bluuebunny/crossref_metadata_2025_split huggingface dataset:
The effects of melt history, crystallization pressure, and crystallization temperature on the crystallization and resultant structure of bulk isotactic polypropylene
Authors: Reinshagen J. H. , Dunlap R. W. 
Published: April 2003

AbstractA study of the effects of constant‐pressure isothermal crystallization on polymer structure was conducted in bulk isotactic polypropylene. The investigation was designed to determine the influence of pressure, temperature, and melt history variables on the structure of this bulk polymer. Results demonstrate that the effects of pressure and crystallization temperature can be quite adequately combined into one processing parameter, undercooling (defined as the melting temperature minus the crystallization temperature), by use of the Clausius‐Clapeyron equation. This parameter is demonstrated to be important in determining the kinetics of crystallization and the resultant structure. The moderate to high undercoolings involved in this study are representative of commercial injection‐molding processes, and a number of conclusions regarding commercial processing are made based on these laboratory investigations.
The effect of poly(vinyl bromide) on the layering of cotton fibers in flame‐retardant cotton/polyester blends
Authors: Boylston Eileen K. , Muller Linda L. 
Published: April 2003

AbstractCotton and cotton/polyester blends treated with phosphorus‐nitrogen polymers and poly‐(vinyl bromide) for flame retardance were examined in the electron microscope. A considerable amount of the poly(vinyl bromide) was retained by the cotton fibers. Expansion studies indicated that the poly(vinyl bromide) acted either as a morphologic adhesive or as a nonpolar matrix impervious to penetration by methacrylate before swelling.
Crystallization of macromolecular domains
Authors: Aharoni Shaul M. 
Published: April 2003

AbstractA theory is presented explaining the crystallization of polymers into thin and flat crystals or lamellae. Following the physical cluster theory, the internal and surface free energy of the “amorphous” macromolecular domain is described. Crystallization proceeds through an internal ordering of the domain, the attachment of the partially ordered domain onto a growth face, and, finally, regularization and domain deformation leading to minimization of both internal and surface free energy of the attached domain and its immediate neighborhood. The resultant fold surfaces comprise adjoining intact or deformed domes composed from proximal‐reentry loops. Although arising from an adaptation of the physical cluster theory to describe the macromolecular domain, the free‐energy equations controlling the crystallization process are essentially the same as those describing the primary nucleation in the prevailing crystallization theories. Segregation according to molecular weight is shown to arise from the size‐dependent ability of the domains to improve their internal ordering. Lamellar thickening is shown to follow a critical‐exponent equation dependent on surface free energy. Experimental data from the literature, corroborating the model, are presented.
Some aspects of photo‐initiated grafting to poly(vinyl alcohol)
Authors: Ogiwara Yoshitaka , Yasunaga Toshio , Kubota Hitoshi 
Published: April 2003

AbstractThree radicals showing singlet, triplet, and quartet, respectively, were observed in the photo‐irradiated poly(vinyl alcohol) (PVA). The signal intensity was increased by the ferric ion (Fe3+) sensitization and the formalization of samples. The triplet component radicals proved to keep fairly stable at room temperature, indicating a high stability of the radical toward warming. Since the Fe3+ sensitization and the formalization of samples brought about a very favorable graft copolymerization, the triple spectrum was assumed to have to do closely with the initiation of graft copolymerization. The spectra of singlet and quartet were assigned to alkoxy and methyl radicals, respectively, originated from the acetyl group remaining in PVA samples and the triplet spectrum to radicals on the α‐carbon of the hydroxyl group in the PVA molecule.
Surface differences and solute permeability in films of certain acrylic–methacrylic ester polymers
Authors: Abdel‐Aziz S. A. M. , Anderson W. , Armstrong P. A. M. 
Published: April 2003

