bluuebunny/crossref_metadata_2025 huggingface dataset:
The low‐melting crystalline modifications of isotactic polybutene‐1
Authors: Holden H. W.
Published: June 2010

The effect of annealing on the low‐melting crystalline modification (III) of isotactic polybutene‐1 has been studied by differential thermal analysis. The extrapolated equilibrium melting point of modification III is estimated to be 109.1°C. with 50% confidence limits at 108.0° and 110.6°C. In the temperature range where annealing effects are observed, conditions are suitable for the simultaneous formation, in the partially melted sample, of modification II and more highly ordered modification III.
Relaxation phenomena in high polymers
Authors: Woodward A. E. , Bauer J. A.
Published: June 2010

The principles of the nuclear magnetic resonance, NMR, and dynamic mechanical methods and their use for the investigation of segmental motion in high polymers are briefly discussed. Mechanical loss‐temperature data have been obtained from 4.2°K. at audiofrequencies for various addition type high polymers along with NMR line‐width or second moment and NMR spin‐lattice relaxation time, T1, data from 77°K. The examples include a linear polymer, polyethylene, PE, four polymers with mono‐substituted repeat units, polypropylene, poly(4 methyl pentene‐1), poly(ethylacrylate) and polystyrene (PS), and three polymers with disubstituted repeat units, poly(methyl methitcrylate), poly(ethyl methacrylate) and poly(alpha methyl styrene). For all but PE and PS NMR line narrowing processes and T1 minima, attributed to methyl group reorientations, are found at low temperatures. Molecular motion, usually occurring above room temperature as a consequence of the glass to rubber transformation, leads to the appearance of a mechanical loss maximum, further NMR line narrowing, and a T1 minimum. Mechanical loss maxima, possibly due in some cases to side‐chain (other than methyl) reorientations and in other cases to main chain oscillations are also evident.
Comparison of solution and gel permeation fractionation of a cis‐1,4‐polybutadicne
Authors: Harmon Dale J.
Published: June 2010

A sample of cis‐1,4‐polybutadiene was fractionated into 10 fractions by a coacervation method and the fractions evaluated by a combination of light scattering, osmometry, and viscosity. Calculation of the number‐ and weight‐average molecular weights from the fractionation data gave good agreement with measurements on the bulk polymer. Reconstitution of the polymer from the fractions also resulted in molecular weight values in agreement with those of the original polymer. Fractionation of the same polymer was carried out by using the Waters gel permeation chromatograph. Comparison of the data from the gel permeation fractionation with that of the coacervation fractionation, treated by the method of Beall, reveals marked differences. The gel permeation fractionation gives an overall wider distribution with lower number‐ and weight‐average molecular weights. The difference may be partially explained by the diffusion of low molecular weight material through the osmotic membranes resulting in high values of M̄n. Isopiestic measurements tend to support lower values of M̄n.
Morphological foundations of plastics processing
Authors: Maxwell Bryce
Published: June 2010

The fundamental thermal and mechanical experiences that a polymer undergoes in a processing operation have been identified and analyzed from the point of view of their effect on polymer morphology and properties. By means of controlling the pressure, temperature, and flow history of the polymer during fabrication processing, morphologies can be produced which result in desired properties. The utility of this approach is illustrated by an example involving an order of magnitude change in environmental stress cracking achieved by controlling internal structure through controlling pressure and temperature history.
Properties and structure of elastomers
Authors: Lal Joginder , Scott Kenneth W.
Published: June 2010

A study of the effect of structure on the dilatometric glass transformation temperatures, Tg, of poly(vinyl alkyl ethers) of reasonably high molecular weight showed that the Tg values of poly(vinyl n‐alkyl ethers) decrease with increasing length of the n‐alkyl group from methyl to n‐octyl. On lengthening the n‐alkyl group, 14% of the specific volume increase is free volume. Branching of the alkyl group of the polymer increased the Tg value. A comparison of poly (vinyl n‐alkyl ethers) and polymers of normal a‐olefins showed that the ether group and methylene group in side chains are equivalent in influencing the glass transformation temperatures. The side chain alkyl group in poly(vinyl alkyl ethers) was varied systematically and the influence of these variations on the dynamic mechanical properties of their vulcanizates was evaluated at 31, 60, and 98°C, The relative position of the curves, relating the dynamic resilience to the dynamic modulus of these polymers, was approximately in the order of their glass transformation temperatures. Dynamic mechanical property data on poly(vinyl n‐pentyl ether) and poly(vinyl 2‐ethylhexyl ether), which have the same Tg values, fall on a common curve characteristic of the test temperature. Apparently, the Tg is a major factor in correlating the dynamic mechanical behavior of these elastomers. The size and shape of the alkyl group appear to be reflected primarily in their effect on the Tg. A direct approach was made for testing an existing hypothesis on the requirement of labile crosslinks for attaining high tensile strength in rubber vulcanizates. This direct approach involved the modification of the labile polysulfidic crosslinks already in existence in natural rubber‐sulfur‐diphenylguanidine vulcanizates to relatively less labile disulfidic or nonlabile monosulfidic crosslinks by reaction with triphenylphosphine. It was demonstrated that highly labile polysulfidic crosslinks are not essential for achieving high tensile strength in natural rubber vulcanizates. Data for the samples which had lost significant amounts of polysulfidic crosslinks by reaction with triphenylphosphine fitted the tensile strength versus 300% modulus curve for the control samples.
Warts in selected species of pine
Authors: Jurbergs K. A.
Published: June 2010

