bluuebunny/crossref_metadata_2025_split huggingface dataset:
CH2 rocking vibrations of polyethylene glycols
Authors: Kuroda Yoko , Kubo Masaji 
Published: April 2003

AbstractMeasurements were made of the infrared absorptions of ethylene glycol and polyethylene glycols (from a dimer to a heptamer) in liquid state. In the case of polyethylene glycols, three distinct peaks appear in the wave number range of CH2 rocking modes. This affords a conclusive evidence in support of the existence of the trans form as well as the gauche form of the O(CH2)2O portion of linear chains. This confirms the result of dipole moment measurements that both gauche and trans forms are realized in the configurations of the lower members of polyethylene glycols in solution. Although it is reported that high molecular polyethylene glycol in crystalline state assumes a highly crumpled helical structure resulting from the gauche minima, the molecular structure of low molecular polyethylene glycols is not restricted to the same helical configuration. These chain molecules take a more or less irregular form resulting from the trans and gauche minima of the internal rotation about single bonds. Ethylene glycol shows only two absorption peaks in the wave number range of CH2 rocking modes. A plausible explanation is presented based on the formation of intramolecular hydrogen bonds.
Controlled boron trifluoride catalysis of epoxy polymerizations
Authors: Wagner Herman B. 
Published: April 2003

AbstractA new technique which permits of the use of boron‐trifluoride for catalysis of epoxy polymerizations is described. The destructive exotherm that ordinarily accompanies contact of this substance with epoxy compounds is avoided by gradual release of the catalyst. This controlled release is accomplished through use of the catalyst in the form of the liquid boron trifluoride‐ethyl ether complex absorbed on a particulate carrier, the component particles being coated with a paraffin barrier layer. Employing this catalyst system a smooth but rapid reaction is obtained starting with all reactants initially at room temperature and without application of external heat. Polymerization is essentially complete within several minutes following addition of the catalyst system.
Molecular distributions in polycondensations involving unlike reactants. I. Gelation
Authors: Case Leslie C. 
Published: April 2003

AbstractA general criterion for gelation in polycondensations having like groups of unequal reactivity has been formulated. In its simplest form, the criterion is that, for gelation, the expectation that a given structure will be propagated is unity, or greater. Several specific cases are treated, and literal expressions relating the gelation point to the reaction probabilities are derived. Included are treatments of systems involving anhydrides and mixtures of acids and glycols. The manner in which kinetic calculations may be used to determine reaction probabilities is summarized. It is found that the inclusion of unsymmetrical reactants significantly increases the degree of polymerization necessary for gelation. However, when anhydrides are used, depending on the relative reaction rates of the anhydride and the acid formed when the anhydride reacts, the degree of reaction necessary for gelation may be either greater or less than that for a similar system using only symmetrical reactants.
An equation for calculating the number of chain scissions in the photochemical degradation of solid polymers
Authors: Flynn Joseph H. 
Published: April 2003

AbstractAn equation is developed for calculating the fractures/chain link from the change in weight‐average molecular weight for the case of the photochemical degradation of a polymer with an initial random molecular weight distribution. From calculations made on the degradation of cellulose with 2537 A. light, it appears that the formation of aldehyde groups and the evolution of hydrogen are in part due to reactions not involving chain scission.
Crosslink density in polybutadiene
Authors: Howland L. H. , Nisonoff A. , Dannals L. E. , Chambers V. S. 
Published: April 2003

