bluuebunny/crossref_metadata_2025_split huggingface dataset:
Grafting of acrylamide to nylon‐6 by the electron‐beam preirradiation technique. II. Kinetic aspects and film permeability
Authors: Haruvy Y. , Rajbenbach L. A. , Jagur‐Grodzinski J. 
Published: April 2003

AbstractSingle‐ and multilayered laminated nylon‐6 films were grafted with acrylamide (AM) using the electron‐beam preirradiation technique. Very high grafting yields were obtained within short time periods. Grafting onto single films was shown to proceed via “diffusion free” pseudo zero‐order kinetics. Grafting onto multilayered films was diffusion controlled. SEM and EDAX measurements indicate uniform grafting of single‐film membranes and asymmetric grafting of membranes prepared by grafting onto multilayered films. The permeability of grafted membranes to a number of permeants was found to increase with extent of grafting. The specific permeability to both water and solutes exceeded that of the dialysis grade cellophone at 500% graft. The selectivity of grafted films towards various solutes had also been found to be higher than that of cellophane.
Interaction of a hindered piperidine stabilizer with hydroxy‐substituted aromatic carbonyl compounds in the photostabilization of polypropylene
Authors: Allen Norman S. , Gardette Jean‐Luc , Lemaire Jacques 
Published: April 2003

AbstractThe effect of a hindered piperidine compound, Bis[2,2,6,6‐tetramethyl‐4‐piperidinyl] sebacate on the photostability and light‐stabilizing performance of hydroxy‐substituted benzophenone and anthraquinone compounds in polypropylene film has been examined using three different light exposure units. The stabilizing effects observed were found to be highly dependent on the utraviolet content (300–340 nm) of the light source. In the absence of this utraviolet component the hindered piperidine compound inhibited the photolysis of all the hydroxy‐substituted compounds, whereas in its presence no protective effect was observed. In fact, direct absorption of ultraviolet light was found to be totally ineffective in photostabilizing the polymer. The protective effects were associated with the ability of the hindered piperidine compound to destroy the hydroperoxides formed during processing. This was confirmed by the observation of no protective action with unsubstituted benzophenone and anthraquinone through both steady‐state and laser flash‐photolysis experiments. A further novel protective effect was observed when the hindered piperidine molecule was linked to the anthraquinone chromophore in the 2‐position to the carbonyl group. In this case photoprotection is associated with an intramolecular excited‐state quenching process.
Assessment of the intrinsic birefringence of partially oriented poly(ethylene terephthalate) yarns
Authors: Garg Sunil K. 
Published: April 2003

AbstractPartially oriented poly(ethylene terephthalate) yarns (PET POY) have been studied with respect to their birefringence, sonic modulus, and stress‐optical properties in an effort to extract the values for the intrinsic birefringences of the crystalline (Δnc°) and amorphous (Δna°) regions. The data have been analyzed within the framework of both the sonic modulus‐birefringence treatment of Samuels and Dumbleton, and the Gaussian rubber elasticity theory using the usual shrinkage stress‐birefringence relations. The following values have been determined: Δnc° = 0.22 and Δna° = 0.19. The work was undertaken to resolve the discrepancy in the published literature values of these two parameters.
Experimental assessment of the thermodynamic theory of the compositional variation of Tg: PVC systems
Authors: Fried J. R. , Lai S.‐Y. , Kleiner L. W. , Wheeler M. E. 
Published: April 2003

AbstractThe glass‐transition temperatures (Tg's) and specific heats (Cp) of poly(vinyl chloride) (PVC) and PVC plasticized with 5–120 phr di(2‐ethylhexyl) adipate (DOA) and tri(2‐ethylhexyl) trimellitate (TOTM) have been determined by differential scanning calorimetry (DSC). Measured Tg's were compared to predictions by the Couchman and Karasz (C–K) thermodynamic theory, three related empirical equations, and a new equation obtained from the C–K relation by assuming the product TgΔCp to be constant. It was found that the Tg's of the PVC/TOTM mixtures are adequately predicted only by the C–K and the derivative relation. The Tg's of the PVC/DOA mixtures follow a sigmoidal or cusp‐like dependence on plasticizer composition as has been observed for some other PVC/plasticizer mixtures. In this case, the approximation afforded by the C–K or derivative equations is still superior to the empirical models over a wide composition range. Dynamic mechanical analysis of the PVC/DOA mixtures suggests that the DSC transitions may consist of two overlapping phase transitions. The reported sigmoidal composition dependence of the DSC Tg's may therefore result from the measured Tg's being weighted towards the temperature corresponding to the predominant dynamic mechanical transition (i.e., the high Tg phase at low plasticizer concentrations and the low Tg phase at high plasticizer concentrations). In such cases of partial phase separation, the C–K or the derivative equation may be used to estimate the composition of the two phases at each overall plasticizer concentration.
Characterization of rubber particle size distribution of high‐impact polystyrene using low‐angle laser light scattering
Authors: Hall R. A. , Hites R. D. , Plantz P. 
Published: April 2003

