resonance and Fourier transform infrared spectroscopy. The results indicate, that in a nonoxidative environment such as nitrogen, PEEK is relatively stable at 400°C for periods up to 6 h. Under oxidative conditions chain scission reactions occur and crosslinks are formed causing a reduction in the crystallizability of the material and discoloration of the polymer. The spectroscopic evidence suggests that the chain cleavage occurs adjacent to the carbonyl functional groups. Subsequent hydrogen abstraction from the aromatic ring then leads to crosslinking between adjacent aryl rings.
Cement hydrate catalyzed hydrolysis of polyimide lightweight materials
Authors: Sugama T. , Kukacka L. E. , Carciello N.
Published: April 2003

Polymide (PI) resins which are produced by an in situ imidization condensation reaction of polyamic acid (PAA) precursors were evaluated for use as binders in high‐temperature performance lightweight cement‐filled material systems. Unfortuanately, the presence of partially hydrated cement in the system led to strength retrogression at room temperature. Significant mechanical failure was observed upon exposure of the specimens to steam at > 150°C. This was found to be due mainly to alkali catalyzed hydrolysis of the functionaries of unreacted PAA adjacent to the cement surfaces and the imide rings of PI matrices. The formation of Ca‐complexed carboxylate salts derived from the hydrolysis resulted in chain scission of the polymer, thereby decreasing the mechanical strength, and making the composites unsuitable for use in aqueous environments.
Nitrogen plasma treatment of polyethylene and polystyrene in a remote plasma reactor
Authors: Foerch Renate , Mcintyre N. S. , Sodhi R. N. S. , Hunter D. H.
Published: April 2003

The effect of a remote nitrogen plasma on polyethylene and polystyrene was studied. The gas flow rate, the dilution of reactant gas, exposure times, and reactor base pressure were all found to have a large impact on the efficiency of nitrogen incorporation. Optimum conditions caused 18 atom % nitrogen to be incorporated within 20 seconds for polyethylene and 10 seconds for polystyrene. Studying a remote nitrogen plasma treated polyethylene sample over a period of 1 month indicated that except for a drop in the % N on initial exposure to air the concentration of nitrogen on the surface remained steady within the experimental limits. Angle resolved photoelectron spectroscopy indicated that nitrogen is incorporated to a depth below the analysis depth of XPS.
Surface characteristics of fluoroalkylsilicone—poly(methyl methacrylate) block copolymers and their PMMA blends
Authors: Inoue Hiroshi , Matsumoto Akihiro , Matsukawa Kimihiro , Ueda Akira , Nagai Susumu
Published: April 2003

Surface properties of fluoroalkylsilicone—poly(methyl methacrylate) block copolymers and their poly(methyl methacrylate) (PMMA) blends have been intensively studied to draw a relationship between surface segregation behavior and adhesion performance. The fluoroalkylsilicone—PMMA block copolymers containing thre kinds of fluoroalkyl side chains (i.e., 3,3,3‐trifluoropropyl) (CF3CH2CH2−, abbreviated as TFP), tridecafluoro‐1,1,2,2‐tetrahydrooctyl [F3C(CF2)5CH2CH2−, TFO], and heptadecafluoro‐1,1,2,2‐tetrahydrodecyl groups [F3C(CF2)7CH2CH2−, HFD] on the siloxane chains were prepared according to the macroazoinitiator method. Contact angle measurement and X‐ray photoelectron spectroscopy (or ESCA) were used to obtain structural information on the surface of the solution‐cast films. A significant effect of fluroalkyl groups on the surface accumulation not only in silicon but also fluorine atoms were observed for relatively long fluoroalkyl side chains (i.e., TFO and HFD). On the contrary, TFP group was found to be effective to orient to the hydrophilic surfaces (i.e. glass‐side surfaces). The surface accumulation of fluoroalkyl groups in the films was also reflected by the 180° peel strength against pressure‐sensitive adhesives as a measure of the adhesion performance. These results indicated that incorporation of relatively long fluoroalkyl groups much enchanced the surface hydrophobicity (and/or oleophobicity) of solution‐cast films in addition to that of the siloxane‐enriched surfaces. The composition and orientation of the functional groups on the surface were also speculated based on ESCA data.
Solvent effect on thermal degradation of polystyrene
Authors: Sato Shimio , Murakata Tadahiro , Baba Syunji , Saito Yasunobu , Watanabe Sinya
Published: April 2003

The thermal degradation of polystyrene (PS) in various kinds of solvents was studied in the temperature range from 300 to 450°C. The conversion of PS to low molecular weight products was dependent on the hydrogen donating ability of the solvents used: Solvents with greater donating ability resulted in less conversion of PS. A different degradation behavior was evident when phenols or other kind of solvents were used. These reaction properties are explained with a proposed degradation mechanism that includes hydrogen transfer steps from solvents to Intermediate PS radicals and from PS to the solvent radicals.
Viscoelastic properties of UV‐curing ink systems
Authors: Amari Takeshi , Kishi Susumu , Watanabe Koichiro
Published: April 2003

