bluuebunny/crossref_metadata_2025 huggingface dataset:
Rapid healing of crazes in ruptured rubber‐toughened plastics
Authors: Takahashi Kiyoshi
Published: April 2003

High‐speed photographic studies in connection with photodensitometry were performed to study craze healing in ABS/MMA sheets occurring within 5 microseconds to 20 milliseconds after rupture. Observations on various parts of the deformed specimens, particularly at a plastic zone in the vicinity of a crack, show that there are two stages of healing; first, a relatively elastic stage, and second, a relatively viscoelastic stage. Results of the observation also indicate that the rate of healing is influenced by the magnitude of plastic strain to which the specimens were subjected. The healing mechanism near an advancing crack is discussed briefly.
Rheological properties of anisotropic poly(para‐benzamide) solutions
Authors: Papkov S. P. , Kulichikhin V. G. , Kalmykova V. D. , Malkin A. Ya
Published: April 2003

A study has been made of the viscous properties of poly(para‐benzamide) (PBA) solutions in dimethyl acetamide, which undergo a transition from an isotopic to an anisotropic (liquid‐crystal) state at a definite concentration C*. The polymer solutions behave in many respects (as regards the concentration and temperature dependence of viscosity, etc.) like solutions of low molecular weight compounds forming a liquid crystal phase, although the transitions are less pronounced in the polymer solutions owing to their polydispersity. It is shown that the viscometric method, being extremely sensitive to C*, is convenient for determining phase diagrams of anisotropic polymer solutions. The values of C* as related to the molecular weight of PBA have been determined, and a general criterion for transition from isotropic to anisotropic solutions established; the latter has the form (CM̄)* ≈ 1.3 × 105 at 20°C. This criterion is in line with the condition for the formation of the liquid‐crystal structure in a dispersion of rodlike particles as proposed by Flory.

Generalized concentration dependences of viscosity have been plotted by reducing concentration to C* and viscosity, to the maximum viscosity at the phase transition point. In investigating the flow properties of PBA solutions we revealed the existence of a yield point in the range of low shear stresses, and an intersection of the flow curves of solutions of different concentration at high shear stresses, which excludes a generalized representation of the flow curves in reduced ordinary‐type coordinates.
Dilute solution behavior of polyelectrolytes. Intrinsic viscosity and light scattering studies
Authors: Tan J. S. , Gasper S. P.
Published: April 2003

The conformational character of a random copolymer of ethyl acrylate and acrylic acid (mole ratio 3:1) has been examined by intrinsic viscosity and light scattering in organic and in aqueous media. The unperturbed dimensions of this copolymer in its un‐ionized state in an organic theta solvent are 1.3 to 1.4 times those obtained for the fully ionized polymer in an aqueous theta solvent. The data also suggest that a change in conformation from a swollen random coil to a compact random coil occurs in aqueous media as a function of ionic strength. These results are interpreted in terms of the hydrophobic interaction of the ester groups on the chain.

An application of the wormlike chain model shows that viscosity data can be used to predict the light scattering results well with in experimental error.
Relation between the critical point and the precipitation threshold
Authors: Šolc K.
Published: April 2003

The relationship between the critical point and the precipitation threshold is examined in the Flory—Huggins approximation with concentration‐independent interaction parameter χ. Approximate explicit expressions for the difference between the critical point and the threshold can be derived by series expansion of threshold conditions. In the first‐order approximation, the concentration difference depends only on the chainlength averages xw, xz, and xz+1, in the second‐order approximation it depends on xw, xz, xz+1, and xz+2, etc. For polymers of low polydispersity, the second‐order approximation gives a good estimate of the concentration difference; for instance, for polymers with exponential distribution and xw/xn < 1.25, the error is lower than ca. 1%. The approximation is not suitable for polymers with xz+1 ≫ xz (including polymers whose cloud‐point curve exhibits a triple point). Irrespective of the polydispersity of the polymer, the threshold as well as the whole cloud‐point curve depend only on the weight‐average and higher averages, xw, xz, xz+1, …, xz+k, where k → ∞; they are, however, independent of the number average xn.
Dynamic viscoelastic properties of unsintered polytetrafluoroethylene
Authors: Sasuga Tsuneo , Takehisa Masaaki
Published: April 2003

The molecular motion of unsintered polytetrafluoroethylene (PTFE) was studied by dynamic viscoelastic measurements. From results for variously heat treated suspension polymerized (molding powder) PTFE, the following conclusions are drawn. Molding powder, as received, has a high degree of crystallinity according to calorimetric results and lower magnitude of the γ relaxation, but the behavior of the β relaxation suggests that the crystals are disordered more than those of the sintered PTFE. The β relaxation peak for an emulsion polymerized PTFE (fine powder) occurs at a higher temperature and is sharper than that for the molding powder, so that the crystals of the fine powder are better ordered than that for the molding powder. The behavior of the β relaxation for the radiation induced‐polymerized PTFE is affected by polymerization conditions, particularly concentration of emulsifier. It is concluded from the results for the unsintered PTFE polymerized by various methods that the nature of crystalline state is decided during the course of simultaneous polymerization and crystallization.
Molding powder as received has a relatively high magnitude of relaxation between 30°C to 180°C, but with little temperature dependence in this temperature range. This relaxation is diminished by gamma‐ray irradiation. Since the molding powder has a complicated morphology, the relaxation in this temperature range is attributed to inter‐particle friction rather than a relaxation associated with motion on the molecular level.
An improved model for crystalline orientation of spherulitic polymers
Authors: Yoon Do Yeung , Chang Catherina , Stein Richard S.
Published: April 2003