AbstractA new application of low‐angle laser light scattering has led to a new instrument capable of characterizing the rubber particle size distribution of high‐impact polystyrene (HIPS) containing particles as small as 0.1 μ. Rubber particle size distributions of several HIPS resins have been characterized, and the particle size ranking of resins using light scattering parallels the ranking of resins using photomicroscopy. Several solvents have been employed to suspend the HIPS rubber particles for the scattering determination. Swelling of the rubber phase has been found to be relatively insensitive to variations in rubber phase crosslinking when methyl ethyl ketone is used to suspend the rubber particles. Particle swelling in methyl ethyl ketone does not detract from the usefulness of the light scattering method for HIPS rubber particle size characterization.
Time‐dependent changes in mechanical properties of neat and reinforced epoxy resins
Authors: Mijović Jovan 
Published: April 2003

AbstractSeveral neat and reinforced epoxy resin formulations were prepared and investigated. Solid glass microspheres, with and without coupling agent, were used as reinforcement. After completion of post‐cure all samples were quenched into an ice‐water bath. Upon removal from the ice‐water bath, dynamic mechanical and fracture properties of all samples were evaluated as a function of time elapsed after quenching. Electron microscopic evidence was obtained for the existence of nodular morphology in all cured systems. The changes in dynamic mechanical and fracture parameters, induced by the sub‐Tg annealing, were described in terms of the model of inhomogeneous thermoset morphology.
Characterization of carboxymethylcellulose: Distribution of substituent groups along the chain
Authors: Gelman Robert A. 
Published: April 2003

AbstractA procedure has been developed for characterizing cellulose ethers on the basis of the distribution of substituent groups along the polymer backbone. This method has been applied to carboxy‐methylcellulose. The technique uses cellulase, a cellulose‐degrading enzyme. Degradation as a function of time is followed by viscosity and reducing sugar measurements. The combination of these data, along with other analytical results, provides information on the number of unsubstituted anhydroglucose residues and the number and average length of blocks of two or more contiguous unsubstituted residues. The results obtained on a series of carboxymethylcellulose samples indicate that the rate of degradation and the number and length of blocks of unsubstituted residues depends not only on the number of substituent groups, but also on other molecular parameters.
Graft copolymerization of acrylonitrile onto bagasse and wood pulps
Authors: Heikal Salwa O. , El‐Kalyoubi Samira F. 
Published: April 2003

AbstractGraft copolymerization of acrylonitrile onto bagasse and wood pulps has been studied using ceric ammonium nitrate as initiator. The effect of order of reactants addition on grafting was examined: three methods were studied. Addition of the pulp to a mixture of initiator and monomer (method A) resulted in more efficient grafting than the other two methods. The reaction produced more grafting at 50°C than at 30°C or at 40°C. The results showed that the monomer and initiator concentrations are the major factors influencing the grafting rate of acrylonitrile. Increasing the acrylonitrile or initiator concentration was accompanied by a substantial increase in graft yields. Increasing the initiator concentration is more effective on polymerization rate than the increase in monomer concentration. The extent of grafting of this monomer can best be controlled by reaction time. Water swelling of pulps significantly affected the grafting rate of acrylonitrile as well as the ceric consumption during grafting. The reactivity of bagasse pulp towards grafting of acrylonitrile is higher than that of wood pulp due to a more open structure of cellulose in bagasse pulp as well as the presence of some lignin which accelerates grafting. Ceric consumption during grafting depends on the nature of the pulp as well as the monomer and initiator concentrations, time, temperature, and the method of grafting. More Ce(IV) is consumed during grafting than during oxidation of the pulps under identical reaction conditions, due to homopolymer formation which accompanied grafting. The ceric consumption by bagasse during grafting or oxidation is somewhat greater than that consumed by wood pulp under similar reaction conditions.
Effect of ultrafine particles on the elastic properties of oriented low‐density polyethylene composites
Authors: Sumita Masao , Ookuma Toshiyuki , Miyasaka Keizo , Ishikawa Kinzo 
Published: April 2003