The warts found on the lumen walls of pine tracheids survive the standard pulping processes and are therefore present in finished chemical pulp fibers. The present work was done to supply more fundamental information concerning the warts in pine wood. Sections and replicas for electron microscopy were prepared from the cambial zone of growing slash and loblolly pine trees. The warts appear on the lumen walls at the end of the cell differentiation phase. A multitude of heterogeneous materials along with the warts can be found at this stage on the lumen walls. The majority appear to be resin droplets which can be removed by hot alcohol extraction. The tracheids in the mature wood have numerous, non‐uniformly distributed particles on their lumen walls. Judging by the distribution patterns and the localities where they are usually found, the warts appear to be sedimentation products originating from the translocation stream of the decomposed protoplasts. Proteinaceous residues, whole cell organelles, microorganisms, and their spores are considered as possible constituents of the warty layer. The species of pine investigated can be rated in the following order according to the increasing number of warts contained: eastern white, sugar, slash, and loblolly pine. The extensive microscopy work revealed some interesting, unreported, morphological characteristics of pine wood.
Derivation of possible chain conformations for poly‐β‐1,4‐anhydroxylose
Authors: Settineri W. J. , Marchessault R. H.
Published: June 2010

An oriented fiber diagram of deacetylated O‐acetyl xylan from white birch has been obtained. The quality of the x‐ray pattern, while better than any reported to date, is still inferior to the various cellulose patterns. Only 14 intensity maxima are recorded and available for analysis. The repeat distance parallel to the chain direction has been directly calculated from the x‐ray data as 14.84 ± 0.3 A. Systematic meridional absences indicate a threefold screw axis along the chain. Using these data, and assuming x‐ray structure parameters for small molecules to apply to the monomer unit in the polymer, the basic repeat unit has been described mathematically. All possible relative settings of two monomer rings consistent with a threefold screw axis and a given repeat distance for a left‐ and right‐handed helix have been calculated and examined. This approach is equivalent to that used for cellulose where the C1OC4,′ angle is allowed to vary in order to satisfy the above conditions. Choice of probable conformations is made by simultaneously considering existing infrared dichroic data for oriented xylan films and generally accepted stereochemical concepts. The problem has been programmed for and run on an IBM 1620 data processing system. The choice of a unique conformation is not possible but evidence seems to favor the left‐handed conformation with a C1OC4 bond angle of about 116°, for which an intramolecular hydrogen bond (O5…︁O3) is possible. The H1…︁ H4′ distance for this conformation is 2.4 A., while the CH2 transition moment vector is strongly perpendicular (88° to the chain axis) as required by the infrared data. None of the right‐handed conformations allowed an (O5…︁O3′) intramolecular hydrogen bond and usually a serious overlap of van der Waals' radii for O2 and H4' atoms was found.
NMR studies of multiple relaxations in polymers
Authors: Slichter W. P.
Published: June 2010

Nuclear magnetic resonance (NMR) spectroscopy has become a valuable method of studying motions of chain segments and substituents in polymer molecules, since it views motion in away that, complements the information from other methods of measurement and since it extends the range of accessible frequencies to a region (∼108 cycles/sec.) that is beyond the usual range of dielectric and mechanical studies. In this report, a brief survey is given of the NMR relaxation processes and their significance to the understanding of thermal motions in solid polymers. The occurrence of multiple relaxation processes is discussed for a series of poly(n‐α‐olefins), poly(alkyl methacrylates), and some important elastomers, including natural rubber, polyisobutylene, and polybutadiene. Correlations are drawn with results in the literature on dynamic mechanical and dielectric relaxation in polymers.
Transition phenomena and solid‐state structure in glassy polymers
Authors: Andrews R. D.
Published: June 2010

The primary and secondary transitions observed in solid polymers have generally been interpreted in terms of the concept of “molecular motions.” A different interpretation is presented here in which these transitions are explained in terms of the thermal breakdown of different types of intermolecular secondary bonding in the solid state. It is assumed that the association‐dissociation equilibria involved are governed by normal thermodynamic considerations. The time‐temperature (or frequency‐temperature) dependence of such transitions can be associated with the “transport rate” (bond formation and breakdown rate) of the dynamic equilibrium involved. The glass transition behavior of polyacrylonitrile and poly(methyl methacrylate) are discussed in terms of the breakdown of dipole‐dipole bonding between chains, and it would appear that, the breakdown of hydrogen‐bonding and van der Waals bonding are involved in the transitions of nylon and polyethylene, respectively. From this point of view, a glass transition is regarded as having considerable similarity to a melting point, and this consequently provides a theoretical justification for the empirically observed correlation between the principal glass transition and the melting point for a wide variety of polymers.
The effect of molecular weight on the crystallization, melting, and morphology of long‐chain molecules
Authors: Mandelkern Leo
Published: June 2010