Mechanical properties such as tensile strength, relaxation modulus, creep compliance, and storage and loss moduli of UV‐curing ink systems were examined at various drying stages. Acrylic‐based binder consisting of epoxy acrylate prepolymer and trifunctional monomer were used as UV‐curing systems. For the UV‐cured specimen containing a large quantity of trifunctional monomer a highly crosslinked network structure was formed at comparatively short irradiation time, however, the sample lacks toughness and nonlinear rheological behavior was observed. On the other hand, for the specimen containing a large amount of epoxy prepolymer, a uniform network structure was formed and the ultimate strength increased with the growing network structure. In the temperature sweep experiments for storage and loss moduli, two transitions were observed. The transition observed above 10°C shifts to higher temperature and becomes broader with increasing irradiation time. The transition which is associated with a relaxation in the crosslinks was observed at −70°C and the height of the G″ peak increased with increasing irradiation time.
Adsorption of γ‐globulin on polymer surfaces having various chemical and physical structures
Authors: Kumakura Minoru , Yoshida Masaru , Asano Masaharu
Published: April 2003

The adsorption of human γ‐globulin on polymer surfaces having various chemical and physical structures was studied. The γ‐globulin adsorption on the crosslinked, rigid polymers of polyethyleneglycol dimethacrylate was considerably affected by the length of oxyethylene chains, in which the hydrophilicity of the polymers increased as the oxyethylene chains lengthened. The γ‐globulin adsorption on the rigid polymers of tetraethyleneglycol dimethacrylate (or diacrylate) was lower than other soft polymers such as hydrogel, owing to the presence of oxyethylene chains. The polymer having a porous structure appeared to be a high adsorption material for the γ‐globulin and the degree of the adsorption varied with pore size.
Graft copolymerization of acrylic acid onto jute fibers initiated by quinquivalent vanadium
Authors: Samal Rajani K. , Dash Sabyasachi , Sahu Abani K.
Published: April 2003

Graft copolymerization of acrylic acid onto jute fibers was carried out with quinquivalent vanadium as initiator in an aqueous sulphuric acid medium under nitrogen atmosphere. The graft yield was influenced by reaction time, temperature, concentrations of acid, monomer, initiator, reaction medium, and base polymer. Grafting has also been carried out in presence of various organic solvents. It has been observed that the maximum graft yield 56.7% was obtained at 50°C for [AA] = 1.453 M, [V+5] = 15 X 10−3 M, acid (2.12 M) and for a reaction time of 6 h. The tensile properties, dye‐uptake ability, and absorption of water and water vapours of the grafts have also been studied.
Thermoplastic matrix composites by aqueous electrocopolymerization onto graphite fibers
Authors: Iroh Jude , Bell J. P. , Scola D. A.
Published: April 2003

Electrocopolymerization of 3‐carboxyphenyl maleimide and styrene onto Hercules AS‐4 graphite fiber surfaces has been successfully carried out from an aqueous solution containing monomers and dilute sulfuric acid. Initiation of copolymerization of the monomers dissolved in a small amount of dimethylacetamide is achieved by constant‐current electrolysis in the cathodic chamber of a three‐compartment electrolysis cell. Polymerization is initiated at the fiber surfaces; little polymer is formed in the cell solution. Electrocopolymerization is very consistent and rapid. The amount of polymer increases predictably with increasing comonomer concentration and current density. Using a 0.4 M (1 : 1) comonomer concentration, 0.0125 M sulfuric acid solution, and a current density of 20 mA/g, more than 60 wt % of copolymer coating per unit weight of graphite fibers is obtained within thirty minutes. Thermal gravimetric analysis showed the copolymer to be very stable at elevated temperatures and has initial and final decomposition temperatures of 430 and 520°C, respectively. The glass transition temperature measurement of the copolymer coatings was carried out by differential scanning calorimetry. A single glass transition temperature was obtained of about 210°C for most samples. The glass transition temperature of the copolymers did not change significantly with changing comonomer feed composition. Functional group and compositional analysis of the copolymer was done by FTIR spectroscopy. The copolymer composition remained relatively the same for copolymers made from different styrene/3‐carboxyphenyl maleimide feed composition, confirming a strong tendency toward alternation for the system.
Characterization of thermosetting polymer mortars
Authors: Vipulanandan C.
Published: April 2003

The behavior of epoxy and polyester mortars were studied under various curing conditions, temperatures, and strain rates. The effect of curing temperatures on the compressive stress–strain relationships of polymers and polymer mortars were also investigated. The properties of interest of the two polymer mortars cured under optimum conditions are the compressive strength, splitting tensile strength, compressive modulus, and compressive stress–strain relationship. The compressive strength of polymer mortars are related to the testing temperature and logarithmic strain rate. The compressive modulus and splitting tensile strength of polymer mortars are related to their compressive strength. A new nonlinear constitutive model is proposed to predict the complete compressive stress–strain behavior of epoxy and polyester polymer mortars.
13C CP/MAS NMR study on alkali cellulose
Authors: Yokota Hiromu , Sei Toshiya , Horii Fumitaka , Kitamaru Ryozo
Published: April 2003