A model is proposed to account for the orientation of crystals in spherulites upon deforming a polymer. The model assumes affine deformation of the spherulite accompanied by three processes of crystal reorientation within the spherulite. These are tilting of molecular chains with respect to the plane of the lamellae, characterized by a parameter K, twisting of the lamallae about the spherulite radii described by η, and rotation of the b crystal axis about the c axis characterized by a third parameter, P. Values of these parameters are fitted to measured orientation functions and compared with experimental measurements of the azimuthal variation of the intensities of the 110 and 200 crystal reflections from low‐density polyethylene. Good agreement is found between the experimental and theoretically predicted intensity variation. Time‐dependent experiments under relaxational and vibrational conditions are also treated by the theory.
Crystallization during polymerization of ethylene: Successive events
Authors: Fisa B. , Revol J. F. , Marchessault R. H.
Published: April 2003

Crystallization processes occurring during polymer synthesis in a nonsolvent medium are discussed. It is concluded that in the case of heterogeneous polymerization of ethylene the polymer is produced as a supercooled liquid surrounding the catalyst particles. These particles then coalesce until a critical size is reached allowing a high nucleation probability. Thus coalescence coupled with polymerization, leads to crystallization at a relatively uniform particle size. Two less usual polymerization catalyst systems, VCl3 produced by a high‐frequency discharge in VCl4 vapor, and the mixture of TiCl4 and Al(CH3)3 vapors (an apparently homogeneous system) are used to illustrate these concepts for polyethylene.
Rubber networks containing unattached macromolecules. I. Linear viscoelastic properties of the system butyl rubber–polyisobutylene
Authors: Kramer Ole , Greco Roberto , Neira Ramon A. , Ferry John D.
Published: April 2003

Mixtures of butyl rubber with polyisobutylene (molecular weights 0.055 and 2.3 × 106) up to 50% by weight were crosslinked by sulfur, leaving the polyisobutylene molecules free to reptate in the butyl rubber network. Linear viscoelastic properties were measured in shear creep for periods up to 5 × 105 sec at 25°C and oscillating shear deformations from 0.1 to 3 Hz, at temperatures from 2 to 63°C. Comparison with the properties of a butyl rubber crosslinked without polyisobutylene showed contributions to creep and mechanical loss attributable to the reptating species. Comparison with the properties of polyisobutylene (higher molecular weight) showed that the relaxation times associated with the reptating species in the upper part of the terminal zone are the same for different polyisobutylene contents (25% and 50%) and for 100% polyisobutylene in which no permanent network is present; their contributions to modulus appear to be proportional to the volume fraction of polyisobutylene to a power of about 2/3. The time required in stress relaxation for the portion of the modulus attributable to the reptating species to decay to half its plateau value is, based on the two molecular weights employed, proportional to the polyisobutylene molecular weight to the third power. The magnitude of the associated mechanical loss and its location on the frequency scale can thus be controlled independently.
Evidence of molecular relaxation derived from transient phenomena in poly(vinyl chloride)
Authors: Lupu A. , Bunget I.
Published: April 2003

Transient currents in poly(vinyl chloride) (PVC) are recorded after the application of a step‐function electric field for various temperatures. By assuming the Fröhlich rectangular distribution function g(τ) of molecular relaxation times, the limits of relaxation times τ are evaluated. Values of the glass‐transition temperature and activation energies of molecular motion determined from a plot of ln τ against 1/T are in satisfactory agreement with those obtained by other methods. By extrapolation to T = ∞, relaxation times are calculated which are in good agreement with those from dielectric loss measurements.
New apparatus for studies on supermolecular structures of thin polymer films by small‐angle light scattering
Authors: Pakuła T. , Soukup Z.
Published: April 2003

The construction and principle of operation of small‐angle light scattering apparatus for studies of supermolecular structure in thin polymer films is described. The apparatus can be used to study changes in spherulite structure during crystallization and changes in films subjected to steady or sinusoidal strain. Typical results with polyethylene films are given.
Photopolarization and depolarization characteristics of poly(N‐vinyl carbazole)
Authors: Pillai P. K. C. , Ahuja R. C.
Published: April 2003

The photoelectret properties of poly(N‐vinyl carbazole) sandwiched between a conducting glass electrode and an aluminum electrode have been studied. Photoelectret polarization was carried out by simultaneous application of an electric field and ultraviolet illumination. The polarization exhibits a linear dependence on the polarizing voltage, polarization time, and illumination intensity, with saturation effects for large values of these parameters. The depolarization current decay is quite fast, which indicates the absence of deep‐trap levels. The ratio of photoelectret charge to the dark polarization charge is found to be 100, which determines the image contrast if the polymer film is used in persistent internal polarization (PIP) electrophotography.
Conformational analysis of poly(ethylene oxide) and model compounds by nuclear magnetic resonance spectroscopy
Authors: Matsuzaki Kei , Ito Hiroshi
Published: April 2003