AbstractThe crosslink density in polybutadiene has been determined by measurement of the polymer molecular weight by osmometry and the primary chain molecular weight by modifier analysis involving radioactive materials. Since the number of polymer molecules is equal to the number of primary chains less the number of crosslinkages, the experimental measurements may be used to calculated the crosslink density. This method can be used to determine crosslink density at a combination of conversions, modifier loadings, and polymerization temperatures which could not be done by other methods. Branching and cyclic structure forming crosslinks are not measured by this method, the principal assumption of which is that one and only one modifier fragment is attached to each primary chain. Initiation and termination processes tend to reduce the validity of this assumption, but these have been minimized by reduction of the amounts of initiator and found insignificant by comparison of different systems. Modifiers which react with polymer in nonterminal positions also reduce the validity so that primary dodecyl mercaptan was not satisfactory as a modifier in this work, while tertiary alkyl mercaptans were. Also, diisopropyl xanthogen disulfide was not satisfactory because of secondary reactions. The crosslink density of polybutadiene prepared in emulsion decreases with decreasing polymerization temperature. At a given molecular weight, the crosslink density does not appear to be a function of conversion within the range studied. At a given polymerization temperature, increasing polymer number average molecular weight was accompanied by increasing crosslink density although the rate of such increase was smaller at subfreezing polymerization temperatures. These results agree with kinetic theory of crosslinking in emulsion polymerization, but actual values are higher than those obtained in comparable systems by the gel point method.
X‐Ray diffraction pattern of a vinylidene cyanide/vinyl acetate copolymer
Authors: Yanko John A. , Hawthorne Anthony , Born John W. 
Published: April 2003

AbstractA film, prepared from the copolymer of vinylidene cyanide/vinyl acetate, was stretched at 145°C. in a silicone oil bath using a draw ratio of one to three. The x‐ray diffraction data indicated that some orientation had occurred during the stretching process. In the stretched film the copolymer chains are separated by a distance of 5.86 A. This lateral chain spacing lies between those values reported for Orlon and polyvinyl acetate. Along the fiber axis of the vinylidene cyanide/vinyl acetate copolymer film, a high degree of disorder exists. As the temperature of stretching decreased from 165 to 145°C., the degree of orientation increased slightly. Amorphous patterns were observed for the films which were stretched in air immediately after being removed from oil baths at 187 and 220°C.
Chromatographic adsorption of polystyrene
Authors: Yeh Si Jung , Frisch H. L. 
Published: April 2003

AbstractThe fractionation of polystyrene by adsorption column chromatography has been investigated at room temperature. The adsorbent used was activated carbon suspended on Celite. The experiments were carried out on mixtures of characterized polystyrene fractions using MEK (a poor solvent), toluene (a better solvent), and tetralin (a good solvent) as eluents. It was found that; (1) the better the solvent, the higher the molecular weight portion which can be eluted out; (2) the better the solvent, the greater the total amount of the polymer which can be recovered from the column; (3) the lower molecular weight homologs are eluted out before the higher molecular weight homologs; (4) by controlling certain factors, e.g., the moisture, the chromatograms obtained were satisfactorily reproducible in detail. By using successively MEK, toluene, and Tetralin, polystyrene can be fractionated in a single passage through a column with about 80% total recovery of the polymer on the column. Optimum fractionation in a single passage is obtained by eluting with appropriate mixtures of the above solvents in order of increasing solvent power of the mixture to the polymer. These results correlate with existing information on the adsorption of polystyrene from solution.
Sorption and diffusion in ethyl cellulose. Part III. Comparison between ethyl cellulose and rubber
Authors: Barrer R. M. , Barrie J. A. , Slater J. 
Published: April 2003

AbstractSorption and diffusion of C4 and C5 hydrocarbons have been studied in thin films of ethyl cellulose in the temperature range 30 to 80°C. Only regions of low penetrant concentration were chosen in order to minimize hysteresis effects associated with slow relaxation of polymer chains. The data have been quantitatively compared with those for the same penetrants in rubber, since ethyl cellulose and rubber are examples of stiff and flexible chain polymers, respectively. In both solution and diffusion some major differences were found between the two types of medium. In rubber the heats of dilution were small and the corresponding positive entropies close to those predicted by the lattice theory of solutions. On the other hand, in ethyl cellulose at low penetrant concentrations the heats of dilution were strongly exothermal and the entropies negative. For both polymers diffusion coefficients of penetrants were dependent upon concentration, but whereas in rubber this concentration dependent decreased rapidly with rising temperature, in ethyl cellulose it was largely independent of temperature. Energy barriers involved in each unit diffusion process were comparable for a given hydrocarbon in rubber and in ethyl cellulose, while the molecular shape of the penetrant molecule substantially influenced the diffusion coefficients in each polymer. Further interpretation of the diffusion coefficients suggested that the involvement of polymer chains in each unit diffusion is much less for ethyl cellulose than for rubber. Explanations are offered, based upon the nature of the chains composing the two media and upon the existence of holes in the ethyl cellulose network, for the essential differences indicated above. The relative efficiency of ethyl cellulose and rubber membranes for gas separation is discussed.
Polymers and copolymers of sodium ethylenesulfonate
Authors: Breslow David S. , Kutner Abraham 
Published: April 2003

