bluuebunny/crossref_metadata_2025 huggingface dataset:
Application of infrared spectrometry to the study of some polymer problems
Authors: Sibilia J. P. , Paterson A. R.
Published: June 2010

Infrared spectroscopy has been applied as a major tool for the investigation of a number of polymer problems. The major products of thermal degradation (300°C.) of polymonochlorotrifiuoroethylene and copolymers with vinylidene fluoride have been Identified and are considerably different depending upon whether or not degradation occurs in nitrogen or oxygen. A mechanism based on random chain cleavage has been proposed for both the homopolymer and copolymer system. A method has also been developed for the determination of the vinylidene fluoride content in vinylidene fluoride‐monochlorotrifluoroethylene copolymers by measuring the —CH— stretching absorption of the —CH2CF2— units in solid films. Absolute values of —CH2CF2‐ content have been determined by high‐resolution NMR and melting point techniques. It has been shown that the intensity of the —CH— stretching absorptions is dependent on the local chain conformation about the —CH2— unit. In another problem the “hardness” of polyethylene waxes has been found to be dependent, on the degree of branching as measured by the methyl absorption at 1378 cm.−1. Molecular weight has been shown to have little effect on the hardness.
Determination of polyacrolein labeled with tritium or carbon‐14
Authors: Carr Robert J. , Gordon B. E.
Published: June 2010

This paper describes methods of analysis for radioactively labeled polyacrolein in solutions, powders, and on paper. The tracers, tritium and carbon‐14, were used because of interferences encountered in some of the analyses. Briefly, the methods involve combustion of the sample in the Sohöniger flask, absorption of the desired product of combustion in a suitable solvent, followed by liquid scintillation counting. For tritium analysis, ethanolic toluene was the absorbent for the product water, and for carbon‐14 methanolic benzylamine was used to absorb the carbon dioxide. Two sources of error in the analysis were discovered, namely, soot and dissolved oxygen. These seriously affected the accuracy and precision of the results. A filtration step followed by an equilibration with air resulted in satisfactory analyses. The use of benzylamine to absorb carbon dioxide has the added advantage of permitting the determination of the weight per cent of carbon by a simple titration with base. The advantages of the tracer method for polyacrolein are (1) specificity, (2) multiple analyses (>20 combustions per day), (3) convenience, and (4) low cost in combustion equipment.
Polymer analysis by high‐resolution NMR, with applications to poly(vinylidene fluoride) and poly(vinyl fluoride)
Authors: Wilson C. W. , Santee E. R.
Published: June 2010

High‐resolution nuclear magnetic resonance (NMR) spectroscopy has been used for the past several years quite effectively in both the qualitative and quantitative determination of the molecular chain structures and compositions of various polymeric systems. Valuable structural information obtained from such NMR studies has included: (1) detailed stereo chemical configuration (both tacticities and stereoblock sizes) of the polymer chains, (2) copolymer compositions, (5) sequence distribution studies in copolymers, (4) determination of modes of monomer addition in both homopolymers and copolymers, and (5) extent of head‐to‐head structures. Currently, only H1 and F19 NMR techniques are being used in the elucidation of organic polymer structures, for reasons primarily of instrumental sensitivity but also involving general applicability. Examples of the utility of F19 and H1 NMR, as well as double‐resonance techniques, to determine chain structure and composition of fluorine‐containing polymers are presented in this paper. In particular, conclusive proof of a substantial amount (10–12%) of head‐to‐head structure and the detailed assignment of the F19 chemical shifts in poly(vinylidene fluoride) is presented. The existence of a very large amount (26–32%) of he ad‐to‐head structure in both experimental and commercial samples of poly(vinyl fluoride) is also shown (although the detailed assignment of the F19 NMR spectral peaks has not yet been completed); this indicates that about one monomer unit in every six or so is added “backwards” to the growing polymer chains during free‐radical homopolymerizations. Increase in the amount of head‐to‐head structure with increase in polymerization temperature is also observed for poly(vinyl fluoride).
Characterization of polymer orientation by birefringence
Authors: Stein Richard S.
Published: June 2010

The birefringence of a polymer may be used for studying orientation, crystallization, and mobility in a polymeric solid. It is a measure of the average of an orientation distribution for the anisotropic molecular segments of a polymer. Its interpretation is complicated by the lack of knowledge of the absolute birefringence of a polymer segment and by the extent of its dependence upon environment. For crystalline polymers, the birefringence may be resolved into contributions from the crystalline and amorphous components. By measurement, together with measurement of crystalline orientation by the x‐ray technique it may be used to resolve the orientational contribution of these two phases. This is complicated by the uncertain effect of disorder within the crystal upon its birefringence. Also form birefringence of the crystalline amorphous interface and by voids must be considered. Birefringence measurements must be made by compensator or by intensity measurement techniques. The latter are susceptible to automatic recording. Measurements may be made on films or fibers. The time dependence of birefringence may be followed during relaxation or during deformation of a sample. When measured as a function or frequency during vibrational deformation the results characterize the orientation processes possible in a given polymer which depend upon morphology, orientation, and sample treatment.
The molecular structure of polyethylene. XVI. Analytical column fractionation
Authors: Kokle V. , Billmeyer F. W.
Published: June 2010