In order to determine the conformation of poly(ethylene oxide) (PEO), 13C satellite spectra of PEO, 1,2‐dimethoxyethane (DME), and dioxane were measured at various temperatures in various solvents, and analyzed. Relations between the coupling constants were derived from the linearity between the parameters N = JAB + JA′B and L = JA′B in AA′BB′ spectra of PEO and DME. The vicinal coupling constants for the individual rotational isomers were obtained from the above relations and the temperature dependences of N and L and the enthalpy differences were calculated in each solvent. The gauche rotamer is more stable than the trans isomer by 250–500 cal/mole in all cases examined.
Electrical conductivity of small ions in polyacrylonitrile in the glass–transition region
Authors: Reich S. , Michaeli I.
Published: April 2003

The electrical conductivity process in a new class of ion‐containing polymers—highly concentrated solid solutions of hydrated perchlorate salts in polyacrylonitrile (PAN)—is described (σdc = 10−7−10−2Ω−1cm−1). A low‐ac instrument (70 cps) is used to measure electrical conductivity. We present a cryogenic system in which the temperature dependence of the conductivity is studied (78–340°K). The ionic character of the conductivity process is established. The conductivity both above and below the glass‐transition (Tg) point is thermally activated with an activation energy of 0.7–0.9 e V for the glassy state (ϵg) and 0.12–0.6 eV for the rubber‐like state (ϵr). The systems described exhibit a compensation effect between the pre‐exponential factor for the conductivity in the glassy state σ0g and the difference in activation energy ϵg – ϵr
Elasticity theory. IV. The stress–strain relation
Authors: Eichinger B. E.
Published: April 2003

The stress–strain relation is analyzed in terms of the gyration tensor

where the sum is over all N atomic groups comprising the elastomeric material. All groups are taken for convenience to have the same mass. This tensor is linear in the strain, and furthermore it may be evaluated from a configuration integral. The definition of the strain by use of Sαβ gives new insight into the connection between statistical and continuum mechanics, and further clarifies the significance of “affine deformation.” Stress components are obtained as derivatives of the (Helmholtz) free energy A with respect to the invariants of Sαβ. The first invariant is just the radius of gyration S2 of the network, and the dependence of A on S2 alone provides a basis for analysis of stress–strain isotherms.
Interaction of inorganic salts with polar polymers. I. Physical properties of phenoxy–calcium thiocyanate mixtures
Authors: Hannon M. J. , Wissbrun K. F.
Published: April 2003

Calcium thiocyanate is appreciably soluble in “Phenoxy” polymer. Solutions of this salt have significantly different physical properties compared to the pure polymer. The glass‐transition temperature Tg is increased, and the kinetics of the glass transition are affected. The melt viscosity and its temperature dependence are increased. The viscosity changes are predicted from the changes in Tg and thermal expansion coefficients, in contrast to ionomers, in which clustering or domain formation cause viscosity to increase. Mechanical properties of the glassy polymers are also affected by the presence of dissolved salt. The most striking effect is an increased resistance to stress cracking by polar organic liquids. This may be related to the Tg increase, or to changes in solubility parameter, as indicated by insolubility of the salt solutions in solvents for the pure polymer. Increased water sorption and electrical conductivity are also results of salt incorporation.
Mechanisms of fracture in an oriented polystyrene
Authors: Doyle M. J.
Published: April 2003

Fracture surfaces of an oriented polystyrene (by stretching 150% at 280°F) show many of the same features observed in the fracture of ordinary polystyrene: craze formation followed by quasi‐viscous separation of the craze layer or by quasi‐brittle fracture along the craze boundary. In cleavage fracture along the direction of orientation, advance fractures are initiated in flat areas covered, if at all, by an extremely thin layer of craze: the initiation of the “crazeles” fractures appears to arise from the orientation of the molecules rather than the presence of impurity particles.
Dynamic mechanical properties of plasticized poly(vinyl chloride)
Authors: Nakamura Kunio
Published: April 2003

The complex compliance in extension of gels of poly(vinyl chloride) (PVC) in di(2‐ethylhexyl) phthalate (DOP) and in tricresyl phosphate (TCP) was measured over the frequency range from 0.6 to 0.006 cps and the temperature range from −66 to 65°C: the weight fractions of DOP and TCP in the gels were 0.32, 0.40, 0.49, and 0.59. Measurements were carried out in an apparatus using forced low‐frequency longitudinal osillations. Data for the gels could not be combined by the method of reduced variables, since there were gradual changes with decreasing temperature, attributable to an increase in crystallinity. Application of the reduction method of Ninomiya and Ferry for solutions of crystalline polymers was found to be successful. The apparent melting temperatures (T′m) were obtained from the temperature dependence of the vertical shift factors. An apparent heat of fusion of ca. 120 cal/mole of monomer unit was found. This melting range was in agreement with that of secondary crystallinity in plasticized PVC reported in calorimetric studies by Juijn. With decreasing temperature, two phenomena occurred in the temperature range from Tg + ca. 80°C to Tg: the vitrification of a concentrated amorphous solution and the slight crystallization of the polymeric component. The larger the difference between Tg and T′m the broader the primary dispersion zone on the frequency scale. This broadening effect was explained as due to the difference in dependence of Tg and T′m on plasticizer concentration, without any need to consider any specific interaction between plasticizer and PVC.
Dependence of thermal diffusion effects in liquids on the physical properties of the dispersing phase
Authors: Gaeta F. S. , Di Chiara A.
Published: April 2003