AbstractSodium ethylenesulfonate polymerizes readily in aqueous solution under the influence of ultraviolet light or in the presence of peroxide catalysts. The most important variable in the polymerization has been found to be the concentration of monomer, increased concentration leading to more rapid polymerization and higher molecular weights. Poly(sodium ethylenesulfonate) has been isolated as a brittle, white solid with weight‐average molecular weights as high as 150,000. Sodium ethylenesulfonate copolymerizes with a variety of water‐soluble monomers: acrylamide, acrylic and methacrylic acids, and their sodium salts. Although copolymerization occurs, water‐soluble copolymers of sodium ethylenesulfonate with acrylonitrile and with methyl acrylate could not be prepared. Water‐soluble copolymers of sodium ethylenesulfonate with vinyl acetate and with vinyl chloride have been made, but they contain only small amounts of acetate and chloride. No copolymers could be prepared with butadiene, isobutylene, styrene, α‐methylstyrene, n‐butyl vinyl ether, allyl alcohol, N‐allylacetamide, maleic acid, or fumaric acid. The copolymerization of sodium ethylenesulfonate with acrylamide and with sodium acrylate has been used to calculate reactivity ratios. From these, sodium ethylenesulfonate has been calculated to have a Q value of 0.19 and an e value of +1.51.
Studies on straining of high polymer solids
Authors: Ito Katsuhiko 
Published: April 2003

AbstractStraining of high polymer solids is experimentally investigated from the standpoint of internal molecular structure. The test specimens used are epoxy cast resins as network polymers and hard polyvinylchloride as linear polymers. The experiment is mainly performed in compression. It is proved that the straining of network polymers is due solely to intramolecular micro‐Brownian motion, named “deformation strain,” and is not true plastic strain, even though strain may be frozen by secondary bonding forces at room temperatures. On the other hand, intermolecular macro‐Brownian motion, named “flow strain,” is further added for the straining of linear polymers. The mutual relations between flow strain and deformation strain on hard polyvinyl chloride are examined under various conditions, such as working and annealing temperature, magnitude of worked strain, rate of strain, etc. The plastic working ability of high polymer solids is discussed in relation to working temperature.
Determination of constants in the intrinsic viscosity–molecular weight equation
Authors: Sharples A. , Major H. M. 
Published: April 2003

AbstractIn the modified Staudinger equation, [η] = Km[Mv]α, the constants Km and α are usually found from measurements of [η] and Mv. As the latter cannot be determined directly, the method adopted in the past has been to prepare fractions, determine Mn or Mw by such absolute methods as osmometry and light scattering, and then to assume that the fractions are sufficiently monodisperse to justify writing Mv = Mn = Mw. An alternative approach has been suggested in this paper, making use of the fact that, for a distribution arising from random degradation, Mv = constant × Mn; it has been shown that the appropriate distribution results from the heterogeneous hydrolysis of cotton. The method has been applied to the case of cellulose triacetate in chloroform and the following results have been obtained: Km = 2.51 × 10−4; α = 1.02.
Polymers and group interactions. VI. Intramolecular acylations on copolymers of styrene and acrylic acid derivatives, a route to poly‐2,4‐methylenetetralone
Authors: Teyssié Ph. , Smets G. 
Published: April 2003

