bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rubber‐modified epoxies. III. Analysis of experimental trends through a phase separation model
Authors: Moschiar S. M. , Riccardi C. C. , Williams R. J. J. , Verchere D. , Sautereau H. , Pascault J. P. 
Published: April 2003

AbstractA phase separation model was used to simulate the morphologies obtained in a system consisting of a diepoxide based on bisphenol‐A diglycidylether cured with a cycloaliphatic diamine, in the presence of an epoxy‐terminated butadiene‐acrylonitrile random copolymer (ETBN). A detailed analysis of experimental factors affecting resulting morphologies was previously reported. The model, based on a thermodynamic description through a Flory–Huggins equation, and constitutive equations for polymerization and phase separation rates, could explain most of the observed trends. A nucleation‐growth mechanism was believed to take place because of the very low values of interfacial tensions for this type of systems. Conditions which would lead to spinodal demixing are also discussed.
Tetrahydropyranyl‐ and furanyl‐protected polyhydroxystyrene in chemical amplification systems
Authors: Hesp Simon A. M. , Hayashi Nobuaki , Ueno Takumi 
Published: April 2003

AbstractTetrahydropyranyl‐ (THP) and furanyl‐ (THF) protected polyhydroxystyrene (PHS) polymers have been investigated for their potential use in conjunction with onium salt acid precursors to yield high‐sensitivity resist systems. The synthesized polymers have high transmittance at 248 nm (the wavelength used in next‐generation excimer laser, KrF exposure tools). At 248 nm the transmittance for a 1‐μm thick film is ∼ 80% (Abs = 0.097 μm−1). The acid sensitivity of the acetal functionality at room temperature is high, requiring careful handling of all materials to prevent any premature deprotection of the hydroxy group. The highest lithographic sensitivities obtained so far with a system consisting of poly(p‐tetrahydropyranyl‐oxy‐styrene) base resin and 1 mol % of bis (p‐tert‐butyl phenyl) iodinium triflate (TBIT) was ∼ 2 mJ / cm2. High‐resolution line and space patterns (0.35 μm) were obtained with a system comprising PHS‐p‐THP and an acid precursor, using an excimer laser step and repeat exposure at 248 nm.
Melt spinning of shear modified plasticized polystyrene
Authors: Qian J. W. , Rudin Alfred 
Published: April 2003

AbstractPolystyrene is not normally shear‐modifiable. Addition of small amounts of plasticizer (butyl benzyl phthalate) result in changes in melt viscosity and elasticity during extrusion. Fiber spinning experiments are shown to provide useful indications of the rheological state of polymers that are sensitive to shear history. Here, the density, modulus and work to rupture of lightly plasticized polystyrene is shown to vary with extrusion history of the material.
Role of itaconic acid in latex particle nucleation
Authors: Lock Michele R. , El‐Aasser Mohamed S. , Klein Andrew , Vanderhoff John W. 
Published: April 2003

AbstractItaconic acid, a carboxylated water‐soluble monomer, was examined in terms of its role in latex particle nucleation when copolymerized with acrylate monomers. From emulsion polymerizations in which the particle number concentrations were followed as a function of monomer conversion, it was found that the greater the amount of itaconic acid present, the larger the final latex particle diameter. This was interpreted as the result of the lower number of primary particles being initially nucleated. The above observations can be explained by the incorporation of the hydrophilic itaconic acid into acrylate oligomeric radicals that initially form. This incorporation increases the water‐solubility of the radicals such that a lower proportion of these radicals is likely to precipitate to form primary particles.
Fracture and structure of highly crosslinked polymer composites
Authors: Cook Wayne D. 
Published: April 2003

AbstractThe fracture toughness of silica filled dimethacrylate resins has been found to increase with the degree of cure of the network, and was previously attributed to increased crosslinking or the concomitant reduction in unreacted monomer (sol species). Studies of the dependence of the polymerization on the photoinitiator concentration and cure time of dimethacrylate resins illustrate the interrelation of the wt % sol and the degree of cure and reveal that a considerable amount of residual monomer remains in undercured networks, as predicted by simple gelation theory. In an attempt at separating the effects of residual monomer and crosslinking on the fracture behavior, several series of filled dimethacrylate and epoxy resins were studied in which the crosslink density and sol levels were independently varied without introducing significant changes in the chemical composition of the network. Although the fracture energy and toughness were raised by increasing the crosslink density in the epoxy resins, no significant variation was found for the dimethacrylates. Saturated analogues of dimethacrylates (used to represent residual monomer) significantly impaired the fracture resistance, suggesting that the reduction in residual monomer is responsible for the improved fracture toughness observed with postcured dimethacrylate networks.
Preparation and characterization of polyelectrolyte copolymers containing methyl methacrylate and 2‐hydroxyethyl methacrylate. I. Polymers based on methacrylic acid
Authors: Wen Shao , Yin Xiaonan , Stevenson William T. K. 
Published: April 2003