A generalization of the radiation‐pressure theory of thermal diffusion in liquids explains the genesis of the forces acting in a condensed phase when heat flows through it. The analytical expressions obtained make it possible to connect such forces originated by the radiation pressure of thermal waves with the transport of matter taking place in solutions or suspensions of particles and also with the ultimate result of this transport, that is, the steady‐state concentrations of the dispersed phase in the hot and in the cold regions of the nonisothermal solution. The form in which the theoretical results are laid down lends itself to direct and unambiguous experimental verification. The confrontation with a few data found in the literature lends support to the theory.
Characterization of macromolecules in liquid solutions by thermal diffusion. II. Dependence of the soret coefficient on the molecular mass of the solute
Authors: Gaeta F. S. , Perna G. , Scala G.
Published: April 2003

Experiments have been carried out, in connection with those mentioned in Part I of this series, with the general aim of checking some predictions of the radiation‐pressure theory of thermal diffusion in the case of macromolecular liquid solutions and in particular with the intent of establishing the dependence of the Soret coefficient on molecular mass of the dispersed particles.

The results confirm the dependence of Soret coefficient on the shape and on the mass of the particles. The analytical expressions obtained by the radiation‐pressure theory of the phenomenon constitute a satisfactory description of the thermodiffusive behavior of such complex systems. The inner constitution of the particles determines the intensity of the radiation pressures exherted by thermal waves; the molecular cross section determines the total force acting on each particle, while the spatial conformation determines the ratio between mass and cross section and at the same time also the hydrodynamical behavior of a particle within the liquid. All these parameters concur in the phenomenon of thermal diffusion, in the way specified by the radiation‐pressure theory of thermal waves, as proved by our experiments.

The possibility of a characterization of macromolecules and supermolecular particles dispersed in a liquid on the basis of their thermodiffusive behavior is demonstrated.
Interaction of inorganic salts with polar polymers. II. Infrared studies of polymer–inorganic nitrate systems
Authors: Wissbrun K. F. , Hannon M. J.
Published: April 2003

Certain inorganic nitrate salts are quite soluble in the polymers studied, namely, cellulose acetate, poly(vinyl acetate), poly(vinyl alcohol), poly(methyl methacrylate), and poly(methyl acrylate). Large effects upon the glass‐transition temperature were observed in those systems where the transition could be readily measured. Large shifts in the infrared spectra of both the inorganic nitrate salts and in the polymer carbonyl and ester ether frequencies have been observed. These observations have been interpreted in terms of complex formation between these polymers and salts in the solid state. The proposed structure of the complex explains the nature of the infrared shifts both for the nitrate salts and the polymers as well as explaining the concentration effects observed. Effects of the solvating environment upon the salt and polymer spectra remain unexplained. The large glass‐transition effects are a result of the degree of solubility of the salts in the polymers and the interactions between them. However, the reason why, in some cases, the change in the transition temperature as a function of concentration goes through a maximum is unclear.
Deformational, swelling, and potentiometric behavior of ionized poly(methacrylic acid) gels. II. Experimental results
Authors: Hasa J. , Ilavský M.
Published: April 2003

The deformational, swelling, and potentiometric behavior of poly(methacrylic acid) gels was measured as a function of the degree of crosslinking, ionic strength, and degree of ionization. The comparison of the stress–strain behavior with theoretical relations derived in the preceding part has shown that the relations are valid only if an increase is assumed in the number of monomeric units in the statistical chain segment with increasing degree of neutralization of the gel. This dependence is affected by the salt content in the swelling solution and is also dependent on the activity coefficient of counterions. The pK0 values for an undissociated gel approach pK0 = 5.0 and increase somewhat with degree of neutralization. The swelling equilibria are in qualitative agreement with theoretical assumptions; their quantitative agreement depends on the activity coefficient of counterions.
Crystal structure of optically active poly(isopropylethylene oxide)
Authors: Takahashi Yasuhiro , Tadokoro Hiroyuki , Hirano Tsuneo , Sato Akira , Tsuruta Teiji
Published: April 2003

The crystal structure of optically active poly(isopropylethylene oxide) was analyzed by x‐ray diffraction. Two molecular chains having twofold screw symmetry pass through an orthorhombic unit cell with parameters a = 12.85 Å, b = 7.52 Å, and c (fiber period) = 5.55 Å and space group P212121‐D. The crystal structure was refined by the constrained least‐squares method. The molecular structure consists mainly of ḠTG sequences and is very similar to the (9/4) helical structure in poly(tert‐butylethylene oxide).
Measurement of the Grüneisen number in polystyrene by brillouin light scattering
Authors: Brody Edward M. , Lubell Cathie J. , Beatty Charles L.
Published: April 2003

