bluuebunny/crossref_metadata_2025_split huggingface dataset:
Relations between dynamic mechanical properties and melting behavior of nylon 66 and poly(ethylene terephthalate)
Authors: Bell James P. , Murayama Takayuki 
Published: April 2003

AbstractNylon 66 films exhibiting form I melting behavior show the γ mechanical relaxation at −140°C. Samples which have form II melting behavior do not show this relaxation. The γ relaxation disappears when material having form I behavior is converted to material having form II behavior by annealing or by cold drawing. The form I and form II types of melting behavior are also found in poly(ethylene terephthalate); the interconversions and thermal behavior of the forms are analogous to the nylon 66 case. In poly(ethylene terephthalate), the β relaxation at −40 to −60°C is present only when form I melting behavior is found. Conversion to form II melting behavior by annealing or drawing (80°C) again causes the relaxation to disappear. No β relaxation was found in amorphous polymer. The γ dispersion in nylon 66 and the β dispersion in poly(ethylene terephthalate) can therefore be associated with the crystalline structure responsible for form I melting behavior. Form I melting behavior has been associated with foldedchain crystals based on previous work. It is therefore postulated that the γ dispersion in nylon 66 and the β dispersion in poly(ethylene terephthalate) are associated with motions in the chain folds. This assignment is not inconsistent with the change in the γ dispersion of nylon 66 with the number of backbone CH2 units, since these will affect the fold structure.
Typical fiber structure
Authors: Ishikawa Kinzo , Miyasaka Keizo , Maeda Masahiko , Yamada Mitsuo 
Published: April 2003

AbstractModel fibers of polyethylene and nylon 6 were strained in the direction of the fiber axis and the internal deformation of the samples was studied by large‐angle and small‐angle x‐ray diffraction. The compression of samples along the fiber axis was successfully carried out, and the results obtained by x‐ray methods yielded more interesting information on the structure of the fibers than was obtained in extension. A model for the structure of the fiber was constructed on the basis of the results on compressed fibers. In this model, crystals are distributed in cylindrical symmetry around the fiber axis keeping a crystal axis tangential to circles in the section normal to the fiber axis. The characteristic crystal axis is the b axis in polyethylene and the a axis in nylon 6. The chain axis of the crystals varies in orientation with respect to the fiber axis. In compression of fibers with such a structure, the crystals rotate around the characteristic axis indicated above. In the case of nylon 6 fiber, only this simple rotation seems to occur, while additional changes occur in polyethylene fibers. However, the simple rotation predominates even in polyethylene fibers. This fiber structure is correlated with the structure of thin films of the materials. This similarity proves the existence of a common mechanism for the origin of the structure of fibers and films.
Chromatographic fractionation of polystyrene: An evaluation of the nature of column fractionation
Authors: Yamaguchi Kinya , Saeda Shigeru 
Published: April 2003

AbstractColumn chromatographic fractionation of polystyrene was carried out with the methyl‐ethyl ketone–methanol system, and effects of various experimental conditions on the fractionation efficiency were studied. For samples with molecular weights below about 6 × 105, neither the temperature gradient (0.7°C/cm), nor the flow rate of solvent (30–270 ml/hr) seriously influences the fractionation efficiency. The effect of temperature gradient becomes apparent only in the high molecular weight region and only if the gradient of the solvent composition is too steep. High flow rates (ca. 125 ml/hr) clearly affect the fractionation efficiency for a high molecular weight sample (Mw = 5.46 × 105). Precipitation chromatography for the fractionation system was calculated from the phase equilibrium data according to the mass transport equation proposed by Schulz et al. The theoretical analysis gives support to the observed dependence of the temperature effect on molecular weight. Comparison of the observed and theoretical relations between elution volume and molecular weight of the fraction, on the other hand, indicates that the process of fractionation is simply elution of polymer off the support without reprecipitation. Certain conditions of polymer deposition on the support are required for optimal results.
Formation of kink bands in oriented polymers
Authors: Robertson Richard E. 
Published: April 2003

