bluuebunny/crossref_metadata_2025 huggingface dataset:
Cationic oligomerization of 1‐hexene catalyzed by EtAlCl2–chloroacetic acid complexes
Authors: Higashimura Toshinobu , Miyoshi Yoshihiro , Hasegawa Hiroshi
Published: April 2003

Lower oligomers (dimer to tetramer) of 1‐hexene were obtained in high yield (65 wt %) with a new cationic complex catalyst, EtAlCl2CCl3CO2H, in n‐hexane at 70°C, trimer being the major product. A strong oxo acid, CF3SO3H, yielded very similar products under the same conditions. Characteristics of the 1‐hexene oligomerization by these two catalysts were the high selectivity for dimers to tetramers and the absence of cracking of the product. In contrast, EtAlCl2 or AlCl3 alone led to oligomers with a higher molecular weight (∼103) and a broad molecular weight distribution, the structure of which was very complicated because of extensive cracking of products. A series of EtAlCl2chloroacetic acid (CClnH3–nCO2H, n = 0–3) complexes were also examined as catalysts. The yield of dimer to tetramer increased with increasing acidity of the chloroacetic acids. The mechanism of the 1‐hexene oligomerization with these complex catalysts was discussed on the basis of the structure of product oligomers.
Structural considerations in case II swelling of crystalline poly(ethylene terephthalate)
Authors: Haga Toshio
Published: April 2003

The Case II swelling in chloroform was discussed with regard to the fine structure for the crystalline PET. The case II swelling was associated with the character of the crystallites. It was inferred that the fine structure related to the Case II behavior was effectively plasticized during the swelling process.
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

Single‐ 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

The 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

Partially 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

The 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

A 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

Several 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

A 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

Graft 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

Spherical 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

The 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

The 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

The 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

The 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

The 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

As 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

Oligomers 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

The 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

The 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

Polystyrene 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

Crosslinking 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

The 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

Diffusivity 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.
Grafting fluorocarbons to polyethylene in glow discharge
Authors: Yagi Toshiharu , Pavlath Attila E. , Pittman Allen G.
Published: April 2003

A systematic surface fluorination of high‐density polyethylene was carried out using CF4, CF3H, CF3Cl, and CF3Br, in a radio‐frequency glow discharge. Based on ESCA and wettability measurements, all of these compounds provided a fluorocarbon layer on high‐density polyethylene surface, but the fluorine to carbon ratio and extractability of the films were strongly dependent on the starting materials and the location of the sample specimen in the reactor chamber as well as the duration of the reaction. The results with vertically held, CF3H‐treated samples showed a high level of nonextractable surface fluorination and very little change in wetting properties before and after extraction with CF2ClCFCl2.
Synthesis and studies of phosphorus‐containing polyurethane foams based on tetrakis(hydroxymethyl) phosphonium chloride derivatives
Authors: Sivriev Hristo , Borissov Georgij , Zabski Leszek , Walczyk Wladyslaw , Jedlinski Zbigniew
Published: April 2003

A phosphorus‐ and nitrogen‐containing polyl is prepared by condensing tetrakis(hydroxymethyl)phosphonium chloride with diethanol amine in aqueous medium. The newly synthesized polyol‐bis(hydroxymethyl)‐N, N‐bis(2‐hydroxyethyl)aminomethylphosphine oxide (AMPO) is used in the preparation of rigid polyurethane foams with a various phosphorus content. With the view to comparing their properties, polyurethane foams are also prepared on the basis of the commercially available flame retardant diethyl‐N, N‐bis(2‐hydroxyethyl)aminomethylphosphonate (Fyrol 6). The flammability, thermal stability, and thermoechanical properties of the polyurethane foams obtained are studied. A certain difference in the behavior of the two modified polyurethane foams is observed. The polyurethane foams with AMPO exhibit a slight increase in the resistance to combustion (oxygen index) and a noticeable improvement in the thermal and mechanical properties. These differences probably arise as a result of structural and functional differences between the two types of phosphorus‐containing flame retardants.
Chelating resin: Pyridine derivatives attached to poly(styrene) beads with spacer group
Authors: Nishide Hiroyuki , Shimidzu Naoki , Tsuchida Eishun
Published: April 2003

The pyridine derivatives were combined to poly(styrene) beads with spacer groups or a graft chain. These spacer‐type and graft‐type pyridine beads formed their Cu complexes with high rates and large stability constants; they act as an effective chelating resin. The pyridine residues were more mobile due to the spacer group and the graft chain, compared with the poly(4‐vinylpyridine) powder.
Chlorinated hydrocarbon coupling agents for mica–polypropylene composites
Authors: Garton A. , Kim S. W. , Wiles D. M.
Published: April 2003