AbstractThe influence of certain aspects of film surface on the diffusion of urea in aqueous solutions through films cast from two acrylic–methacrylic ester polymers has been investigated. Greater rate of permeation by urea occurred in films of both polymers when the lower surface (that in contact with the substrate during casting) was the entry surface for urea than when the upper surface (that in contact with the atmosphere during casting) was the entry surface. Furthermore, this difference between the upper and lower surfaces was more marked in film cast from one of the polymers; and scanning electron micrographs of films of the two polymers revealed differences in gross surface structure. Changes occurred in both upper and lower film surfaces during exposure to urea solution, the lower surface developing larger pores on exposure while smaller pores were observed on the upper side after exposure. The upper‐lower surface differences occurred in films of both polymers. The less hydrophilic film (Eudragit RS100) was associated with lower overall permeation rate for urea and smaller postpermeation mean pore size on both upper and lower surfaces than the more hydrophilic film (Eudragit RL100). The relationship between permeability and changing microscopic appearance of the surfaces is discussed and pictorial evidence of porous structure presented.
Determination of antioxidants in polypropylene by liquid chromatography
Authors: Wims Andrew M. , Swarin Stephen J. 
Published: April 2003

AbstractPolyolefins, such as polypropylene, are subject to thermal and oxidative degradation and are not used in practical applications unless protected by several antioxidants. Liquid exclusion (LEC) and liquid adsorption (LAC) chromatography have been used to determine the antioxidants in commercial polypropylenes and molded parts. Although a LEC analysis takes as long as 3 hr, LAC separations can be obtained in less than 15 min. Prior to the chromatographic measurements, the antioxidants were extracted from the talc‐filled polypropylene using tetrahydrofuran (THF) and Methylene chloride (CH2Cl2) for the LEC and LAC separations, respectively. Room‐temperature extraction of the additives as a function of time showed that 24 hr was sufficient for THF. A comparison of the LEC chromatogram for a freshly molded part to that for a part which was heat treated showed not only the depletion of certain antloxidants but also showed that the antioxidant distearyl 3,3′‐thiodipropionate (DSTDP) thermally decomposed to give stearyl propionate. Mass spectrometry was used to confirm the identity of the additives in the polypropylene without extraction. The “life” af several polypropylenes was also measured by thermogravimetric analysis and compared to the concentration of DSTDP.
The synthesis and properties of several polypropargylpyridinium and polypropargylbipyridinium polyelectrolytes and their simple and complex tetracyanoquinodimethane ion‐radical salts. I. Electrophysical properties
Authors: Kabanov V. A. , Aliev K. V. , Richmond J. 
Published: April 2003

AbstractPoly(propargylpyridinium chloride), poly(propargy1‐4‐vinylpyridinium chloride), poly(propargyl‐2,2‐bipyridinium chloride), poly(propargyl‐1‐methyl‐2,2‐bipyridinium methylsulfate chloride), poly(N‐ethyl‐vinylpyridinium bromide), and poly(propargyl‐2‐hydroxyquinolium chloride) were synthesized and a number of simple and complex, tetracyanoquinodimethane ionradical polyelectrolytes were prepared from them. An attempt was made to understand how the molecular structure of these compounds manifests itself in their observed electrophysical properties. Our results show increased electroconductivity in cases of simple and complex ion‐radical polyelectrolytes where the conjugated bond polymer “backbone” is in close proximity to dipyridyl polarizing side groups.
Copolymers of maleic anhydride‐14C and vinyl acetate as standards in an automated titration method for combined anhydride
Authors: Campbell D. R. 
Published: April 2003

AbstractCopolymers of maleic anhydride and vinyl acetate containing 6 to 54 wt‐% maleic anhydride were prepared in both toluene and methyl ethyl ketone by employing carboxyl‐14C‐labeled anhydride of demonstrated radiochemical purity. The standard copolymers thus prepared were used as reference materials in development of an automated titrimetric method for combined anhydride that had a standard deviation of 1.7 wt‐% at an anhydride level of approximately 50%. The semimicrotechnique described is based on dissolution of the polymer in methyl ethyl ketone–aqueous alkali, addition of an aliquot of this solution to a slight excess of hydrochloric acid, and back titration of the excess of acid with standard alkali. The technique effectively prevents hydrolysis of the acetate groups of the copolymer.
Photo‐induced radicals in glucose and cellobiose
Authors: Kubota Hitoshi , Ogiwara Yoshitaka , Matsuzaki Kei 
Published: April 2003