The properties of molecular weight fractions of linear polyethylene, encompassing the range 3 × 103 to 1.5 × 106, which were isothermally crystallised at low undercooling at. atmospheric pressure, were studied. Marked changes in various thermodynamic and mechanical properties are observed with molecular weight, which can be attributed to the finite sine of the crystallites in the chain direction and to the ratio of the crystallite size to the extended‐chain length. Electron microscopic examination of fracture surfaces indicates the formation of striated, lamella crystallites over the complete molecular weight range although the ratio of crystallite size to extended‐chain length varies from approximately unity at the lower molecular weights to extremely small values for the higher molecular weights. Concomitant with the changes in properties and sizes, the interfacial free energy of a mature crystallite increases significantly with molecular weight. Based upon these experimental results, a crystallization mechanism is developed which has as its basic tenents the relation between the critical size initiating nucleus and the extended‐chain length and the spatial requirements of chain units in random conformation in the interzonal regions. For molecular weights above which extended‐chain crystals are formed, the analysis and experiment indicate that the interfarnal region associated with the basal plane is of a nonregular structure, and that a significant number of chain units, which connect different crystallites, must exist, in a non‐ordered conformation. It is concluded that lamella‐type crystallites in bulk‐crystallized polymers are not to be associated with an interface comprised of regularly folded chains. The assumptions that either an initiating or growth nucleus is comprised of regularly folded chains or that such a structure is an equilibrium requirement, are not substantiated by experiment.
Rheological properties of polystyrene melts
Authors: Onogi Shigeharu , Kato Hideo , Ueki Shiro , Ibaragi Toshio
Published: June 2010

Dynamic viscosity η′, dynamic rigidity G′, and apparent viscosity ηα of fractions and blends of polystyrene having different molecular weight and distribution have been measured at high temperatures by means of a concentric cylinder‐type rheometer which enables us to measure not only dynamic but also steady‐flow properties. The values of η′ and G′ as functions of frequency for each sample at different temperatures (130–240°C.) can be superposed according to the usual time‐temperature superposition principle, giving master curves covering a wide range of frequency. The shift factors αT obtained from η′ and G′ for a given material are practically the same, and αT for materials having different molecular weight and distribution are also almost the same. The absolute value of complex viscosity as a function of angular frequency coincide very well with the apparent, viscosity as a function of rate of shear, indicating that the empirical law by Cox and Men fits the experimental results well. The dynamic viscosity curves for various samples unite in one curve above ω = 1000 sec.−1, and this united portion corresponds to the transition region. The effect of bimodal distribution of molecular weight, and the change of frequency dependence of viscosity‐molecular weight relation have been discussed, and emphasis has been placed on the significance of intramolecular motion or micro‐Brownian motion to the flow properties of polymer melts at higher rates of shear or frequencies.
Synthesis and Polymerization of cis, cis‐1‐Methylcyclooctadiene‐1,5
Authors: Valvassori A. , Sartori G. , Turba V. , Lachi M. P.
Published: June 2010

l‐Methyl‐cis, cis‐cyclooctadiene‐1,5 was obtained by mixed butadiene‐isoprene dimerization in the presence of a catalyst prepared by treating nickel acetylacetonate with lithium boron hydride in the presence of triphenyl phosphite. In analogy with cis, cis‐cyclooctadiene‐1,5, methyleyclooctadiene can be polymerized, in the presence of the Al(iC4H9)3 + TiCl4 eatalytic system (molar ratio of Al to Ti = 0.5), to an essentially saturated product. Also in this case a transannular polymerization of the following type occurs: magnified image In the terpolymerization with ethylene and propylene, on the contrary, methyl cyclo‐octadiene reacts, in the presence of catalysts prepared from vanadium and alkyl aluminum compounds, by opening of the nonsubstituted double bond. The IR spectra of the monomer and of the polymers are here described.
Effect of Polymer Structure on Crosslinking Efficiency and Molecular Chain Scission/Crosslinking Ratio in a Dicumyl Peroxide‐Sulfur Vulcanizing System
Authors: Lal Joginder , McGrath James E.
Published: June 2010

Molecular chain scission (p), crosslinking (q), and crosslinking efficiency (Z) were determined by sol‐gel technique for several poly(vinyl alkyl ethers) in a dicumyl peroxidesulfur vulcanization system. For isomeric poly(vinyl butyl ethers), p, q, and Z decreased as follows: n‐butyl > isobutyl > sec‐butyl. However, the ratio), p/q, was essentially unchanged. Lengthening the n‐alkyl group from ethyl to n‐butyl did not significantly change p, q, or Z values. Increasing the length from n‐butyl to n‐octyl almost doubled the Z value and halved the p value. The data for poly(vinyl n‐butyl ether) and poly(1‐heptene) indicate that replacement of the ether group by the methylene group did not appreciably affect the Z value; however, p was significantly increased. Poly(propylene oxide), in which the ether linkage is in the backbone of the polymer chain, had the highest p/q and the lowest Z values among these polymers. An analysis of the data shows that both p and q values are quite low. The infrared spectra of the low‐molecular‐weight, soluble portion of poly(propylene oxide) obtained by curing showed the presence of carbonyl, carbon‐carbon double bond and hydroxyl groups.
A Novel Colorless Transparent PAN Produced by a Bulk Polymerization Process with Sulfinic Acid‐Hydrogen Peroxide Initiator
Authors: Shavit Nehemia , Konigsbuch Mordechai
Published: June 2010