The incorporation of small amounts of a chlorinated hydrocarbon wax into polypropylene (PP) when making mica–PP composites is shown to produce a layer of degraded chlorinated hydrocarbon at the interface between the polymer and the reinforcement. Mica is shown to accelerate the thermal degradation of the chlorinated hydrocarbon, and the chlorinated hydrocarbon, or its degradation products, are shown to react with hydrocarbon analogues of the polymer. As well as modify the chemical nature of the interface, the layer of degraded chlorinated hydrocarbon is shown to modify the morphology of the interface by inhibiting the ability of the mica to nucleate the crystallization of PP from the melt.
Urethane‐based stabilizers for radiation‐crosslinked polyethylene
Authors: Shkolnik S. , Rajbenbach L. A.
Published: April 2003

Unsaturated urethane‐based stabilizers for use in radiation‐crosslinked polyethylene were synthesized. Aromatic amine moieties were attached to allylic and acrylic monomers by means of aromatic or aliphatic diisocyanates. The synthesized stabilizers were incorporated in high‐density polyethylene films which were subjected to electron beam irradiation. The oxidative stability of the films prior to and after extraction was determined by DTA in the temperature range 185–210°C and compared with samples treated with commercial amine‐bearing antioxidants. Tensile strength and gel content were also determined. Best results were obtained with a stabilizer prepared from equimolecular amounts of allyl alcohol, tolylene‐2,4‐diisocyanate and N‐phenyl‐1,4‐phenylenediamine. Estimated lifetimes at 70°C of stabilized irradiated polyethylene samples were calculated.
Catalysis of the reaction between isocyanates and protonic substrates. III. Influence of the addition of a cosolvent on the polyurea foaming process
Authors: Merckaert P. , Jérôme R. , Teyssié Ph.
Published: April 2003

Polyurea foams can be produced from nonmiscible water and polyisocyanates. The addition of a cosolvent improves the homogeneity of the reaction medium and enhances the effectiveness of any catalyst, preferably soluble in water. Cosolvents, exhibiting an intrinsic catalytic activity, display a regulating effect on the rise profile of the foams and allow for defining performant and less expensive formulations.
Finite‐element and boundary‐element analysis of craze micromechanics
Authors: Bevan L.
Published: April 2003

The two numerical methods are used to estimate craze surface displacements and stresses for both isolated crazes and crazes at crack tips. The results are compared with the predictions of craze micromechanics models. The investigation includes the computation of the craze surface stress profile required to maintain a given craze opening displacement profile. The boundary element program requires less computer time than the finite element one, and similar results are obtained. The analysis also considers the craze surface displacement profile corresponding to an assumed craze surface stress distribution. The element methods produce results which are approximately the same as those obtained using the model of Verheulpen‐Heymans and Bauwens.
Modelling of reversible poly(ethylene terephthalate) reactors
Authors: Kumar A. , Gupta S. K. , Gupta B. , Kunzru D.
Published: April 2003

The second stage of batch poly(ethylene terephthalate) (PET) reactor with bis(2‐hydroxyethyl) terephthalate (BHET) as the feed has been simulated. In this stage, the overall polymerization is not diffusion limited and is known to be a complex reaction. In this work it has been assumed to consist of polycondensation, reaction with monofunctional compounds (cetyl alcohol), redistribution, and cyclization reactions. The forward and reverse steps of each of these have been modelled in terms of the rate constants involving functional groups and the reacted bonds. The equations for the calculation of the molecular weight distribution (MWD) in batch reactors have been written and solved numerically. The MWD reported in this work is assumed to include the monofunctional products only, and, for the case where ethylene glycol is not removed from the reaction mass, it was found to be unaffected by the choice of the redistribution rate constant (kr). Since the removal of ethylene glycol is not mass transfer controlled, its concentration in the reaction mass is assumed be given by the vapor–liquid equilibrium existing at the pressure applied on the reactor. In this work, the level of ethylene glycol concentration, yg ([G]/[P1]0), has been taken as a parameter, and, on application of vacuum, the MWD results were found to vary with kr with the sensitivity increasing with yg. It was then shown that the importance of the redistribution reaction is enhanced when the cyclization reaction also occurs. The effect of vacuum on the performance of the reactor has been studied by varying yg. For yg less than 0.01, the change in the MWD of the polymer becomes very small. The effects of polymerization temperature and initial concentration of monofunctional compounds on MWD were found to be small.
Dilute solution behavior of a cationic polyelectrolyte
Authors: Kienzle‐Sterzer Carlos , Rodriguez‐Sanchez Dolores , Rha Chokyun
Published: April 2003