AbstractSpherical fine particles with various diameters (70, 160, and 400 Å and 35 μ) were mixed with low‐density polyethylene (LDPE). The oriented composites were made by necking drawing. Thus the oriented polymer composites were hexagonal symmetric. Their elastic properties were determined by five compliances or stiffness constants. Four of them, i.e., S33, S11, S13, and S44, were determined for the oriented composites filled with 70‐Å and 35‐μ fillers. All the compliances of the 70‐Å filler composites decrease with filler content, whereas in those of the 35‐μ filler composites this relation was reversed. The Young's moduli of the oriented composites filled with relatively small particles (70, 160, and 400 Å) in the restretching directions 0, 45, and 90° against the original draw axis increased with filler content and with decreasing filler size, whereas those of the 35‐μ filler composites decreased with filler content. These results show that extremely small particles comparable to the size of the LDPE in the crystalline region exert a considerable reinforcing effect on the oriented polymer matrix.
Viscometric properties of poly(dimethylsiloxane) filled with spherical silica particles
Authors: Cantu T. S. , Caruthers J. M. 
Published: April 2003

AbstractThe shear viscosity and primary normal stress coefficient were measured for colloidal dispersions of monodisperse silica spheres in poly(dimethylsiloxane). The viscometric properties of the dispersions were a function of the shear rate, particle diameter, and the volume fraction of particles. Dimensional analysis of rheological properties of colloidal dispersions of spherical particles in a second‐order fluid was performed, and the experimental data were analyzed in terms of the appropriate dimensionless groups. The reduced shear viscosity of the colloidal dispersions was a function of the volume fraction of particles and the reduced shear stress (or reduced shear rate). The reduced primary normal stress coefficient was a function of the volume fraction of particles, the reduced shear rate, and the Weissenberg number.
Acid–base and dyeing properties of Nigerian Merino, Yankasa, and Merino–Yankasa crossbred wools
Authors: Kazmi M. S. , Mathieson A. R. 
Published: April 2003

AbstractThe acid–base titration curves of three wools, Merino, Yankasa, and a ⅝–⅜ Merino–Yankasa crossbred wool, grown in Nigeria, were measured at 25°C in the presence of varying amounts of sodium chloride. Amino acid analysis was carried out on these wools and correlated with the acid–base properties. The isoionic point and titration curves of Merino and the crossbred wool are similar, while those of Yanakasa are somewhat different. The acid–base behavior was interpreted by the Gibbs–Donnan treatment for the acid titrations and the pK01 values for the carboxyl groups obtained, showing the existence of normal and salt‐linked carboxyl groups in these wools. Dyeing tests with acidic and basic dyes have shown that the crossbred wool responds almost as well as Merino. Together with the similarity of its mechanical properties, it seems that this crossbred wool is suitable for all the textile applications for which Merino wool is normally preferred.
The kinetics of photoinitiated polymerization of 1‐vinyl‐2‐methylimidazole
Authors: Joshi Makarand G. , Rodriguez Ferdinand 
Published: April 2003

AbstractThe kinetics of isothermal, photoinitiated, solution polymerization of 1‐vinyl‐2‐methylimidazole (MVI) was studied using the standard dilatometric technique. The photoinitiators used were aromatic carbonyl compounds. Most of the experiments were carried out using methanol as solvent, but other solvents were also used. The reaction follows the classical kinetic scheme for free radical polymerization. The activation energy for the polymerization is 3.9 kcal/mol. The polymerization is greatly accelerated by the presence of water in reaction medium. Among the three photoinitiators tried, 2,2′‐diethoxyacetophenone (DEAP) has the highest quantum efficiency for the polymerization of MVI.
Studies on the light‐focusing plastic rod. XIII. Photocopolymerization of methyl methacrylate–vinyl esters of aromatic carboxylic acid
Authors: Koike Yasuhiro , Kimoto Yoshihiko , Ohtsuka Yasuji 
Published: April 2003