Brillouin light scattering has been used to measure the sound velocities in polystyrene of two different molecular weights. The variation of sound velocity with temperature is related to volumetric expansion of the polymer. Using the thermal expansion data of Fox and Flory we have determined the Grüneisen number, γ, below the glass transition to be 4.4 and 4.3 for low‐ and high‐molecular‐weight polystyrenes, respectively, and 5.1 and 5.6 above the glass transition. These numbers compare reasonably well with the value of 3.9 determined by Wada et al. Our measured values are in good agreement with Barker's “bundle of chains” model.
Crystallinity and the effect of ionizing radiation in polyethylene. III. An experiment on the irradiation‐induced crosslinking in n‐hexatriacontane
Authors: Patel G. N. , Keller A.
Published: April 2003

Samples of n‐hexatriacontane irradiated in the crystalline and molten states were compared as regards the GPC chromatograms of the partially crosslinked products. From differences in the elution volumes it could be inferred that there is a greater trend for random linking along the chain in the sample irradiated in the melt as opposed to preference for end‐type linking in the samples irradiated as crystals. In the course of this work the applicability of the GPC technique for detecting short (methyl) branches and for distinguishing between the position of these branches along the chain has also become apparent.
Crystallinity and the effect of ionizing radiation in polyethylene. IV. Effect of segregation of low molecular weight chains on determination of main‐chain scission in linear polyethylene
Authors: Patel G. N.
Published: April 2003

Different single crystal preparations of polyethylene with (unfractionated) and without (partially fractionated) low molecular weight chains were irradiated at room temperature. G(crosslink) was determined from the gel point. It is shown that in addition to the molecular weight and molecular weight distribution of polymers, G(crosslink) is determined by three more parameters: thickness of crystalline core, amount of amorphous surface layer, and degree of interlamellar contact. Unlike unfractionated polyethylene, partially fractionated polyethylene showed almost 100% gel at about 250 Mrad. To obtain the same amount of gel, unfractionated polyethylene required a much higher dose than that required by partially fractionated polyethylene. Molecular weight distribution of sol fractions of unfractionated and partially fractionated polyethylene was studied by gel permeation chromatography (GPC) and the solubility data analyzed by Charlesby–Pinner plots. It has been shown that the unattainability of 100% gel from unfractionated polyethylene is due to segregation of low molecular weight chains during crystallization which need very high doses for complete gelation.
Crystallinity and the effect of ionizing radiation in polyethylene. VI. Decay of vinyl groups
Authors: Patel G. N.
Published: April 2003

Freeze‐dried single crystals of unfractionated Marlex 6009 polyethylene were irradiated at various doses up to 100 Mrad. Analysis of the data of the present work and those of others showed that the decay of vinyl groups can be best described by second‐order kinetics. The decay rate constant is found to increase with decrease in original concentration of vinyl groups. It has been concluded that the increase in the decay rate constant with decrease in initial vinyl concentration is due to a decrease in crystallinity. Some supporting evidence has been presented for this conclusion.
Elastic–inelastic behavior of PET and nylon 66 monofilaments under lateral compression
Authors: Batra Subhash K. , Syed Nuruzzaman
Published: April 2003

Results of experiments on short lengths of nylon 66 and PET monofilament specimens, subjected to lateral compressive force between two parallel platens, are described. In the experimental procedure the change in the compressed diameter and the area of contact were determined as a function of the applied force. From these data elastic moduli in lateral compression were estimated. The load–deformation behavior beyond the elastic range exhibited a yield‐like phenomenon. SEM examination of the deformed specimen suggest the possible modes of deformation in the post‐yield behavior. It is inferred that the yield occurs due to concentration of deformation along the maximum shear planes. The deformed specimens also show specific forms of fracture initiation and growth.
Morphology of gamma‐irradiated, low‐density, bulk polyethylene
Authors: Besmann Theodore , Greer Raymond
Published: April 2003

Low‐density bulk polyethylene was subjected to gamma radiation doses between 0.1 and 100 megarads. Surfaces produced by fracture at liquid nitrogen temperatures were studied using scanning electron microscopy. The unirradiated polyethylene and polymer irradiated to 0.1 megarad had spherical units with a diameter of about 0.15 micron lying on the fracture surface. The units lay along the edges of the lamellae and were formed by the fracture that was, therefore, not entirely brittle. Polyethylene irradiated between 1 megarad and 100 megarads exhibited spherical voids, with a diameter of about 0.1 micron in the fracture surface. The voids have been produced either by the evolution of gas in the polymer during irradiation, the most likely mechanism, or as a function of the fracture mechanism only.
Deformation of oriented polyethylene
Authors: Pope D. P. , Keller A.
Published: April 2003

