bluuebunny/crossref_metadata_2025 huggingface dataset:
A thermodynamic and kinetic study of the dissociation of arachin
Authors: Williams R. K. , Naismith W. E. F. , Tipper C. F. H.
Published: April 2003

The dissociation of arachin has been studied over a range of pH values, ionic strengths, temperatures, and protein concentrations and standard energy values have been calculated. The standard entropy changes and standard heat contents were found to be lower than would be expected and possible reasons for this are discussed. The Kc values varied on altering the protein concentration and are considered to be dependent on a function of the ratio of concentration to ionic strength.
Logarithmic thermal degradation of a silicone resin in air
Authors: Doyle Charles D.
Published: April 2003

The weight‐loss of a methyl‐phenyl silicone resin was determined over the temperature range from 135 to 240°C. and up to approximately 10% volatilization. Weight‐fraction volatilized varied linearly with the logarithm of time. The history of such logarithmic processes is reviewed briefly. The empirical rate‐equation is discussed in terms of the data. On the basis of a surface‐removal experiment, and on the basis of the chemistry of the degradation, a mechanism of Fickian diffusion is proposed, wherein the diffusion coefficient varies exponentially as the degree of crosslinking and shrinkage, while the concentration gradient of volatilizable molecules remains constant.
Molecular weight of ethyl cellulose by dielectric dispersion of solutions in solvents of low dielectric constants
Authors: Scherer Philip C. , Hawkins M. C. , Levi D. W.
Published: April 2003

The critical frequencies for ethyl cellulose solutions were determined by a “differential” bridge method in carbon tetrachloride, benzene, and toluene. Correlations between the critical frequency and degree of polymerization were found to be similar to those previously reported. Intrinsic viscosity data for ethyl cellulose in four solvents of low dielectric constant are also included.
Lithium‐initiated copolymerization of styrene and methyl methacrylate. II. A propagating radical‐ion
Authors: O'Driscoll K. F. , Tobolsky A. V.
Published: April 2003

It has been shown that lithium‐initiated copolymerization of styrene and methyl methacrylate yields an unusual copolymer since it contains appreciable quantities of styrene. The probable nature of this copolymer is discussed, and it is suggested that lithium may act as an electron exchange type of initiator.
Copolymerization of trialkyl aconitates with vinylidene chloride
Authors: Marvel C. S. , Mano Eloisa B.
Published: April 2003

Reactivity ratios for the copolymerization of trimethyl aconitate and vinylidene chloride have been determined. Some copolymers of vinylidene chloride with trimethyl, triethyl, and tri‐n‐butyl aconitate have been reported. The stabilizing effect of aconitic esters on the color of polyvinylidene chloride has been confirmed.
On certain peculiarities of the structure of fibrous proteins and polymers
Authors: Andreeva N. S. , Iveronova V. I.
Published: April 2003

Analysis is made of the system of parallel chain molecules which has a long‐range order in the arrangement of the structural units along the chains, and a short‐range order in the packing of molecules. A solution has been obtained of the problem of scattering x‐rays on such a system. Analysis of the correspodence between theoretical results and the results for certain fibrous proteins and polymers has been made. This analysis shows that in some parts of these substances there are regions where the parallel chains are arranged without any correlation to the packing of the units of neighboring chains.
Über zusammenhange zwischen dem vernetzungsgrad und der degradation von naturkautschuk
Authors: Tkáč A. , Kellö V.
Published: April 2003

Oxidation reactions, as followed by infrared spectrometry, may serve as a measure for judging the relative extent of oxidative degradation and crosslinking of two independent parallel reactions subsequent upon the primary destruction. Such information can be derived from a kinetic analysis of the processes taking place in the rubber as a result of the absorption of energy, using the expression w = (k/b) (1 − e−bη) (1 − η). Since in this equation k is proportional to the rate of chain branching (which leads predominantly to oxidation), and b is proportional to the rate of recombination of the radicals (leading to crosslinking), the total degree of crosslinking will increase with increasing values of b/k. This assumption has been verified experimentally for the thermal and photochemical ageing of rubber, both in the absence of additives and in the presence of sulfur, of vulcanizing mixtures, and of copper as a catalyst of oxidation. At increased temperatures and pressures (130°C., 3 atm.) in the absence of vulcanizing additives and in a nitrogen atmosphere, radicals of long life are formed; this leads to an increased rate of the subsequent oxidative degradation. The number of active centers formed, and hence the final extent of oxidation, is a function of the time of exposure to the increased temperature.
Adsorption of certain high polymers by carbon black in dilute solutions
Authors: Yurzhenko A. I. , Maleyev I. I.
Published: April 2003

Adsorption experiments were made to determine the time required for a complete adsorption of certain highly molecular substances from solutions. Aluminum oxide was preliminarily subjected to hydrophobization by caproic acid. Samples of polystyrene, polyisoprene, and polyethers of acrylic and methacrylic acids, ranging from methyl to heptyl inclusive, were taken as objects of the experiments. In all cases the time required for a complete extraction of the substances from solution was shown to be directly proportional to square of the characteristic viscosity. “Bad” solvents take a shorter time to effect a complete adsorption. The investigation of adsorption of polyethers of acrylic and methacrylic acids has shown that the increase in the alcohol radical influences the velocity of the adsorption process as a whole in different ways. While the increase in the alcohol radical of the polyacrylic ethers reduces the time required for a practically complete adsorption of the substance, in the case of polyethers of methacrylic acid the reverse relation was observed. Hydrophobic aluminium oxide is shown to adsorb polymethyl acrylate from solution reversibly.
Polymerisationsauslösung durch hydroperoxyde
Authors: Schröder G.
Published: April 2003