AbstractThe light‐focusing plastic rod (LFR) was prepared by the photocopolymerization of methyl methacrylate (MMA) with vinyl phenylacetate (VPAc) and vinyl benzoate (VB), using benzoyl peroxide (BPO), benzoin (BN), and benzoin methyl ether (BME) as an initiator. The LFR with high transparency and steep refractive‐index distribution was obtained using the MMA–VPAc pair and the BME. The difference in the index distributions under BPO, BN, and BME initiations was clarified in terms of the photoinitiation rate and the accompanying thermal polymerization during the photocopolymerization process. The light scattering intensity from the LFR was related to the heterogeneity of the copolymer composition and the compatibility between the M1 and M2 polymers. The comparison of the light scattering theory with the experimental data indicated that the much less scattering intensity from the MMA–VPAc LFR than the MMA–VB LFR should be attributed to the good compatibility between the MMA and VPAc polymers, and scarcely attributed to the index difference between the VPAc and VB polymers.
Effect of concentration and type of plasticizer on some physical properties of poly(vinyl chloride)
Authors: Watkinson K. , Mohsen R. 
Published: April 2003

AbstractThe effect of four different types and concentrations of plasticizers on some physical properties of poly(vinyl chloride) (PVC) has been studied. DOP, DOA, TTP, and Hex were used as plasticizers in concentration levels of up to 24% of PVC weight. The plasticized and unplasticized PVC were processed into sheets by compression molding. The sheets were tested for their vicat softening point, shore D hardness, flexural properties, and dynamic fatigue. It was found that the vicat softening point, shore D hardness, flexural yield strength, and flexural modulus decrease with increase in plasticizer concentration, though in some cases a threshold concentration must be passed before these effects can be observed. Close similarities were always found in the behavior of DOP and DOA and also between TTP and Hex. It was found in the study of flexural fatigue properties of PVC plasticized by DOP that an increase in plasticizer concentration led to a decrease in load bearing ability only at stress levels above 20 MPa.
Protection effects of condensed bromoacenaphthylene on radiation deterioration of ethylene–propylene–diene rubber
Authors: Morita Yohsuke , Hagiwara Miyuki , Kasai Noboru 
Published: April 2003

AbstractAs a continuation of a series of the studies on the flame and γ‐radiation resistant modification of ethylene–propylene–diene rubber (EPDM), condensed bromoacenaphthylene (con‐BACN) as a newly developed flame retardant was synthesized and its effects on the radiation resistance of EPDM were investigated. The radiation resistance evaluated by measuring tensile properties of irradiated sheets of 2 mm thck was found improved greatly by adding con‐BACN together with ordinary rubber ingredients but decreased by decabromodiphenylether (DBDPE) that has bromins in aromatic rings as con‐BACN. When EPDM sheets of 1 mm thick were irradiated in oxygen at a dose rate of 1 × 105 rad/h, the weight swelling ratio increased with increasing dose, indicating that oxidative main chain scission is predominant under the irradiation conditions. On the other hand, crosslinking was shown to be predominant in nitrogen. From the results of the swelling experiments with different additives, it was concluded that DBDPE accelerates both the main chain scission in oxygen and the crosslinking in nitrogen. In contrast to this, con‐BACN reduced the chain scission in oxygen. This observation was accounted by the assumption that the influence of the oxidative chain scission is partly compensated by the concurrent crosslinking which takes place through additions of con‐BACN to substrate polymers even in the presence of oxygen.
The utilization of DSC in studies of oligomers
Authors: Varnell W. D. , Harrison I. R. , Roberts D. R. 
Published: April 2003

AbstractOligomers are potentially useful as well characterized models for studying the chemical and physical properties of their long chain homologues. These model compounds are often available only as mixtures which must be separated. This separation may be accomplished using chromatographic techniques, i.e., GPC. Polydispersity (Mw/Mn) is often used as a criteria for the extent to which separation has been achieved. Values of polydispersity of 1.01–1.03 are considered indicative of very narrow fractions in the high polymer area. A purpose of this paper is to show that such low values of polydispersity are misleading when applied to oligomers containing 2–20 repeat units. Further, the existence of a single “sharp” melting endotherm is not necessarily proof that one has separated out a single molecular weight component. An intimate mixture of different molecular weight oligomers can give a single narrow endotherm.
Degradation of organic coatings. I. Hydrolysis of melamine formaldehyde/acrylic copolymer films
Authors: Bauer D. R. 
Published: April 2003