The deformation of polyethylene in terms of structural processes has been investigated by low‐and wide‐angle x‐ray diffraction in the case of low‐density and, to a lesser extent, high‐density polyethylene. The samples possessed a range of simple textures which enabled the deformation processes to be identified. The results are interpreted in terms of a model of stacks of lamellae which have axes along the original draw direction and which deform by lamellar slip, chain slip, and lamellar separation. In most cases these processes accounted for the macroscopic strain but in some cases discrepancies were observed which could be accounted for by inhomogeneous deformation or by the effects of a distribution of lamellar thicknesses. Attempts were made to identify fibrillar slip, without success. The relative contributions of the various deformation processes are examined as a function of temperature and sample treatment by defining a compliance constant for each process. Below room temperature, the results are consistent with expectations based on the α and β mechanical relaxations, whereas the unusual effects at high temperatures are attributed to gradual melting. The compliance constants are also found to depend on the annealing temperature of the sample, and are used to predict the mechanical anisotropy. The volume changes accompanying lamellar separation are examined. They were less than expected in low‐density polyethylene, but satisfactory agreement was obtained in high‐density polyethylene. A general relation is suggested between volume changes and the lateral development of the lamellae. Hence in narrow lamellae the interlamellar layer can contract laterally whereas the greater constraints imposed by wide lamellae lead to void formation. Other effects examined include the reversibility of the processes which is most marked in the case of chain slip and which is explained by the presence of restoring forces in the amorphous regions including the fold surface. Finally, the differences between low‐ and highdensity polyethylene are highlighted, emphasizing the part played in the deformation by the amorphous component.
Heat capacity of fluoropolymers
Authors: Lee W. K. , Choy C. L.
Published: April 2003

The heat capacities of poly(vinyl fluoride), poly(vinylidene fluoride), and polytrifluoroethylene have been measured between 80 and 340°K. The results can be expressed as the sum of two terms: the optical contribution calculated from the vibrational band assignments in the literature and the acoustical contribution calculated according to the Tarasov continuum model. Combining our data with those for polyethylene and polytetrafluoroethylene, it is concluded that the force constant for one‐dimensional intrachain interaction is approximately constant for all polymers with carbon backbones. The force constant for three‐dimensional interchain interaction is one order of magnitude smaller than the one‐dimensional force constant, and decreases when the hydrogen atoms in polyethylene are replaced by fluorine atoms. The thermodynamic functions for the three polymers have been evaluated. Glass transitions at 228°K and 305°K have been found in poly(vinylidene fluoride) and polytrifluoroethylene, respectively.
Crystallization and melting of polyethylene under high pressure. II. Effect of pressure on melting behavior of various types of crystals
Authors: Maeda Yoji , Kanetsuna Hisaaki
Published: April 2003

The effect of pressure on the melting point and volume of fusion of polyethylene was studied by high‐pressure dilatometry. Starting materials were crystallized slowly from the melt under pressures of 1500, 3500, 5130 kg/cm2, and 1 atm. It has been shown that the unusual behavior observed at pressures above 4000 kg/cm2 is due to crystallization and melting of two kinds of extended‐chain crystals differing in thermal stability. These are designated as ordinary extended‐chain and highly extended‐chain crystals, respectively. The relation between pressure P and melting temperature Tm of folded‐chain, ordinary extended‐chain, and highly extended‐chain polyethylene was determined precisely. At pressures up to about 3000 kg/cm2, plots of P against Tm for the crystal forms have almost the same curvature and then become parallel. But at pressures above 4000 kg/cm2, ordinary extended‐chain crystals show a linear increase of Tm with a constant slope of about 70 atm/deg. Curve for the highly extended‐chain crystals changes in slope from 70 to 50 atm/deg at pressures between 3500 and 4300 kg/cm2, and then show a sharp increase of Tm with increasing pressure. Experiments show that the meltingpoint curve of the highly extended‐chain crystals overlaps that of the ordinary extended‐chain crystals at pressures below 4000 kg/cm2. Annealing experiments with folded‐chain and ordinary extended‐chain crystals have been made under high pressure. It is suggested that the formation of highly extended‐chain crystals occurs stepwise through the formation and reorganization of ordinary extended‐chain crystals from the original folded‐chain crystals by a mechanism of partial melting and recrystallization at pressures above 4000 kg/cm2.
Theory of the epitaxial crystallization of polymers on alkali halide substrates. II. Polyoxymethylene and polythiomethylene
Authors: Mauritz K. A. , Hopfinger A. J.
Published: April 2003

The epitactic behavior of a single chain of polyoxymethylene and of polythiomethylene on alkali halide substrates has been simulated by computing the coulombic, induced dipolar, and dispersion–repulsive potential energies as a function of polymer–substrate geometry. Inspection of the total potential energy surface for a polyoxymethylene chain in a 9/5 helix reveals a favorable alignment in which the chain is parallel to the substrate surface ((001) cleavage plane) with specific positioning along rows of positive charge. This preferential orientation has been found to be independent of lattice matching between the substrate and deposited phase. An identical mode of orientation is predicted for a polyoxymethylene chain and a polythiomethylene chain, both in the 2/1 cis‐planar conformation. The theoretical results for polyoxymethylene are in agreement with available experimental evidence, whereas the outcomes of the calculations performed on polythiomethylene should be considered predictive study to be complemented by a future experimental investigation.
Matrix ENDOR of polyenyl radicals in polymers
Authors: Helbert John N. , Wagner Burkhard E. , Poindexter Edward H. , Kevan Larry
Published: April 2003