AbstractPhoto‐induced radicals in glucose and cellobiose, the model compounds of cellulose molecule, were studied by ESR spectrometry. Very poor formation of radicals in glucose as compared to those in cellobiose was observed. However, a spectrum showing a singlet line was easily produced by the use of light involving shorter wavelengths. It was estimated to be due to the radical formed at the reducing C1 position of glucose molecule. By paper chromatography, the photo‐irradiated cellobiose was confirmed to split into glucose through scission of glucosidic bonds in the molecule. The ESR spectrum of the acid‐hydrolyzed cellulose similar to that of the unhydrolyzed sample was a seven‐line spectrum, but the relative signal intensity was here markedly low. This phenomenon seems to be caused by the reduction of amorphous portion in the samples due to acid hydrolysis. It was concluded that the glucosidic bonds in cellobiose and cellulose molecules are very active toward light and play an important role in the radical formation in photo‐irradiated samples.
Shrinkage behavior of oriented PVC by thermomechanical analysis
Authors: Tobias John W. , Taylor Lynn J. 
Published: April 2003

AbstractThis paper describes a novel application of thermomechanical analysis. Observation and measurement of the thermal recovery of stresses induced in oriented PVC by stretching at elevated temperature is achieved by the modification of a commercial TMA instrument. Employment of an electronic signal differentiation system, in combination with this instrument, permits the simultaneous recording of the rate of shrinkage as a function of temperature. Specific examples are given which demonstrate the performance of the instrument and illustrate its application to problems of practical interest, such as effects of stretching and annealing conditions on shrinkage behavior.
Composites obtained by encapsulation and collimation of glass fibers within a thermoplastic matrix by means of polymerization
Authors: Baer Massimo 
Published: April 2003

AbstractStyrene and acrylonitrile monomers are polymerized in an aqueous suspension system in the presence of chopped glass strands. Under certain conditions, in the course of SAN polymerization, it is possible to align the glass strands in a parallel array (collimate) to form capsules varying in shape from tapes to cylinders. The parallel stacking of glass strands within the capsules allows for high glass loadings and results in glass microfibers completely wetted and imbedded in the polymeric matrix. The mechanism of encapsulation and collimation is discussed and is shown to be critically affected by several factors, the most important being: the preferential wetting of the strands by the monomers, the nature of the glass surface, the monomer composition, the type and concentration of protective colloid used in the suspension polymerization, and the type and intensity of agitation. The fiber glass composites obtained by encapsulation are found to have mechanical properties superior to those obtainable by conventional commercial routes.
Gas permeation of polymer blends. I. PVC/ethylene–vinyl acetate copolymer (EVA)
Authors: Shur Young J. , Rånby Bengt 
Published: April 2003

AbstractThe transport behavior of O2 and N2 were studied for series of physical blends of PVC with EVA having different vinyl acetate (VAc) contents in the EVA (45 and 65 wt‐%) and using different milling temperatures (160° and 185°C). The polymer blends were further characterized by dynamic mechanical measurements, density measurements, and x‐ray diffraction. At higher VAc content in EVA and with higher milling temperature, the rate of permeation (P) and the rate of diffusion (D) decrease, and the activation energy of D (from Arrhenius plots) increases. Furthermore, the experimental density values of PVC/EVA‐45 blends agree well with calculated values, assuming volume additivity of the two components, while those of PVC/EVA‐65 blends are higher than the calculated densities. These results are interpreted as due to denser packing of polymer molecules and increased PVC‐EVA interaction at higher VAc content and with higher milling temperature, indicating better compatibility between the blend components. The x‐ray diffraction data give no evidence of crystallinity. Sharp increases in P and D values at about 7.5% EVA (by weight) are found for PVC/EVA‐45 blends (in agreement with our previous work) but not for PVC/EVA‐65 blends. This is interpreted as due to a phase inversion at increasing EVA content in the former blends but not in the latter blends. The dynamic mechanical measurements show that the PVC/EVA‐65 blends milled at 160°C behave largely as semicompatible systems with maximum interaction between the two polymers at compositions of about 50/50 by weight.
Removal of alcohols, amines, and aliphatic acids in aqueous solution by NS‐100 membrane
Authors: Fang Herbert H. P. , Chian Edward S. K. 
Published: April 2003