AbstractAcidic polyelectrolyte copolymers containing 2‐hydroxyethyl methacrylate (HEMA), methyl methacrylate (MMA), and methacrylic acid (MAA) were prepared by free radical polymerization to high conversion in solution. Copolymer yields were obtained by gravimetry (all in the 30–50% range), relative molecular weights estimated by intrinsic viscosity measurements (all in the 50–70 cc/g range), tacticity by 13C nuclear magnetic resonance (NMR) spectroscopy (all polymers predominantly syndiotactic with some atactic content), and composition by acid/base titrations in conjunction with 1H‐NMR spectroscopy (all close to the monomer charge ratios). Acid strengths or apparent pKa's were examined as a function of extent of ionization. Measurements performed in water indicated that the compact/extended coil transformation in predominantly syndiotactic polymethacrylic acid occurs also in copolymers of similar tacticity containing moderate to high concentrations of MAA. The apparent pKa of such polymers containing only small amounts of MAA did not vary with extent of ionization, indicating a low degree of interaction between the acid groups. In copolymer pairs containing similar amounts of MAA but differing HEMA and MMA contents, the polymer containing more HEMA appeared the stronger acid, presumably due to a better solvation of that polymer which would increase the net spatial charge–charge separation and decrease cooperative effects that lead to suppressed ionization.
Mooney scorch time of epoxidized natural rubber
Authors: Poh B. T. , Tan B. K. 
Published: April 2003

AbstractThe scorch property of accelerated sulfur vulcanization of three grades of expoxidized natural rubber (viz. ENR 10, ENR 25, and ENR 50) was studied by using Mooney Shearing Disk Viscometer in the temperature range of 100–180°C. Effects of accelerator types, concentration of accelerator, and carbon black on ENR 10 were also determined. Results obtained indicate a similar scorch behavior as that reported earlier for SMR L. However, some differences in the magnitude of scorch times in the temperature and concentration studies are observed between ENR and SMR L. These differences are attributed to the activation of a double bond by the adjacent epoxide group in ENR, the effect being more significant for a higher degree of epoxidation of natural rubber. In the case of ENR 50, differential scanning calorimetry measurement suggests that additional crosslink occurs via a ring‐opening reaction at about 155°C. Based on first‐order reaction kinetics, the apparent activation energy of vulcanization for the rubbers studied is estimated and discussed.
A simulation of the enthalpies of fusion of unplasticized poly(vinyl chloride)
Authors: Obande O. P. 
Published: April 2003

AbstractEnthalpies of fusion were measured by differential scanning calorimetry for PVC compounds processed within the range 150°–220°C by twin‐screw extrusion or compression molding. It was observed that the effects of polymer molar mass (K‐value) or sample formulation on values of the experimental enthalpy change follow identical pattern as effects of the same parameter on elastic response established by rheometry. It was assumed that the “amorphous” phase is made up of a matrix of locally ordered chain segments and occluded free‐volume and that this matrix constitutes what is described as “secondary crystallinity” of bulk PVC. On the basis of this assumption, a model was developed incorporating a parameter for the contribution of enthalphy of relaxation of free volume to the observed enthalpy of fusion of the secondary crystallinity. Graphical comparison of the simulated enthalpy changes with the measured values produced accurate measures of the critical temperature where a change in melt flow activation energy has been established by rheometry. The comparison further predicts that if PVC was processed below 190°C, an increase in shear intensity should reduce the free‐volume content of the product, while processing above 200°C should result in the converse. Also, with increasing processing temperature above 200°C a shear‐independent linear decrease in free‐volume of the bulk product is suggested to be operative. Thus, the material produced by extrusion or compression molding between 190 and 200°C should be least dense and least crystalline in line with previous observations.
Performance of treated hybrid fiber reinforced‐thermoplastic composites under extreme conditions. IV. Use of glass fiber and sawdust as hybrid fiber
Authors: Maldas D. , Kokta B. V. 
Published: April 2003