AbstractThe circumstances of the formation of kink bands have been investigated with a newly designed shearing device and light and electron microscopes. Kink bands having sharp edges and reflection symmetry about the edges were formed and studied in the two crystalline polymers, high‐density polyethylene and isotactic polypropylene, but could not be formed in the two glassy polymers, poly(4,4′‐dioxydiphenyl‐2,2‐propane carbonate) and poly(2,6‐dimethylphenylene oxide). The characteristics of the oriented polymer that promote kink bands seem to be easy slip along the orientation axis, and resistance of the oriented fibrils to length changes. Kink bands were found to initiate at sites of shear stress concentration, where the fibrils are first deformed into an S‐shaped curve, that then tightens and finally collapses into kinks.
Melting temperatures of poly(2,6‐dimethyl‐1,4‐phenylene oxide) in methylene chloride solutions: Thermodynamic analysis
Authors: Shultz A. R. , McCullough C. R. 
Published: April 2003

AbstractMelting temperatures were observed visually for poly‐(2,6‐dimethyl‐1,4‐phenylene oxide) in methylene chloride at nine concentrations (polymer weight fractions ranging from 0.0042 to 0.2362). The data were analyzed upon the assumptions that ΔHu and ΔSu, the molar heat and entropy of fusion per polymer unit, are constant over the temperature range studied, and that a Flory‐Huggins chemical potential expression with a concentration‐independent pair interaction parameter, χ1 = (0.5 + ψ1) + ψ1Φ/T, satisfactorily describes the polymer unit activity in the binary solutions. Computation gave ΔHu = 1404 cal/mole of units (therefore Δh = 11.7 cal/g), ψ1 = −0.5691, and Φ = 342.4°K. The effect of using various combinations of data points upon the values of these three parameters, as determined by least‐squares linear regression treatment of the melting temperature expression, is indicated.
Scattering of light from deformed regions surrounding voids and inclusions in high polymers
Authors: Stein Richard S. , Wilkes Garth L. 
Published: April 2003

AbstractThe Hv cloverleaf scattering pattern sometimes found for amorphous polymers can arise from the birefringent region caused by the strain surrounding a void or an inclusion in a polymer. The form of such a pattern may be theoretically explained by extension of a theory due to Goldstein.
Dielectric properties of polystyrene and some polychlorostyrenes from 4°K to room temperature
Authors: McCammon R. D. , Saba R. G. , Work R. N. 
Published: April 2003

AbstractDielectric measurements of carefully purified specimens of polystyrene and poly(2,3,4 or 3,4‐chlorostyrene) have been obtained at audio frequencies ranging from 0.1 to 20 kHz and at temperatures between 4 and 300°K. Each of the samples exhibits a dielectric loss maximum in the range 15–50°K. The temperature of the maximum loss decreases with the addition of a substituent which lowers the symmetry of the pendant phenyl group. The results are explained by a model which invokes a coupling mechanism between two distinct modes of side group motions. This same model also explains some results of previously reported measurements of mechanical losses in similar polymers.
Mixed crystal infrared study of chain folding in crystalline polyethylene
Authors: Bank M. I. , Krimm S. 
Published: April 2003

AbstractInfrared spectroscopic studies have been made of mixed crystals of linear polyethylene and perdeuteropolyethylene. On the basis of normal vibration analyses by Tasumi and Krimm it had been shown that the study of crystal splittings of internal chain modes in such mixed crystals could provide information on the geometry of chain folding. The present results, which include a study of n‐paraffin (C36) mixed crystals, confirm these predictions. They show that (110) folding predominates in dilute solution grown crystals, and that this is transformed to (200) folding in melt‐crystallized polymer. Folding with adjacent re‐entry is favored, a random re‐entry model being clearly eliminated.
Dielectric relaxation of high polymers in the solid state
Authors: Ishida Yōichi 
Published: April 2003

AbstractDielectric relaxation processes observed in solid polar polymers seem to be generally classified into three kinds. Amorphous polymers with flexible polar side groups usually show two kinds of relaxation process. The high‐temperature process is attributed to the large scale conformational rearrangements of the main chains, while the low‐temperature one results from the motion of side groups. We shall call the former αa relaxation and the latter β relaxation, where the subscript refers to the amorphous phase. Even in amorphous polymers without flexible side groups, two processes are observed. The molecular mechanism of high temperature one is the same as the αa relaxation. The low‐temperature one is due to the “local relaxation mode” of the main chains. We shall call it also β relaxation because of the similarity of the observed characteristics. Semicrystalline polymers show two relaxation processes classified as αa and β, although their behavior is modified by crystallization. When the crystallinity is greatly increased, a third relaxation process with associated with crystalline phase appears. We shall call it αc relaxation, where the subscript means the crystalline phase. The effects of chemical structure, stereoregularity, pressure, and crystallization on the dielectric behavior can be explained consistently based on the above molecular mechanisms.
Studies of branching in polyvinyl acetate
Authors: Graessley William W. , Hartung Ralph D. , Uy William C. 
Published: April 2003