An analytical procedure for the solvent‐gradient elution fractionation of polyethylene has been devised and applied to both linear and branched polyethylenes. The procedure utilizes selective polymer deposition, programmed solvent composition to keep the polymer:solvent ratio below 1:10,000 at all stages, and reparation of the sampler into several hundred fractions. A smaller number of these fractions is characterized by dilute solution viscosity. New, self‐consistent viscosity‐molecular weight relations are derived which give improved agreement in weight‐average molecular weights observed directly by light scattering, derived from whole polymer viscosities, and derived from fractionation date. Number‐average molecular weights derived from fractionation data are in good agreement with those measured directly. Digital computer techniques are described for deriving integral and differential distribution curves, as well as average molecular weights. Typical results are presented. The broad molecular weight distribution curves in linear polyethylenes are confirmed. For many samples, the differential distribution curve has no peak above the lowest, molecular weight measured, in the neighborhood of 1,000.
Crystalline character in polymers
Authors: Peterlin A.
Published: June 2010

The original fringed micelle model of a crystalline polymer solid assumed two phases, submicroscopical bundled chain crystals embedded in an amorphous matrix. Every macromolecule passed alternately through crystalline and amorphous regions. This model ideally represented the crystallization with highly stretched rubber, but failed to explain spherulites and lamellar single crystals. The folded chain model of the lamellae grown from dilute solution postulated in a polymer solid the inclusion of all the material in single crystals (one phase model). The amorphous x‐ray diffraction pattern and the density defect were due to crystal defects, particularly to the chain folds at the crystal surfaces. Later development has brought both models closer together. In spite of rather regular chain folds with immediate re‐entry there are some chains folding back in a switchboard manner. In a sample crystallized from melt there are still more chains incorporated in two different crystals so that the intervening portion is prevented from crystallization. Together with uncrystallizable components, such tied molecules are constituting an amorphous phase of the very same type as assumed by the fringed micelle model. The basic improvement of the new model is just the comprehension of the important role of chain folds in establishing a discontinuity between the crystals and the amorphous material. A particularly important problem in crystalline polymers is the plastic deformation and the resulting high orientation in drawn fibers and films. From the experiments with single crystals, one learned the basic mechanism of deformation, i.e., phase transformation, twinning, chain tilt, and slip which finally leads to complete break up of original crystals into smaller blocks which are incorporated in the pulled out fibrils. The tied molecules in such highly oriented material are markedly strained and aligned which show up in a decrease of entropy and enthalpy as compared with a completely relaxed amorphous phase. The decrease in enthalpy quantitatively explains the conspicuous depression of sorption, dyeability, diffusion, and permeability of drawn fibers and films.
The diffusion of gases through filled polymers
Authors: Kwei T. K. , Arnheim W. M.
Published: June 2010

The diffusion of oxygen and arson through poly(vinyl acetate) filled with 12% by volume of titanium dioxide was studied. It was found that the activation energy of gas diffusion in each case was about 56% of the corresponding value fur diffusion in the unfilled polymer above its glass transition temperature. Furthermore, the activation energies for diffusion in the filled polymer appeared to be the same at temperatures above and below the transition temperature, in contrast with the observation by Meares that the activation energy for diffusion in the unfilled polymer has a higher value above Tg. The decrease in the activation energy of gas diffusion as a result of filler incorporation is discussed in terms of the possible decrease in the internal pressure of the filled system. It is postulated that a decrease in the configurational entropy of the polymer accompanies the incorporation of the filler. The explanation is consistent with the results of organic vapor sorption experiments.
The thermal expansion of cellulose, hemicellulose, and lignin
Authors: Ramiah M. V. , Goring D. A. I.
Published: June 2010

The thermal expansion of wood constituents has been measured dilatometrically both in the dry and the water‐swollen state. Dry measure meats were made with mercury as the confining liquid on samples pressed into dense pellets at elevated temperatures and pressures. Between −30 and 30°C, the thermal expansion coefficients for various celluloses and hemicelluloses ranged from 5.1 to 6.0 × 10−4 ml./g./°C. For lignin, the coefficient increased to about 10 × 10−5 ml./g./°C. A second order transition was noted in all samples at 19–33°C. A further transition at 8G‐110°C. was detected for the dioxane lignin, periodate lignin, and Avory cellulose. All transitions in the dry state produced an increase in the expansion above the transition temperature. In the water‐swollen state, samples were in the form of powders or broken pellets, with distilled water as the confining liquid. The thermal expansion coefficients of the water‐swollen samples were several times as great as the expansion coefficients measured in the dry state. The second order transition near 20°C. persisted, but in water the transition was negative with expansion decreasing above the transition temperature. Analogous results were obtained for glucose and cellobiose, both in the dry state and in solution. The transition in the dry state is attributed to increased thermal motion caused by the rupture of weak hydrogen bonds. The large and interesting discrepancy found in the expansion of the water‐swollen materials is interpreted as arising from the perturbation of the water structure by the hydrophilic surfaces of woody macromolecules, and a quantitative assessment of this effect is attempted.
The alkane dithioether and the polysulfide crosslinking of cellulose
Authors: Clingman A. Lionel , Schwenker Robert F.
Published: June 2010