Bulk polymerizations of aerylonitrile (AN) yielding transparent polyacrylonitrile (PAN) were reported in two accompanying papers.1,2 The plastic products obtained were, however, colored. The previously known PAN plastic, products by cast molding of powder polymer, was also colored due to pyrolysis. A novel colorless transparent PAN plastic was discovered in a bulk polymerization process, carried out under specified conditions, employing a p‐toluenesulfinic acid (TSA)‐H2O2 initiation system. The process involves a spontaneous transformation, at high degrees of conversion. from a heterogeneous polymerizing mixture to a homogeneous transparent PAN. The effect on the transformation of temperature, volume of the system, concentrations of the initiators, added p‐toluenesulfonic acid (TSOA), H2SO4, and plasticizer, as well as the role of air supply and monomer added during the process are reported. It was found that, for a given system with a defined set of parameters, there is an intermediate range of rates of polymerization which is optimal for the transformation process. The coloration of PAN in polymerization processes employing various initiators is discussed and possible factors preventing coloration in the TSA‐H2O2 system are suggested.
Interpretation of Infrared Spectra of Nylons in the Straight Chain Conformation
Authors: Jakeš J.
Published: June 2010

Infrared spectra of nylons in the straight‐chain conformation were interpreted on the basis of frequency–phase curves of the polymethylene chain and of the theory of interaction of a periodic chain with endgroups. In CH2 rocking‐twisting and twisting‐rocking frequencies, no appreciable interaction of neighboring nylon monomer units takes place; in CH2 wagging frequencies this interaction is fairly strong. The interpretation was confirmed by a normal coordinate calculation of out‐of‐plane frequencies.
Chlorine on Tertiary Carbon in Poly(vinyl Chloride)
Authors: Caraculacu A. , Wichterle O. , Schneider B.
Published: June 2010

Copolymers of vinyl chloride with isopropenyl chloride were used to prove the possibility of determining the contents of chlorine bound to the tertiary carbon atom (ClT) both by infrared spectra in the region of C—Cl stretching vibrations, and by a specific phenolytic reaction. Samples of PVC were prepared bymethods which, according to literature, should lead to highly branched polymers. We were not able to find any ClT in these samples by the above methods, even though their sensitivity was several times higher than the expected degree of branching.
Adiabatic Compressibilities of Polymer Solutions. II. Dilute Solutions of Cellulose Acetates
Authors: More W. R.
Published: June 2010

Adiabatic conipressibilitias of solutions of a secondary ccllrilose acetate and cellulose triacetate in representative solverits are obtained from measurements of sound velocity and density at 25°C. By assuming solvent molecules concerned in solvation to be incompressible etfectively, degrees of solvation are estimated from the adiabatic compressibilities of the solntioiis arid solvents. Where comparison is possible degrees of solvation for the secondary acetate are in general agreement with the results of some other methods of estimation. Those for the triacetate agree with degrees of solvation estimated by use of other methods. Degrees of solvation for the secondary acetate generally show a marked decrease with iiicreasing molar volume of solvent. The degree of solvation obtained with acetonitrile is an exception and it is suggested that the mode of interaction of acetonitrile with the polymer differs from that of the other solvents. The degrees of solvation of the secondary acetate do not generally siiggest a stoichiometric association of solveiit molecules and functional groups of the polymer and with solvents of smaller molecalar size the degrees of solvation exceed one solvent molecule per functional group of polymer. In the case of the triacetate one molecule of chloroform or methylene chloride seems to be associated with each acetyl group.
Thermal Degradation of Poly(α‐Chloroacrylonitrile)
Authors: Grassie X. , Grant E. M.
Published: June 2010

Product analysis and infrared spectral evidence show that the thermal degradation of poly(α‐chloroacrylonitrile), like that of poly(vinyl chloride), consists of the libration of hydrogen chloride from groups of adjacent units. It is, however, at least 80° less stable than poly (vinyl chloride), Kinetic and thermal data are in accordance with the radical mechanism for the degradation of poly(vinyl chloride) proposed by Stromberg, Straus, and Achhammer. Although the instability of this material renders it useless for normal commercial applications, it may be a useful model for the investigation of some of the problems associated with the use of poly(vinyl chloride).
Die kationische polymerisation von phenylglyzidylather mit bortrifluorid
Authors: Sjcar E. , Lunak S.
Published: June 2010

The kinetics of pheriyl glycidyl ether polymerization in dichloroethane using boron trifliioride as a catalyst was studied. The polymerization is very fast in the absence of water and both the conversion obtained and the reaction rate depend only on boron tri‐ fluoride concentration. The initial rate of polymerization decreases and the yield in‐ creases with increasing water concentration. The rate of polymerization depends on boron trifluoride and monomer concentration.
Phase relations in the ternary system atactic polystyrene‐atactic polypropylene‐toluene
Authors: Berek D. , Lath D. , Ďurďovič V.
Published: June 2010