Dilute solution behavior of a cationic polyelectrolyte was studied with respect to acetic acid concentration using chitosan. The reduced viscosity, ηsp/C, of chitsan solutions increases with a decrease in the polymer concentration. For a given polyelectrolyte concentration, the specific viscosity is higher at lower acid (acetic) concentration, indicating the expansion of the polyelectrolyte chain due to electrostatic repulsion as a result of the interactions between chitosan and the solvent. The relationship between intrinsic viscosity [η]∞ and acetic acid concentration suggests no conformational transition of the chitosan molecules and possible formation of intramolecular hydrogen bonds during the shrinking of the hydrodynamic domain of the polyions.
Aging and performance of structural film adhesives. I. A comparison of two high‐temperature curing, epoxy‐based systems
Authors: Pearce P. J. , Davidson R. G. , Morris C. E. M.
Published: April 2003

The room temperature aging of two epoxy adhesives, both of which are cured at 177°C and contain the moisture sensitive resin triglycidyl (4‐aminophenol), has been examined. It has been found that hydrolysis of this resin is the major cause of reduction in epoxide content during aging. This in turn is largely responsible for the deterioration in the performance, especially at high temperatures, of bonded joints made with aged adhesive. The advantages of using high purity resins in adhesive formulations have been demonstrated.
Viscoelastic behavior of segregated networks
Authors: Lipatov Yu. S. , Rosovizky V. F. , Maslak Yu. V.
Published: April 2003

Temperature dependences of real E′ and imaginary E″ parts of the complex dynamic modulus for new types of so‐called segregated networks were investigated. These networks are formed by three different elastic active network chains which chemically interact one with another, distinct from interpenetrating networks. Networks based on oligourethane acrylate, methyl methacrylate, methacrylic acid, and epoxy resin taken at various ratios were investigated. The viscoelastic characteristics were determined on different stages of the network structure formation. For such networks, a very wide peak E″ is typical, which is connected with a high degree of microphase segregation. The mutual influence of the constituent networks on their relaxation maxima was observed.
Graft copolymerization of methyl methacrylate onto wool using thallium (III) ions as initiator
Authors: Misra Sivananda , Sahu Gangadhar
Published: April 2003

The graft copolymerization of methyl methacrylate onto wool initiated by thallium (III) perchloric was investigated in aqueous perchloric acid medium. The rate of grafting was evaluated varying the concentrations of the monomer, initiator, acid, and temperature. The rate of grafting was found to increase with the increase of the monomer and the initiator concentration. The graft yield was found to decrease upon increasing the acid concentration. Increase of temperature was accompanied with the increase of the graft yield. From the Arrhenius plot the overall activation energy was calculated to be 4.7 kcal/mol. The effect of inhibitors, various solvents, cationic and anionic surfactants, and different inorganic salts on the graft yield was studied. The grafting was considerably influenced by chemical modification of wool prior to grafting. A suitable kinetic scheme has been proposed, and a rate equation has been derived.
Saccharification of douglas‐fir wood by a combination of prehydrolysis and pyrolysis
Authors: Shafizadeh Fred , Stevenson Thomas T.
Published: April 2003

A process has been investigated for the saccharification of wood, involving prehydrolysis, lignocellulose pyrolysis, and tar hydrolysis. In this process, ground wood was first prehydrolyzed to remove the more readily hydrolyzable hemicelluloses. The residual lignocellulose was then pyrolyzed rapidly to provide a tar containing levoglucosan and its condensation products. The tar was hydrolyzed to convert these products to glucose. Laboratory experiments have shown that this process can convert a common softwood such as Douglas‐fir to 14% char and 42% hexoses. This amounts to a 59% recovery of the hexoses: 32% from prehydrolysis and 27% from pyrolysis. The prehydrolysis served not only to remove hemicelluloses, but also to increase the yield of glucose from pyrolysis and subsequent tar hydrolysis. It has been shown that this enhancement is due to the removal of inorganic ash and the catalytic effect of trace amounts of acid remaining in the lignocellulose.
Fourier‐transform infrared study of uniaxially oriented polytetrafluoroethylene
Authors: Yeung C. K. , Jasse B.
Published: April 2003