New crosslinked cellulose derivatives were obtained from the reactions of potassium disulfide andn‐alkane‐α‐ω‐dithiols with partial tosyl or brosyl esters of native cellulose. Treated cotton print cloth showed significant improvement in wet and dry wrinkle recovery over untreated. Alkane dithioether crosslinks, —S(CH2)nS—, of different lengths (2–10 CH2 groups) were introduced. Treatment with aqueous or ethanolic solutions of potassium disulfide resulted in the formation of polysulfide crosslinks, such as tetrasulfide. The effect of crosslink length on the physical properties of the modified cottons was studied, and it was found that fabric wrinkle recovery tended to decrease as crosslink length increased. It was also found that the tosyl and brosyl cellulose esters were degraded by alkali. This degradation is ascribed to the loss of primary sulfonyloxy groups with subsequent hydrofuranol ring formation in the case of the anhydroglucose units involved.
The optical rotation of wood xylans
Authors: Gutmann P. J. , Timell T. E.
Published: June 2010

Previously derived equations relating the specific rotation and chemical composition of 4‐O‐methylghicurono‐xylans and arabino‐4‐O‐methylglucurono‐xylans have been found to be partly incorrect because of the assignment of an erroneous value to the rotatory contribution of the 4‐O‐methyl‐α‐D‐glucuronosyl xylose residue. The correct value was calculated from the known molar rotations of xylobiose and 22‐(4‐O‐methyl‐α‐D‐glucuronosyl) xylotriose. Approximately the same values were obtained from the specific rotations of five carefully purified 4‐O‐methylglucurono‐xylans, containing different proportions of acid side chains, and from the rotations of an aldopentaouronic and an aldohexaouronic acid. A revised equation was used for estimating the specific rotation of several arabino‐4‐O‐methylglucunmo‐xylans from various softwoods. Contrary to the earlier results, a satisfactory agreement was found to exist in most cases between found and calculated values.
Theory of light scattering from oriented and fiber structures
Authors: Stein R. S. , Erhardt P. , Van Aartsen J. J. , Clough S. , Rhodes M.
Published: June 2010

Recent progress in the theory of scattering by spherulites of crystalline polymers is reviewed. The consequences of arbitrary optic axis orientation, periodicity of optic axis orientation and of spherulite deformation are described. The transmission of light by a film of a crystalline polymer having spherulitie or lower degrees of order of crystalline orientation is discussed. A theory of the scattering of light from such a film having nonrandom correlation in crystalline orientation is developed. The dependence of the scattered intensity on the polarization directions of the incident and scattered light is shown to depend upon a parameter which characterizes the nonrandomness.
Small angle light scattering from deformed spherulites. Theory and its experimental verification
Authors: Samuels Robeht J.
Published: June 2010

The observed small angle light scattering (SALS) from deformed spherulites is described by the theory of an anisotropic spheroid in an isotropic medium. Experimental verification of the theory, based on SALS data from both photographic and photometric measurements on isotactic polypropylene films, is presented. The theory led to a method for experimentally determining the extension ratio of the deformed spherulite and the radius of the original undeformed spherulite from the SALS pattens.
Light scattering from polymer films
Authors: Wallach M. L.
Published: June 2010

A variety of films were examined by low angle laser light scattering to yield information on the size, shape, and orientation of superstructure. Films of poly(ethylene terephthalate) and polypropylene give distinctive scattering patterns in the form of two‐ and four‐leaf clovers which change with polarization direction, stretching, heat setting, and heat relaxation. Changes in pattern geometry vary systematically with film properties, x‐ray, and polarized infrared structural parameters. In one‐way oriented poly(ethylene terephthalate) films, the quadrant, leaves tend toward the equator and elongate with increased draw, taking on a fiberlike appearance, whereas with two‐way drawn films the leaves shift away from the equator and patterns become more circular with increased second direction draw. Melt‐pressed, quenched, unnucleated, polypropylene films show a characteristic spherulitic type pattern. The higher the quench temperature, the larger the spherulites become. Calculated spherulite diameters increase with quench temperature up to 15m for temperatures of 60°C. Upon drawing, the patterns elongate owing to Spherulite deformation and internal reorganization of crystallites, taking on a fiberlike geometry. Nucleated and slowly cooled resins show very little scattering and no spherulitic quadrant leaves. Heat setting usually led to the appearance of new pattern features characteristic of new structures. Heat relaxation tended to smear out the Scatterning patterns as a result of the disappearance of superstructure.
Small angle scattering by a three‐component system. Testing the theory for light scattering
Authors: Coalson R. L. , Marchessault R. H. , Peterlin A.
Published: June 2010

Light‐scattering data from solvent‐exchanged, highly swollen gel cellophane were compared with the scattering theory for a three‐component system (crystalline fraction, amorphous fraction, and imbibition liquid) originally developed for the scattering of x‐rays. A rather good agreement, between theoretical and experimental data is obtained in angular dependence and dependence on the refractive index of the imbibition liquid. But the calculated “zero” angle intensities are some orders of magnitude larger than the observed values. This effect must be due to the variation of the internal electric field which is influenced not only by the local polarizability but also by the shape of the region under consideration and by the polarizability of the surrounding area. This effect does not occur with x‐rays since the refractive index is then unity. With visible light one must conclude that the absolute scattering intensity, I(O) is much more affected than the angular dependence which is sufficiently well described by the composite correlation function of the three‐component system.
Mechanical relaxation in polychlorotrifluoroethylene
Authors: Crissman John M. , Passaglia E.
Published: June 2010