AbstractThe intramolecular cyclization of 50/50 styrene‐acrylic acid (or derivatives) copolymers has been investigated; the purpose of this work was the synthesis of a high molecular weight poly‐2,4‐methylenetetralone. The cyclization of styrene‐(meth)acroyl chloride copolymers in the presence of aluminum chloride gives under rather mild experimental conditions high yields of tetralone units, together with some tricyclic units of the hexahydrophenalenedione type. This cyclization reaction was, however, always concomitant with a strong degradation of the polymeric chains: it results from the formation of a carbonium ion on the main chain through a secondary decarbonylation reaction, as shown by chemical determination. The cyclodehydration of a styrene(meth)acrylic acid copolymer was carried out with good yields in an acetylating mixture, in the presence of various catalysts such as zinc chloride, polyphosphoric acid, or phosphorus oxychloride. The cyclization to tetralone units is concomitant with the formation of anhydride groups, and in the case of acrylic acid, of enol‐ester groups: the alkaline hydrolysis of the products yields terpolymers of styrene, acrylic acid, and methylenetetralone. Moreover, using polyphosphoric acid or phosphorus oxychloride, the intrinsic viscosity of the cyclized copolymers remains important, even at rather high degree of conversion. The cyclization of styrene‐methyl(meth) acrylate copolymers in heterogeneous medium, in polyphosphoric acid, was also carried out; the degradation process is very small. The methacrylic ester copolymers undergo, however, an important gelification, while the acrylic copolymers yield, besides the usual tetralone units, some tetracyclic units of the tetrahydro‐3,4‐benzophenanthrene type.
Radiation crosslinking of rubber—effect of additives
Authors: Turner D. T. 
Published: April 2003

AbstractThe effect of a range of additives on the crosslinking of rubber by pile radiation has been investigated. Retardation of crosslinking has been correlated with the reactivity of the additive towards free radicals. At least two‐thirds of the crosslinks can be stopped by large amounts of radical acceptor. Preliminary results with a butadiene‐styrene copolymer and with Co‐60 γ‐radiation also indicate the importance of free radicals. Some halogenated compounds increased the degree of crosslinking.
The surface tension of viscous polymers
Authors: Tarkow Harold 
Published: April 2003

AbstractA procedure is described for measuring the surface tension of polymeric liquids whose bulk viscosity is at least 1500 times that of glycerol. The procedure is based on the determination of the force necessary to separate two spheres held in contact by the test liquid. A series of silicones was examined. Following a relatively sharp rise in surface tension for the lower members, the rate of increase in surface tension with bulk viscosity is extremely small and seems to be approaching a constant value.
Polymerization of acrylonitrile by boron trifluoride in amide solvents
Authors: Campbell Tod W. 
Published: April 2003

AbstractThe observed activity of boron fluoride‐dimethyl formamide as a catalyst for the polymerization of acrylonitrile has been studied. It has been found that oxygen is a necessary third component, and that the polymerization is a free radical process. Evidence is presented that oxygen reacts with acidic complexes of dimethylformamide to give peroxides of the type HCON(CH3)CH2OOH, which acts as typical peroxide initiators.
Vinyl acetate emulsion polymerization
Authors: O'Donnell J. T. , Mesrobian R. B. , Woodward A. E. 
Published: April 2003

AbstractVinyl acetate emulsion polymerization at 70°C. using potassium peroxydisulfate as initiator and a partially hydrolyzed polyvinyl acetate as emulsifying agent has been studied. In agreement with the Smith and Ewart scheme for emulsion polymerizations, the polymerization rate was found to be independent of the total monomer amount present and approximately dependent on the 3/5 power of the emulsifier concentration. Instead of a 2/5 power dependence on initiator concentration for the rate of polymerization, a 0.7 power dependence was found. From surface tension measurements an “apparent critical micelle concentration” was determined for aqueous solutions of the emulsifier. However, light scattering studies gave no indication that aggregates of the emulsifier exist in aqueous solutions.
Viscoelastic properties of concentrated polymer solutions
Authors: Takemura Tetuo 
Published: April 2003

