bluuebunny/crossref_metadata_2025_split huggingface dataset:
Time–temperature superposition of time‐dependent birefringence for low‐density polyethylene
Authors: Onogi Shigeharu , Asada Tadahiro , Fukui Yoshiharu , Fujisawa Takeo 
Published: April 2003

AbstractThe time‐dependent birefringence has been measured simultaneously with the stress relaxation on quenched and annealed low‐density polyethylene at various temperatures from 10 to 70°C. The strain‐optical coefficient increases generally with increasing time, and approaches the equilibrium value, which depends upon the temperature. When the strain‐optical coefficient at a fixed time is plotted against temperature, it first increases and then decreases after passing through a maximum at Tmax with increasing temperature. The higher the degree of crystallinity, the higher are the equilibrium values of the strain‐optical coefficient and Tmax. The curves for strain‐optical coefficient versus time and relaxation modulus versus time below Tmax can be superposed well by a horizontal shift along the abscissa. The optical shift factor obeys the original WLF equation, while the mechanical shift factor is much larger than the optical one. The molecular mechanisms corresponding to this dispersion of the strain‐optical coefficient and viscoelastic αc absorption peak near Tmax are discussed.
Time–temperature superposition of the dynamic birefringence of polyethylene
Authors: Takeuchi A. , Stein R. S. 
Published: April 2003

AbstractThe dynamic strain‐optical coefficient of low‐density polyethylene is found to decrease with increasing frequency and increase with increasing temperature (at temperatures up to 60°C.). It is found that a series of curves representing the real, K′, and imaginary, K″, parts of the frequency variation of the strain‐optical coefficient obtained at various temperatures up to 60°C. may be superposed by translation along the frequency axis. The temperature dependence of the shift factor corresponds to an Arrhenius type equation with an activation energy of the order of 25 kcal./mole. This may be compared with the similar value obtained by Takayanagi for the αc′ mechanical loss and with the dynamic x‐ray diffraction values reported by Kawaguchi et al., but is somewhat lower than the value of 34 kcal./mole reported by Onogi et al. from birefringence relaxation studies. Takayanagi has ascribed the αc′ peak to cooperative motion of crystalline and amorphous regions of the sort that might be involved in the suggested sliding of lamellae over each other. At temperatures higher than 80°C., horizontal superposition is not possible.
Déformation plastique des hauts polymères vitreux soumis á un système de contraintes quelconque
Authors: Bauwens Jean‐Claude 
Published: April 2003

AbstractThe theory of rate processes has been applied by Eyring to the plastic flow of solids, but he considers only the case of simple shear. Some assumptions concerning a generalization of this theory for an arbitrary strain tensor are here proposed and discussed. The components of the deformation and the work done by the deviator of the stress during the elementary flow process are evaluated. According to these results, it can be proved that the yield condition of Huber, Hencky, and von Mises is valid when there is no hydrostatic stress. The discrepancy between the yield stresses corresponding to tensile and compressive tests is explained by the influence of the hydrostatic component and evaluated by taking account of the amount of free volume required for an elementary jump. The calculated value agrees with the experimental data. Measurements of the inclination of Lüder's bands and deformation components on poly(vinyl chloride) flat bars strained by tensile tests are in good agreement with the proposed theory.
Carbon black reinforcement in preswollen rubbers. Part II
Authors: Cotten G. R. 
Published: April 2003

AbstractThe mechanism of carbon black reinforcement was studied by examining stress–strain properties of preswollen (i.e., cured in the swollen state then deswollen) SBR‐1500 vulcanizates and the effect of heat treatment on such samples. It was found that the supercoiling of molecular chains leads to a purely viscous response at low elongations. On heating of preswollen samples, molecular rearrangement at the carbon black surface occurs, leading to a considerable increase in modulus. The activation energy of that process was determined by using the superposition principle.
Diffusion in glassy polymers. IV. Diffusion of methyl ethyl ketone in atactic polystyrene above the critical concentration
Authors: Odani Hisashi 
Published: April 2003