Measurements of the viscoelastic functions Δ, G', G″, J′, and J″ as functions of temperature from −180 to +180°C. have been obtained, using a torsion pendulum apparatus, for several samples of polychlorotrifluoroethylene having widely different crystallinities as determined by density. The low crystallinity samples show two relaxations: a very broad one (γ) centered at about −35°C. which appears to be split into two processes, and one (β) at 84°C. In the higher crystallinity samples, a third process (α) appears at about 137°C., and the high temperature side of the γ relaxation peak is lower in magnitude as compared to the lower crystallinity specimens. For the β peak, which is assumed to be associated with the glass transition, the peak value for G″ is essentially independent of crystallinity, while both Δ and J″ show decreases in magnitude with increasing crystallinity. The relationship between the magnitude of the relaxation peak and crystallinity, and dependence of this relationship upon the viscoelastic function chosen to characterize the relaxation are discussed.
Effect of polar forces on the viscoelastic properties of poly(propylene oxide)
Authors: Moacanin J. , Cuddihy E. F.
Published: June 2010

When lithium perchlorate is dissolved in ethers, volume contractions are observed which are caused by strong interaction forces between the field of Li+ and polarizable ether oxygens. The effect of these forces on the viscoelastic properties of both low (commercial PPG 2025) and high molecular weight/poly(propylene oxide), containing varying amounts of dissolved lithium perchlorate (LP), was investigated by means of dilatometric, modulus, and damping constant measurements over a temperature range between ‐SO and 80°C. The glass transition temperature, Tg, for PPG 2025 was raised from −70 to 40°C. for 25 wt.‐% LP. Neither modulus nor damping curves could be superposed on the reduced T‐Tg temperature scale. Below 15 wt.‐% LP the various properties could be interpreted as resulting from the superposition of the behavior of free polyether segments with that of segments nearest neighbors to LP. Above 15 wt.‐% LP no free segments are left. The behavior of the high molecular weight polyether was similar, except that below 15 wt.‐% LP the single Tg observed for PPG 2025 was split in two transitions, Tg for the polyether at −65°C, and another at −10°C. The latter is believed to be a transition for polyether helices stabilized by LP situated in the helix core.
Calculation of the elastic constants and the lattice energy of the polyethylene crystal
Authors: Odajima Akira , Maeda Takashi
Published: June 2010

To calculate the elastic constants, (Cij), of the polyethylene (PE), Born's dynamical theory of long wave method has been used for a model of interatomic interactions representing inter‐ and intramolecular force fields. Among various types of interaction potentials between nonbonded atoms, two sets of H‐H, C‐H, and C‐C interaction potentials have been adopted which give the best results in reasonable agreement with the data of the lattice parameters and the angle between plane of the zigzag chain and crystallographic axis in the PE lattice. It has been also verified that the lattice energy of PE can be calculated successfully by using the present, potentials. In order to calculate the elastic constant, H‐H and C‐H interactions with close distances have been taken into account for the intermolocular force fields. On the other hand the Urey‐Bradley force field has been used for intramolecular interactions. An expression is obtained which relates Horn's force constants to the macroscopic elastic constants in the orthorhombic system. The calculation has been also made on Cij in a rigid model of molecular chain, but it is found that the increments of elastic constants due to the rigid model are at most a few per cent. The elastic moduli along the a, b, and r, axes and also the normal of the (110) plane have been derived from Cij and compared with values experimentally determined by x‐ray diffractometry. Furthermore, the space averages for compressional, shear, and Young's moduli of PE polycrystals oriented in all directions, and the T3 low‐temperature dependence of heat capacity are discussed.
Dislocations in polyethylene crystals
Authors: Lindenmeyer P. H.
Published: June 2010

A summary is given of recent work on the observation of dislocations in polyethylene crystals and the results are discussed in terms of the crystal‐defect model of polymer structure. Both inter‐ and intralamellar dislocations have been observed and their Burger's vectors determined. Most dislocations were observed to be imperfect or partials, indicating that there exist low energy stacking faults. Annealing single crystal brought about approximately a thousandfold increase in the dislocation density which indicates that dislocations are involved in the process of thickening. The observation of dislocation networks in the folds between lamella prove that these folds are sufficiently regular to pack crystallographically. Observed interactions between inter‐ and intra‐lamellar dislocations show that the interlamellar dislocations are glissile and therefore interlamellar slip can occur by a dislocation motion. These observations lend considerable support to the crystal‐defect model of polymer structure. However, it is pointed out that this model does not conflict seriously with tlie statistical equilibrium theory of polymer crystallization. Dislocations are non‐equilibrium defects and hence would not exist under true equilibrium conditions.
Fluorescence method for studying molecular orientation in polymer solids
Authors: Nishijima Yasunori , Onogi Yoshihiko , Asai Takeo
Published: June 2010