The phase transition from cellulose to alkali cellulose (Na‐Cell) and the phase structure of Na‐Cell have been investigated by CP/MAS 13CNMR spectroscopy. It has been found from the 13CNMR spectra that both crystalline and noncrystalline components of cellulose decrease in resonance intensities in the transition process from cellulose to Na‐Cell I, suggesting that the noncrystalline and the crystalline regions of cellulose are converted to Na‐Cell simultaneously. The conversion model is considered as follows: The crystalline part imposes some restriction on the swelling of the noncrystalline part of cellulose, but the conversion of both parts to Na‐Cell may be possible when the swelling prevails in the whole microfibril as a result of the penetration of the alkaline solution into the crystalline part. Secondly, the 13C spin‐lattice relaxation times (T1) have been measured to elucidate the phase structure of Na‐Cell. Though two T1 values are obtained for each carbon of Na‐Cell except for C6 carbon, Na‐Cell has a homogeneous solid structure which is composed of the crystalline regions with a small heterogeneity.
Threshold tear strength of carbon black filled rubber vulcanizates
Authors: Bhowmick Anil K. , Neogi Chanchal , Basu S. P.
Published: April 2003

Threshold tear strength of unfilled and filled Natural Rubber (NR) and Styrene‐butadiene Rubber (SBR) vulcanizates has been determined. Carbon black (N‐220, N‐375, N‐330, N‐550, and N‐660) and china clay are used as fillers. Threshold tear strength varies from 80 J/m2 to 1200 J/m2. Threshold tear strength is found to be dependent on filler loading, nature of filler, and small strain modulus. The results are explained with the help of strain energy density, tear tip diameter, and the excess energy required to stress the many bonds before breaking one of them.
A highly fluorinated epoxy resin: Post‐curing and transition behavior
Authors: Twardowski T. E. , Geil P. H.
Published: April 2003

The post‐curing and transition behavior of a highly fluorinated epoxy resin system was characterized. The material was found to have low temperature transitions similar to those found in DGEBA. The cure was discovered to be inhibited by the presence of CO2. The glass transition was broad and near room temperature, resulting in rapid aging characteristics.
Rheokinetic changes during polyurea reactions in solution
Authors: Wang K. J. , Hsu T. J. , Lee L. James
Published: April 2003

The viscosity rise and conversion profile of polyurea reaction in solution were measured using a Haake viscometer and an FTIR, respectively. In a three‐component polyurea system, it was found that the liquid–solid transition is dominated by the microphase separation from the formation of hard segments. The formation of soft segments mainly contributes to the initial viscosity buildup. A series of experiments were carried out to study the effects of resin composition, solvent concentration, and reaction temperature on the viscosity rise and gelation of polyureas.
The ductile–brittle transition in macroscopic tensile tests on polyethersulfone
Authors: Plummer C. J. G. , Donald A. M.
Published: April 2003

In tensile tests of polyethersulfone it is found that, as the temperature is raised, samples of low molecular weight exhibit a ductile–brittle transition. Thus, this normally tough polymer becomes less so at evaluated temperatures. Ultimately as the temperature is raised to close to Tg, more ductile behavior returns as homogeneous deformation occurs. For high molecular weight samples, at the strain rates used (∽ 10−4 s−1) ductile behavior was found at all temperatures with a neck forming as deformation proceeds. These findings can be rationalized in terms of a disentanglement model for craze formation: crazing via a disentanglement mechanism will be favoured by low molecular weight and high temperature, thus allowing craze‐initiated fracture to intervene before shear deformation has taken place. A comparison is made both with earlier work on thin films of polyethersulfone and with a theoretical model.
Radiation‐induced grafting of regenerated cellulose hollow‐fiber membranes
Authors: Lim S. L. , Fane A. G. , Fell C. J. D.
Published: April 2003

Gamma ray radiation‐induced grafting was carried out on regenerated cellulose hollow‐fiber membranes as the substrate polymer and empolying a number of monomer and solvent systems. The monomers used include styrene, maleic acid, acrylonitrile, acrylamide, and acrylic acid. Characterization of the graft copolymers was done by measuring their tensile properties in terms of breaking loads and breaking extensions. Permeating properties of the modified membranes were also assessed by measuring the water flux of each membrane. Membranes grafted with styrene showed improved tensile and permeation properties, while co‐irradiation graftings using acrylamide and acrylic acid as monomer only showed improved tensile properties but not the permeation properties of virgin membranes. For a given monomer, the pre‐irradiation grafting technique generally produced membranes with lower water fluxes than those produced using co‐irradiation grafting.
Solid phase graft copolymerization: Effect of interfacial agent
Authors: Lee Sunggyu , Rengarajan Ramesh , Parameswaran Vetkav R.
Published: April 2003