Parameters of the phase equilibrium of the system atactic polypropylene‐atactic polystyrene‐toluene (volume of phases, molecular weight, and relative and total concentration of polymers in both phases) as a function of concentration of polymers and temperature have been studied. Considerable changes of the parameters were found in the vicinity of the point at which formation of one‐phase systems occurs. Limiting miscible concentrations and temperatures in which the system becomes homogeneous for various molecular weights of both polymers have been determined. On the basis of the Flory‐Huggins theory the polymer‐polymer interaction parameter α23 has been calculated from the parameters of the phase equilibria as well as from the critical parameters of the system. The value of the interaction parameter depends on the temperature and the concentrations of polymers in the system. From our results we can obtain a very approximate value of the interaction parameter [α23] for a homogeneous mixture of polypropylene‐polystyrene in the absence of solvent. This value could be a measure of the compatibility of a pair of polymers.
Polymerisation von oktamethylzyklotetrasiloxan mit thermolabilen katalysatoren
Authors: Laita Z. , Hložek P. , Buček B. , Jelinek M.
Published: June 2010

Low molecular weight silanolates of tetramethylammonium hydroxide and tetrabutylphosphonium hydroxide have been prepared. The kinetics of octamethylcyclo‐tetrasiloxane polymerization induced by either of these bases was studied and the activation energies were determined. It was found that the activities of these catalysts were much greater than that of the potassium silanolate (about 50–150 times). Nevertheless the activation energies did not differ from those found for polymerizations catalyzed by alkali metal silanolates (19.5 kcal./mole). The polymerization rate of the octamethylcy‐clotetrasiloxane‐tetramethylammonium silanolate system is thus comparable to the polymerization rate of the potassium silanolate‐tetradecamethylcycloheptasiloxane system, which is the most reactive of the low molecular cyclic poly (dimethyl siloxanes). Also the decomposition of the silanolates of the onium compounds was studied. It was found that tetramethylammonium silanolate is more stable than the phosphonium compound, the half‐time of decomposition at 100°C. of the former being more than five times that of the latter. Activation energies of the decomposition were also different: 42 kcal./mole for the ammonium compound and 28.5 kcal./mole for the phosphonium compound. This corresponds to a different proposed mechanism of the reaction, as described by Ingold. The most striking feature is that the decomposition follows first‐order kinetics. By analogy with experiments performed by Ingold and his co‐workers, we expected the second‐order kinetics in this medium of low dielectric constant. The first‐order kinetics was found even if excess potassium silanolate was added at 120°C. The rate of decomposition remained unaffected, the half‐time of decomposition being 27 min. This agrees quite well with the value of 24 min. found at the same temperature in the absence of potassium silanolate.
Interpolymer transformations in polymer mixtures initiated by peroxides: The system polyethylene‐polyisobutylene‐dicumyl peroxide
Authors: Šimǔnková D. , Rado R. , Letz J.
Published: June 2010

The decomposition of dicumyl peroxide in polyethylene‐polyisobutylene mixtures initiates, along with the crosslinking of polyethylene and the degradation of polyiso‐butylene, the formation of an interpolymer as a consequence of the interpolymer combination of macroradicals. Analysis of the kinetics of these transformation processes involves obtaining data for the transformation of the individual polymers in toluene solution, verification of the derived quantitative relations for the model system polyethylene‐low molecular weight only polyisobutylene, and finally application of these relations to a mixture of high molecular weight polymers. On the basis of the obtained results, the physical import of the individual kinetic parameters is interpreted, and the values are compared for the two types of mixtures.
Untersuchungen über die verfärbung von polyacrylnitril. IV. Polymeranaloge umsetzungen an durch erhitzung verfärbtem polyacrylnitril
Authors: Fester W.
Published: June 2010

Ultraviolet and infrared spectroscopy indicated that the primary discoloration of polyacrylonitrile during heating was due to the formation of conjugated carbon double bonds. This conclusion was supported by hydrolysis experiments. In the polyacrylic acid obtained from polyacrylonitrile after heat treatment the C°C stretching band could not be observed in the infrared spectrum because of the wide carbonyl band; therefore poly(allyl alcohol) was prepared from the acrylic acid via poly(methyl acrylate). In the infrared spectrum of this deeply colored polymer a carbon‐carbon double bond frequency was found. Oxidative cleavage of the poly(acrylic acid) obtained from heat‐treated and discolored poly(acrylic acid) by KMnO4 yielded an amount of CO2 increasing with increasing discoloration of the polymer. This supports the presence of conjugated carbon double bonds in the poly(acrylic acid). On the basis of the reactions carried out on the polymers in this work the assumption seems justified that the primary discoloration of polyacrylonitrile is due to formation of a system of conjugated double bonds in the carbon chain rather than to hydrogenated naphthyridine rings.
Polymerization of isobutylene catalyzed by aluminum tribromide
Authors: Chmelíř M. , Marek M. , Wichterle O.
Published: June 2010