A new method for measuring molecular orientation in polymer solids is developed involving the use of the polarization phenomena of fluorescence emitted from fluorescent groups dispersed in the media. This fluorescence method makes it possible to measure not only the extent of orientation but also the types of orientation. The theoretical background of this method is described and the theoretical patterns of the angular distribution of degree of polarization of fluorescence are given for several types of orientation, including random, perfect uniaxial, partial uniaxial, and perfect biaxial orientations. It is proved that this method is applicable to symmetrical biaxial orientations for which other optical methods fail to provide information. The procedure of this method is to measure the angular distribution of polarized components of fluorescence intensity emitted from the oriented samples. Examples are given for various orientations of poly(vinyl alcohol) films. The process of transformation in orientation pattern is observed in the course of biaxial stretching of the film. An apparatus for continuous measurements is described.
Polyisobutene Degradation in Laminar Flow: The Effect on Molecular Weight Distribution
Authors: Porter Roger S. , Cantow Manfred J. R. , Johnson Julian F.
Published: June 2010

Polyisobntene solutions in n‐hexadecane and 1,2,4‐trichlorobenzene have been mechanically degraded in laminar flow under known and homogeneous stresses up to 105 dyne/cm.2 and at several temperatures in a thin‐film, rotational concentric cylinder viscometer. The polymer studied had an Mv of 8.0 × 105 and a broad and completely defined molecular weight distribution. The molecular weight distribution of the starting polymer and the distributions resulting from polymer exposure to shear fields of various intensities were established by both gradient elution and gel permeation fractionation techniques. The data provide an evaluation of the threshold for shear degradation and the efficiency of energy input in achieving polymer reaction. The results aid in understanding the mechanism of reaction and the effect of shear degradation on molecular weight distribution.
A Comparison of Molecular Weight Distributions for Polyisobutenes as Determined from Gel Permeation and Gradient Elution Chromatographic Fractionations
Authors: Cantow Manfred J. R. , Porter Roger S. , Johnson Julian F.
Published: June 2010

Molecular weight distributions for polyisobutenes of broad and narrow molecular weight distribution have been determined by gel permeation and gradient elution chromatography. The molecular weight range covered was from 2,000 to over 1,000,000. Calibration of the gel permeation chromatograph was based on narrow fractions of polyisobutene. This eliminated the uncertainty as to chain extension that exists if the calibration is made with one polymer and applied to a different polymer. Comparison of results from the two methods of determining molecular weight distributions showed, in general, good agreement. Distributions from the gel permeation method were found to be somewhat broader than the known distribution. However, results from the gradient, elution method are of necessity narrower than the real distribution becaues only a finite number of fractions can be evaluated. Column efficiency, as measured in terms of theoretical plates, is found to be dependent on the sample used to make the measurement. It was concluded that the gel permeation method gives molecular weight distributions for polyisobutene with reasonable accuracy and that the method should be entirely satisfactory for comparison of distributions.
Alkaline Polymerization of Caprolactam. XXI. Dissociation of Alkali Metal Salts of 6‐Caprolactam in the Polymerization of 6‐Caprolactam
Authors: Šittler E. , Šebenda J.
Published: June 2010

According to the accepted mechanism of the anionic polymerization of 6‐caprolactam the chain growth proceeds through addition of lactam anion to the imide group. For the evaluation of rate constants it is necessary to know the concentration of lactam anions in the reaction system. The dissociation constants of lithium, sodium, and potassium salts of 6‐caprolactam in the melt of caprolactam at 100–150°C. were determined by measuring the electrical conductivity of the system. At 120°C. the dissociation constants of the Li, Na, and K salts of caprolactam were found to be 1 × 10−10, 4.9 × 10−7, and 3.6 × 10−5, respectively. The heat of dissociation for sodium caprolactam was found to be 70 kcal./mole and that for the potassium salt was 50 kcal./mole. In the course of the polymerization the caprolactam cis‐amide groups are converted to trans‐amide groups of the polymer chain. The basicity of trans‐amides differs from that of cis‐amide, and therefore the basicity of the reaction mixture is changed in course of polymerization. We measured the dissociation constants of sodium caprolactam and the course of polymerization in the presence of linear N‐alkylamides and polyamides. According to the higher acidity of the trans‐amide groups the dissociation constant rises with increasing content of alkylamide. However, the minor part of anions is formed by lactam anions and therefore the polymerization proceeds more slowly in the presence of polycaprolactam or other trans‐amides. In activated anionic polymerization this influence of trans‐amides disappeared which may be explained by the formation of acidic products formed from imide groups. This lower basicity was proved by measurement of the dissociation of sodium salt in the presence of imides. Additions of amides derived from acetic acid increased the rate of the activated and non‐activated polymerizations.
Nonlinear Relaxation in Polymer Solutions
Authors: Friš P.
Published: June 2010

The Lagrangian function describing an isolated polymeric chain is developed in Taylor series. The solution in the first approximation, which corresponds to Rouse's model with nonconstant hydrodynamic interaction, describes the nonlinear behavior of the solution. The finding of the equation of state is converted to the eigenvalue problem for linear operator.
Einfluss der Schmelzbedingungen auf die isotherme Kristallisation von Polypropylen
Authors: Rybnikář F.
Published: June 2010