AbstractIntegral absorption and desorption of methyl ethyl ketone in atactic polystyrene were studied as functions of film thickness at 25 and 45°C. with concentrations above the critical concentration of the system. In all cases investigated, the reduced absorption and desorption curves for films of different thicknesses did not give a single curve, though the individual absorption and desorption curves appeared to have the shape expected from the Fickian diffusion mechanism. The initial slopes of the reduced curves increased with increasing film thickness for both absorption and desorption. The quantity R0, the value of the reciprocal of the half‐time for absorption or desorption extrapolated to zero concentration increment, provides a measure of absorption rate at a given initial concentration. The dependence of R0, on film thickness was almost unaltered in the concentration region concerned at both temperatures. The values of the mutual diffusion coefficient D of the system were calculated by assuming absorption and desorption processes for hypothetical film of infinite thickness to be controlled by the purely Fickian mechanism. The values of D evaluated by this method agreed quite well with those deduced by Kishimoto from steady‐state permeation measurements.
NMR studies of polymer solutions. II. Polyethylene
Authors: Liu Kang‐Jen 
Published: April 2003

AbstractThe intramolecular structure of polyethylene in solution was studied by a high‐resolution nuclear magnetic resonance technique. Highly purified n‐alkanes (99.5%) from C5H12 to C36H74 were used as its oligomers. The NMR spectra of the polyethylenes (oligomers) are very sensitive to the solvents used. The internal methylene protons of all polyethylenes of various chain length resonance at an identical frequency in carbon tetrachloride. A sharp transition in the NMR spectrum of polyethylene in α‐chloronaphthalene at 35°C. was observed at n‐C17H36, above which there exist two distinguishable NMR peaks for internal methylene protons, and below which (fewer carbons) only a single peak was seen. The NMR spectra of the internal methylene protons of the polyethylenes (oligomers) taken in benzene are very similar to those taken in pyridine. They are not as easily resolved as those NMR spectra taken in α‐chloronaphthalene solutions. The effect of the size of the aromatic solvent molecule on the NMR spectra of the internal methylene protons of the polyethylenes (oligomers) in solutions was demonstrated by using aromatic solvents of various sizes, such as chlorobenzene, α‐chloronaphthalene, and 9‐chloronathracene. The results indicate that the formation of polymeric structure of the internal methylene groups in the polyethylene chain is very sensitive to the size of the solvent used. The interaction of the solvent with the methylene groups of the polyethylenes varies as a function of chain length; it is stronger for those low member n‐alkanes and decreases gradually to an asymptotic value.
Mechanical structures in polymer melts. I. Measurements of melt strength and elasticity
Authors: Busse W. F. 
Published: April 2003

AbstractThe standard methods of measuring the elastic properties of polymer melts are briefly reviewed and a method of measuring another combination of viscoelastic properties, the melt strength, is described. Data are presented on the melt strength of various types of polyethylene resins and on ionomer resins. The effects on various viscoelastic properties of branching or of the addition of fine fibrils of Teflon perfluorocarbon resin are reported.
Molecular weight distribution and thermal characterization of polydimethylsilmethylene
Authors: Levin G. , Carmichael J. B. 
Published: April 2003

Abstract1,1,3,3‐Tetramethyl‐1,3‐disilacyclobutane (I) was polymerized under the following conditions with H2PtCl6·6H2O as catalyst: (a) addition of I dropwise to a large excess of catalyst at room temperature, producing [(CH3)3SiCH2(CH3)2Si]2O in 90% yield; (b) polymerization at room temperature in the presence of 10% water with 23 ppm Pt, yielding 9% conversion to low molecular weight polymer after 4 weeks; (c) polymerization in an open vessel (25°C., 7 ppm Pt, M̄n = 1.2 × 105), a closed vessel (100°C., 28 ppm Pt, M̄n = 1.7 × 105), in a closed tube after twice freezing and evacuating (25°C., 23 ppm Pt, M̄n = 2.9 × 105); (d) polymerization in an oxygen atmosphere (25°C., 17 ppm Pt, M̄n = 2.7 × 105). The molecular weight distributions of the polymers with M̄n = 1.2 × 105 and 1.7 × 105 was studied by gel‐permeation chromatography. Ratios of M̄w/M̄n are 3.1 and 2.7, respectively. In both cases a long tail of high molecular weight polymer is evident. Interpretation of the molecular weight distributions is qualitatively discussed on the basis of a postulated seven‐step mechanism. Water is shown to be a source of chain termination. Evidence is presented for the existance of SiOSi and SiOH in the silmethylene polymers. Negligible cyclization occurs. Orders of thermal stability measured by DTA and TGA for polydimethylsilmethylene (A), polydimethylsiloxane (B), and polysiobutylene (C) are: in He, A > B > C; in air, in air, B > C ≅ A. A fractionally precipitated polydimethylsilmethylene had a weight loss of less than 5% by 600°C. by TGA analysis at 10°C./min. in He.
Effect of chlorosilanes on the radical polymerization of styrene and methyl methacrylate
Authors: Minoura Yuji , Enomoto Yasushi 
Published: April 2003

