bluuebunny/crossref_metadata_2025_split huggingface dataset:
Relaxation phenomena in high polymers
Authors: Woodward A. E. , Bauer J. A. 
Published: June 2010

AbstractThe 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

AbstractA 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

AbstractThe 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

AbstractA 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

AbstractThe 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

AbstractAn 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

AbstractNuclear 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

AbstractThe 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

AbstractThe 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

AbstractDynamic 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

Abstractl‐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

AbstractMolecular 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

AbstractBulk 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

AbstractInfrared 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

AbstractCopolymers 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

AbstractAdiabatic 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

AbstractProduct 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

AbstractThe 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.