bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dilute solution properties of styrene–acrylonitrile and styrene–methyl methacrylate copolymers. II. Short‐range and long‐range interactions from intrinsic viscosity data
Authors: Reddy C. Rami , Kalpagam V. 
Published: April 2003

AbstractExperimental data on styrene–acrylonitrile (St–AN), and styrene–methyl methacrylate (St–MMA) copolymers reported in Part I of this series are tested by “two‐parameter” theoretical relations. The Fox–Flory (F–F) parameter K is estimated using the F–F, Stockmayer–Fixman (S–F), and Inagaki–Ptitsyn (I–P) equations. In general, the K values obtained by the F–F equation are low for the three St–AN copolymer samples in the systems studied while the values obtained from S–F and I–P equations agree within the limits of experimental error. Values of K obtained from Kurata–Stockmayer (K–S) equation for sample SA1 agree with values obtained by the S–F and I–P equations. The specific solvent effect on the K values is discussed. Values of the unperturbed dimension r̄02/M̄w, calculated from the K values estimated from the S–F equation and from the homopolymer data are compared. Except in one case, the calculated r̄02/M̄w values from homopolymer data are low in comparison with the values obtained from experimental data, which shows that the presence of the repulsive interactions between unlike monomer units brings about an expansion of copolymer molecule. The effect of composition on the steric factor σ values is discussed. The long‐range interaction parameter B, the excess interaction parameters ΔBAB, and χAB are calculated. The effects of composition and solvent on these parameters are discussed.
Dielectric behavior of aqueous solutions of sodium polyphosphates of low degree of polymerization
Authors: Van Beek W. M. , Odijk T. J. , Van Der Touw F. , Mandel M. 
Published: April 2003

AbstractThe dielectric relaxation behavior of three sodium polyphosphates with different but low degrees of polymerization in aqueous solution (without salt) has been investigated between 8 kHz and 100 MHz. The highest molecular weight sample (DP 338) exhibits two dispersion regions as is generally observed with synthetic polyelectrolytes at higher degrees of polymerization and is interpreted, according to the theory of van der Touw and Mandel, by attributing a certain flexibility to the polymer chain. The experimentally determined relaxation time of the high‐frequency dispersion is in fair agreement with the theoretically calculated value. For the lowest molecular weight sample (DP 112) the experimental results can best be described by a single dispersion curve pointing to a rigid, more or less stretched, conformation of the polyion in agreement with theoretical predictions. For the sample of intermediate molecular weight (DP 198) the situation is borderline as it is possible to describe the relaxation behavior by either one or two dispersion regions; it is, however, concluded from an analysis of the dielectric results that the average conformation is rather extended, but not completely rigid.
Deformation morphology of polyester single crystals
Authors: Shrawagi Suresh R. , Thomas Edwin L. 
Published: April 2003

AbstractTruncated, six‐sided single crystals of a 10–16 linear polyester were grown from dilute solution in hexanol, deposited onto Mylar film, and uniaxially deformed at room temperature. For elongations below 10%, the crystals deform uniformly; however, above 20% elongation many cracks spanned by fibrils of 300 Å diameter develop approximately normal to the applied stress direction. Depending on the position of the crystal relative to the draw direction, lateral buckling pleats and cleavage cracks can also occur. Collapse of the nonplanar crystals onto the substrate with a resulting nonuniform adherence of the crystal influences the deformation. The deformation morphology is compared to that of truncated sixfold sector polyethylene crystals. Most notably, in contrast to polyethylene, {010} fold sectors do not deform differently from {110} fold sectors and phase boundaries between {110} and {010} fold sectors do not fracture easily.
Characterization of oriented low‐density polyethylene samples by differential scanning calorimetry
Authors: Pope D. P. 
Published: April 2003