AbstractThe mechanical properties and dimensional stability of hardwood aspen in the form of sawdust and surface‐treated glass fiber‐polystyrene composites were evaluated under various extreme conditions, e.g., variation in the testing temperature (from +25° to −20°C), exposure to boiling water and heat in an oven at +105°C. The compatibility of wood fiber with glass fiber and with polystyrene improved by precoating the wood fiber with a coupling agent, e.g., 8% isocyanate, 4% silane and polymer. The mechanical properties of the composites, in particular, treated sawdust/glass fiber‐filled composites, increased under extreme conditions in comparison with those filled with nontreated sawdust/glass fiber. Under the same conditions, dimensional stability also supports this observation.
Structural and electrical behavior of polyacrylonitrile‐polypyrrole composite film
Authors: Bhat N. V. , Sundaresan E. 
Published: April 2003

AbstractPolyacrylonitrile‐polypyrrole composite films were prepared by a vapor phase technique. The films obtained by this method have high conductivity and good mechanical properties. Growth of polypyrrole on the surface of polyacrylonitrile was investigated by electron microscopic studies. Electrical properties of composite films were investigated as a function of FeCl3 content as well as polypyrrole uptake. The current‐voltage characteristic suggest an ohmic conduction. The conductivity of these composite films was measured as a function of temperature yielding an activation energy of 0.16 eV.
Blends of polyurethane carboxylates with styrene vinylpyridinium copolymers
Authors: Rutkowska Maria , Eisenberg Adi 
Published: April 2003

AbstractThis is a continuation of an ongoing investigation of miscibility enhancement via ionic interactions in urethane‐styrene blends. The present study deals with a polyurethane which contains in the hard segments pendant carboxylate groups neutralized by ammonium ions while the polystyrene contains pendant vinyl pyridinium methyl iodide groups. Miscibility of the styrene is seen with the hard segments of the urethane because of ion pair/ion pair interactions. Methanol extraction raises the Tg because it eliminates low molecular weight components, without removing the microions.
Properties of PET fibers with high modulus and low shrinkage (HMLS). I. Yarn properties and morphology
Authors: Rim P. B. , Nelson C. J. 
Published: April 2003

AbstractClassical morphological analysis has been performed on novel PET fibers of high modulus and low shrinkage (HMLS). As expected, amorphous orientation controls the degree of shrinkage and tenacity. The uniqueness of these materials is derived from a high “effective” crosslink density which results in a high retractive force during elevated temperature shrinkage and significant stress‐amplification during room temperature extension. Although the morphological origin of the high effective crosslink density is unknown, it is speculated that the interfibrillar regions contribute to the observed behavior by suppressing yielding.
Stress relaxation behavior of short kevlar fiber‐reinforced thermoplastic polyurethane
Authors: Kutty Suni L. K. N. , Nando Golo K. B. 
Published: April 2003

AbstractStress relaxation behavior of short Kevlar fiber‐reinforced thermoplastic polyurethane (TPU) is studied with respect to strain level, strain rate, fiber loading, and fiber orientation and temperature. The existence of a two‐step relaxation mechanism for unfilled stock and a three‐stage relaxation mechanism for the fiber‐filled stock is reported.
Evaluation of DGEBA
Authors: Tamareselvy K. , Sheela M. S. , Kalliyanakrishnan V. , Pal S. N. 
Published: April 2003

AbstractAnalytical studies using chemical, spectral, and chromatographic methods have been carried out for four commercial diglycidyl ether of bisphenol A (DGEBA) resins (AER, EER, DER, and NER) in order to evaluate the essential parameters of DGEBA for synthesizing 2,2‐bis [4‐ (2‐hydroxy‐3‐methacryloyloxypropoxy)] phenyl propane (BIS‐GMA), an impportant precursor for dental composites. Parameters such as epoxy equivalent weight, hydroxyl value, and hydrolyzable chlorine content have been estimated. The role of these parameters in determining the final purity of BIS‐GMA has also been discussed.
On oxygen plasma‐treated polypropylene interfaces with air, water, and epoxy resins. II. Epoxy resins
Authors: Occhiello E. , Morra M. , Morini G. , Garbassi F. , Johnson D. 
Published: April 2003