Es wird versucht, den Mechanismus der Radikalbildung aus organischen Hydroperoxyden in homogener Lösung aufzuklären. Die scheinbare Diskrepanz, dass die bekannte thermische Zersetzung von Hydroperoxyden in Lösung kinetisch nach der 1. Ordnung verläuft, dagegen die Katalyse der Autoxydation ungesättigter Verbindungen durch Hydroperoxyde in einer Reaktion 2. Ordnung erfolgt, wird diskutiert und durch eine Arbeitshypothese überwunden. Ihre experimentelle Nachprüfung durch dilatometrische Verfolgung von Polymerisationen lieferte kinetische Ergebnisse, die sich durch folgende einfache Annahmen deuten lassen: (1) Hydroperoxyde bilden in Gegenwart von Styrol freie Radikale nach der Gleichung:
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Styrol greift also in die Startreaktion ein. (2) In Methylmethacrylat und Vinylazetat bilden Hydroperoxyde Radikale nach der Gleichung:
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(3) Alkylperoxy‐Radikale (ROO·) bewirken einen zusätzlichen Kettenabbruch durch Reaktion mit Makroradikalen:
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The X‐ray diffraction, birefringence, and infrared dichroism of stretched polyethylene. II. Generalized uniaxial crystal orientation
Authors: Stein Richard S.
Published: April 2003

A general method for describing the crystal orientation in a uniaxially oriented crystalline polymer is presented. It is shown that two orientation functions may be quantitatively evaluated from x‐ray diffraction data. The variation of these during mechanical and thermal treatment may be studied. These functions are sufficient to completely characterize the crystal contribution to birefringence and infrared dichrosim. By subtracting the crystal contribution from the total birefringence or dichroism, the amorphous orientation may be characterized.
The X‐ray diffraction, birefringence, and infrared dichroism of stretched polyethylene. III. Biaxial orientation
Authors: Stein Richard S.
Published: April 2003

A set of functions for characterizing the crystal orientation in a biaxially oriented crystalline polymer is proposed. The additional orientation functions may be determined from a measurement of the variation of x‐ray intensity with tilt angle of a film. From these functions and those described in Part II, the crystal contribution to the birefringence and the infrared dichroism of normal and tilted films may be calculated.
Dielectric properties of polymonochlorotrifluoroethylene
Authors: Nakajima Tatsuji , Saito Shogo
Published: April 2003

The dielectric properties of three kinds of polymonochlorotrifluoroethylene having various degrees of crystallinity were studied. The measuring instruments by which the dielectric properties can be measured over a wide range of frequency are briefly described. The dielectric measurements for three samples are made over a frequency range 0.1 to 106 cycles/sec. and a temperature range of −50 to 140°C. The main conclusions from the experimental results are as follows. Two dielectric dispersions observed would be due to the polar groups in amorphous regions. At the melting temperature, the positions of the two dispersions would coincide with each other. The energies of activation for the two loss processes are 16.8 and 57.0 kcal., respectively. Interpreting from the variation of the magnitude of the dielectric dispersion with temperature, the glass transition temperature of this polymer extends over the wide range from −80 to 60°C. For the low temperature dispersion, the value of Cole‐Cole's parameter β has constant value of 0.3 below 20°C. and increases with temperature above 20°C.
The polymerization of acrylamide with chlorate–sulfite initiator
Authors: Suen T. J. , Jen Yun , Lockwood Janet V.
Published: April 2003

Acrylamide was polymerized in aqueous solution with chlorate‐sulfite initiator under the following conditions: temperature, 15–75°C.; pH, 1.5–3.9; monomer concentration, 0.3–1.1 mole/liter; NaClO3 concentration, 0.26–2.1 × 10−4 mole/liter; and Na2‐SO3 concentration, 0.79–6.3 × 10−4 mole/liter. The weight‐average molecular weight of the polymers formed under these conditions is in the range of 1–3 × 106. It was found that up to 40–50% conversion, the following rate equation holds:

where Rp is the overall rate of polymerization, [M] the instantaneous monomer concentration at time t, and [M]0 the initial monomer concentration. At 50°C., K = 6.9 ± 0.9 l. mole−1 sec.−1 Activation energy within the temperature range studied was found to be 7.3 kcal./mole. The value of k/kt at 50°C. was estimated to be about 30 l. mole−1 sec.−1 The rate dependence on [M]5/2[M]−3/20 is explained by assuming that the polymer formed binds part of the remaining monomer. The presence of ferrous ions in the polymerization system increases the rate but decreases the molecular weight of the polymer formed. Up to 3.6 × 10−3 mole/l. of [Fe++], the rate is affected in such a manner that

Chromic ions tend to retard and nickel ions tend to accelerate the rate of polymerization. It was found that HSO3− is an effective chain transfer agent. Its chain transfer constant was estimated to be about 0.17.
Polyvinylacetophenone: Preparation, reactions, and depolymerization
Authors: Kenyon William O. , Waugh George P.
Published: April 2003