AbstractStyrene (St) and methyl methacrylate (MMA) were polymerized by azobisisobutyronitrile at 50°C. in the presence of silanes such as tetramethylsilane, trimethylcholorosilane, dimethyldichlorosilane, methyltrichlorosilane, and tetrachlorosilane. The polymerization rates of both St and MMA in the presence of silanes were nearly equal to those in the absence of silanes. On the other hand, the molecular weights decreased gradually as the concentration of chlorosilane increased. The chain transfer constants of all the silanes in the polymerization of St and MMA at 50°C. were calculated by Mayo's equation. The chain transfer constants of Me4Si, Me3SiCl, Me2SiCl, MeSiCl3, and SiCl4 were 0.31 × 10−3, 1.25 × 10−3, 1.78 × 10−3, 1.92 × 10−3, and 2.0 × 10−3, for St and 0.13 × 10−3, 0.22 × 10−3, 0.245 × 10−3, 0.27 × 10−3, and 0.30 × 10−3, for MMA, respectively. From these results, it was found that the SiCl bond was radically cleaved. The Qtr values of the silanes, in the same order as above, were found to be 1.03 × 10−4, 2.33 × 10−4, 2.83 × 10−4, 3.10 × 10−4, and 3.35 × 10−4, respectively and the etr values were +0.58, +1.30, +1.50, +1.48, and +1.43, respectively.
Graft polymers from poly(vinyl chloride) and chlorinated rubber
Authors: Rao S. Prabhakara , Santappa M. 
Published: April 2003

AbstractGraft polymers from poly(vinyl chloride) (PVC) and chlorinated rubber (CIR) with side chains of poly(methyl methacrylate) (PMMA), poly(methyl acrylate) (PMA), or poly(ethyl methacrylate) (PEMA) were synthesized. For this purpose, a vinyl monomer was polymerized in the presence of small quantities of PVC or CIR with benzoyl peroxide as catalyst. The graft polymers were separated from both homopolymers by precipitation with methanol from methyl ethyl ketone solutions of the reaction products and the grafting efficiency was calculated. The graft polymers were characterized by infrared spectra, elemental analysis, NMR, and osmometric or light‐scattering determinations. From the results it is concluded that the PVC or CIR molecules contain side chains of PMMA, PMA, or PEMA. The graft polymers showed higher molecular weights, and the values of second virial coefficient for these polymers were much different from those of the starting polymers.
Ladder polyphenoxazines
Authors: Stille J. K. , Freeburger M. E. 
Published: April 2003

AbstractTwo ladder polyphenoxazines have been prepared by the polymerization of 4,6‐diaminoresorcinol dihydrochloride (I) with 2,5‐dihydroxy‐p‐benzoquinone (III), or 2,5‐diacetoxy‐p‐benzoquinone (II) and with 2,5‐dihydroxy‐3,6‐dichloro‐p‐benzoquinone (IV) in a hexamethylphosphoramide (HMP) solvent. When tetrahydrofuran (THF) was the polymerization solvent, the reaction of I with II or IV produced a linear poly‐Shiff's base which could be converted to the ladder polymer by heating in HMP. The thermal stability of the ladder polyphenoxazines was surprisingly poor; a slow decomposition started at ca. 275°C. under nitrogen.
Polymerization of styrene with ZrCl4 and ZrCl3 in combination with Al(C2H5)3
Authors: Malhotra S. L. , Deshpande A. B. , Kapur S. L. 
Published: April 2003

AbstractThe polymerization of styrene with two catalyst systems consisting of Al(C2H5)3 in combination with ZrCl4 or ZrCl3 has been studied. The rate of polymerization with catalyst concentration was first‐order with ZrCl4 system and second‐order with ZrCl3 system, but at higher catalyst concentrations in both cases, the rate progressively decreases and finally attains a low value. The rate of polymerization is, however, proportional to the square of the monomer concentration in both the cases. The overall energy of activation was 10.9 kcal./mole and 6.45 kcal./mole in these systems. The polymers obtained with ZrCl4 were of lower molecular weights as compared to those obtained with ZrCl3. The polymers in both the cases had amorphous character.
Benzimidazole‐ and oxadiazole‐modified aromatic polyimides
Authors: Frost L. W. , Bower G. M. , Freeman J. H. , Burgman H. A. , Traynor E. J. , Ruffing C. R. 
Published: April 2003