AbstractThe melting behavior of samples of oriented low‐density polyethylene is examined as a function of annealing temperature and time, subsequent heat treatment, and irradiation dose. Three types of endotherm are identified which are attributed to primary melting of the lamellae, to melting of the products of reorganization during the scan, and to melting of material crystallized during cooling from the original annealing temperature. Irradiation was found to suppress the refolding which normally occurs when a sample is heated above its annealing temperature, but also produces an increase in melting point. The behavior of similar samples prepared from high‐density polyethylene is briefly considered.
Photoconductivity of poly(N‐acryloylcarbazole)
Authors: Okamoto Ken‐Ichi , Itaya Akira , Kusabayashi Shigekazu 
Published: April 2003

AbstractThe photoconductivity of poly(N‐acryloylcarbazole) (PACz), with the pendant carbazolyl group only a short distance from the skeletal chain of the polymer but separated from it by a carbonyl group, is investigated and compared with that of poly(N‐vinylcarbazole) (PVCz). There is no significant difference between PACz and PVCz in the temperature, light intensity, and spectral dependences of the photocurrent. The photoconductivity of PACz, however, is much inferior to that of PVCz and even to that of poly(N‐carbazolylethylvinylether), a representative vinyl polymer with pendant carbazolyl groups far from the skeletal chain. The poor photoconductivity of PACz is discussed in relation to the intensity of the electronic interaction between neighboring carbazolyl groups in the polymer chain and to singlet exciton migration. It is attributed mainly to an extremely low efficiency of extrinsic carrier generation via a singlet exciton, which is due to the poor electron‐donating character and the extremely short lifetime of a singlet exciton in the presence of the carbonyl group.
The thermal degradation of polyoxymethylene produced by solid‐state polymerization
Authors: Pearson A. W. N. , Groves G. W. 
Published: April 2003

AbstractThe thermal degradation of polyoxymethylene produced by the solid‐state polymerization of trioxane crystals has been studied. Changes in small‐angle and wide‐angle x‐ray patterns, weight loss, and density have been measured in specimens heated in air at 175°C, 185°C, and 195°C. The polyoxymethylene contained material in two different crystallographic orientations, which behaved differently. Material in the so‐called “twin” orientation melted preferentially at 185°C and 195°C, and at 185°C resolidified on cooling in parallel to the main orientation, in a lamellar structure. At 195°C, randomly oriented material was produced on resolidification. At 175°C, there was no evidence of melting or the formation of a lamellar structure, but the twin material was preferentially degraded so that only material in the main orientation remained after a time of 1500 min. The more rapid loss by degradation of the twin material was attributed to its having a lower molecular weight than the material in the main orientation.
Quantitative information from x‐ray diffraction of nylon‐6 yarns. I. Development of a model for the analytical description of equatorial x‐ray profiles
Authors: Heuvel H. M. , Huisman R. , Lind K. C. J. B. 
Published: April 2003

AbstractA wide‐angle x‐ray method has been developed by which quantitative structural information can be obtained on nylon‐6 yarns. To this end, experimental equatorial diffractometer scans measured in transmission were fitted to a mathematical model describing the profiles as the envelopes of three bell‐shaped functions. Four different models were investigated using, respectively, Gauss, Lorentz (Cauchy), Logistic, and Pearson‐VII functions. The last model, which can be regarded as a generalized Lorentz function, gave the best fit. On the basis of a statistical analysis of the results of well‐separated x‐ray peaks, two parameters could be fixed. Another reduction of the number of parameters was achieved by interrelating the peak areas of the two outer reflections. These reductions widened the applicability of a computer program based on the aforementioned model to highly overlapping x‐ray peaks. So the whole variety of x‐ray scans, which can be obtained from nylon‐6 yarns made under widely varying process conditions, can be well described. The fitting procedures provide unique solutions and hence objectively determined parameters.
Kinetics of swollen surface layer formation in poly(vinyl chloride)–solvent system
Authors: Lapčík L. , Panák J. , Kellö V. , Polavka J. 
Published: April 2003