Polyvinylacetophenone was made by the Friedel‐Crafts reaction of acetyl chloride or acetyl bromide on polystyrene, in carbon disulfide, using aluminum chloride. Similar reactions, using bromoacetyl bromide or chloroacetyl chloride, gave insoluble polyvinylphenacyl halides. A soluble, low‐molecular‐weight polyvinylphenacyl chloride was obtained using chloroacetyl chloride and monomeric styrene. Polyvinylphenacyl bromides of limited Solubility were obtained by direct bromination of polyvinylacetophenone. Vacuum pyrolysis of polyvinylacetophenone gave p‐vinylacetophenone monomer in good yield. At atmospheric pressure, the product was about half p‐vinylacetophenone and half p‐ethylacetophenone. At intermediate pressure, an intermediate proportion was obtained.
Polar effects in the copolymerization reactions of aconitic acid and some of its esters with nonpolar monomers
Authors: Orr R. J. , Williams H. Leverne
Published: April 2003

Studies of the copolymerization of aconitic acid and some of its esters with nonpolar monomers indicate that electrostatic effects occur due to the acid hydrogen of the free acid. These changes are such that normal methods of interpretation of reaction data no longer apply. A method of interpretation, based on a treatment by Laidler and Landskroener, of the effect of dipole‐dipole interaction on the reaction rate is presented. This interpretation is tested with the experimental results available.
Solution properties of polyvinyl acetate
Authors: Cotten G. R. , Sirianni A. F. , Puddington I. E.
Published: April 2003

The depression of the vapor pressure over solutions of fractionated polyvinyl acetate in benzene and ethanol was studied using a differential manometer. The Huggins' equation was obeyed within the concentration range used, i.e., up to 10% solute concentration. The semiempirical constant μ was evaluated for different fractions and was found to vary with the average molecular weight of the polymer. The heat and entropy of dilution were calculated for one fraction in benzene solution, and the results are discussed in terms of the existing theories of high polymer solutions.
The permeation of water vapor through polyethylene
Authors: Klute C. H. , Franklin P. J.
Published: April 2003

A critical survey of the literature has been made relative to the permeation of water vapor through films of polyethylene. For conventional polyethylene, reported values of permeability range from 0.015 to 0.074 gm. mm./m.2 day cm. Hg at 25°C. Reported activation energies range from 6,590 to 14,540 cal./mole°C. It appears that the highest activation energies are associated with the lowest permeability coefficients. Recent investigations of the permeability of intermediate and high‐density polyethylenes are not in agreement with one another The explanation is offered that part of the transport of water vapor through these materials occurs by Fickian diffusion through the amorphous fraction of the polymer and part occurs by passage through micropores in the polymer film. The expectation exists that a superior water‐vapor barrier could be developed using ultralinear, crystalline polyethylene of high molecular weight. However, an incisive experimental test of this supposition would first have to be concerned with a more complete characterization of polyethylene in the solid state than has heretofore been employed in diffusion and permeability studies.
Some light‐scattering evidence of critical concentration in dilute polymer solution
Authors: Bigelow C. C. , Cragg L. H.
Published: April 2003

Evidence of a critical concentration effect in dilute polymer solution has been obtained from light‐scattering measurements in two ternary systems of the type polymer A–polymer B–solvent S. The root‐mean‐square end‐to‐end distance, (r2)1/2, of A was measured in a series of mixed solvents (B–S), differing from one another only in respect Of CB, the concentration of polymer B. The (r2)1/2 vs. CB curve exhibited a slight dip in the system polystyrene–polyvinyl acetate–benzene and a slight peak in the system polystyrene–polyvinyl acetate–butanone, at values of CB close to but not identical with the critical concentrations determined viscometrically for the same systems. The size, nature, and location of these light‐scattering critical concentration effects are briefly discussed in the light of similar but better established viscosity effects.
Details on the half‐life of polymeric free radicals
Authors: Gehman H. , Goldfinger G. , Kolczynski J. R.
Published: April 2003

A model is presented that is based on the experimental conditions prevailing during photopolymerization in a free falling stream. When some simplifying assumptions are applied it is possible to correlate quantities which are potentially measurable, such as yield of reaction and number‐ and weight‐average molecular weights, with the spread of times elapsing between subsequent addition steps. In other words, the average time elapsed can be refined to a time distribution curve. In the model, the time elapsed between initiation and forcible termination is subdivided into t time elements. During each of these it is assumed that exactly one of the following must occur: the growth of the free radical to one larger by one monomer unit, natural termination without any change of size, or nothing. The sum of the probabilities of those events, called, respectively, s, f, and i, is, of course, exactly 1. Considering forcible termination of all polyradicals still surviving after t time elements, one can calculate size and weight distribution curves.
Friction constants of chain molecules with excluded volume
Authors: Stockmayer W. H. , Albrecht A. C.
Published: April 2003

The validity of the Flory‐Fox treatment of the friction constant is investigated for chains with excluded volume with the aid of theories due to Kirkwood and to Fixman. It is found that the effective hydrodynamic radius of a linear macromolecule is less affected by excluded volume than the radius of gyration, and hence that the Flory‐Fox number P should decrease slightly with increasing molecular weight or solvent power.
Effect of physical state during the electron irradiation of hydrocarbon polymers. Part II. Additional experiments and discussion pertaining to trapped radicals in hydrocarbon polymers
Authors: Lawton Elliott J. , Powell R. S. , Balwit J. S.
Published: April 2003