The effect of melting temperature and time on the crystallization mechanism of various polypropylene samples has been investigated. It was found that during polypropylene melting two opposite processes take place. The first process consists of destroying the normal heterogenous nuclei, persisted above the melting point. The second process represents a formation of new heterogenous nuclei that cannot be destroyed in an additional melting process. The polypropylene samples could be divided in two groups according to the type of heterogenous nucleation predominating under usual melting conditions. The melting temperature has a more pronounced effect on the variation of the number of nuclei than does the melting time.
Contribution au Probleme de la Corrosion et du Vieillissement des Plastiques
Authors: Bossu B. , Dubois P. , Lecordier Et M.
Published: June 2010

With frequent reference to the recent Russian book by M. B. Neiman, Aging and Stabilization of Polymers, the authors show that the important advances made in the field are based upon knowledge of the reaction kinetics of degradation by heat, oxidation, photooxidation, hydrolysis, and mechanochemical action. The synergy in the effects of these factors and in the search for economical mixtures of stabilizers and anti‐oxygens is illustrated by numerous examples. Bell‐shaped curves are considered, showing the rise from zero to a maximum and the subsequent return to zero, concerning the daily variation of total radiation and its seasonal variations at various latitudes. The energy distributions between ultraviolet, visible, and infrared are also given. The standardization of a radiation hydrothermal cycle, taking into account the extremes of temperature and of relative humidity encountered in moderate and tropical climates, is considered. Special cycles are suggested for arctic and desert climates. The authors give an example of a cycle and a prototype of climatizer, using a triphare or xenon source capable of establishing such cycles, with the possibility of applying a mechanical stress under various conditions. The correlation between natural and artificial aging is discussed.
Infrared Spectra and Structure of Poly‐e‐methylcaprolactam and of e‐Methylcaprolactam–Caprolactam Copolymers
Authors: Schmidt P. , Schneider B. , Čefelín P.
Published: June 2010

It was found that poly‐e‐methylcaprolactam can exist both in the amorphous and in the ordered state. Amorphous poly‐e‐methylcaprolactam may be transformed to the ordered state by treatment with water. In the ordered state, poly‐e‐methylcaprolactam chains assume the B conformation. The conformational structure and state of order of various‐e‐methylcaprolactam‐caprolactam copolymers was determined.
Studium der Polymerisation von Bis(glycerinmonoallyläther)fumarat mittels Infrarot Spektroskopie
Authors: Vlček Jiří Klaban Jaroslav , Mleziva Josef
Published: June 2010

Bis(glycerin monoallyl ether)fumarate (I) was prepared by a reaction of fumaric acid with an excess of allyl glycidyl ether. This compound has proved to be a reactive monomer in a blend with the unsaturated polyester resins for the preparation of lacquers which after suitable initiation dry in air into a hard film. In this work the role of the double bonds in the polyfunctional monomer in the network and the nature of the relative reactivity of the allyl and fumarate bond with and without oxygen. The problem was studied by infrared spectroscopy on model compounds and the bis(glycerin monoallyl ether)fumarate. To trace the fumarate trans‐bond we used the 773 cm.−1 bond; for the allyl bond, that at 930 cm−1. As an internal standard for the quantitative valuation we chose the carboxyl zone. It was ascertained that the allyl and fumarate bonds polymerize with each other and that the copolymerization is influenced by the presence of oxygen.
Initiator—Cocatalyst Interaction in Trioxane Polymerization
Authors: Kučera Miloslav , Hladký Eduard , Majerová Karla
Published: June 2010

Polymerization of trioxane dissolved in an organic solvent is kinetically a very complex process. The polymerization proper is influenced by the initiator–cocatalyst interaction. The usual cocatalyst, practically always present in trioxane, is water. This compound, however, takes part in several reactions simultaneously; in the absence of any other cocatalyst its presence is necessary for initiation and propagation. It takes part also in chain transfer and is removed from the system by the transfer reaction. Loss of water is accompanied by changes of the overall rate of polymerization of trioxane melt. The actual concentration of initiator decreases in the course of polymerization. Another factor which can seriously complicate the polymerization is the change of the dielectric constant of the medium, if it differs from that of trioxane. The loss of water and of initiator has been analyzed, and relationships have been derived describing with sufficient accuracy certain cases of polymerization of trioxane in the presence of a solvent.
Low‐Temperature Relaxation of Some Polyamides
Authors: Bareš J. , Janáček J.
Published: June 2010