Solvents or interfacial agents have been used as media to perform various polymerization reactions. The selection of solvents to provide the appropriate medium for the reaction has opened up a totally new area for research. In the present study, three solvents, viz., toluene, decalin, and tetralin, were investigated in the preparation of polypropylene‐maleic anhydride copolymers by solid phase graft copolymerization. The graft level was quantitatively determined by wet chemical methods and qualitative confirmations were made by Fourier transform infrared spectroscopy. It was found that toluene and decalin increased the surface area for reaction by swelling the polymer. The graft level increased with an increase in concentration of toluene and decalin. In the case of tetralin, the graft level decreased as the concentration of the solvent in the reactant mixture increased. It was experimentally observed that unlike toluene and decalin, tetralin did not cause swelling of the polymer at the reaction conditions. Therefore, the surface area available for reaction would be less when tetralin is used. Moreover, since tetralin dissolves the polymer rather than causing it to swell, the contact area for the reaction is further diminished by the formation of a monomolecular layer of solvent insulating the monomer from the polypropylene.
Characterization of polymer blends and alloys by constrained profile‐analysis of X‐ray diffraction scans
Authors: Murthy N. S. , Minor H. , Akkapeddi M. K. , Buskirk B. Van
Published: April 2003

The composition of polymer blends and alloys and the crystallinity and crystallite size/perfection of each of the components are determined by X‐ray diffraction (XRD) methods. A profile‐fitting procedure is used to resolve the XRD scan into crystalline and amorphous peaks corresponding to each of the polymers. The procedure uses templates derived from the XRD scans of the homopolymers as constraints. The usefulness of this method for studying the influence of blending and grafting is illustrated by analyzing the data from two‐component blends with and without the graft copolymer compatibilizer.
Surface‐active agents based on propoxylated lignosulfonate
Authors: Hornof V. , Hombek R.
Published: April 2003

A commercial lignosulfonate was modified by the addition of propylene oxide. The products obtained had a degree of propoxylation ranging from 19% to 49%. The modified lignosulfonates retained high solubility in water and high salinity tolerance, while their interfacial activity increased dramatically in comparison with the original lignosulfonate. Aqueous solutions of propoxylated lignosulfonates exhibited very low interfacial tensions (down to 10−1−10−2mN/m) against both a pure hydrocarbon (isooctane) and a crude oil (Lloydminster crude).
A mechanistic interpretation of the zero order release from pendent chain‐linked glassy and swollen hydrogels
Authors: Shah S. S. , Kulkarni M. G. , Mashelkar R. A.
Published: April 2003

Zero order release of active ingredients, physically dispersed in the glassy hydrogels has been ascribed in the past to the case II transport of the penetrant medium into the glassy matrix (phase erosion). Surface erosion of the polymer by dissolution has also been shown to result in the zero order release of the dispersed/dissolved active ingredient. This communication reports the zero order release of the pendent chain‐linked p‐nitro benzoic acid and 2,4‐dinitro benzoic acid from glassy as well as swollen hydrogel matrices. The results have been elucidated on the basis of increase in the diffusivity of the active ingredient released by hydrolysis and the concomitant increase in the degree of swelling of the polymer matrix. This is the first reported finding of zero order release of an active ingredient from the matrix device as a result of bulk erosion.
Preparation of ABS (acrylonitrile/butadiene/styrene) latexes using hydroperoxide redox initiators
Authors: Daniels E. S. , Dimonie V. L. , El‐Aasser M. S. , Vanderhoff J. W.
Published: April 2003