The previous paper discusses the effect of physical state during the irradiation on the fate of the polymer radicals produced. Additional experiments relating to trapped radicals in hydrocarbon polymers are discussed. Three different methods of detection were used; namely, infrared absorption at 5.8 μ, electron paramagnetic resonance, and gasuptake by the irradiated polymer. Conditions for producing trapped radicals at room temperature are that the polymer exist in the crystalline, glassy, or highly crosslinked form during irradiation. Radicals trapped in the crystalline or glassy areas can dissipate either as the result of heating the polymer above Tm or Tg or else by exposure to a radical scavenger, e.g., oxygen or ethylene. The lifetime of radicals trapped in Marlex‐50 can be many thousands of hours at room temperature. Radical decay will take place even with storage in vacuum if given enough time. The decay is arrested by holding the sample at liquid nitrogen temperature. Loss in radical activity in Marlex‐50 when stored in vacuum is due mainly to delayed crosslinking. Trans‐vinylene and vinyl do not appear to enter into the reaction responsible for the decay. A comparison of the decay of radicals trapped in unbranched Marlex‐50 with that in a branched low‐density polyethylene when stored in ethylene, oxygen, and vacuum was made. The results suggest that although radicals are trapped in the crystalline regions of both polymers, there are differences between the two crystals—the crystals in the low‐density polymer do not appear to be as tight as those in the Marlex‐50. Delayed oxidation reactions occurring in the crystalline regions of irradiated Marlex‐50 when stored in oxygen at room temperature require a number of intermediate steps before appearing as carbonyl. An average of 5 molecules of oxygen per polymer radical was used in forming carbonyl. Delayed main chain scissions occur during this process which cause severe embrittlement and loss in physical properties. Significant improvements in physical properties of Marlex‐50 can be achieved through irradiation, but radicals must not be left trapped in the polymer.
Crystalline modifications of cellulose. Part II. A study with plane‐polarized infrared radiation
Authors: Mann J. , Marrinan H. J.
Published: April 2003

The bands due to stretching of OH groups in celluloses I, II and IIII have been studied with plane polarized infrared radiation. The spectra show that all three crystalline modifications contain OH groups which make an angle much smaller than 55° with the chain direction, while other OH groups make angles greater than 55° with this direction. The former OH groups are attributed to intramolecular hydrogen bonds which join successive glucose residues in the cellulose chain. It is shown that ether oxygen atoms must participate in the hydrogen‐bonding systems in all three modifications. The symmetries of the cellulose chains and the relationship between the two chains in the unit cell are discussed in relation to the number of distinguishable OH groups. Structures are described which are in agreement with the infrared results and with the stereochemical considerations presented in Part III of this series. The frequencies of the bands due to intramolecular hydrogen bonds suggest that the chains in cellulose I have a different molecular form from those in celluloses II and IIII. This difference may not be very large, however, in relation to the accuracy with which polymer structures are normally determined.
Freezing point depression of polymer solutions and gels
Authors: Kawai Tōru
Published: April 2003

The freezing point depression of polymer solutions was measured in the concentration range 5% to 30% (by volume of polymer), particular attention being paid to avoid excess supercooling. The polymer‐solvent combinations investigated were polystyrene‐benzene, polyvinyl acetate‐benzene, cellulose acetate‐acetic acid, and polyvinyl alcohol‐water. Through the proper adjustment of the rate of cooling, the freezing curves showed a sharp break, from which the freezing points were determined as a function of polymer concentration with sufficient accuracy to permit discussions of the thermodynamic properties of these polymer solutions. The discussion of these data was made in terms of the interaction parameter, μ, well known in the theory of polymer solutions. The new feature brought out in this work is the marked change of μ with polymer concentration. For all the polymer‐solvent systems studied, fairly rapid fall in μ was observed with increasing concentration. Such behavior in μ is important because it is in no way specific to these systems and leads to the expectation that, for polymer solutions in general, μ (or, at least μs, the entropy contribution to μ) should fall progressively as the polymer concentration is increased, with a corresponding increase in the degree of overlapping of the excluded volumes of polymer molecules. The earlier theories of polymer solutions require improvement in this direction. In the cases of the systems, cellulose acetate‐acetic acid and polyvinyl alcohol‐water, the orientation and strong heat of mixing effects must also be considered because of the polar nature of the components. In order to carry out further quantitative discussion on the results obtained, we must wait until more complete theories of polymer solutions will be developed. It has become apparent, nevertheless, that the freezing point determination furnishes our best source of information concerning the thermodynamic properties of polymer solutions. As for aqueous solutions of polyvinyl alcohol, possible effects of the intermolecular junction points which might be produced in the solution on cooling upon the results were examined, but negative results were obtained. Finally, a possibility was suggested for development of this method to permit extensions to lower and higher concentration ranges than those covered by the present work, the latter (higher concentration range) including gels produced by polymer networks and assemblages of moist fibers.
A theoretical study on the mechanism of Ziegler‐type polymerizations
Authors: Uelzmann Heinz
Published: April 2003

The polymerization of olefins with Ziegler catalysts is an intercomplex ion polymerization taking place on two metal atoms. A cationic initiation occurs on a cation of a transition element. In the case of a stereospecific polymerization the activated monomer orients toward and inside a negative complex ion (for instance of aluminum) into which it migrates by adding a propagation starter (R−, H−). In this complex anion all further cationically activated monomers propagate anionically until termination occurs by H− abstraction.
Cyclopolymerization. I. Polydiacrylylmethane
Authors: Jones J. F.
Published: April 2003