AbstractThe kinetics of formation of a swollen surface layer by diffusion of liquid solvent into solid poly(vinyl chloride) in the glassy state has been studied. The apparent Fickian diffusion coefficients of cyclohexanone, cyclopentanone, tetrahydropyrane, 1,2‐dichloroethane, N,N‐dimethyl‐formamide, and monohalogen derivatives of benzene in PVC is calculated with the use of Crank's model for discontinuous change of diffusion coefficient with concentration. It is found that the apparent activation energy for diffusion is in the range 6–17 kcal/mole and is dependent on the polarity of the solvent molecule.
Phase structure in a polyurethane above soft segment Tg via calorimetric and NMR techniques
Authors: Froix M. F. , Pochan J. M. 
Published: April 2003

AbstractThere is much controversy in the literature concerning the nature of the thermal transitions observed for segmented polyurethanes. In this study calorimetric and NMR data on a polyurethane reveal ordered structures similar to that previously observed. However, based on a recently observed semi‐ordered polymeric phase and the observation of a time‐dependent calorimetric effect not observed previously, the data are interpreted in terms of a high‐temperature short‐range order and a low‐temperature long‐range order. The former appears to form faster and annealing of both ordered phases increases their thermal stability.
Isotactic poly(pentene‐1): Form III
Authors: Moser M. , Boudeulle M. , Chanzy H. 
Published: April 2003

AbstractA new crystalline form of isotactic poly(pentene‐1) was obtained from dilute solution in amyl acetate. We have designated it as form III. The morphology and structure of isothermally crystallized samples were investigated by electron microscopy and electron and x‐ray diffraction. This crystalline modification can be indexed on an orthorhombic unit cell (cell dimensions: a = 21.20 ± 0.05 Å, b = 11.48 ± 0.05 Å, c = 14.39 ± 0.05 Å (fiber axis) and probable space group P212121).
The effect of ion aggregation on some melt properties of styrene ionomers
Authors: Shohamy E. , Eisenberg A. 
Published: April 2003

AbstractThe dynamic modulus, G′, and viscosity, η′, in the melt were determined for styrene ionomers containing up to 7.7 mole‐% sodium methacrylate in the frequency range of 10−2 to 40 rad/sec, at various temperatures. The same parameters were determined for the methyl ester of these ionomers, as well as for some acid samples. It was found that in the temperature range studied the time–temperature superposition principle was applicable to the salts as well as to the esters and acids. Furthermore, it was found that the shapes of the G′ versus ω plots for the three types of polymers were identical for a particular molecular weight and comonomer concentration, and independent of whether the sample was in the acid, ester, or salt form. The temperatures required to achieve superposition were, however, quite different. This temperature difference, ΔT (between the salt and the ester), was found to be a function of the ion concentration, c. The shape of the plot of ΔT versus c suggests that the structure of the ionic aggregates changes in the range of 4–5 mole‐% of ions.
Deformation structures in solid‐state extruded polyethylene
Authors: Kolbeck A. G. , Uhlmann D. R. 
Published: April 2003

AbstractDeformation structures resembling kink bands have previously been reported in a number of oriented semicrystalline polymers which have undergone various modes of deformation. In the present work, such structures have been observed and studied in solid‐state extruded polyethylene which has been processed to give a biaxial, “single crystal” texture. Deformation of this material by bending followed by unbending has been observed to lead to shear during the bending stage and to void formation during the unbending stage. The kink bands which form during this treatment exhibit a single morphology regardless of the axis of bending so long as the direction of compression during bending is parallel to the original extrusion direction. Besides intracrystalline slip, which is known to contribute at least in part to the process of kink band formation, mechanisms involving interlamellar slip and interfibrillar slip are also considered. These mechanisms are considered in terms of three distinct experimental observations: the relationship between the kink boundary and the x‐ray long period, the process of void formation during unbending, and the single characteristic morphology of the kink bands.
Investigation of relaxation processes in linear polyethylene in the 10−9 sec region by means of high‐resolution neutron spectroscopy
Authors: Peterlin‐Neumaier T. , Springer T. 
Published: April 2003