Solution polymerization of isobutylene in heptane, catalyzed by aluminum tribromide, takes place at high rate even at low catalyst and monomer concentrations, without addition of water as cocatalyst. The overall rate of polymerization is of first order with respect to the monomer and of second order to the catalyst. The activation energy of the polymerization is practically zero within the temperature range investigated (‐60 to +20°C.). A value of −3.9 kcal. has been found for the “activation energy of degree of polymerization”; the extrapolated ceiling temperature is +131°C. Additions of water substantially decrease the rate of polymerization. The concentration of residual moisture in the polymerization apparatus was so low that no detectable isobutylene polymerization catalyzed by boron trifluoride or titanium tetrachloride was observed. Additions of water were necessary for polymerization in the presence of these two catalysts.
Photopolymerization of vinyl monomers initiated by pentaaminecobalt (III) complexes
Authors: Delzenne G. A.
Published: June 2010

The polymerization of acrylamide in aqueous solution can be initiated by free radicals formed during the irradiation of pentaaminecobalt(III) complexes with light of wavelengths corresponding to the charge transfer band of the initiators. The kinetics were studied for two different cobalt(III) complexes: the chloropurpureosalt [CoCl(NH3)5]‐Cl2 and the roseosalt [Co(H2O)(NH3)5](NO3)3. In both cases the dependence of the rate of polymerization on the initiator concentration indicates a termination reaction due to an oxidation of the growing chains by the metal complexes. The effect of the chloro complex on the photopolymerization rate of acrylamide initiated by riboflavine showed the same termination activity. A termination constant, kt = 1.5 × 103 liter/mole‐sec., could be calculated. The first‐order dependence of the rate of polymerization on the monomer concentration for the initiation by the chloro complex agrees with an internal charge transfer during the photochemical activation of the initiator. The second‐order dependence of the rate of polymerization on the monomer concentration for the initiation by the aquo complex can be attributed to a substitution of the coordinative bonded water by a monomer molecule. An electron transfer within the intermediate complex agrees with the observed initiation.
Regulation of molecular weights of polymers in emulsion
Authors: Dvořák E. , Hrabák F.
Published: June 2010

Dependence of the apparent transfer constant of diisopropyl xanthogen disulfide on the rate of emulsion copolymerization of butadiene with styrene was followed up in various emulsifiers. On the basis of data obtained the relation was derived between both the relative and apparent transfer constant and the rate of polymerization.
Changes of blood haptoglobin in acid media
Authors: Pavlíček Z. , Kalous V.
Published: June 2010

The behavior of blood haptoglobin, isolated from Cohn's fraction IV, has been studied in acid solutions. Titration curves, differential absorption spectra, and measurements of optical rotation indicated that in the region below pH 5.0 the haptoglobin molecule undergoes important structural changes. Haptoglobin with altered conformation is unable to bind hemoglobin, and for this reason it cannot be determined on the basis of its increased peroxidase activity.
Polymerization of acrylonitrile initiated by organomagnesium compounds
Authors: Erussalimskii B. L. , Kulevskaya I. V. , Masurek V. V.
Published: June 2010

The polymerization of AN at −75°C. in various systems with the participation of the organomagnesium compounds was studied. For the system AN–BuMgCI. Bu2O–toluene kinetic data are given and a reaction scheme including the deactivation of the catalyst is proposed. The initial period of the polymerization is characterized by first order with respect to the catalyst and second order with respect to the monomer. On the basis of: (a) the proportionality of the molecular weight of PAN to the conversion, (b) the independence of the polymer molecular weight on the catalyst concentration, and (c) narrow molecular weight distribution of the polymer obtained at relatively high conversion. the absence of the termination reactions of the growing chains is suggested. The maximum molecular weight of the polymer attained in the systems AN–RMgX–toluene was 435.000. The efficiency of the process in the hydrocarbon media increases sharply in the presence of catalytic quantities of dimethylformamide (DMF) and dimethyl sulfoxide. As it is shown for the system Bu3Mg2I–DMF–toluene, the interaction of the catalyst components at −75°C. leads only to the formation of a complex of the type RMgX DMF. The addition of RMgX to the carbonyl group of DMF can be observed only at a higher temperature.
Solid‐state radiation polymerization of triselenane to polyselenomethylene
Authors: Carazzolo Gianalvise , Mammi Mario
Published: June 2010

Triselenane, the cyclic trimer of selenoformaldehyde (CH2Se)3, subjected to gamma irradiation, has been partially converted into crystalline polyselenomethylene (CH2Se)n, The solid‐state polymerization has been proved to take place in two directions, parallel to the two [hhO] and [hhO] diagonal axes in the ab plane of the trimer orthorhombic unit cell. The polymer crystal lattice is orthorhombic with a = 5.37 A. b = 9.03 A., c = 4.27 A., and space group P212121; the polymer chains are helicoidal with their axes parallel to c.
Elution fractionation of poly(vinyl chloride)
Authors: Garbuglio C. , Mula A. , Chinellato L.
Published: June 2010

Two samples of PVC of different stereoregularity were elation fractionated by using the eyclohexanone‐ethylene glycol system under various experimental conditions. Inversions of viscosity in the less soluble fractions were shown in some cases and were found to be related to crystallinity effects. They were eliminated by operating at high temperature and by precipitating the polymer on the support by rapid cooling of the solution. Some data are reported on the M.W.D. of the fractions which seem to indicate a satisfactory efficiency of the fractionation method used.
Optical investigation into the crystallization of polyolefines from dilute solutions
Authors: Scholte Th. G.
Published: June 2010