The low‐temperature relaxation process of polycaprolactam, methyl‐substituted poly‐caprolactams, and other linear polyamides was studied by dielectric methods in the temperature range from – 140°C. to +50°C., and in the frequency range from 100 cps to 10 Mc./sec. In some of these polymers the temperature dependence of the complex shear modulus of elasticity was also measured at a frequency of about 1 cps. The methyl substituent provokes an increase of relaxation times of dielectric dispersion in poly‐γ‐methylcaprolactam and a decrease of relaxation times in poly‐ϵ‐methylcaprolactam. This decrease is ascribed to the increase in steepness of the potential barrier owing to a close attachment of dipole to the methyl‐substituted group. Irrespective of its position, the methyl substituent has been found in all cases to cause an extension of the distribution of relaxation times of shear modulus towards lower temperatures, as compared with the dispersion of nonsubstituted polyamides. The dependence of the widths of the distribution of dielectric relaxation times upon the temperature and the degree of crystalline arrangement have been discussed. For the copolymer of caprolactam. 7‐aminoheptanoic acid, and aminoundecanoic acid, which possess the same concentration of polar groups per unit of chain length as poly(hexamethylene sebacamide), a narrower distribution of relaxation times has been found. On the basis of ideas concerning low‐temperature dispersion it is possible to explain also higher relaxation times of low‐temperature dispersion occasioned by low molecular weight substances by an increase of the mean friction factor.
Inhibited Thermooxidative Degradation of Polyesters. Oxidation of Poly(ethylene Adipate) and Poly(ethylene Sebacate)
Authors: Gömöry I. , Štímeľ J. , Reya R. , Gömöryová A.
Published: June 2010

The noninhibited and inhibited oxidation of poly(ethylene adipate) and poly(ethylene sebacate) polyesters was studied at temperatures of 130–200°C. Oxygen absorption curves, typical for autocatalytic processes, were obtained. Hydroperoxides formation was not confirmed even at lower temperatures. Induction periods and maximal rates of oxygen absorption were estimated. Activation energies calculated from temperature dependence of induction periods and of maximal rates were 19–22 kcal./mole. Addition of 0.5% of 2,2′‐methylene bis(4‐methyl‐6‐tert‐butylphenol), N,N′‐diphenyl‐p‐phenylene‐diamine, and tri‐octylphenyl phosphite extends induction period 5–50 times. Inhibitor concentration changes during the induction period led to the conclusion that after inhibitors' consumption the reaction is inhibited by the products of direct attack of oxygen on the inhibitor. This supposition was verified on using oxidized inhibitors and it was proved that these are more effective than the inhibitors of original structure.
Structure and Solution Properties of Radical‐Initiated Poly(vinyl Chloride)
Authors: Kolínsk M. , Kolínský M. , Ryska M. , Bohdanecký M. , Khatochvíl P. , Šolc K. , Lím D.
Published: June 2010

The dependence of the structure of poly(vinyl chloride) on precipitation conditions during polymerization was investigated. Properties of polymers prepared in 2,4,6‐trichloroheptane, 2,4‐dichloropentane, sec‐butyl chloride, and isohexane were compared. The character of the polymerization ranged from homogeneous to heterogeneous. The polymers were fractionated in the system tetrahydrofuran–water. Molecular weights of the fractions were determined by osmometry and light scattering in cyclohexanone and tetrahydrofuran. The ratio M̄w/M̄n of the fractions varied in the range 1.1–1.8. It was found that for all the polymers investigated the same relation between [η] and M̄w is valid. Samples prepared by heterogeneous polymerization to a low conversion do not therefore exhibit an appreciable amount of branching with long side chains. These results are compared with the behavior of high‐conversion polymers and of branched samples prepared by copolymerization of vinyl chloride with divinyl adipate.
Solubility and Diffusion Behavior of Benzene in a Vinyl Acetate‐Methyl Acrylate Copolymer
Authors: Garrett T. A. , Park G. S.
Published: June 2010

Equilibrium sorption and the kinetics of sorption of benzene have been obtained in a 46% vinyl acetate‐54% methyl acrylate copolymer at temperatures from 25 to 55°C. and at equilibrium concentrations up to 0.19 volume fraction of benzene (V). The ther‐modynamic diffusion coefficient (Dt) obtained from the sorption rates can be fitted by a relationship of the kind suggested by Wilkens and Long: In Dt = In Do + AV ‐ BV2 but the data are not accurate enough for the A/B ratio to give useful information about the system. By using suitable values for Ao and Bo the relationship Dt = RT/Ao exp { ‐Bo/fv} due to Fujita enables the temperature and concentration dependence of the free volume fv to be calculated. The resulting relationship fv = 0.025 + 0.00043[T ‐ (21 ‐ 280V)] suggests a glass transition of 21°C. for the copolymer. The Flory‐Huggins interaction parameter x is calculated from the equilibrium data and the figure obtained, 0.36, is much closer to the value for polyvinylacetate than to polymethylacrylate. This is also true of the Do values.
Structure and properties of rubber networks. Part I
Authors: Meissner B.
Published: June 2010

The relationship between the concentration VG of elastically effective network chains and structural parameters of the network (the concentration CG of chemical crosslinks in the gel and number‐average molecular weight Mn,G of primary macromolecules in the gel) has been studied on dicumyl peroxide vulcanizates of natural rubber, both undiluted and diluted with paraffin oil prior to crosslinking. On assuming the polymer distribution of molecular weights to be of the Schulz type, the relations between the two network parameter, the sol fraction and the degree of polydispersity of the initial polymer have been derived and used for the calculation of CG and Mn,G from sol fraction data. An equation relating VG to CG, Mn,G and to the concentration E of potential entanglements has been proposed and compared with experimental data. Very good agreement has been obtained in the whole range of variables both for undiluted and diluted natural rubber, the value of E being lower in the presence of the diluent. Published experimental data on isobutyleneisoprene rubber likewise have been shown to conform to the proposed equation. A structural interpretation consistent with this equation is attempted.
Formation and properties of preswollen networks. I
Authors: Bates R. F. , Howard G. J.
Published: June 2010