The 80/20 (w/w) azeotropic styrene/acrylonitrile mixture was copolymerized at 35, 50, and 70°C in crosslinked polybutadiene seed latexes of varying particle size (range 113–242 nm) using the t‐butyl or cumene hydroperoxide/sodium formaldehyde sulfoxylate dihydrate/EDTA‐chelated Fe+2 redox initiator. Other initiators used for comparison were: (1) ammonium persulfate at 70°C; (2) ammonium persulfate/sodium bisulfite redox initiator at 35 and 50°C; (3) oil‐soluble, 2,2'‐azobis(2,4‐dimethylvaleronitrile) at 50°C. The following polymerization parameters were varied systematically: (1) polybutadiene seed latex particle size; (2) monomer/polymer swelling ratio; (3) polymerization temperature; (4) type and concentration of initiator; and (5) mode (and duration) of initiator addition. The following parameters were determined: (1) polymer yield (final conversion); (2) variation of conversion with time; (3) morphology of the latex particles; (4) amount of coagulum; and (5) fraction of styrene/acrylonitrile monomer mixture grafted to the polybutadiene seed latex (defined here as grafting efficiency). For polymerizations using the t‐butyl or cumene hydroperoxide/sodium formaldehyde sulfoxylate dihydrate/EDTA‐chelated Fe+2 redox initiator, the rates of polymerization were faster, the grafting efficiencies were greater, and the amounts of coagulum were greater at 70°C than at 50 or 35°C. The rates of polymerization were decreased by decreasing the concentration of redox initiator or adding it incrementally. A 1.00/1.00/0.08 (w/w) t‐butyl or cumene hydroperoxide/sodium formaldehyde sulfoxylate dihydrate/EDTA‐chelated Fe+2 ratio gave reasonable polymerization rates at 35 and 50°C, and a 0.48/1.00/0.07 ratio, at 70°C. The latexes were stabilized during polymerization with 3% (based on seed solids) nonionic Igepal CO‐990 at 35°C, and 6% at 50 and 70°C. The grafting efficiency increased with decreasing particle size of the polybutadiene seed latex and decreasing monomer/polymer ratio. The rate of polymerization increased with decreasing monomer/polymer ratio. The monomer/polymer ratio also affected the morphology of the particles; higher values gave inclusions of poly(styrene‐co‐acrylonitrile) in the polybutadiene particles. There were no significant differences in polymerization kinetics or grafting efficiency between the t‐butyl and cumene hydroperoxides.
Multiphase materials with lignin. VIII. Interpenetrating polymer networks from polyurethanes and polymethyl methacrylate
Authors: Kelley Stephen S. , Ward Thomas C. , Glasser Wolfgang G.
Published: April 2003

Several types of interpenetrating polymer networks (IPNs) from polyurethane/polymethyl methacrylate (LPU/PMMA) on the basis of lignin were prepared. All composites were judged to possess two phase morphology. The composition and the presence of crosslinking were found to influence the thermal and mechanical properties of the solvent‐cast films. The mechanical properties were assessed by dynamic mechanical analysis and by tensile testing, and they were found to vary consistently with composition and the presence of crosslinks. The modulus behavior of the different IPNs could be explained by models which accounted for either dual phase continuity or phase inversion.
Radiation grafting of MMA onto PVC films
Authors: Hegazy El‐Sayed A. , Ebaid A. R. , El‐Sharabasy S. A. , Mousa A. M. , Hassan A. Y.
Published: April 2003

An approach to the problem of producing poly(vinyl chloride) (PVC) graft copolymer exhibiting good mechanical properties and electrical resistance that suits its uses as an electrical insulator has been investigated. Graft copolymerization of methyl methacrylate (MMA) onto PVC using γ‐radiation as initiator has been studied. PVC was chemically modified, and the effect of the change in its chemical and physical structure on its properties was investigated. In this grafting system, different solvents were tried and it was found that the most suitable diluent for the grafting of MMA onto PVC films is methanol. An appreciable improvement in tensile properties of the graft copolymer was achieved. The most suitable degree of grafting, concerning electrical insulation efficiency, was found to be near 80%. Gel determination in the graft copolymer was carried out, and a crosslinked network structure was formed. Increasing the crosslinking content in the graft copolymer leads to a decrease in the extent of swelling due to the less diffusivity of the solutions through such network structure.
An improved kinetic model for the autocatalytic curing of styrene‐based thermoset resins
Authors: Lam P. W. K. , Plaumann H. P. , Tran T.
Published: April 2003

The cure behavior of styrene‐based thermosets such as orthophthalic polyester, isophthalic polyester, and vinyl ester resins is characterized using both isothermal and dynamic differential scanning calorimetry (DSC) techniques. In the conventional autocatalyzed kinetic model, it is assumed that the isothermal cure reaction of a thermoset goes to completion, which usually leads to a poor fit with the DSC kinetic data. It appears from the conversion‐time profiles that the cure reaction reached a plateau value (αu) less than unity. This is not unexpected, as the molecular mobility of the resin system decreases as the network cures. In this work, we have refined the model to remove this restrictive assumption by taking the total ultimate conversion (αu) into account in the computation. This improved model permits us a better prediction of the course of the cure reaction of the styrene‐based thermosets under isothermal and dynamic conditions. In addition, the cure kinetics of the three thermoset resins are studied and compared on the basis of several kinetic parameters including conversion, cure rate, reaction rate constant, heat of cure reaction, half‐life, and Arrhenius parameters. The reactivity of these resins when arranged in ascending order is found to be: vinyl ester < orthophthalic polyester < isoththalic polyester.
Synthesis and water absorbility of base‐hydrolyzed starch‐g‐poly(acrylonitrile‐co‐sodium allylsulfonate)
Authors: Kejun Yao , Benlian Wang
Published: April 2003