AbstractXPS, SEM, SSIMS, FTIR‐ATR, water‐in‐air, and air‐in‐water contact angle measurements have been used to unambiguously characterize the locus of failure of PP/epoxy joints. In the case of untreated PP, the fracture has been found adhesive, whereas in oxygen plasmatreated PP, it is cohesive, within bulk PP, but close to the modified PP‐bulk PP interface. The smoothness of fracture surfaces allowed us to exclude mechanical interlocking effects. Shear‐strength measurements showed that the mechanical strength of the joint was improved by plasma treatment. Preliminary thermal equilibration of the plasma‐treated PP sample and changes in the curing cycle of the epoxy resin did not change either the locus of failure or the shear strength of the joint. The reason is probably because the number of polar functions left at the surface after thermal equilibration is sufficient to induce adhesion. The mechanical strength of the PP surface layer may be the determining factor. Fracture energy calculations showed that the observed locus of failure is the same as predicted on the basis of surface energy considerations.
Hydrolytic degradation of nonoriented poly(β‐propiolactone)
Authors: Mathisen Torbjörn , Lewis Monica , Albertsson Ann‐Christine 
Published: April 2003

AbstractThe hydrolytic degradation of poly(β‐propiolactone) with a molecular weight Mw of 32,000 has been studied in a buffered salt solution (pH 7.2) at 37°C. Within 42 days, the embrittlement of the samples made tensile strength measurement impossible, which is due to the rapid reduction of molecular weight, 50% reduction after 49 days. The maximum weight due to water absorption was measured to 1.2 wt %, reached after 2 days. The absorbed water acts as a plasticizer in poly(β‐propiolactone) observed by the displacement in the maxima of the tan δα peak. A fast increase of crystallinity in the samples has been observed during the first 50 days of degradation, with the increase continued up until 190 days, after which a decline of the crystallinity can be observed, indicating hydrolityc degradation of the crystalline part of the samples. The mass loss of the samples becomes prominent after 150 days of immersion and reached a value of 14.6% after 260 days.
Studies on modification of some flammability characteristics by plasma. II. Polyester fabric
Authors: Akovali G. , Takrouri F. 
Published: April 2003

AbstractCold plasma treatment of polyester fabric in the presence of several volatile monomers containing expected flame retardant elements was made and some of the flammability characteristics of the plasma/monomer‐treated fabric were studied. The plasma treatment on the fabric caused a slight decrease in both oxygen index values and burning rates. It is believed that crosslinking outweighs the effect of grafted elements. The results of wettability and TGA tests as well as SEM data are included.
Self‐vulcanizable rubber blend systems based on epoxidized natural rubber and chlorosulfonated polyethylene: Effect of blend composition, epoxy content of epoxidized natural rubber, and reinforcing black filler on physical properties
Authors: Mukhopadhyay Sujata , De S. K. 
Published: April 2003

AbstractMill mixed blend of epoxidized natural rubber and chlorosulfonated polyethylene forms a self‐vulcanizable rubber blend during molding at high temperatures in absence of any vulcanizing agent, which is confirmed by FTIR studies. The extent of vulcanization reaction not only depends upon time and temperature of molding but also on the level of epoxidation in ENR and its proportion present in the blend. Physical properties of the blends are comparable to that of conventional rubber vulcanizates. Such blends can be reinforced by carbon black filler.
Butadiene polymerization with nickel compounds: Effect of cocatalysts
Authors: Throckmorton M. C. 
Published: April 2003

AbstractThe preparation of a high cis‐1,4‐polybutadiene, using a novel ternary catalyst system composed of triethylaluminum, a soluble nickel compound, and boron trifluoride diethyl etherate has been reported in the literature. The present paper reports the polymerization results obtained when the triethylaluminum was replaced with other alkylaluminums and the BF3 · Et2O was replaced with other BF3 complexes or HF · Et2O. When utilizing BF3 · Et2O, both the polymerization rate and the polymer DSV decreased significantly as the length of the alkyl group in the alkylaluminum increased from C1 to C6. However, the length and nature of the alkyl group had virtually no effect when utilizing BF3 · phenolate (BF3 · 2C6H5OH) and only a small effect with HF · Et2O; although the length of the alkyl group had no significant effect when using BF3 complexes of aromatic aldehydes, the branched alkyl groups gave greater polymerization rates than did the corresponding n‐alkyls. In summary, the strongly acidic complexes, BF3 · phenolate and HF · etherate, promoted rapid polymerization when employed with any of the alkylaluminums. However, with other BF3 complexes, the alkylaluminum selected had an important influence upon either the conversion and/or the polymer DSV.
Structural changes on plasma irradiation of ethyl–cyanethyl cellulose as revealed by infrared spectroscopic technique
Authors: Zhao Qiang , Long Fujin , Liu Xushu 
Published: April 2003