With the aid of a modified Sofica light‐scattering apparatus an investigation was carried out of the crystallization of polyolefines from dilute solutions in several solvents. The intensity of the light scattered at various angles was determined as a function of time in the initial period of crystallization. Both linear polyethylene and polypropylene in p‐xylene and in 1‐chloronaphthalene showed the formation of disk‐shaped crystals, which, after their formation, rapidly grew.
Luminescence spectra of impure molecules and polymer matrix structure
Authors: Egorov G. P. , Moisya E. G.
Published: June 2010

Luminescence spectra of anthracene solutions in polyethylene matrices were studied for various solute concentrations at 77°K. The impurity spectrum appeared to be a summation of at least two spectra corresponding to different types of interstitial dispersion of anthracene in crystalline and amorpous regions of polyethylene. The sensitivity of impurity electronic spectra to structural effectson the polymer matrix (variation in crystallinity, quenching) was found to be high. This leads to the assumption that impurity electronic spectra may serve as an “indicator” of structural transformations in the polymer (this possibility is illustrated with the cold‐drawing of polyethylene). Also noted were unusually large energy spacings for electron transitions which occur with different interstitial arrangements of impurity in polyethylene. These result from specific intermolecular interactions within the crystalline and amorphous regions, and thus characterize the morphology of the polymer.
A study of structural changes taking place upon orientation and in the process of annealing oriented polymers
Authors: Zubov Yu. A. , Selikhova V. I. , Tsvankin D. Ya. , Markova G. S. , Kargin V. A.
Published: June 2010

The reversible character of the deformation of polyethylene films containing well‐defined spherulitic structures was shown by optical microscopy. The sizes of crystalline and defect (amorphous) regions were derived from theoretical calculations based on the data of small‐angle x‐ray diffraction. The specimens were obtained by annealing them in the stretched state. The dependence of the long period on the annealing temperature for oriented fibers of polyethylene, polycaproamide, and polypropylene was found. The possibility of irreversible and reversible structural changes was shown by means of a small‐angle x‐ray diffraction method.
Vibrational and NMR spectra and conformational analysis of stereoisomers of 2,4‐pentanediol, 2,4,6‐heptanetriol, and the corresponding acetates
Authors: Doskočilová D. , Štokr J. , Votavová E. , Schneider B. , Lím D.
Published: June 2010

NMR and infrared spectra of pure stereoisomers of 2,4‐pentanediol, 2,4‐pentanedioldiacetate, 2,4,6‐heptanetriol, and 2,4,6‐heptanetrioltriacetate were measured in different solvents at several temperatures. The structure of rotational isomers was determined by analysis of the methylene proton band in NMR spectra and by analysis of vibrational spectra. From temperature changes of NMR and infrared spectra, conformational equilibria of various stereoisomers were determined. The consequences of the present findings for the interpretation of polymer spectra are discussed.
The kinetics and mechanism of thermal and thermal‐oxidative degradation of formaldehyde polymers
Authors: Dudina L. A. , Karmilova L. V. , Tryapitsyna E. N. , Enikolopyan N. S.
Published: June 2010

Thermal degradation processes are of great importance in the case of polyoxymethylene. Establishment of the mechanism of oxidative decomposition is particularly important, because it proceeds under conditions when depolymerization is predominant over oxidation. The basic kinetic regularities of thermal and thermal‐oxidative degradation of polyoxymethylenes have been determined, and differences have been observed; that depend on the chemical nature of endgroups. Thermal degradation proceeds as depolymerization with generation of active centers at the chain end for POM hydrate, and following the “random law” for end‐capped POM and copolymers. The “kinetic” chain is shorter than the “substance” one. Formaldehyde participates in chain transfer of POM degradation. A method has been proposed for determining the true activation energy of reactions that are more complicated due to heat transfer. The true E of POM for different end groups has been determined. The thermooxidative decomposition proceeds as depolymerization initiated by oxygen and follows the “random law.” Oxygen has an inhibiting effect by reacting with active centers of POM. The degradation rates and accumulation of formic acid depend on the nature of end groups, and HCOOH acts as an accelerator. The most probable sources of HCOOH were proposed, and the active centers of POM degradation are shown to be of a dual nature. The mechanism of degradation and some principles of stabilization are proposed.
Untersuchungen Über die Lineare Volumennachwirkung bei Amorphen Hochpolymeren
Authors: Goldbach G. , Rehage G.
Published: June 2010

Measurements of isothermal‐isobaric volume retardation occurring in atactic polystyrene after temperature and pressure jumps applied to the material are reported. The volume post‐effect could be measured at very small deviations from internal equilibrium and therefore linear retardation behavior was obtained. In this case, different kinetic theories give an exponential time dependence of volume deviation from the equilibrium value due to the presence of a single reatrdation time. This prediction was not corroborated by our experiments. It was found that the isothermal‐isobaric volume post‐effect could not be described, at least with styrene, by a single retardation time but that it was necessary to assume a retardation time distribution.
Grafting some polymers on a glass surface treated with titanium tetrachloride
Authors: Lipatova T. E. , Skorynina I. S.
Published: June 2010