AbstractResults are presented of neutron incoherent scattering experiments on isotropic linear polyethylene samples of high (80%) and low (48%) crystallinity in the temperature range between −180°C and +85°C for values of the scattering vector between 0.29 Å−1 and 1.81 Å−1 obtained with a high resolution backscattering spectrometer (Δħω = 0.25 − 1.0 μeV) and between 0.57 Å−1 and 2.4 Å−1 with a time‐of‐flight spectrometer (Δħω = 420 μeV). From a comparison of the results on these samples one concludes that relaxation takes place predominantly in the noncrystalline regions. This motion cannot be adequately accounted for by any of the existing models for the γ‐process. Therefore, a more liquidlike motion is suggested. Diffusion of shorter chain segments has also been ruled out since it is too slow to be observed. A simplified model of protonic jumps between equidistant sites located on the periphery of a circle of radius 2.5 Å reproduces the experimental results well. For the average time between successive CH2‐group reorientations one obtains τ1 = τ0 exp(EactRT) with τ0 = (2.0 ± 1.5) × 10−13 sec and Eact = (4.5 ± 1.0) kcal/mole. The values join up well with those for the γ‐process observed by NMR. It has been concluded that 60–90% of the protons in the noncrystalline regions participate in this motion.
The temperature dependence of the equilibrium and instantaneous compliances of low molecular weight polystyrene melts
Authors: Gray R. W. , Harrison G. , Lamb John 
Published: April 2003

AbstractThe equilibrium compliance of three low molecular weight polystyrene melts has been determined over the range 15–70°K above Tg from dynamic viscoelastic measurements using alternating shear. Results are favorably compared with the previous results of Plazek and O'Rourke obtained from creep measurements, but agreement with predictions based on the Rouse theory is obtained only in the case of the highest molecular weight sample.
Swelling of nylon 6 film due to water sorption
Authors: Inoue Kazuo , Hoshino Sadao 
Published: April 2003

AbstractDimensional changes in nylon 6 film on absorption and desorption of water were studied as functions of time and the amount of absorbed water. For absorption, a plot of film expansion versus the square root of time was sigmoidal in the initial region and did not coincide with the sorption curve: the latter was linear in the same region. This behavior is very similar to that reported for nylon 6 fiber by Kunzman. A theoretical analysis based on certain assumptions about the molecular state of nylon 6 gave good agreement with experimental results. By this analysis it was shown that the characteristic swelling behavior arises from instantaneous relaxation of the polymer molecules and is not connected with a time lag between water absorption and expansion of the polymer, as Kunzman proposed.
An x‐ray and conformational study of Kapton H
Authors: Conte G. , D'Ilario L. , Pavel N. V. , Giglio E. 
Published: April 2003

AbstractPotential energy calculations were performed on the isolated chain of Kapton H (KH) in order to obtain information on the most probable conformations. A model with a COC angle of 130° and with the segments joining the ether oxygens forming a planar zigzag chain satisfactorily fits the x‐ray experimental data. Although the equatorial reflections are very few and diffuse, it seems likely that the space group is P21 and the unit cell parameters are a = 4.66 Å, b = 32.9 Å, c = 5.96 Å, β = 100°. The observed density is in agreement with two monomers in the unit cell. An intrachain vector distribution map was computed by rotating (angle θ) the pyromellitic acid dimide (DIPA) unit about the NC bond in the KH monomer. This map was compared with a one‐dimensional Patterson synthesis calculated along b, the fiber axis, to establish the value of θ. Van der Waals' energy calculations were subsequently accomplished in the crystal as a function of θ and of the rotation around the helical axis of the KH chains. The results allowed us to choose a reasonable macromolecular conformation and packing in the crystal. KH is mainly ordered along the fiber axis but shows little order in the packing of adjacent helixes. The macromolecules are held together by Van der Waals' and, probably, by charge‐transfer forces.
Mutual selective exclusion of unlike polymers in dilute solution and its measurement by light scattering
Authors: Kratochvíl Pavel , Vorlíček Jiří 
Published: April 2003