Infrared measurements of the dichroic ratio of polytetrafluoroethylene absorption bands provide a valuable method of determination of the orientation of chains as well in crystalline regions as in amorphous ones. The 1452 cm−1, 1545 cm−1, and 2362 cm−1 combination bands are convenient for measuring crystalline orientation while the 703 cm−1, 740 cm−1, and 786 cm−1 bands lead to amorphous orientation. The 1795 cm−1 (crystalline), 720 cm−1, and 774 cm−1 (amorphous) absorption bands are shown to be complex ones and thereby unusable for measuring orientation.
One‐point determination of intrinsic viscosity for polycarbonate, poly(phenylene oxide), and polyetherimide
Authors: Nero John R. , Sikdar Subhas K.
Published: April 2003

Intrinsic viscosity determination for polymers can be simplified and considerable time and effort saved via a single measurement of relative viscosity at a known concentration. Several workers have proposed one‐point intrinsic viscosity methods. Of the methods in the literature, two one‐point methods were found to be as accurate as the multiple‐point graphical extrapolation procedure. These two methods, one due to Solomon and Ciuta and a nomographic technique due to Khan and Bhargava, were successfully applied for the intrinsic viscosity determination of three polymers: polycarbonate, poly(phenylene oxide) and polyetherimide.
Microencapsulation of water‐soluble materials using a copolymer of poly(vinyl chloride)
Authors: Safdy Max E.
Published: April 2003

Microencapsulation of aqueous materials by the technique of organic phase separation using copoly(vinyl chloridevinyl alcoholvinyl acetate) (91:3:6% by weight) resulted in microcapusules which were isolable as a free‐flowing powder and were storable after drying. Using a dye marker in the core, the dried microcapsules were found to release the core contents through the spherical wall membrane in the presence of an exogenous aqueous medium. A technique was found for conveniently coating the dried microcapsules onto filter paper, and the partial constituents of an indicator system were encapsulated and coated onto filter paper pretreated with the complementary color‐forming constituents. The rate of color development in the wetted paper‐microcapsule system was used to assess the relative rate of release of the microcapsule core contents. Crosslinking of the poly(vinyl chloride) copolymer prior to encapsulation resulted in an attenuation of release of the microcapsule core contents.
Neutral organophosphoryl methyl ester–metal chloride interactions as applied to the dechlorination of catalyst residues in polypropylenes prepared by solventless processes
Authors: Karayannis Nicholas M. , Khelghatian Habet M. , Skryantz John S.
Published: April 2003

A novel method of dechlorinating catalyst residues in polypropylenes prepared by solventless processes is reported. The method is based on the reaction of the metal chlorides present in these residues with neutral organophosphoryl methyl esters, such as trimethyl phosphate and dimethyl methylphosphonate. These reactions lead to the formation of M[OP(O)(OCH3)2]n or M[OP(O)(CH3)(OCH3)]n complexes, with evolution of the chloride in the form of methyl chloride. Experimental evidence presented demonstrates that inclusion of one of the preceding esters in the stabilizer package of polypropylene powders prepared by the bulk polymerization process and containing 300–650 ppm Cl, followed by extrusion and pelletization, can result in practically complete dechlorination (Cl content less than 5 ppm) of the polymer.
Studies on polymer ignition and development of a relative hazard ranking method
Authors: Miller Bernard , Martin J. Ronald , Turner Rudolph
Published: April 2003

The argument is presented that a primary determinant for polymer ignition is the rate of heat input during thermal decomposition. An experimental protocol is described in which a conventional thermogravimetric analyzer is used to monitor the behavior of polymeric solids brought to ignition by exposure to preheated air. The data obtained are used to establish the minimum heating rate required for ignition and the initial decomposition temperature at that critical rate. These two properties are then combined to give a numerical ranking value which seems to be a reasonable indicator of a material's ignitability hazard potential. Data for a variety of polymers and mixed systems are presented.
Processable heat‐resistant polymers. XIII. Structure–property relationship in polyamideimides
Authors: Maiti Sukumar , Ray Atanu
Published: April 2003