It is shown that when polymerization of styrene, dimethacrylate(bistriethyleneglycol)‐phthalate and epoxy resin takes place in the presence of the glass fiber treated with TiCl4 or SnCl4, the grafting of polymers onto the glass surface proceeds. The amount of grafted polymer depends on the reaction temperature and conditions of treatment of the fiber. By means of polarography it was established that TiCl4 is firmly bonded with glass surface and, as a consequence, noticeable reinforcement of the fiber takes place. It is shown that due to inhomogeneity of the glass surface, grafting is realized in some separate places and grafted polymer is there in the form of little gammas of a size that changes from 2 to 14 μ. Some investigation of the peculiarities of grafting were also fulfilled and data on tensile strength of glass fiber before and after grafting some polymers in different conditions of treatment onto it were obtained. Grafting of styrene was also realized onto the surface of PVA film treated with TiCl4, as PVA can be considered a model of a glass fiber due to the existence of the surface OH groups of it. All these data enable us to conclude that OH groups of the glass forming some complexes with catalyst molecules are centers of grafting.
Some peculiarities of cationic polymerization of trioxane
Authors: Enikolopyan N. S. , Irzhak V. J. , Kravchuk I. P. , Plechova O. A. , Rakova G. V. , Romanov L. M. , Savushkina G. P.
Published: June 2010

The polymerization of trioxane in various solvents and in the presence of different catalysts has been investigated. Effect of the catalyst on the induction period was studied and the kinetic criterium for establishing the nature of the induction period was suggested. The maximal rate of polymerization is first order with respect to the catalyst concentration and of different high orders with respect to the monomer concentration, depending on the solvent. The polymer molecular weight is proportional to the extent of conversion, the slope being dependent on temperature. The explanation of this phenomenon involves reactions of chain transfer with scission occurring in these systems.
Superconductivity of organic polymers
Authors: Little William A.
Published: June 2010

A recent suggestion that superconductivity might be able to occur in certain types of organic macromolecules at temperatures near room temperature will be discussed. A crude description of the microscopic theory of superconductivity will be given first and from this it will be argued why superconductivity should be able to occur in certain highly specific types of organic macromolecules. Why the transition temperature for the onset of superconductivity should be high compared to that of metallic superconductors will be discussed together with recent developments in the field.
Anisotropy of electrical conductivity in doubly oriented nylon 66
Authors: Seanor D. A.
Published: June 2010

The electrical conductivity of doubly oriented nylon 66 has been studied as a function of direction over the temperature range 23–150°C. Measurements were made (a) along the chain axes, (b) along the hydrogen‐bonded planes perpendicular to the chain axes, and (c) perpendicular to the hydrogen‐bonded planes. A complicated dependence of conductivity on pretreatment was found. In general the conductivity over the whole temperature range was anisotropic, being least along the chain axes and, after a number of thermal cycles, greatest along the hydrogen‐bonded planes perpendicular to the chain axes. Below 120°C. the activation energy of conductivity was also anisotropic. At temperatures higher than 120°C. the temperature dependence is isotropic. The anisotropy of the activation energy and conductivity are explained in terms of activated mobility and structural parameters. Water vapor had a pronounced effect on the conductivity. It lowered the activation energy of conductivity while increasing the overall conductivity in an anisotropic manner. The conductivity along the chain axes was again less than that parallel and perpendicular to the hydrogen‐bonded planes. The activation energy of conductivity along the chain axes was equal to that parallel to the hydrogen‐bonded planes. The increase in conductivity caused by the adsorption of water was greatest along the chain axes. Four factors may contribute to the observed effects: (a) increased dielectric constant, (b) increased carrier concentration, (c) increased charge carrier path length, and (d) plasticization.
Conductivity of iodine
Authors: Ham Joe S.
Published: June 2010

An anisotropy of the electrical conductivity is observed in single crystals of iodine both by direct electrical measurement (a.c. and d.c.) and by thermally generated noise. These observations are inconsistent with the much smaller anisotropy found by Simhony and co‐workers in the drift mobility unless one invokes a complex band structure or assumes that the light alters the properties of the crystal during the drift mobility measurements.
Crystallinity from thermal measurements
Authors: Dole Malcolm
Published: June 2010

The problems involved in the determination of the fraction of crystallinity by thermal measurements are discussed. It is shown that in certain cases specific heat measurements themselves can be used to estimate the fraction of crystallinity. In the case of specific heat data on single crystals of polyethylene obtained by Karasz and Hamblin the specific heats are a linear function of the reciprocal fold length and can be extrapolated to infinite fold length to obtain the specific heat of 100% crystalline polyethylene. This extrapolated value is compared with other estimates and is used to calculate the fraction of crystallinity of polyethylene of different forms. Within the experimental uncertainties it would appear that estimates of the crystallinity from calorimetric, x‐ray, dilatometric, and infrared measurements are all in substantial agreement.
Polyimide fibers
Authors: Irwin R. S. , Sweeny W.
Published: June 2010

The excellent high temperature properties of aromatic polyimides, well known in films and enamels, have also been demonstrated in fibers. Current investigations show that experimental aromatic polyimide fibers have a very high level of thermal and dimensional stability and property retention at high temperatures, as well as a good, all‐round level of other fiber properties.