A copolymer of allyl alcohol and styrene has been crosslinked in solution by reaction with diacid chlorides. The reaction rate is first order in acid chloride but of complex order in hydroxyl. Measurements are reported of the extent of reaction at gelation and of gel time as a function of concentration and of the size of the crosslinker. The fraction of crosslinks formed intramolecularly is calculated: the value of this fraction depends strongly on dilution and, to a lesser extent, on the length of the crosslinker chain. The swelling and compressional modulus of gels prepared in solution (preswollen networks) depend on dilution and crosslinker size in the same general manner as does the fraction of intramolecular links.
Cationic polymerization of 2,5‐dimethyl‐l,5‐hexadiene
Authors: Marek M. , Roosová M. , Doskočilová D.
Published: June 2010

The polymerization of 2,5‐dimethyl‐l,5‐hexadiene, catalyzed with boron trifluoride and titanium tetrachloride, has been studied. The reaction was followed up in the temperature range of −78 to 20°C. in a solution of heptane, of dichloroethane, and without solvent. The polymers obtained were soluble in heptane, dichloroethane, and ether, showing only a low content of double bonds. The course of the polymerization depended on the type of catalyst and the polarity of the medium. On the basis both of the properties and the structure of the polymer it is possible to assume an intra‐intermolecular growth reaction which is cationically initiated.
The nonlinear response and rupture of lightly crosslinked elastomers
Authors: Halpin J. C.
Published: June 2010

Recently a molecular treatment of nonlinear rubberlike viscoelasticity was advanced which centers around the precept that the nonlinear response is due to the nonlinear character of the stress‐strain curve while the relaxation mechanism remains invariant to large stress or deformations. Excellent agreement was found for highly crosslinked systems, the result being in substantial agreement with classical kinetic theory. The experimental and theoretical work presented here extends this treatment to lighter cross‐linked systems where substantial disagreement is found between classical theory and experiment. Attributing this disagreement to a deficiency in the treatment of the mechanics of long‐range motions in imperfect network structures, it is possible to outline an integrated treatment of the long time creep in the plateau region, the “C2 effect,” the tensile strength maximum as a function of the crosslink density and the so‐called “unique” properties of salt cured carboxylic rubbers. Experimental evidence is presented which shows that lightly crosslinked SBR exhibits properties indistinguishable from the salt‐cured carboxylic vulcanizates.
A modified apparatus for the fractionation of polymers by precipitation chromatography
Authors: Poláček J. , Schulz L. , Kössler I.
Published: June 2010

A modified precipitation chromatography apparatus, designed to operate with periodie temperature changes of the entire column, permitted fractionation of larger amounts of polymer. To verify the efficiency, 5 g. of a poly(methyl methacrylate) specimen were fractionated.
Non‐newtonian viscosity of dilute polymer solutions
Authors: Subirana Juan A.
Published: June 2010

A model is developed to calculate the influence of the shear rate on the intrinsic viscosity of dilute solutions of nondraining polymer coils. The polymer molecule is substituted by an equivalent ellipsoid with internal flow currents such that the macromolecule yields to the liquid flow and follows it up to a certain extent. The dimensions of the ellipsoid are obtained by equating the hydrodynamic deforming forces to the statistical restoring forces of the polymer chain. The intrinsic viscosity of the solution can then be calculated as a function of the shear rate.
Kinetic study of aminolysis of poly(vinylene carbonate) and related model compounds
Authors: Nemirovsky V. D. , Skorokhodov S. S.
Published: June 2010

The kinetics of poly(vinylene carbonate) (PVC) and ethylene carbonate (EC) aminolysis with n‐butylamine (BA) in DMF solution was investigated. The EC aminolysis is catalyzed by final product and by BA itself but the reaction kinetics follows satisfactorily the equation –d[BA]/dr = k[BA][EC]; k2 increases with an increase in the [BA]0. The rate of the PVC aminolysis is considerably higher than that of EC aminolysis under the same conditions. Comparison of these data with those on the aminolysis kinetics for several model compounds and for EC in the presence of carbamates enables one to conclude that the catalysis occurs by the opened monomeric unit adjacent to the reacting one. The catalytic action is likely to be connected with the carbamate groups.
Copolymerization of fluoroketones with vinyl acetate
Authors: Litt M. , Bauer F. W.
Published: June 2010

We have studied the free‐radical copolymerization of vinyl acetate (VAc) with hexa‐fluoacetone (6FK) and symdichlorotetrafluoroacetone (4FK) through the carbonyl group. The carbon of the carbonyl group is attacked by the growing radical. A strong penultimate effect was found for both copolymerizations (fluoroketone does not homopolymerize). Reactivity ratios were as follows: VAc/6FK − r1 = 0.12 ± 0.01, r1′, = 4.1† 0.5; VAc/4FK ‐ r1, = 0.41 ± 0.02, r1′, = 5.6 ± 0.3. The mechanism of chain termination is also discussed. We conclude that the main transfer step is dismutation of the fluoroketyl radical to a trihalomethyl radical and a trihalomethyl ketone polymer end.