Grafting of mixed vinyl monomers, acrylonitrile (AN) and sodium allylsulfonate (SAS), onto starch was carried out in aqueous, gelatinized corn starch by using ceric ammonium nitrate (CAN) as an initiator at 30°C under a nitrogen atmosphere. Conversion (%) and percent graft (%) were determined as a function of (1) molar ratios of feed composition, (2) concentration of CAN, (3) HNO3 concentration, and (4) reaction temperature. The monomer, SAS, is found to decrease percent graft of mixed monomers onto starch. The graft copolymer, starch‐g‐poly(AN‐co‐SAS), can be hydrolyzed by varying amounts of aqueous NaOH at 80–100°C to obtain base‐hydrolyzed starch‐g‐poly(AN‐co‐SAS). The hydrolyzed product is an excellent water absorbent, which absorbs 1900 times its weight of deionized water. Water retention reached over 90% at 10 kg/cm2, and the toleration of electrolyte (synthetic urine) attained was better than that of hydrolyzed starch‐g‐polyacrylonitrile (H‐SPAN).
Gravimetric measurements of steady‐state moisture uptake in spin‐coated polyimide films
Authors: Pranjoto Hartono , Denton Denice D.
Published: April 2003

Polyimide (PI) is an insulating polymer that is finding increased use in the semiconductor industry as an intermetal dielectric, passivation coating, and planarization layer. It has a low dielectric constant (3.5 at audio frequencies) and can be processed at temperatures below 450°C. These features make PI attractive to the integrated circuit industry. One disadvantage of this material is that, like most polymers, it is hygroscopic. Moisture can lead to such reliability problems in integrated circuits as increased insulator conductivity, loss of adhesion, and corrosion. It is important to quantify the moisture uptake in polyimide so that the reliability implications of its use can be fully understood. In this study, the steady‐state moisture uptake of the model PI pyromellitic dianhydride‐oxydianiline (PMDA‐ODA) is reported. The moisture uptake is measured using a Cahn 1000 Microbalance with a 1‐μg resolution. The samples are prepared by spin‐coating one or more layers of the precursor polyamic acid onto 2‐in silicon substrates. The moisture uptake in these polymers is found to be linearly related to ambient relative humidity, and the maximum moisture uptake by weight is 3.2%. The moisture uptake in PI is also shown to be a bulk absorption rather than a surface adsorption phenomenon.
Crystallization, tensile, and impact behavior of polypropylene/polybutadiene blend
Authors: Gupta A. K. , Ratnam B. K.
Published: April 2003

A blend of isotactic polypropylene (PP) and polybutadiene (PBu), in the composition range 5–35 wt % PBu content, prepared by mixing in a two‐roll mill, is studied for crystallization, tensile, and impact behavior. Variations in crystallization behavior and the resulting morphology and structure are observed in both differential scanning calorimetry (DSC) and X‐ray diffraction measurements on this blend as a function of blend composition. Impact and tensile properties are studied in the entire blend composition range. Analysis of tensile properties data in terms of the various theoretical models is attempted to obtain better insight into the interphase adhesion and stress concentration effect in this blend. The effects of blend composition on the state of dispersion and morphology of dispersed phase droplets and correlation of tensile properties with the crystallization parameters of PP component are also presented.
Arylidene polymers III. A new route for the synthesis of conjugated polymers and copolymers of arylidenecycloalkanones, characterization, and some molecular orbital studies of its model
Authors: Abd‐Alla Mohamed A. , El‐Shahawy Anwar S.
Published: April 2003

A new class of polyconjugated polymers, namely poly(2,5‐arylidenecyclopentanone) and poly(2,6‐arylidenecyclohexanone) has been obtained by condensation of cyclopentanone or cyclohexanone with terephthalaldehyde using alcoholic potassium hydroxide as a catalyst. Copolymerization of the corresponding monomers was also carried out. To characterize these polymers model compounds were prepared from cyclopentanone or cyclohexanone and benzaldehyde. The structures of the model compounds were elucidated by IR, NMR, and elemental analyses. DSC measurements, thermogravimetric, and X‐ray analyses. From the SCF‐CI calculations, the 2,5‐dibenzylidenecyclopentanone, as a model compound, has the trans form. Furthermore, the charge densities of this model, its anionic and cationic forms, as well as the ionization potential and the electron affinity have been calculated.
Thermoanalytical characteristics of polycarboxylic acids investigated as durable press agents for cotton textiles
Authors: Trask‐Morrell B. J. , Andrews B. A. Kottes
Published: April 2003

Polycarboxylic acids are of great interest to the cotton textile industry as durable press agents because they do not release substances that require mandatory monitoring. Differential scanning colorimetric (DSC), thermogravimetric (TG), and differential thermogravimetric (DTG) techniques were used to study the thermal characteristics of a series of 10 polycarboxylic acids. Samples included di‐, tri‐, and tetra‐functional compounds some of which contained olefinic linkages, hydroxyl substituents, and cyclic structure. Thermogravimetric data at simulated fabric cure temperatures was used to assess the potential of a compound for use as a textile finishing agent. In high‐temperature studies the compounds were readily distinguishable in DSC analyses. General characteristics such as increases in total heats of reactions were found to be related to the number of functional groups. These results also provided support for a mechanism for the reaction of polycarboxylic acids with cellulose through an anhydride intermediate.
The nature of adhesion in composites of modified cellulose fibers and polypropylene
Authors: Felix Johan M. , Gatenholm Paul
Published: April 2003