AbstractBatch polymerizations of vinyl acetate were conducted at 60°C and 72°C, and rate constants for branching were established from the variation of M̄n and M̄w with extent of conversion. The calculated branching densities (branch points per polymer molecule) are slightly higher at 72°C for all conversions. Selected samples were saponified and reacetylated to determine the amount of branching through the acetate group. Changes in M̄n, M̄w, and [η] indicate 63%, 75%, and 70%, respectively, of saponificable branches. These percentages are independent of branching density in the original polymer. Molecular weights extrapolated to zero conversion appear to be unchanged by saponification and reacetylation, showing that short chain branching through the acetate group is absent, or at least very infrequent.
Drawing of single‐crystal mats of linear polyethylene
Authors: Ishikawa Kinzo , Miyasaka Keizo , Maeda Masahiko 
Published: April 2003

AbstractDrawing of single‐crystal mats of linear polyethylene has been investigated. Drawing is possible at temperatures higher than about 90°C. The drawing is accompanied by distinct necking, with a large decrease in the thickness of the mat and a very high maximum draw ratio, sometimes over 30. The maximum draw ratio is approximately proportional to the thickness of the lamellae. This behavior strongly suggests the unfolding of chains during drawing. A change of orientation of crystal axes occurs before necking without change of lamellar orientation. The a axis orients in the drawing direction; the b axis orients perpendicular to the direction of drawing; and the chain axis tilts away from the thickness direction of the mat. The structure of films drawn from mats is characterized by a distinct double orientation of crystals. This biaxial orientation in the drawn films has a high degree of correlation with the orientation of crystal axes observed before necking, and suggests that necking takes place in such a way that the chain tilts gradually about the b axis and ultimately unfolds. The postulate of formation of transitory two‐dimensional crystals in necking seems useful in explaining the double orientation in the drawn film. The orientation behavior of crystal axes observed before necking is not always similar to that observed in the deformation of a single crystal. The difference is thought to be due to the effect of forces induced by drawing that act in the direction normal to the lamellae within a mat.
Extended‐chain crystals. IV. Melting under equilibrium conditions
Authors: Prime R. Bruce , Wunderlich Berhard 
Published: April 2003

AbstractDilatometric melting experiments were performed on an extended‐chain crystalline polyethylene with a broad molecular weight distribution and on four samples crystallized from fractionated polyethylenes. The melting curves were compared with computer calculations based on the assumption of eutectic separation. For the fraction of lowest molecular weight, agreement between experiment and calculation was achieved. The melting behavior of all other samples indicated that only for molecular weights up to 10,000–12,000 did eutectic separation occur. The higher molecular weight portion of each sample crystallized in the form of mixed crystals. Of the experimental maximum melting‐point lowering of these mixed crystals, 0.1–0.9°C is due to the lower molecular weight diluents. Another 2–3°C lowering in melting point is due to the fact that the phase diagram of polyethylene mixed crystals has a minimum.
Poly[tris(diorganophosphinato)alanes]
Authors: Flagg Edward E. , Schmidt Donald L. 
Published: April 2003

AbstractPoly[tris(diorganophosphinato)alanes], [Al(OPRR′O)3]n, were synthesized in which the organic moieties (R,R′) contained from one to eighteen carbon atoms. Polymeric properties depended upon the organic moieties; polymers were fusible, tractable, and flexible when the organic moieties contained six or more carbon atoms. Soluble polymers were prepared by using mixtures of symmetrical and unsymmetrical phosphinates. One polymer, poly{bis[n‐butyl(benzyl)phosphinato]di‐n‐octylphosphinatoalane}, exhibited a degree of polymerization greater than 1000 and an exceptionally high intrinsic viscosity of 37 dl/g. The properties of the different polymers are discussed, and feasible structures are proposed.
Thermal degradation of poly(vinyl chloride). I. Structural effects in the initiation and decomposition chain lengths
Authors: Gupta V. P. , St. Pierre L. E. 
Published: April 2003