AbstractEthyl–cyanethyl cellulose was treated with oxygen plasma using the RF glow discharge technique. Three different plasma‐treated samples, including gel fraction, soluble fraction, and newly polymerized product by small moleculars given off by ethyl–cyanethyl cellulose, were obtained. With the infrared spectroscopic technique, the structural differences caused by plasma were studied. The effect of different gas plasma N2, Ar, and O2 on the structure of ethyl–cyanethyl cellulose was also studied.
Crosslinked latex blends based on gelatin: Synthesis, morphology, thermal, and mechanical properties
Authors: Ramaraj B. , Rajalingam P. , Radhakrishnan Ganga 
Published: April 2003

AbstractLatex blends of different compositions of poly(methyl methacrylate‐co‐n‐butylacrylate) and gelatin have been synthesised in latex form with crosslinking agents. These latex blends were characterized by thermal and mechanical properties. The morphology of cross‐linked latex blends were studied by scanning electron microscopy (SEM).
Hydrophobic polymer films plasma‐polymerized from CF4/hydrocarbon and hexafluroacetone/hydrocarbon mixtures
Authors: Inagaki N. , Tasaka S. , Mori K. 
Published: April 2003

AbstractPolymer films were deposited from the plasma polymerization of the mixtures of hydrocarbons, ethane, ethylene, and acetylene, and tetrafluoromethane (CF4) or hexafluoroacetone (HFA). The surface properties, the advancing contact angle of water, and surface energy of the films deposited and the chemical composition at the outermost layer of the films are discussed from the data of the angular XPS measurements. The plasma polymers deposited from the CF4/hydrocarbon and HFA/hydrocarbon mixtures contained fluorine atoms whose content depended on the CF4 or HFA concentration of the mixtures. The hydrophobicity of the films deposited could not be determined by the fluorine content of the films but by the chemical composition of the fluorine moieties at the outermost layer of the films. The CF3 moieties rather than the CF2 and CF moieties contribute largely to the hydrophobicity of the films. The plasma polymer films deposited from the HFA/acetylene (87.5 mol % HFA) showed higher hydrophobicity (the surface energy is 9.7 mJ/m2) than those from the CF4/acetylene mixture (87.5 mol % CF4) (the surface energy is 13 mJ/m2).
Epoxy–imide resins based on bis (carboxyphthalimide)s
Authors: Adhinarayanan K. , Packirisamy S. , George Reena S. , Rao V. Lakshmana , Ramaswamy R. 
Published: April 2003

AbstractEpoxy–imide resins have been obtained through the reaction of Araldite GY 250 (diglycidylether of bisphenol‐A and epichlorohydrin; difunctional) and Araldite EPN 1138 (Novolac‐epoxy resin; polyfunctional) with bis(carboxyphthalimide)s derived from 4,4′‐diaminodiphenylsulfone, 3,3′‐diaminodiphenylsulfone, 4,4′‐diaminodiphenylmethane and 4,4′‐diaminodiphenylmethane and trimellitic anhydride. For each epoxy‐imide resin system, epoxy equivalent to carboxy equivalent ratio has been optimised to obtain the maximum tensile lap shear adhesive strength on stainless steel substrates at room temperature. The lap shear strength at 100, 150, and 175°C has been determined for the optimum ratio. Araldite EPN‐1138‐based systems give the lap shear strength of 141–182 kg/cm2 at room temperature for the optimum compositions and retain about 84–100% of the lap shear strength at 150°C. Araldite GY‐250‐based systems have lap shear strength of 183–193 kg/cm2 and retain 76–84% of the lap shear strength at 150°C except for the one cured with bis (carboxyphthalimide) prepared from 4,4′‐diaminodiphenylmethane, which retains only 17% of the lap shear strength. Among the systems studied, Araldite GY 250 cured with bis (carboxyphalimide) synthesized from 3,3′‐diaminodiphenylsulfone appears to be the best, retaining 75% (138 kg/cm2) of the lap shear strength at 175°C.