AbstractRemoval of alcohols, amines, and aliphatic acids in single‐solute aqueous solution in the concentration range from 0.001 to 0.01M have been studied using the NS‐100 membrane. All the tests were conducted at 600 psig, 25°C, and a flow rate of 0.30 gpm. The mechanism of solute separation by the NS‐100 membrane differs from that of the cellulose acetate membrane. There was no significant correlation between the removal and the hydrogen bonding ability of the organic solute. Instead, for a given organic solute, its removal increases with the increases in the degree of crosslinkage of the skin layer of NS‐100 membrane, and is proportional to its degree of ionization (or degree of dissociation). For organic compounds having a same functional group, the removal of a compound increases with the increase in molecular weight and/or molecular branching. All of these are attributable to the relative nonpolarity and the anion exchanger characteristics of the membrane as well as to the steric resistance for the solute to permeate through the membrane.
Electric field‐induced piezoelectricity in polymer film
Authors: Zimmerman R. L. , Suchicital C. , Fukada E. 
Published: April 2003

AbstractAn apparatus is devised for measuring the real and imaginary components of the piezoelectric strain constant d = d′ − id″ for polymer films with a d.c. bias field. Electric fieldinduced piezoelectricity is observed for films of several types of polymer. The ratio of the piezoelectric constant to the d.c. bias field gives (ϵ + κ)/G where ϵ is the dielectric constant, κ is the electrostriction constant, and G is the elastic constant. The temperature dependence of the field‐induced piezoelectricity gives, therefore, combined information of dielectric and elastic properties of polymers. After heating to about 95°C followed by cooling to room temperature, maintaining a constant d.c. basis on a poly(vinyl chloride) film, piezoelectricity is observed at null d.c. field, which suggests the introduction of a residual polarization in the films.
Polymerization of organic compounds in an electrodeless glow discharge. V. Amines and nitriles
Authors: Yasuda H. , Bumgarner M. O. , Hillman J. J. 
Published: April 2003

AbstractPolymerizations of amines and nitriles in a glow discharge generated by inductive coupling of 13.5‐MHz radio frequency are investigated by employing the measurement of closed‐system pressure change. It is found that nitrogen in those compounds are incorporated into polymer in a nearly stoichiometric manner and that the polymerization of those compounds are very much similar to that of hydrocarbons. Hydrogen detachments, opening of double bond and/or cyclic structure, opening of triple bond including CN, and opening of aromatic and heteroaromatic structures contribute to polymerization of amines and nitriles.
The effect of photodegradation of polystyrene on its permeability characteristics
Authors: Greenwood R. , Weir N. A. 
Published: April 2003

AbstractThe diffusion (D) and permeability (P) coefficients for 14CO2 in polystyrene films which had been irradiated by short‐wave ultraviolet (253.7 nm) radiation under vacuum and in oxygen were determined in the temperature range of 20° to 55°C. Both D and P decreased with increasing exposure, the vacuum‐irradiated sample showing significantly greater decreases, presumably on account of a larger extent of crosslinking which was possible in the absence of oxidation. A good correlation was observed between crosslinking and decreasing P and D values. The solubility coefficients for all irradiated samples increase with increasing dose. Activation energies for diffusion increase with increasing irradiation, particularly for the vacuum‐irradiated samples. Reductions in P and D values are interpreted in terms of free‐volume decreases due to crosslinking and other modifications, while the increasing activation energies are attributed to the increasing energy requirements for creation of free volume in modified polymers.
Rheogoniometry of molten blends of polystyrene and styrenic ionomers
Authors: Iwakura Kenji , Fujimura Toshikazu 
Published: April 2003

AbstractThe rheological properties of the molten blends between polystyrene (PS) and styrenemethacrylic acid copolymer (S‐MAA) or its metallic salts were determined with a Weissenberg rheogoniometer, and the mixed structure and the processability were discussed. Results were as follows. (1) The viscosities of the salts increased and the compliances decreased with increasing density of ionic crosslinkings. (2) The viscosities of the molten blend between PS and S‐MAA or its salt increased steeply even at lower shear rate and the Newtonian flow region was not observed. (3) This shear‐sensitivity of viscosity in low shear rate region increased with increasing temperature. (4) The effect of temperature on the viscosity of these blends deviated from the simple Arrhenius plot. (5) Some network structures are suggested for the blends between PS and S‐MAA salts but they may be broken eventually under high shear rate or at high temperature. Therefore, the mixed structures and the flow mechanisms of these molten blends seem to change with shear or temperature.
Surface fluorination of transparent polymer film
Authors: Shimada Junichi , Hoshino Mitsutoshi 
Published: April 2003