EPR and matrix ENDOR spectra have been examined for polyenyl radicals in γ‐irradiated PVF, PVF2, PVC, and PMMA polymers. Proton matrix ENDOR is observed for all four polymers, and fluorine matrix ENDOR for PVF and PVF2. By line shape analysis of the ENDOR spectra obtained under comparable conditions, delocalization diameters for the unpaired electron of the polyenyl radical in each polymer are obtained. These diameters indicate extensive delocalization over 5–7 carbon double bonds for the polyenyl radicals investigated. It is suggested that these conjugated and crosslinked radiation products account for the observed nondevelopment of electron beam resist PMMA material at high radiation charge densities.
The distribution of stereochemical configurations in polystyrene as observed with 13C NMR
Authors: Randall James C.
Published: April 2003

13C NMR configurational assignments are made for an amorphous polystyrene sample examined at 25.2 MHz and 120°C. The assignments are based strictly on a one‐parameter Bernoullian fit that was in satisfactory agreement with the nine observed methylene relative intensities. The methylene regions of the 13C NMR spectra of a polystyrene were examined before and after hydrogenation of the side‐chain phenyl substituents. It was concluded that ring current effects have influenced the 13C methylene chemical shifts substantially and are limited largely to contributions from adjacent phenyl substituents. In addition, aromatic substituent parameters are reported that can be used in conjunction with the Grant and Paul parameters for calculating chemical shifts in aromatic hydrocarbons and polymers. Finally, it is concluded that free‐radical and n‐butyllithium‐prepared polystyrenes have essentially atactic structures with meso additions favored over racemic additions by approximately 55/45.
Temperature dependence among the grant and Paul parameters as derived from 13C NMR polymer spectra
Authors: Randall James C.
Published: April 2003

Improvements in the 13C NMR Grant and Paul parameters as applied to polymers have been obtained by noting that the “corrective terms” can be temperature‐sensitive. A corresponding temperature sensitivity was not observed for the primary parameters, α through ϵ. Results are given for a hydrogenated polybutadiene and six different ethylene–1‐olefin copolymers where the standard deviation between calculated and observed chemical shifts has been improved from 1.04 to 0.30 ppm. Since the “corrective terms” in the Grant and Paul empirical analyses of chemical shifts reflect the conformational character of polymers, it is shown that values for these terms can best be obtained directly from the system under study.
Basic modes of three‐dimensional polymer crystal associations: Interlocked single crystals and crystal halves
Authors: Lotz B. , Kovacs A. J. , Wittmann J. C.
Published: April 2003

Tridimensional associations of lamellar polymer single crystals, grown from dilute solutions, are described as derived from their sedimentation patterns. These associations include interlocked crystals and decorating crystal halves. The origin of these crystals and their mutual orientation are discussed and tentatively interpreted by specific interactions between the fold surface and the crystallizing chains.
Approximate relations among compliance functions of linear viscoelasticity for amorphous polymers
Authors: Riande Evaristo , Markovitz Hershel
Published: April 2003

In the glass–rubber transition region of viscoelastic behavior of amorphous polymers, it is found that

is a good first approximation. Here J(t) is the value of the shear creep compliance at time t and J″(1/t) is the value of the shear loss compliance at an angular frequency of 1/t. Previous approximations related the creep compliance to the storage compliance. When J(t) is proportional to tm, where m is a positive constant, J″(1/t) is within 30% of J(t) for m > 0.6. Over the entire range,

is a better approximation than either of the other two. The relaxation modulus G(t) is hardly ever a good approximation for the loss modulus G″(1/t).
Electrospray mass spectroscopy of macromolecule degradation in the electrospray
Authors: Teer Dan , Dole Malcolm
Published: April 2003

As previously shown, by electrospraying dilute polystyrene (PS) solutions gas phase macroions can be produced. Degradation of the PS in the electrospray was tested by collecting the electrosprayed PS and measuring its number‐average molecular weight osmotically. About 10% degradation was observed when using negative voltages, but the degradation was considerably reduced when the electrospray occurred in the presence of SF6 gas. No degradation was apparent in the case of positive sprays. A quantitative analysis of the results was made difficult by a small less of PS in the nitrogen gas stream and by diffusion of lighter ions to the vertical wall of the spray chamber. The latter effect did not occur at the highest spray voltage used, −24 kV.
A theoretical analysis of the effect of solvent on the Kerr constant of dilute polymer solutions
Authors: Fortelný I.
Published: April 2003

A new model in which solvent molecules are regarded as discrete particles is used for investigating the influence of solvent orientation near a polymer chain and of the anisotropy of the internal electric field on the Kerr effect in a polymer solution. The relation derived for the Kerr constant consists of two parts containing nine terms each in the general case (the physical meaning of the terms is briefly discussed). Relations for the above effect in a nonpolar isotropic solvent, and explicit calculations of the Kerr constant for a simple model of a rigid polymer molecule are given.
Orientation of crystallites in lightly crosslinked isotactic polypropylene crystallized from the melt under uniaxial compression
Authors: Kitamaru R. , Hyon S.‐H.
Published: April 2003

A lightly crosslinked polymer film was made from isotactic polypropylene by gammaray irradiation in an acetylene atmosphere. When the crosslinked polymer film was crystallized from the melt under uniaxial compression, a unique alignment of crystallites is found. The (040) crystal plane is preferentially oriented parallel to the film surface at relatively low degrees of compression, and the (110) and (130) crystal planes are oriented parallel to the film surface at higher degrees of compression. The origin of these orientations, analogous to that previously found in a lightly crosslinked polyethylene, is discussed.
Measured and calculated solubility of polymers in mixed solvents: Monotony and cosolvency
Authors: Wolf B. A. , Blaum G.
Published: April 2003

By a study of two ternary systems, 4‐heptanon–1‐chlorobutane–poly(methyl methacrylate) and 2‐butanol–1‐chlorobutane–poly(methyl methacrylate), differing only in one component of the mixed solvent, two types of demixing behavior are demonstrated: i.e., a monotone change with composition of the mixed solvent (monotony), of which the first system is a good example, and the synergistic behavior (cosolvency) exhibited by the second system. The situation can be seen most clearly from the binodal edges (precipitation thresholds as a function of solvent composition) which were constructed from various types of sections through the binodal surface of the systems.