AbstractIt is shown that the relaxation time spectra of concentrated polymer solutions are obtained on the basis of molecular theory using the network structure model. These spectra are considered to be reflecting two kinds of relaxation mechanisms; (a), the vibrational modes between network structures, (b) the vibrational modes of intra‐chain submolecules in the network. In this paper the vibrational modes of each mechanism are calculated independently. The results show that the wedge‐type distribution of the relaxation spectrum can be obtained from the mechanism (b) and the box‐type distribution can be obtained from the mechanism (a), respectively, and that the deviations from Ferry's master curves originate from interactions between these networks. Good agreement is shown between this theory and experiments.
Crystallization in natural rubber. V. Chemically modified rubber
Authors: Gent A. N. 
Published: April 2003

AbstractMeasurements are described of the rate and final extent of crystallization at a temperature of −25°C. in natural rubber which has been modified by the chemical combination of sidegroups to the rubber molecule. The substances added were six thiol acids. Their efficiencies in retarding crystallization are compared with that previously reported for peroxide crosslinking and with the value predicted by a simple banned volume treatment for crystal nucleus formation. They are found to be generally greater than the large value predicted theoretically. Possible reasons for this are discussed.
Dynamic mechanical properties of nylon 66 and the plasticizing effect of water vapor on nylon
Authors: Quistwater J. M. R. , Dunell B. A. 
Published: April 2003

AbstractThe dynamic tensile modulus and energy loss have been measured for nylon 6‐6 at 35°C. over a wide range of humidity in forced longitudinal vibration experiments. The frequency range covered was about 3 to 30 cps. (radian frequency 20 to 200 sec.−1). Dispersion of mechanical properties was observed with changing humidity, the maximum in the loss factor, tan δ, occurring at about 70% RH. Small variation of energy dissipation with change in frequency is such as to suggest that the dispersion region extends over a wide frequency range and that at low humidity an energy loss maximum should be expected at a frequency below one cycle per second. Increase in the amount of water adsorbed by the nylon with increasing relative humidity leads to plasticization of the fiber and consequent increase in freedom of motion of chain segments in the amorphous region of the fiber. Examination of individual runs shows that the dynamic modulus tends to increase with increasing frequency and that the increase is of a reasonable order of magnitude for the relaxation phenomena involved.
Glass transition temperatures of copolymers
Authors: Wood Lawrence A. 
Published: April 2003

AbstractThe Gordon‐Taylor equation relating the glass transition temperature θ of a copolymer to the glass transition temperatures θ1 and θ2 of the homopolymers is equivalent to

where c1 and c2 are the weight fractions of the constituents and A1 and A2 are constants. It can be recast into the following forms suitable for linear plots

and

where k = A2/A1. Data from the literature on 10 copolymer systems, including butaciene‐styrene copolymers, give linear plots, verifying the equation within experimental error. However, the observed value of k is in most cases significantly smaller than the ratio of the differences of the volume‐temperature coefficients for each homopolymer in the rubbery and glassy states, as required by the derivation of Gordon and Taylor. The glass transition temperature (in °C.) for a butadiene‐styrene copolymer prepared by emulsion polymerization at 50°C. may be calculated from the weight fraction c2 of bound styrene as

and for a similar 5° copolymer as
The fractionation of polyethylene
Authors: Hawkins S. W. , Smith H. 
Published: April 2003

AbstractFour of the new high‐density polyethylenes and one conventional high‐pressure, low‐density polyethylene have been fractionated by a fractional solution technique. The number‐average molecular weights, infrared absorption spectra, and densities of the fractions were measured by standard techniques, modified where necessary to accommodate the low solubility of the new high‐density polyethylenes. The results show: (1) The solubility of polyethylene is determined primarily by a shape parameter—number of methyl groups per hundred carbon atoms—rather than molecular weight. (2) Crystallinity is not a reliable index of the solubility of polythene unless considered in relation to molecular weight. (3) The unusual physical properties of the new high‐density polyethylenes arise from their having an essentially unbranched molecular structure rather than high molecular weights.