The attempted synthesis of diacrylylmethane by the acylation of methyl vinyl ketone with ethyl acrylate produced exclusively the homopolymer of diacrylylmethane. This new polymer is linear and is composed of recurring methylene dihydroresorcinol units. An anionic mechanism is proposed for the cyclopolymerization of diacrylylmethane. Polydiacrylylmethane undergoes chemical reactions which are characteristic of beta diketones and proof for structure of the polymer is based on solubility, fusibility, infrared absorption, ultraviolet absorption, and enol titration data.
Cyclopolymerization. II. Polyacrylic anhydride
Authors: Jones J. F.
Published: April 2003

A linear high polymer composed of repeating α‐methylene glutaric anhydride units has resulted from the controlled cyclopolymerization of acrylic anhydride. Proof for the linear nature of this polymer is based upon solubility and thermoplastic behavior. Proof for the cyclic nature of the polymer is based upon the lack of residual unsaturation. The molecular weight of linear polyacrylic anhydride has been altered by the use of chemical modifying agents in the polymerization recipe. Linear polyacrylic anhydride undergoes characteristic carboxylic anhydride reactions.
Static electricity in polymers. I. Theory and measurement
Authors: Shashoua Victor E.
Published: April 2003

A versatile instrument, The Static Propensity Tester, was constructed for the measurement of the rate of electrostatic charge build up and decay on polymer films and fabrics. The tester was used for measuring the rates of both positive and negative potentials in the voltage range of 1000–10,000 volts. From such studies it was observed that above a certain minimum potential, it always took longer for charge to build up on a sample than to decay. Also, the rate of charge decay was found to be dependent on the exposed surface area of a sample as well as its electrical resistance. The loss of charge from a given substance was postulated to occur by two processes, a conduction process through the substrate and a radiation process through the atmosphere. In addition, polymers were found to exhibit a charge selectivity for the sign of the applied voltage, i.e., wool had a faster negative charge decay rate whereas cellulose had a faster positive decay rate. The root‐mean‐square half life of charge decay for positive and negative voltages was found to follow an exponential type law with respect to magnitude of charge and relative humidity. A simple test was devised for characterizing the antistatic behavior of polymers.
The copolymerization characteristics of ethyl α‐acetoxyacrylate
Authors: Unruh C. C. , Laakso T. M.
Published: April 2003

The copolymerization characteristics of ethyl α‐acetoxyacrylate with four different monomers have been investigated, and the reactivity ratios r1 and r2 determined in the case of each comonomer pair. The monomers used were styrene, methyl methacrylate, vinyl acetate, and ethyl acrylate. From these data were calculated the Q and e values for ethyl α‐acetoxyacrylate. It is apparent that this monomer resembles ethyl acrylate very closely in its copolymerization characteristics.
Molecular weight–viscosity relationship of gamma‐irradiated octadecyl vinyl ether and octadecyl methacrylate
Authors: Fee Jeanne G. , Port William S. , Witnauer Lee P.
Published: April 2003

Octadecyl vinyl ether and octadecyl methacrylate monomer were polymerized by means of gamma radiation from a cobalt‐60 source. The weight‐average molecular weight and the intrinsic viscosity of the resulting polymers were determined. The constants K′ and a were 0.25 × 10−4 and 0.75, respectively, for poly(octadecyl methacrlylate) and 22.4 × 10−4 and 0.35, respectively, for poly(octadecyl vinyl other).
Dynamic mechanical properties of irradiated polyethylene
Authors: Butta E. , Charlesby A.
Published: April 2003

Dynamic mechanical properties of eight samples of polyethylene irradiated to various extents have been determined over a temperature range from −70 to +280°C. and a frequency range from 103 to 2 × 104 cycles/sec. At room temperature, minimum values in Young's modulus and maximum values in damping factor are observed for a critical radiation dose. Three transition points Tg, Ts, and Tm are exhibited by the sound velocity‐temperature curves; these may be associated with the transition from the glass state, the softening of the amorphous regions, and the melting of the crystallites, respectively. With increasing dose, Tm, decreases and Tg, increases, while Ts shows a minimum for a radiation dose equal to the critical value. At temperature above the melting point of the crystallites Tm, lightly crosslinked samples show rubber‐like elasticity, but highly crosslinked samples show the same dynamic mechanical behavior as highly crosslinked amorphous materials. Results are discussed and explained on the basis of the partial crystallinity of polyethylene and of the changes that irradiation causes on the molecular structure.
Infrared spectroscopy of polyethylene terephthalate
Authors: Daniels W. W. , Kitson R. E.
Published: April 2003

The absorption spectra of polyethylene terephthalate, polyethylene‐D4 terephthalate and polyethylene terephthalate‐D4 were investigated. From these spectra and those of other known compounds, assignments were made for most of the bands in the 2 to 15 micron region. The 13.7 μ band was shown to be due to the out‐of‐plane bending of the aromatic hydrogen. The bands in this region known to vary in intensity with crystalline/amorphous ratio of the polymer were shown to be present in the spectrum of ethylene dibenzoate and to behave in an analogous manner with changes of state. From a study of this model compound and other considerations, rotational isomerism was postulated as the origin of the variation in intensity of these bands. Carboxyl and hydroxyl endgroup bands were identified and used to determine polymer number‐average molecular weight in good agreement with values obtained by osmotic pressure methods. A band arising from ether linkages (which are formed via dehydration during polymer synthesis) was identified.
Thermal degradation of polymethacrylonitrile. IV. Formation and decomposition of ketene‐imine structures
Authors: Grassie N. , McNeill I. C.
Published: April 2003