AbstractThree series of aromatic primary diamines were synthesized. The first series of three contained one or two hydrazide groups. The second series of five contained one or two oxadiazole groups. The third series of four contained one or two benzimidazole groups. Reaction of each diamine with either pyromellitic dianhydride or 3,4,3′,4′‐benzophenonetetracarboxylic dianhydride gave a series of soluble polymeric amic acids, from which films of good thermal stability were cast. The heat‐cured films were either oxadiazoleimide or benzimidazole‐imide polymers, depending upon the diamine used. When hydrazide‐amic acid polymers were heated, the conversion of amic acid to imide was essentially complete before any substantial portion of the hydriazide linkages were converted to oxadiazole. The latter conversion was accompanied by degradation. A better method of preparation for these polymers is through the oxadiazole contaning diamines. One hydrazide‐imide polymer was prepared from trimellitic anhydride and was converted to an oxadiazole‐imide by heating. The reaction of equimolar quantities of a dianhydride with 3,5,2′‐triaminobenzanilde gave a soluble polymer which was converted to a benzimidazole‐imide by heating.
Lewis acid‐catalyzed reactions on polystyrene
Authors: Gaylord N. G. , Hoffenberg D. S. , Matyska B. , Mach K. 
Published: April 2003

AbstractThe action of aluminium halides upon polystyrene was studied as a function of the nature of the reaction medium and of the concentration of catalyst. It was demonstrated that polystyrene undergoes crosslinking, the extent of which is particularly important in chlorinated aliphatic solvents and at high catalyst concentrations. In additions, phenyl rings of the polymer are alkylated and halogenated by the solvent or catalyst. Infrared spectroscopic investigation of the structure of the products indicated that in most cases crosslinking was connected with the formation of 1,4‐disubstituted, and eventually 1,2,4‐trisubstituted benzenes. In carbon tetrachloride medium, meta substitution was also detected. In products obtained when polystyrene was treated with high amounts of the Lewis acid in CCl4 medium degrees of substitution even higher than three were probable.
Morphology of nascent polyolefins prepared by Ziegler‐Natta catalysis
Authors: Blais P. , Manley R. St. John 
Published: April 2003

AbstractThe morphology of nascent (i.e., as‐polymerized) Ziegler‐Natta polymers was studied by optical and electron microscopy and x‐ray and electron diffraction. Observations were made on six polyolefins: polyethylene, polybutene, polypropylene, polystyrene, poly‐4‐methylpentene‐1, and polyisoprene. These polymers were synthesized by using conventional techniques by polymerizing the undiluted monomer or monomer–diluent mixtures with a preformed heterogeneous catalyst obtained by reacting a titanium halide and aluminium alkyl. After the reactions were terminated the polymers were subjected to suitable purification treatments and stored in the wet state. Observations in the optical microscope revealed that, in most cases, the polymers is formed as discrete hollow particles with a fibrous texture, but in a few instances, depending upon experimental conditions, it could also form as fibrous sheets or webs. More detailed observations in the electron microscope showed that the polymer is composed of a profusion of fibrils 200–1000 A. in width and of indefinite length. The fibrils themselves have a fine structure as indicated by the presences of lamellae running prependicular to their length. Various interpretations of this appaerent structure are discussed. The x‐ray and electron diffraction studies show that the molecular chain axis is oriented prependicular, or nearly so, to the plane of fibril lamellae and suggest that the molecules are folded within the lamellae in a manner analogous to conventional polymer single crystals. As fibril formation is observed under most conditions of polymerization it is considered to be basic to the mechanism of Ziegler‐Natta catalysis. It is proposed that the fibrils are formed by the crystallization of polymer chains growing from the active sites on the catalyst surface. The process is likened to root growth in whiskers, new materials being added at the base or root. The detailed mechanism of fibril formation and of the organization of the fibrils into larger structural formations are obscure, but several possibilities are discussed.
Polymer reactions. II. Thermal decomposition of polyethylene hydroperoxide
Authors: Chien James C. W. 
Published: April 2003

AbstractPolyethylene hydroperoxide (PEH) was prepared by low‐temperature autoxidation initiated by AIBN. Over 85% of the total hydroperoxyl groups decompose by a rapid process, the remainder dissociate at about one‐tenth of that rate. The results are the same whether PEH is decomposed in solution or in the solid state. Large amounts of scavenger have no effect on these decompositions; there is no radical‐induced processes. The results suggest mechanisms of decomposition involving neighboring group assistance.
Polymer reactions. IV. Thermal decomposition of polypropylene hydroperoxides
Authors: Chien James C. W. , Jabloner H. 
Published: April 2003