In order to compare experimental results with theoretical calculations, we first characterized the binary subsystems. The polymer solutions, representing conventional (endothermal) theta systems, were investigated by light scattering and cloud point measurements. For the cosolvent 2‐butanol–1‐chlorobutane the necessary thermodynamic information was accessible from vapor pressure measurements. Applying the Prigogine–Patterson theory to the polymer solutions and using the single‐liquid approximation of Scott for the ternary systems yielded theoretical binodal edges in good agreement with experiment except for the branch belonging to mixed solvents rich in 2‐butanol. This finding is explained by an abnormal amplification of preferential solvation effects due to the existence of an association equilibrium of the alcohol via hydrogen bonds.
Tensile properties of ultradrawn polyethylene
Authors: Capiati Numa J. , Porter Roger S.
Published: April 2003

High‐density polyethylene filaments prepared by a solid‐state deformation in an Instron capillary rheometer show unusually high crystal orientation, chain extension, axial modulus, and ultimate tensile strength. The Young's modulus and ultimate tensile strength have been determined from stress–strain curves. Gripping of this high modulus polyethylene has been a problem heretofore, but the measurement of ultimate tensile strength has now been made feasible by a special gripping procedure. Tensile moduli show an increase with sample preparation temperature and pressure. Values as high as 6.7 × 1011 dyne/cm2 are obtained from samples extruded at 134°C and 2400 atm and tested at a strain rate of 3.3 × 10−4 sec−1. The effect of strain rate and frequency on modulus has also been evaluated by a combination of stress–strain data and dynamic tension plus sonic measurements over nine decades of time.
Crystalline isomeric polyester block copolymers. Scanning calorimetry and density measurements
Authors: O'malley James J.
Published: April 2003

A series of isomeric polyester block copolymers were synthesized by coupling hydroxyl‐terminated poly(hexamethylenesebacate) (HMS) and poly(2‐methyl‐2‐ethyl‐1,3‐propylene sebacate) (MEPS) with hexamethylene diisocyanate. Poly(HMS) is crystalline, whereas poly(MEPS) is amorphous. All of the block copolymers, including one containing only 28% HMS were found to crystallize. DSC, density, and optical microscopy were used to measure the thermal transition temperatures and the degree of crystallinity. The data indicate that block copolymerization causes a small depression in the melting point and that the degree of crystallinity of the HMS block in the copolymer is more a function of molecular weight than it is of copolymer composition. Crystallization appears to be the major driving force for phase separation in this isomeric copolymer system.
On the transition from paraffinic to polymeric behavior: Mechanical properties
Authors: Crissman J. M.
Published: April 2003

An attempt has been made to determine what influence chain folds may have on the α and γ mechanical loss peaks in linear polyethylene. In so doing, one long‐chain n‐paraffin (C94H190) and two low molecular weight polyethylene fractions have been examined with mechanical relaxation, differential scanning calorimetry (DSC), and low‐angle x‐ray diffraction techniques. The data suggest that chain folds play a prominent role in both the α and γ processes but that other factors such as polydispersity and/or branching are also important.
Quantitative structural characterization of the melting behavior of isotactic polypropylene
Authors: Samuels Robert J.
Published: April 2003

The melting behavior of restrained isotactic polypropylene fibers is examined quantitatively in terms of the influence the anisotropic structural state of the polymer has on the observed properties. Two endotherm peaks are observed to occur in some of the samples. The formation and location of the multiple peaks are determined by the orientation of the noncrystalline chains, and is independent of the fabrication path used to achieve that orientation. Above a certain minimum orientation of the noncrystalline chains, multiple endotherm peak formation occurs. The high‐temperature endotherm (T2M) extrapolates to an ultimate melting point for fully oriented noncrystalline chains of 220°C, while the lower‐temperature endotherm (T1M) extrapolates to an ultimate melting point of 185°C. Noncrystalline chain orientation influences the endotherm temperature through its changing configurational entropy. It is shown quantitatively that the noncrystalline polymer must be considered as plastically deformed, since rubber elasticity theory is not followed as predicted. The melting behavior of isothermally crystallized samples are also reported to further elucidate the nature of the observed endotherms.
Pressure quenching and chain‐extended crystallization of polyethylene
Authors: Morris R. B. , Bassett D. C.
Published: April 2003

Recent work has shown that so‐called chain‐extended crystallization of polyethylene is crystallization of the newly discovered hexagonal phase. This hypothesis is supported by experiments on the pressure quenching of molten polyethylene.