AbstractThe interaction of unlike polymer molecules (components 2 and 4) in a ternary solution can be regarded as selective exclusion or desorption of one polymer by another. A relation is derived between the coefficient of selective sorption and the interaction parameters A24 and A244 which are analogs of the second and third virial coefficients. The ratio between the apparent light‐scattering molecular weight and the true value for a polymer solute in a ternary system with one component of a binary solvent polymeric is more involved than in a ternary system in which both solvent components are of low molecular weight. Under certain conditions, the introduction of polymer component 2 into a dilute solution of polymer component 4 may lead to a decrease in the total intensity of scattered light.
A simple phenomenological approach to the thermal behavior of glasses during uniform heating or cooling
Authors: Hutchinson J. M. , Kovacs A. J. 
Published: April 2003

AbstractThermal behavior of glasses, as observed from the isobaric variations of volume, v, and enthalpy, H, is analyzed in terms of retardation kinetics. A phenomenological theory involving a single retardation time, τ, is developed, assuming that molecular mobility is controlled essentially by the actual free volume, or configurational entropy of the glassy specimen. The characteristic features of the v and H isobars, as derived from the theory, are examined as a function of the thermal history of a typical glassy specimen. The respective contributions of temperature and structural parameters to τ, are also discussed in terms of the characteristic parameters of the isobars. The theoretical predictions are compared with some dilatometric data obtained with an atactic polystyrene. The comparison reveals the limitations of the theoretical treatment and suggests that glass‐transition phenomena involve more than one retardation mechanism.
Determination of composition of ethylene–propylene copolymers by intrinsic viscosity
Authors: Delmas Geneviève , Daviet Viviane , Filiatrault Danielle 
Published: April 2003

AbstractIntrinsic viscosities have been measured at 25° on five ethylene–propylene copolymer samples ranging in composition from 33 to 75 mole‐% ethylene. The solvents used were n‐C8 and n‐C16 linear alkanes and two branched alkanes, 2,2,4‐trimethylpentane and 2,2,4,4,6,8,8‐heptamethylnonane (br‐C16). This choice was based on the supposition that the branched solvent would prefer the propylene segments and the linear solvent the ethylene segments, due to similarity in shape and possibly in orientational order. It was found that [η]n − [η]br ≡ Δ[η] is indeed negative for propylene‐rich copolymers, zero for a 56% ethylene copolymer, and positive for ethylene‐rich copolymers. The Stockmayer–Fixman relation was used to obtain from Δ[η] a molecular‐weight independent function of composition. The quantities (Δ[η]/[η])(1 + aM−1/2) and Δ[η]/M are linear with the mole percent ethylene in the range investigated with 200 ≤ a ≤ 2000. The possibility of using these results for composition determination in ethylene–propylene copolymers is discussed. Intrinsic viscosities in the same solvents are reported for two samples of a terpolymer with ethylidene norbornene.
The drawing behavior of linear polyethylene. I. Rate of drawing as a function of polymer molecular weight and initial thermal treatment
Authors: Capaccio G. , Crompton T. A. , Ward I. M. 
Published: April 2003

AbstractThe drawing behavior of a series of linear polyethylene homopolymers with weight‐average molecular weight (M̄w) ranging from 67,800 to ∼3,500,000 and variable distribution (M̄w/M̄n = 5.1−20.9) has been studied. Sheets were prepared by two distinct routes: either by quenching the molten polymer into cold water or by slow cooling below the crystallization temperature (∼120°C) followed by quenching into cold water.When the samples (2 cm long) were drawn in air at 75°C using a crosshead speed of 10 cm/min it was found that for low M̄w polymers the initial thermal treatment has a dramatic effect on the rate at which the local deformation proceeds in the necked region. At high M̄w such effects are negligible. An important result was that comparatively high draw ratios (λ > 17) and correspondingly high Young's moduli could be obtained for a polymer with M̄w as high as 312,000. It is shown how some of the structural features of the initial materials (mainly studied by optical microscopy, small‐angle x‐ray scattering and low‐frequency laser Raman spectroscopy) can be interpreted in terms of the molecular weight and molecular weight distribution of the polymers. Although crystallization and morphology can be important at low M̄w, it suggested that the concept of a molecular network which embraces both crystalline and noncrystalline material is more helpful in understanding the drawing behavior over the whole range of molecular weights.