The reaction of ketene‐imine structures in polymethacrylonitrile is most conveniently followed by observing the disappearance of the 2012 cm.−1 peak in the infrared spectrum. These structures are stable to 120°C. in the bulk material but disappear rapidly in solution at lower temperatures. Like simple ketene‐imines they are destroyed by addition of water, chlorine, methanol, and hydrogen sulfide. Thermal decomposition in cyclohexanone solution in the temperature range 65–90°C. is a second‐order process. The second‐order rate constant decreases with increasing polymer concentration although, within experimental error, it is independent of the ketene‐imine concentration. The rate constant can also be depressed by addition of polymethyl methacrylate. These observations have been interpreted in terms of diffusion (viscosity) control of the reaction rate. Ketene‐imine structures are formed during polymerization by reaction of the growing polymer radical in the form
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By preparing a series of polymers at the same temperature (30°C.) but with different initiator concentrations and determining their ketene‐imine contents, it has been possible to show that the ketene‐imine structures are formed predominantly in the termination step. The ketene‐imine form of the radical appears not to be reactive enough to add monomer readily in a propagation process. The mechanism of the thermal disappearance of ketene‐imine structures is not clear. In particular it is difficult to correlate the second‐order kinetics with the chain‐scission process which is associated with the reaction. There is some evidence, however, that the extent of this chain scission is a measure of ketene‐imine concentration.
The degradation of polymer molecules in solution under the influence of ultrasonic waves. Part I. Kinetic analysis
Authors: Ovenall D. W. , Hastings G. W. , Allen P. E. M.
Published: April 2003

Starting from the assumption that a polymer molecule in solution will only degrade under the influence of ultrasonic irradiation if both the resulting fragments are greater than Pe/2 in size, where Pe is the so‐called limiting degree of polymerization, rela tionships are derived giving the rate of degradation in terms of rate of breaking of bonds. If dBi/dt the rate of breakage of bonds in molecules of size Pi, the proposed rate equations are: dBi/dt = k(Pi – Pe)ni for Pi > Pe and dBi/dt = 0 for Pi ⪕ Pe, where k is a constant characteristic of the system and ni is the number of molecules of size Pi. Solutions of this equation are given for three sets of conditions.
A theory for the high field conductance of polyelectrolytes
Authors: Wissbrun Kurt F. , Patterson Andrew
Published: April 2003

Using a theory based on that of Onsager for the dissociation field effect, the authors have shown it is possible to explain the dependence of the Wien effect or polyelectrolyte samples on concentration, molecular weight, and gegenion mobility. The theory has been used to calculate a parameter, q, interpreted as representing a function of polyion size. It has been shown that for samples of polystyrenesulfonic acid the variation of q with increasing neutralization showed a constant polyion size, as would be expected of a fully charged polyion when only the gegenions are exchanged; a sample at a smaller concentration had a larger polyion, as would be expected. For samples of polyacrylic acid, the variation of q with increasing neutralization was initially similar to that revealed by viscosity or light scattering measurements—a rapid increase in polyion size. In our measurements, however, the size remained relatively constant over a considerable range of neutralization and then decreased slightly. This is interpreted as meaning that the ions removed from the polyion are those near the surface, and that the radius of importance in this particular experiment is more nearly the radius of the extended polyion cylinder and not a radius computed from the end‐to‐end separation of the polyion.
The dissolution of water‐insoluble polymers in the surfactant solution. The polyelectrolyte‐like behavior of the dissolved polymers
Authors: Isemura Toshizo , Imanishi Akira
Published: April 2003

Polymers, such as polyvinyl formal (PVF) and polyvinyl acetate (PVAc), which are insoluble in water, dissolved in anionic surfactant solution. Polymer solutions of PVF, PVAc, and polyvinyl alcohol in surfactant were studied viscometrically and electrophoretically. The polymer forms a complex with the surfactant, the behavior of which is similar to that of polyelectrolyte. The complex is negatively charged and migrates to the anode. With dialysis of the solution of polymer‐surfactant complex against running water, the polymer separates out; however, the polymer does not separate out of undialyzed solution, even if the solution is diluted to far less concentration than the CMC of the surfactant. Thus the dissolution of the polymers in the surfactant solution is due to the oriented adsorption of surfactant ions on the polymer molecule. The amount of adsorbed surfactant ions was estimated. The adsorption might be of the Langumuir type.
Copolymers of acrylic acid and N‐vinylpyrrolidone‐2
Authors: Uelzmann Heinz
Published: April 2003

Acrylic acid and N‐vinylpyrrolidone‐2 copolymerize readily in tetrahydrofuran. High yields of copolymers are obtained if not more than 3 moles of N‐vinylpyrrolidone‐2 are used per mole acrylic acid.
On the mechanism of polymerization retardation by aromatic nitro compounds
Authors: Ihrig Judson L. , Wong Rose K. L.
Published: April 2003