AbstractThe hydrolysis of melamine formaldehyde crosslinked acrylic copolymer films has been studied using infrared spectroscopy. It has been found that during hydrolysis, crosslinks between the acrylic copolymer and the melamine crosslinker are broken and that crosslinks between melamine molecules are formed. The rate of hydrolysis depends on the following: (1) the type of crosslinker used (partially alkylated melamines hydrolyze faster than fully alkylated melamines); (2) the amount and strength of acid catalyst used and whether or not the catalyst can be extracted from the coating during hydrolysis; (3) the initial crosslink density; (4) the hydrolysis temperature. In some formulations, it can be expected that virtually all of the acrylic–melamine crosslinkes will be hydrolyzed. However, due to the formation of melamine–melamine crosslinks, the overall crosslink density does not necessarily decrease significantly as a result of this hydrolysis.
Solubility parameters in polyoxetanes: Poly(oxetane), poly(3,3‐dimethyl oxetane), and poly(3,3‐diethyloxetane)
Authors: Perez E. , Gomez M. A. , Bello A. , Fatou J. G. 
Published: April 2003

AbstractThe solubility parameter of poly(oxetane), poly(3,3‐dimethyloxetane) and poly(3,3‐diethyl oxetane) has been estimated by measuring solution viscosities. Values of δ = 9.4, 7.9, and 7.9 cal1/2·cm−3/2 for each polymer were obtained and compared with those calculated from empirical methods. The 3‐dimensional solubility parameter approach has been also applied in order to get additional information on the effect of structural modifications on the main chain in the solubility behavior.
Chemical modification of polystyrene. I. Electrophilic substitution of polystyrene with aromatic anhydrides
Authors: Biswas Mukul , Chatterjee Shakuntala 
Published: April 2003

AbstractPolystyrene has been modified by electrophilic substitution reaction with phthalic anhydride and pyromellitic dianhydride. The products have been characterized by physical characteristics, solubility differences, elemental analysis, infrared spectra, ion‐exchange capacity, and pH metric titration. The ultimate thermal stabilities of these modified polymers are better than the same for the unmodified polystyrene.
Crosslinking of polypropylene glycol with divalent metal salts of mono(hydroxyethyl) phthalate, anhydride, and bisepoxide
Authors: Matsuda Hideaki , Miyoshi Noriyuki 
Published: April 2003

AbstractCrosslinking of polypropylene glycol with divalent metal salts of mono(hydroxyethyl) phthalate, anhydride, and bisepoxide is investigated. The anhydride and bisepoxide were hexahydrophthalic anhydride and bisphenol A diglycidyl ether. The metal carboxylate groups catalyzed the crosslinking reactions. The Mg carboxylate group showed higher catalytic activities than the Ca carboxylate group. The rubbers containing Mg showed much better physical properties than those containing Ca, due to higher interionic attraction of Mg++ and better homogeneity. In addition, tensile strength of the cured rubbers at about the same soft block contents depended largely upon that of the hard block. Resistances to water and chemical attack, stress–relaxation, and thermal behavior are also discussed.
Water permeation of polymer films. IV. Teflon FEP
Authors: Sacher E. , Susko J. R. 
Published: April 2003

AbstractThe evaluation of the permeation parameters of water for Teflon FEP has shown that permeation is a dual mode process: Water is initially adsorbed onto the polymer surface in a layer; because the residence time of the layer is short, little is ultimately absorbed. The diffusion process is disrupted at the onset of molecular motion, at the glass transition, due to an increase in effective tortuosity. Variations of the permeation parameters with thickness suggest a skin, of total thickness near 25 μm, whose permeation parameters differ from those of the bulk.
Solvent diffusion in molten polyethylene
Authors: Vrentas J. S. , Duda J. L. , Lau M. K. 
Published: April 2003

AbstractDiffusivity data are presented for the o‐xylene–polyethylene system in the temperature range 125–175°C. The diffusion coefficient increases slightly as the solvent concentration increases near the pure polymer limit. Although the concentration and temperature dependences of the diffusivity for this system are different from what are typically observed for polymer–solvent systems, they are consistent with the free‐volume theory of diffusion.