Cellulose fibers were surface modified with polypropylene–maleic anhydride copolymer. The physical properties of such fibers were characterized by contact angle measurements, and the chemical structure was identified with ESCA and FTIR. ESCA showed that the modifying agent was localized at the surface of the fibers. The modified fibers were compounded with polypropylene, and composites with various amount of fibers were manufactured by injection molding. All mechanical properties were improved when treated fibers were used. SEM showed improved dispersion, wetting of fibers, and adhesion. The nature of adhesion was studied using FTIR. It was found that the surface modifying agent is covalently bonded to the fibers through esterification. The degree of esterification is enhanced by activating the modifying agent before fiber treatment. This study has shown the effects of treatment conditions on activation of reactive species and chemical reaction between fiber and modifying agent. Moreover, a better understanding has been achieved of the nature of adhesion for the system.
Real‐time monitoring of the cure reaction of a TGDDM/DDS epoxy resin using fiber optic FT‐IR
Authors: George G. A. , Cole‐Clarke P. , St. John N. , Friend G.
Published: April 2003

The feasibility of using remote FT‐IR spectroscopy to monitor the gelation reaction of an epoxy resin used in advanced composite materials has been studied. The commercial epoxy resins MY720 and MY721, consisting mostly of tetraglycidyl 4,4′‐diaminodiphenyl methane (TGDDM) were cured with diaminodiphenylsulfone (DDS) in a microcapillary cell connected to an FT‐IR spectrometer by single silica fiber optics. By operating in the near‐IR, direct measurement of the consumption of epoxide and primary amine and growth in hydroxyl groups was possible. It was found that the primary amine band at 5067 cm−1 was the most sensitive for rapid and accurate real‐time monitoring of the cure reaction up to gelation. The temperature dependence of amine consumption from 135 to 180°C gave an activation energy of 70 kJ mol−1 for the cure reaction in agreement with DSC. Several artefacts involved in using fiber optic FT‐IR in this way have been identified.
Polymer‐supported molybdenum and vanadium catalysts for epoxidation of alkenes by alkyl hydroperoxides
Authors: Stamenova R. T. , Tsvetanov C. B. , Vassilev K. G. , Tanielyan S. K. , Ivanov S. K.
Published: April 2003

Polymer‐supported molybdenum and vanadium catalysts were synthesized using gel‐type crosslinked copolymers with microheterogeneous structure. The supports were composed of inert ethylene–propylene rubber and crosslinked high molecular weight poly(ethylene oxide) matrices and polymeric ligands grafted or forming interpenetrating networks: poly(acrylic acid), poly(methacrylic acid), poly(4‐vinylpyridine), and polyvinyl alcohol. Catalytic activity and selectivity of some of these complexes were tested in epoxidation of styrene by ethylbenzene hydroperoxide. Molybdenyl cations are strongly coordinated with pyridine‐containing copolymers giving catalysts of high activity and selectivity. They provide conversion and selectivity above 70%. Because of the microheterogeneous mosaic‐like structure of the supports, better accessibility of the active sites is achieved.
The flocculation of cane sugar muds with acrylamide–sodium acrylate copolymers
Authors: Crees O. L. , Senogles E. , Whayman E.
Published: April 2003

The flocculation of cane sugar muds with commercial acrylamide–sodium acrylate copolymers has been investigated through the measurement of settling rates and residual turbidities. The flocculation efficiencies of the copolymers were observed to depend on their composition, microstructure, and molecular weight, and the zeta potential of the mud particles. Adsorption of polymer at the surface of the particles was shown to occur through interaction with the acrylate groups. The experimental results are consistent with a bridging mechanism for the flocculation process, in which an observed optimum copolymer composition is associated with polymer adsorption which is sufficiently strong to resist mild shear forces yet allows the extension of polymer “loops” and “tails” into solution.
Kinetics of hydrolysis and thermal degradation of polyester melts
Authors: Seo Kab S. , Cloyd James D.
Published: April 2003

Polyester melts exhibit two discrete degradation rates depending on the moisture content in the solid state. The initial fast rate is very sensitive to the moisture content while the later slow rate is not sensitive to the moisture content. The former is attributed to hydrolysis and the latter is attributed to thermo‐oxidative degradation. A combined kinetic equation which represents both hydrolysis and thermo‐oxidative degration of the polyester melt is proposed. The model equation agrees well with the experimental data. A method to determine hydrolytic and thermal degradation rate constants, moisture content, molecular weight for polyesters by means of a melt viscometry is discussed.
Effect of mineral and organic acids on radiation grafting of styrene onto polyethylene
Authors: El‐Assy Nasef B.
Published: April 2003