AbstractFour poly(vinyl chloride) samples containing different structural irregularities were thermally decomposed. The rates of HCl evolution were compared to the rates of radical generation in the samples. Orders of stabilities related to the structural entities for the initiation of decomposition and for the chain lengths of HCl evolution were established.
Vinyl polymerization with Fe(III)–thiourea as initiator system. Part II. Kinetics: Predominant primary radical termination
Authors: Mandal B. M. , Nandi U. S. , Palit S. R. 
Published: April 2003

AbstractThe rate of polymerization Rp of methyl methacrylate initiated by Fe(CIO4)3 and thiourea (TU) in tert‐butyl alcohol is indepenent of [Fe(III)] and [TU] in the concentration range studied. In contrast to Rp, the degree of polymerization DP changes markedly with the change in the initiator concentration. DP is overwhelmingly lower than is expected in a standard radical polymerization at the same Rp. Further, Rp is proportional to the square of the monomer concentration. Initiation efficiency is less than one. Independent experiments proved that in the azobisisobutyronitrile‐initiated polymerization the Rp and DP are negligibly affected by [Fe(CIO4)3] or [TU], though high [TU] brings about high induction periods. The results of Fe(III)‐TU‐initiated polymerization have been interpreted in terms of the predominant termination of polymer radicals by primary radicals.
Characterization of styrene–acrylonitrile copolymer by pyrolysis gas chromatography
Authors: Vuković R. , Gnjatovic V. 
Published: April 2003

AbstractSamples of styrene–acrylonitrile (SAN) copolymer of different compositions, molecular weights, block copolymers, and a blend of styrene and acrylonitrile homopolymers were prepared and characterized by the method of pyrolysis gas chromatography. On decomposition of SAN copolymer samples at 645°C, eleven components were identified, the most important of them being styrene, acrylonitrile, and propionitrile. By examination of the pyrolyzate composition during pyrolysis of the SAN copolymer of different compositions, it was established that the propionitrile yield was definitely decreased when the acrylonitrile concentration in copolymer was about 60 mole‐%. Further, from the propionitrile yield, we could distinguish random SAN copolymer from the styrene‐acrylonitrile homopolymer blend, and on the basis of propionitrile yield some information on the molecular structure of the copolymer could be obtained. The styrene yield depends linearly on the copolymer composition. This permits determination of copolymer composition on the basis of the styrene yield. Furthermore, the effects of decomposition temperature and of molecular weight on the yields of styrene and acrylonitrile were examined.
Interfacial syntheses of polyphosphonate and polyphosphate esters. II. Dependence of yield and molecular weight on solvent volumes and concentrations of comers in basic polymerization of hydroquinone and phenylphosphonic dichloride
Authors: Millich F. , Carraher C. E. 
Published: April 2003

AbstractThe interfacial polymerizations of hydroquinone with phenylphosphonic dichloride, in the presence of barium hydroxide or sodium hydroxide, were studied and contrasted. Polymer yields and molecular weights were shown to vary with concentration of the comer reactants, with the comer ratio, and with the relative amounts of carbon tetrachloride and aqueous phases, but not with concentration of barium ion. The latter supports the impression that the reaction zone is situated in the aqueous phase. The method of Millich and Carraher, employing pH control, yields products of high molecular weights and some results which are distinct from those achieved with the use of sodium hydroxide.
Polymerization of coordinated monomers. III. Copolymerization of acrylonitrile–zinc chloride, methacrylonitrile–zinc chloride or methyl methacrylate–zinc chloride complex with styrene
Authors: Ikegami Tadashi , Hirai Hidefumi 
Published: April 2003