AbstractTransparent polymer film was fluorinated by contacting with fluorine gas. The fluorinated layer depth was determined from the visual spectrum. The relation between fluorinated depth d and reaction time t was represented by d = k·t½. This result indicates that fluorine diffusion plays a predominant role in forming the diffusion profile. The apparent activation energy of fluorine gas diffusion into polystyrene (PS) and polycarbonate (PC) was 2.8 kcal/mole and 6.6 kcal/mole, respectively. The refractive index distribution from surface to center, which corresponds to the fluorine content in the layer, was determined by interference microscopy. PS and PC showed nearly stepwise change of refractive index. On the other hand, poly(methyl methacrylate) showed a gradual change. These results are compatible with fluorine analysis data and IR spectra of the fluorinated polymers. On the basis of these results, antireflecting layers on plastic lens or plate, plastic optical fiber, or fiber sheet were formed.
Absorption of water by graft copolymers of cotton with methyl methacrylate using high‐resolution NMR
Authors: Mousa A. M. , Aziz Akram 
Published: April 2003

AbstractGraft cotton fibers containing poly(methyl methacrylate) were initiated by ultraviolet radiation. High‐resolution NMR was used to study the nature of water absorption by these graft copolymers and also by mixtures of cotton fibers with the corresponding homopolymers. Results obtained help in investigating the structure of the copolymers and to differentiate, in a simple way, between true graft copolymers and mechanical mixtures or coated fibers.
Chemical modification of acrylonitrile copolymers: Reaction of cationic copolymers with ethylene oxide
Authors: Courtney J. M. , Gilchrist T. 
Published: April 2003

AbstractCopolymers of tertiary amines have been reacted with ethylene oxides gas. The reaction induces low temperature cyclization and increases polymer hydrophilicity. When the co‐polymer is in film form, water permeability is dependent on ethylene oxide processing time and temperature.The behavior of the copolymer films when treated with ethylene oxide is contrasted with the effects due to thermal treatment of acrylonitrile copolymers.
Stress wave‐initiated fracture in amorphous thermoplastics
Authors: Hagerman E. M. , Mentzer C. C. 
Published: April 2003

AbstractSeveral brittle thermoplastic materials, including polystyrene, SAN, and PMMA, were tested in tension using a spectrum of testing rates up to 15,000 in./min (630 cm/sec). At test velocities below 7000 in./min (294 cm/sec), the materials behaved “classically” with strength properties increasing, elongation decreasing, and single fractures generally forming. At rates between 7000 and 9000 in./min (294 and 378 cm/sec), a transition from classical to stress wave‐initiated fracture was observed. The mechanical properties, the nature of the fracture, and the nature of the crazing preceding fracture were shown to be profoundly affected when the materials were strained at rates sufficient to initiate stress wave fracture. Under these conditions, the apparent load‐carrying capabilities of the materials were reduced by an order of magnitude.
Changes in the morphology of cast nylon 6 through copolymerization
Authors: Kubota Hideo , Nowell Joseph B. 
Published: April 2003

AbstractCorrelations were made between several physical and mechanical properties and crystal morphology for copolyamides composed of caprolactam and either capryllactam or laurolactam as a minor comonomer. Incorporating a comonomer into the nylon 6 chain decreases the crystallinity and crystal size and, in addition, depresses the melting point of the polymer much more than predicted by the classical Flory theory on random copolymers. This fact, along with the change in the x‐ray diffraction patterns, indicates that small amounts (up to 10 mole‐%) of comonomer can enter the polymer crystals without any basic change in the α‐form crystal structure. The variation of copolyamide densities with comonomer content also supports this theory. The initial moduli of the copolyamides, when tested above their glass transition temperatures, obey a linear relationship with the reciprocal of the amorphous content of the polymers. The impact strength increases dramatically with decreases in crystallinity and crystal size. Some of these materials have extremely large ultimate elongations and have glass transition temperatures below room temperature.