In vinyl polymerization retarded by aromatic nitro compounds, the growing chain reacts with the retarder to form stabilized products. The locus of radical attack has been reported as taking place at an aromatic carbon or at a nitro‐group oxygen. A direct experimental test has been devised to permit a choice between these alternatives. Rates of racemization of optically active nitrobiphenyl derivatives used as retarders in polymerizing systems have been compared with rates in nonpolymerizing monomer. These compounds were found to racemize more rapidly in the presence of polymerizing methyl methacrylate or vinyl acetate. Benzoyl peroxide initiator was not responsible for the considerable difference in racemization rate. The results support the view that primary attack of the growing chain is upon the nitro group and not at an aromatic carbon atom.
Electron spin resonance studies of radicals trapped in polymers
Authors: Atherton N. M. , Melville Harry , Whiffen D. H.
Published: April 2003

Elelctron spin resonance measurements have been used to follow radical concentrations in the copolymerization of methyl methacrylate and glycol dimethacrylate at 23 and 0°C. and the decay of such radicals. The results have been interpreted to give a qualitative picture of the radical trapping process. It has also been shown that the allyl group in allyl methacrylate is comparatively unreactive and does not take much part in either the polymerization of this monomer or its copolymerization with glycol dimethacrylate. Acrylonitrile and α‐methyl acrylonitrile have been shown to give different electron spin resonance spectra illustrating the effect of a chain methyl group. This parallels electron resonance studies of γ‐irradiated acrylates and methacrylates.
The polymerization of acrylonitrile in aqueous solution
Authors: Dainton F. S. , Seaman P. H. , James D. G. L. , Eaton R. S.
Published: April 2003

The kinetics of polymerization of acrylonitrile in aqueous solution when initiated (a) by Fenton's reagent and (b) photochemically using various photosensitizers have been determined dilatometrically over a wide range of conditions. Whenever ferric salts are either present initially or generated in situ, some polyacrylonitrile radicals (S*) are always destroyed by the reaction;

for which k = 6.7 × 10−5 exp { −2.3 kcal./RT} . mole−1 sec.−1. Reaction (1) may be suppressed by addition of fluoride ion. When Fe3+OH− is used as the photosensitizer for 3130 A. light, the intensity exponent x is given by 1 > x > 0.5, being larger the greater [Fe(III)]. This effect is also due to reaction (1) competing with mutual termination, and measurements of d[Fe(II)]/dt confirm this and lead to values of the primary quantum yeild in agreement with published values. The rotating sector technique can be applied and gives kp = 3 × 107 exp { −4.1 kcal./RT} and kt = 3 × 1013 exp { −5.4 kcal./RT} l. mole−1 sec.−1. From observations of the small photo after‐effect, the “build up” to the steady state in both (a) and (b) above, and the effect of mechanical agitation on all these phases of the reaction, it is concluded that some of the observed rate is due to polymerization of radicals buried in polymer particles, P* (one radical per particle) utilizing adsorbed monomer. In mechanically undisturbed systems, P* particles are constant in number throughout the steady state, decay slowly and bimolecularly during the after‐effect, but are not oxidized by Fe(III). The presence of these particles is responsible for the changing order with respect to [m1] from two to unity as [m1] is increased. The value of [m1]c, the concentration at which this changae of order takes place, is dependent on the rate of initiation and air temperature in a way which reconciles previously published conflicting rate equations.
Sur le greffage du polyméthacrylate de méthyle sur le caoutchouc d'Hévéa
Authors: Kobryner W. , Banderet A.
Published: April 2003

La polymérisation de méthacrylate de méthyle par un catalyseur convenable en présence de caoutchouc naturel conduit à la formation d'un mélange composé de polyméthacrylate de méthyle libre, de caoutchoue n'ayant pas réagi et de polymère greffé. Après avoir mis au point la séparation du P.M.M. libre, les auteurs ont élaboré une méthode permettant de détacher les chaǐnes latérales polyméthacryliques greffées sur le tronc polyisoprénique en le détruisant à l'ozone. On a étudié, et on tient compte de la faible degradation que subit le P.M.M. par ce traitement. Les masses moléculaires du P.M.M. libre et du P.M.M. libre et du P.M.M. greffé a permis d'étabir les deux courbes de distribution. Une série de polymères greffés a été préparée en faisant varier les proportions de caoutchouc, de monomère et de catalyseur. On a examiné l'influence de chacun de ces facteurs sur le nombre et la masse des greffons, ainsi que sur le rendement en P.M.M. greffé. On constate que si l'on peut effectivement obtenir des longueurs de greffons très variables, il ne semble pas possible de fixer plus qu'un nombre assez limité de greffons par gramme de caoutchouc. Il apparaǐt que les chaǐnes de P.M.M. libre sont systématiquement plus longues que les chaǐnes greffées. Sur la base de cet ensemble de résultats, les auteurs proposent un mécanisme, selon lequel le greffage se produit uniquement par une réaction de terminaison par combinaison entre le macroradical polyisopréne et les chaǐnes du P.M.M. en croissance.
Irradiation grafting of styrene to high pressure and low pressure polyethylene films
Authors: Hoffman Allan S. , Gilliland E. R. , Merrill E. W. , Stockmayer W. H.
Published: April 2003