Novel isomeric polyamideimides were synthesized by reacting the diacid chloride of 2‐(4‐carboxy phenyl)‐1,3‐dioxoisoindoline‐5‐carboxylic acid and o‐, m‐, and p‐phenylenediamine at 30–70°C using polar solvents. The reactivity of the isomeric amines in the polycondensation reaction was studied. The isomeric effects on the physical, chemical, thermal, and electrical properties of the polymers were also studied. The polymers were found to be soluble in highly polar solvents such as DMF, DMAC, NMP, DMSO, m‐cresol, etc. Thermal analysis indicated that polymers were thermostable and that their thermal stability follows the order para > meta > ortho. X‐ray diffraction data revealed that para polymer is crystalline in nature. Dielectric properties with the variation of frequency at room temperature indicated that the dielectric constant and dielectric loss of the polymers follow the order ortho > meta > para.
Electrophoretic deposition of polymers. II. Polyimides: A coulombic study
Authors: Alvino W. M. , Fuller T. J. , Scala L. C.
Published: April 2003

Quantitative studies on the electrophoretic deposition of a polyimide polymer were carried out over the voltage range 25–100 V dc. Deposition yield was related to voltage, time, and coulombs and was found to obey Faraday's laws of electrolysis. Equations relating yield to voltage and coulombs were obtained from the plotted data. Results of coulombic studies indicate that the effective equivalent weight of the polymeric species being deposited is between 6800 and 7500 (i.e., amount deposited per faraday). The coulombic yield is 75 mg per coulomb. Information and speculation on the size and composition of the electroactive species are presented.
New hydantoin vinyl ether polymers
Authors: Eldin Sameer H.
Published: April 2003

The title hydantoin vinyl ether polymers are water‐soluble alternating copolymers of a hydantoin vinyl ether (HVE) and maleic anhydride (MA). The copolymerization parameters are ∼0 and 0.06, respectively. The HVE/MA polymers were compared with reference poly(vinyl pyrrolidone) (PVP) and methylvinylether (MVE)/MA polymers, of approximately the same specific viscosity, with regard to two key properties: solution viscosity and complexing capability (iodine). The HVE/MA polymers gave higher solution viscosities than PVP. When compared to MVE/MA, solution viscosity was lower initially but considerably higher after standing for a longer period of time. The inverse viscosity/time relationship observed for the MVE/MA polymer was not apparent in the case of HVE/MA. With regard to complexing capability the HVE/MA polymers proved to be clearly more effective. This is thought to be due to the HVE/MA polymer structure which offers two lactam groups plus two carboxyl groups for complexing vs. one lactam and two carboxyl groups, respectively, in the case of the reference polymers.
Elevated temperature aging of HIPS
Authors: Chen. C. C. , Habibullah M. , Sauer J. A.
Published: April 2003

The effects of aging at 85°C on a rubber‐modified polystyrene (HIPS) have been studied as a function of aging time in both air and nitrogen. Four different types of physical measurements were carried out on the aged samples. These included mechanical relaxation measurements, tensile stress–strain measurements, creep measurements at several stresses, and measurements of fatigue lifetime under applied tension–compression stress. Aging in nitrogen is largely a physical aging process and results in higher modulus, higher tensile strength, and longer delay times to the onset of accelerating creep deformation. But tensile ductility and fatigue lifetime tend to reduce, and there is no change in location of Tg of the rubber phase. Aging in air involves both chemical and physical aging, and the changes that occur depend on which process dominates. For long‐time aging of 150 h or more, the rubber‐phase Tg is shifted to higher temperatures and the associated loss peak is broadened due to crosslinking. Also, the tensile strength, tensile ductility, creep delay time, and fatigue life all reduce. These effects are attributed to oxidative attack and embrittlement. SEM micrographs reveal variations in fracture surface morphology due to the mode of testing and to the aging medium.
On‐line measurement of surface tension and density with applications to emulsion polymerization
Authors: Schork F. J. , Ray W. H.
Published: April 2003

Three process sensors are discussed, one for the determination of surface tension and two for the determination of liquid density. All three methods are on‐line, compatible with digital data acquisition systems, and capable of monitoring flowing process streams. The instruments are described and calibration data are given. Two mathematical models of the bubble tensiometer are developed. Data showing the application of these instruments to the monitoring of batch and continuous emulsion polymerization are given.
Flammability limits of some polymer pyrolysate–air mixtures
Authors: Day M. , Suprunchuk T. , Wiles D. M.
Published: April 2003

Several textile fabrics have been heated in a closed cell and the flammability limits of the gaseous products produced determined. In addition the energy released on combustion of these gaseous products has been measured in order to obtain an indication of the heat feedback capabilites of the fabric. Comparison of the data obtained was made in order to provide an indication of the flash fire potential of the materials and their contribution to a potential fire hazard situation.