AbstractThe thermal decomposition of polypropylene hydroperoxide (PPH) consists of two consecutive reactions. The initial, faster reaction has rates up to 60 times that of the slower process. The former is largely suppressed by the addition of an excess of 2,6‐di‐tert‐butyl‐p‐cresol. The course of reaction is the same in either solid state or in solution. The results are consistent with an intramolecular radical‐induced mechanism for the initial reaction. This faster reaction consumes about 70–95% of the total hydroperoxides. The decomposition of PPH yields a maximum of about 1.8 radicals. Samples prepared from crystalline and amorphous polypropylenes have identical decomposition kinetics.
Polymerization of vinylcyclopropanes. II
Authors: Takahashi Takako 
Published: April 2003

Abstract1,5‐Type polymerization of vinylcyclopropane proceeding by the opening of both the double bond and the cyclopropane ring was found. Some other vinylcyclopropane derivatives, 1,1‐dichloro‐2‐vinylcyclopropane, 1,1‐dibromo‐2‐vinylcyclopropane, isopropenylcyclopropane, 1‐methyl‐1‐vinylcyclopropane, 1,1‐dichloro‐2‐methyl‐2‐vinylcyclopropane, and cis‐ and trans‐1‐chloro‐2‐vinylcyclopropane, were investigated. The observation of infrared spectra, NMR spectra, and other data indicated that the radical polymerization of these compounds gave principally 1,5‐type polymer, while in cationic polymerization 1,2‐type was predominant. The behavior of the polymerization was discussed in terms of the stability of a cyclopropylcarbinyl ion or radical which is formed in the initiation and propagation steps.
Polymerization of tetrahydrofuran by AlEt3–H2O promoter system: Rate of propagation reaction
Authors: Saegusa Takeo , Imai Hirosuke , Matsumoto Shu‐Ichi 
Published: April 2003

AbstractKinetic studies were carried out on the polymerization of tetrahydrofuran with catalyst systems of aluminum alkyl–epichlorohydrin. As aluminium alkyl species AlEt3, AlEt3–H2O (1:0.1 to 1:1.0), and “oxyaluminum ethyl” were employed. The polymerizations with these catalysts are characterized by a mechanism of stepwise addition without chain transfer or termination, which is expressed by the kinetic relation Rp = Kp[P*] ([M]–[M]e), where [M] and [M]e are the instantaneous and equilibrium concentrations of monomer and [P*] is the concentration of propagating species calculated from the amount and molecular weight of the product polymer. The determination of the rate constant kp for these catalysts has shown that the polymerization rate varied considerably with the change of aluminum alkyl species, i.e., with the water‐to‐aluminum ratio, but the propagation rate constant itself varied very little. The variation of polymerization rate was, therefore, attributed primarily to the differences in concentration of the propagating species, i.e. the efficiency of the catalyst in forming propagating species. The catalyst efficiency was closely related to the acid strength of the aluminum alkyl species, which was estimated from the magnitude of shift of the xanthone carbonyl band in the infrared spectrum of its coordination complex with aluminum alkyl. The maximal catalyst efficiency was attained at about [H2O]/[AlEt3] = 0.75.
Sorption of water vapor by poly(vinyl alcohol): Influence of polymer crystallinity
Authors: Takizawa Akira , Negishi Takao , Ishikawa Kinzo 
Published: April 2003

AbstractThe influence of crystallinity on water sorption behavior by poly(vinyl alcohol) (PVA) was studied by using a PVA of low crystallinity (15% crystalline by x‐ray analysis) and an annealed sample there from (46%) crystalline. With the increase of crystallinity, the sigmoid shape (which is a characteristic for the sorption isotherm of the low crystalline polymer) diminishes. The B.E.T. plots of the isotherms are linear between the relative vapor pressures of 0.1 and 0.4 as usual, and deviate from straight lines in the higher pressure range in the direction of a larger sorbed quantity than that predicted by the B.E.T. theory. This tendency is regarded as a kind of dissolution, and the Flory‐Huggins interaction parameter χ1 was calculated. In both polymers, the χ1 versus pressure relation has a maximum, while overall χ1 values are smaller in the polymer of low crystallinity. The maximum point (which lies in the higher pressure region in case of the less crystalline sample) is considered to be a transition point from a phenomenon controlled mainly by an adsorption mechanism to a phenomenon controlled mainly by a dissolution mechanism. Accordingly, the separation of the isotherm into adsorption and a dissolution components was made, and the polymer fraction which contributes to the dissolution mechanism versus pressure relation was calculated. The result indicates that the crystalline region observed by x‐ray analysis may partly contribute to the dissolution process at room temperature.