AbstractThe 1:1 or 2:1 complex of acrylonitrile, methacrylonitrile, or methyl methacrylate with ZnCl2 was copolymerized with styrene at the temperature of 0–30°C without any initiator. The structure of the copolymer from methyl methacrylate complex and styrene was examined by NMR spectroscopy. The complexes of acrylonitrile or methacrylonitrile with ZnCl2 gave a copolymer containing about 50 mole‐% styrene units. The complexes of methyl methacrylate yielded an alternating copolymer when the feed molar ratio of methyl methacrylate to styrene was small, but with increasing feed molar ratio the resulting copolymer consisted of about 2 moles of methyl methacrylate per mole of styrene. The formation of a charge‐transfer complex of styrene with a monomer coordinated to zinc atom was inferred from the ultraviolet spectra. The regulation of the copolymerization was considered to be effected by the charge‐transfer complex. The copolymer resulting from the 2:1 methyl methacrylate–zinc chloride complex had no specific tacticity, whereas the copolymer from the 1:1 complex was richer in coisotacticity than in cosyndiotacticity. The change of the composition of the copolymer and its specific tacticity in the polymerization of the methyl methacrylate complex is related to the structure of the complex.
Precipitation of some nonionic polymers by octylammonium thiocyanate
Authors: Saito Shuji 
Published: April 2003

AbstractThe effects of various alkylammonium thiocyanates (ethyl, butyl, hexyl, and octyl) on aqueous solutions of polyvinylpyrrolidone (PVP) and poly(vinyl alcohol–acetate) copolymer (PVA‐Ac) were studied and compared with the effects caused by the respective chlorides. Whereas the PVP solution was hardly affected by the chlorides, it was precipitated by n‐octylammonium thiocyanate (OASCN) at dilute concentrations and dissolved at higher concentrations. On taking the effects of ammonium chloride and thiocyanate on the solubility of PVA‐Ac as references, with increasing of alkyl chain length, alkylammonium chlorides raised the polymer solubility steadily; on the contrary, the thiocyanates at dilute concentrations, except for ethylammonium thiocyanate, lowered it, and OASCN at dilute concentrations, except for ethylammonium thiocyanate, lowered it, and OASCN at dilute concentrations was a particularly strong salting‐out agent. The amount of binding of OASCN to the polymers in the precipitated systems was measured. The precipitation was attributed to ion‐pair binding of OASCN to the polymers, and the mechanism was discussed in terms of the interaction between the water structure‐breaking SCN− and the water structure‐making hydrophobic groups.
Alternating copolymerization of polar vinyl monomers in the presence of zinc chloride. III. NMR study of methyl methacrylate–styrene copolymer
Authors: Yabumoto Shigeru , Ishii Kiyoshi , Arita Koichiro 
Published: April 2003

AbstractThe copolymer composition curve of the methyl methacrylate–styrene copolymer obtained by the copolymerization in the presence of ZnCl2has more alternating tendency than that of ordinary methyl methacrylate–styrene copolymer obtained by radical copolymerization. The fine structure of the copolymer was examined by NMR, and the mechanism of the propagation step of the copolymerization in the presence of ZnCl2, which was proposed in the first report of this series, was verified.
Transient analysis of a viscoelastic torsion pendulum
Authors: Glauz R. D. 
Published: April 2003

AbstractThe transient torsion pendulum of arbitrary cross section is analyzed as a device for obtaining physical properties of a viscoelastic material. The damped sinusoidal motion yields a damping factor and frequency from which the complex modulus is computed. The particular cases of circular and rectangular cross section are considered with tables and approximations simplifying the practical application of the method.
Poly(ester‐acetals) from azelaaldehydic acid‐glycerol compounds
Authors: Miller W. R. , Awl R. A. , Pryde E. H. , Cowan J. C. 
Published: April 2003

AbstractPoly(ester‐acetals) have been prepared from isopropylideneglyceryl azelaaldehydate dimethyl acetal and from methyl azelaaldehydate glycerol acetal. Acid hydrolysis of isopropylideneglyceryl azelaaldehydate led to oligomeric poly(ester‐acetals) with six to seven repeating units and carboxylic acid endgroups from which the sodium salt and the methyl ester could be prepared. The polymer sodium salt showed some surfactant properties. Methyl azelaaldehydate glycerol acetal, a mixture of geometric and structural isomers, was polymerized under typical polyesterification conditions. Lime was the best catalyst found. Molecular weights of 5000 to 12000 were obtained. Some of these polymers contained significant quantities of calcium as the carboxylate salt. A tough elastomer was prepared by heating a poly(ester‐acetal) with p‐toluenesulfonic acid and zine oxide.