A study has been made on the effect of mineral and organic acids on the radiation‐induced graft polymerization of styrene onto low‐density polyethylene films. Effects of different solvents and dose rate of irradiation on the grafting yield were also investigated. The influence of irradiation time and monomer concentration in the presence and absence of acid on the initial rate and grafting yield was studied. The dependence of the grafting rate on monomer concentration was found to be of the order 1.34 (in absence of acid), 0.61 (in presence of HCl), and 1.25 (in presence of oxalic acid). Such acid enhancement of the radiation grafting process is of practical importance from an economical point of view.
Development of seawater‐resistant polyurethane elastomers for use as sonar encapsulants
Authors: Stack G. M. , Miller J. M. , Chang E. Y.
Published: April 2003

Polyurethane systems based on aliphatic diisocyanates were evaluated for suitability for use as underwater transducer encapsulants. A preliminary evaluation was performed to select the most promising urethane systems for further development. An investigation was then undertaken to determine the effect of compositional changes on the properties of these urethanes. The compositional parameters investigated were the soft‐segment molecular weight, the prepolymer isocyanate content, the composition of the cure formulation, and the cure stoichiometry. These urethanes were subjected to long‐term aging in seawater. It was found that this exposure did not significantly effect the physical or dynamic mechanical properties of the urethane.
Sorption and transport of aqueous salt solution in polyurethane membrane at 25, 44, and 60°C
Authors: Harogoppad Shivaputrappa B. , Aminabhavi Tejraj M. , Balundgi Ramachandra H.
Published: April 2003

Sorption and transport of aqueous salt solutions in polyurethane elastomer has been investigated over the temperature interval of 25–60°C by using an immersion/weight gain method. The size of the ions has no significant effect on the penetrant transport coefficients. The sorption data have been explained in terms of the simple Fickian model. Attempts have also been made to estimate the transport parameters by applying corrections to include the spatial diffusivity of the liquids within the polymer sample. Temperature dependence of the transport coefficients has been used to estimate the activation parameters from the Arrhenius plots.
Depolymerization of poly(ethylene terephthalate) resin under pressure
Authors: Chen J. Y. , Ou C. F. , Hu Y. C. , Lin C. C.
Published: April 2003

The process of depolymerization of PET resin by EG glycolysis under pressure is investigated. The kinetics of this pressurized depolymerization of PET resin is discussed. It was found that the rate of depolymerization is dependent of temperature, pressure, and concentration ratio of EG to PET. The rate of depolymerization is proportional to the square of EG concentration and faster than that under atmospheric pressure. Glycolyzed products under pressure consist of the PET monomer, BHET, and oligomers, mostly dimer and trimer. An equilibrium between BHET and oligomers is attained quickly soon after the depolymerization step is completed in the case of a higher ratio of EG/PET used. In the case of lower ratio of EG/PET, the final product now consists of higher molecular weight of oligomers rather than monomer, dimer, and trimer.
Characterization of imidazole‐cured epoxy–phenol resins
Authors: Heise M. S. , Martin G. C. , Gotro J. T.
Published: April 2003

The physical and chemical properties of the diglycidyl ether of bisphenol A (DGEBA) cured with different concentrations of bisphenol A (BPA) and 2‐ethyl‐4‐methylimidazole (EMI‐24) were examined using Fourier transform infrared spectroscopy, differential scanning calorimetry, dynamic mechanical and dielectric analyses, and solvent extraction studies. The effects of the phenol‐epoxide and the secondary hydroxyl (R‐OH)‐epoxide reactions on the network formation process were analyzed using a recursive modeling technique to obtain expressions for the weight‐averaged molecular weight, the weight fraction solubles, and the gel point as a function of the extent of cure and the epoxide‐phenol reactant ratio. The sol fraction and the gel point predictions from recursive modeling studies of the network formation process agreed with the results obtained from the extraction studies. The results from the network modeling studies were also related to the thermal and rheological properties of the resin during cure.
Ion‐exchange copolymers based on tetrafluoroethylene, hexafluoropropylene, and acrylic acid
Authors: Kostov G. K. , Atanasov A. N.
Published: April 2003

Peroxide‐induced copolymerization of tetrafluoroethylene (TFE) with hexafluoropropylene (HFP) and acrylic acid (AA) at different molar ratios of monomers, reaction time, pressure, and initiator concentration was studied. By means of IR spectroscopy and temperature and phase characteristics of the copolymers obtained it was proved that a ternary copolymer of TFE, HFP, and AA was synthesized. Fluoro‐containing polymers with ion‐exchange capacities up to 0.8 meq/g were obtained. The composition of binary TFE‐HFP and ternary TFE‐HFP‐AA copolymers and some of their characteristics were determined. Copolymerization takes place mainly in the stationary state with an induction period. Polymerization rate R ∼ [In]0.7, which is presumably connected with chain transfer reaction to AA.