The cobalt‐60 gamma irradiation of high pressure and low pressure (Marlex‐50) polyethylene films immersed in styrene monomer to produce graft Polymers was studied as a function of dose, temperature, and film thickness. It was found that grafting generally increased with dose, but reached a level for all films at 10–20°C. and an average dose rate of 228,000 rad/hr., where the grafting was higher for the thinnest films (1.5–2 mils) than the thicker films (up to 20 mils). At 40 and 70°C. and an average dose rate of 93,500 rad/hr., the grafting increased approximately linearly with dose for all films. The post‐effects were also studied and found to be more significant for higher film thickness, higher Polymer crystallinities, and lower temperatures. Observations of the hetergeneity found in the grafted films were described, photos were shown, and these effects were discussed. It was concluded that for the dose rates employed, grafting was probably diffusion‐controlled for all films at 10–20°C. and perhaps for the thicker films at 40°C. The effects of changes in the various independent and dependent variables on the grafting mechanism were discussed and a qualitative picture of this mechanism was described. It was then concluded that the different polycrystalline natures and different thicknesses of the films (as they affected the monomer diffusion rate), and the dose rate or rate of initiation of free radicals were among the most important factors in determining the mechanism and resultant efficiency of grafting.
Graft copolymers from natural rubber latex using visible, ultraviolet, and γ‐ray initiation
Authors: Cooper W. , Vaughan G. , Miller S. , Fielden M.
Published: April 2003

Graft copolymers have been prepared from natural rubber latex and methyl methacrylate using visible, ultraviolet, and γ‐radiation. The influence of monomer concentration, temperature, radiation intensity, and, in the case of photoinitiation, photosensitizer concentration, on polymerization rates and molecular weights have been studied. The proportion of graft polymer is very high initially but falls with conversion and with increase in monomer concentration. Photoinitiated grafting depends on the photosensitizer and on temperature, but with γ‐initiation the fraction grafted is independent of temperature. In the latter case the high proportion of graft cannot be explained in terms ofthe relative G values and concentrations of monomer and rubber. The fall‐off in proportion of graft with conversion is thought to result from microscopic heterogeneous regions formed during polymerization, which are believed to increase in size as polymerization proceeds, thereby reducing further the possibility of grafting. Degradation of previously grafted polymer by prolonged irradiation is not of consequence in this case. Molecular weights of grafted and ungrafted polymers are very similar, except at low monomer concentrations, and a marked feature of this system is their constancy with change in all reaction conditions other than monomer concentration. Estimates of the utilization of radiation energy have been made and it is concluded that on an energy basis γ and photoinitiated reactions are of comparable efficiency.
The production of graft copolymers from poly‐α‐olefin hydroperoxides
Authors: Natta G. , Beati E. , Severini F.
Published: April 2003

The catalytic and autocatalytic hydroperoxidations of the surface of filaments and laminae of isotactic and stereoblock poly‐α‐olefins have been studied. The peroxidation of atactic and stereoblock polymers in solution has also been examined. Peroxidized polymers have been used as radical initiators in the polymerization of vinyl monomers to achieve their grafting on poly‐α‐olefin chains. Some properties of these graft polymers, e.g., antishock properties of polystyrenes grafted on poly‐α‐butene, have been reported.
Morphologische strukturen in polyäthylenen, polyamiden und anderen kristallisierenden hochpolymeren
Authors: Eppe R. , Fischer E. W. , Stuart H. A.
Published: April 2003

Bei der Kristallisation von Niederdruckpolyäthylen aus Lösung in dünnsten Filmenerhält man lamellen‐bzw.fibrillenartige Einkristalle, in denen nach Elektronenbeugungsmessungen die Molekülketten senkrecht zur Lamellenbene bzw. zur Längsrichtung der Fibrillen stehen. Die Moleküle müssen also gefaltet sein. Bei sehr verschidener Wachstumsgeschwindigkeit der kristallographischen Ebenen entarted die Lamellen zu stäbchenartigen Fibrillen. Auch bei der Kristallisation von Lösungs‐ und Schmelzfilmen (bulk‐material) kann die Lamellenstruktur nachgewiesen werden. Lamellen bzw. Fibrillien stellen also eine unter sehr verschiedenen Kristallisationsbedingungen entstehende morphologische Grundform dar. Elektronenoptisch und genetisch sind sie Einkristalle. Zur Erklärung der Molekülfaltung sowie der Entstehung von Lamellen konstanter Dicke wird ein bestimmter Keimbildungsmechanismus diskutiert. Bei der Kristallisation von Polyurethan aus dem Glaszustande zeigen die elektronenmikroskopischen Versuche, dass auch hier morphologische Grundformen entstehen. Ihre Ausbildung kann auch im Röntgenkleinwinkeldiagramm verfolgt werden. Amorphes, glasklares Terylen zeigt schon beim Tempern bei 110° Sphärolithe, deren Wachstum lichtmikroskopisch beobachtbar ist. Die Molekülketten müssen also bereits weits unterhalb des Schmelzbereiches eine viel grössere Kettenbeweglichkeit besitzen, als bisher angenommen. Genügend teif abgeschrecktes Polyurethan ist im Elektronenmikroskop strukturlos und zeight auch keinerlei Kleinwinkelstreuung. Auch hier zeight sich zwischen der Ausbildung morphologischer Strukturen und den scharfen Röntgenkleinwinkelinterferenzen ein enger Zusammenhang. Das alte Bild des Kristallin‐amorphen Gefüges vermag die hier geschilderten Erscheinungen nicht zu erklären.