bluuebunny/crossref_metadata_2025 huggingface dataset:
Generalized approach to adhesion via the interfacial deposition of amphipathic molecules. II. Adhesion of polyethylene to aluminum
Authors: Schonhorn Harold
Published: April 2003

Oriented monolayer adhesives of radioactive stearic acid have been employed to bond polyethylene to aluminum. Bonding time, bonding temperature, and rate of peel are several of the parameters that were varied to determine their effect on the final peel strength. Techniques for maximizing the resistance to peel are discussed and incorporated in this communication. Peel strengths in excess of 100 lb./in. width are reported with stearic acid as the monolayer adhesive. The peel forces obtained in the present investigation are more than two orders of magnitude greater than those reported in the literature. The only limitation being the cohesive strength of the thermoplastic adhered. Kaeble's peel force theory is described and adapted to our experimental data. Reasonably good agreement is obtained for low peel strengths (≤25 lb./in. width).
Crystallization in starch: The role of ions in the lyotropic series
Authors: Khairy M. , Morsi S. , Sterling Clarence
Published: April 2003

The crystallization (retrogradation) of starch from solution has been investigated as a function of electrolyte composition and concentration. The anion effects follow a lyotropic series which causes retrogradation in the approximate descending order: CNS‐, (PO4≡, CO3=), I‐, NO3−, Br‐, Cl‐, C2H3O2‐, F‐, SO4=. Cations also tend to follow the lyotropic series of Ba++, Sr++, Ca++, K+, Na+, Li+. Increasing concentrations of most salts (except for NaF and MgSO4) result in decreased precipitation of starch. The descending order of ions in the lyotropic series is best explained in terms of the decreasing polarity and decreasing relative intensity of electric charge, due either to increasing ion symmetry or to increasing area of charge distribution as a result of resonance among several configurations. It is suggested that the polar, higher charge intensity in ions at the upper end of the series brings about charging of the starch molecule, which leads to solubilization because of (1) the repulsion of the similarly charged molecules and (2) the aggregation of a water mantle about each molecule.
Polyamides containing phosphorus. II. Structural effects on softening and glass transition temperatures
Authors: Pellon Joseph
Published: April 2003

Glass transition temperatures as a function of structure for phosphorus‐containing polyamides and polyamides containing other heteroatoms are analyzed in terms of the effect of polarity, steric behavior, and bond flexibility differences. The side‐chain alkyl or aryl group carried by phosphorus was expected to increase chain mobility (lower glass transition temperatures) by separating chains and reducing intermolecular interaction. This general effect is offset by decreased mobility due to the greater polarity of the phosphorus groups, and the intramolecular steric hindrance to rotation caused by the alkyl or aryl group on phosphorus. Glass transition temperatures indicate the following order of bond flexibility: (CH2NCH2 ≈ CH2SCH2≈ CH2OCH2)> CH2P(R)CH2 ≈ CH2CH2CH2. The phosphorus‐to‐carbon bond showed no enhanced flexibility over a carbon‐to‐carbon bond.
Ultimate tensile properties of elastomers. I. Characterization by a time and temperature independent failure envelope
Authors: Smith Thor L.
Published: April 2003

The tensile stress at break (σb) and the associated ultimate strain (ϵb) of an elastomer depend on (1) the chemical and topological characteristics of the polymeric network, and (2) the test conditions under which rupture is observed. To separate these effects, the ultimate tensile properties can often be characterized by a “failure envelope” defined by values of σb and ϵb determined at various strain rates over a wide temperature range. Provided time—temperature superposition is applicable, such data superpose on a plot of log σbTϵ/T versus log ϵb, where T is the test temperature (absolute) and T0 is an arbitrarily selected reference temperature. The resulting failure envelope is independent of time (strain rate) and temperature and thus it depends only on basic characteristics of the polymeric network. To illustrate the characterization method, data on two styrene—butadiene gum vulcanizates, SBR‐I and SBR‐II, were analyzed. For SBR‐I, values of σb and ϵb obtained over extensive ranges of strain rate and temperature superposed to give a failure envelope. Data at elevated temperatures also gave a reliable value for the equilibrium modulus. For SBR‐II, data obtained at various temperatures under conditions of constant strain and constant strain rate yielded identical failure envelopes; this strongly suggests that the failure envelope is independent of the test method. A theoretical consideration of the time‐to‐rupture associated with different test methods showed that for given values of σb and ϵb the time‐to‐rupture from the following types of tests should increase in the order: constant strain < constant stress < constant strain rate < constant stress rate.
Random and block copolymers of poly(tetramethyl‐p‐silphenylene‐siloxane) and polydimethylsiloxane
Authors: Merker Robert L. , Scott Mary Jane , Haberland G. G.
Published: April 2003

High molecular weight block copolymers having the structure [(CH3)2SiO]a[(CH3)2‐Si‐p‐C6H4‐Si(CH3)2O](b)n, can be conveniently prepared from the copolymerization of hydroxy end‐blocked dimethylpolysiloxanes and p‐bis(dimethylhydroxysilyl)benzene by use of essentially nonequilibrating catalysts, such as tetramethylguanidine di‐2‐ethylhexoate or n‐hexylamine 2‐ethylhexoate. The values of a and b above may be altered by employing hydroxy‐ended dimethylpolysiloxane of different degrees of polymerization or by preforming tetramethyl‐p‐silphenylene‐siloxane units. If the length of a segment is maintained at a constant value in the copolymers decreasing the mole ratio a/b results in higher tensile strengths and higher melting points which are manifestations of increased degrees of crystallinity. If the mole ratio a/b is held constant, increasing the length of the a and b segments leads to higher melting points and higher tensile strengths again reflecting an increase in the degree of crystallinity. High molecular weight copolymers [η] ranging from 1.0 to 2.1, possessing unstressed (unvulcanized) gum tensiles of 1000–2700 psi and elongations of 500–1000% can be readily obtained by the methods described.
Copolymerization of styrene. I. Copolymerization with styrene derivatives containing nitrile groups in the side‐chain
Authors: Kreisel Moshe , Garbatski Uri , Kohn David H.
Published: April 2003

Styrene was copolymerized in bulk with cinnamonitrile, benzylidenemalononitrile, ethyl benzylidenecyanoacetate, and atroponitrile at 80°C. up to low conversions. The usual reaction scheme of copolymerization fitted only the pair styrene‐atroponitrile. The kinetic scheme of the other three pairs fitted the scheme proposed by Barb, taking into account the effect of the penultimate unit.
Mean square length of random polypeptide chains and the length of protein fibers
Authors: Crewther W. G.
Published: April 2003

Application of statistical mechanical theory gives the expression r2 = 27.9n − 20.3 relating the mean square end‐to‐end length, r2, of a random polypeptide chain in the trans‐form and n, the number of amino acid residues in the chain. The corresponding expressions for the cis and nonplanar forms are r2 = 8.6n − 0.8 and r2 = 15.5n − 4.8 rrespectively. The first of these equations has been used to obtain an expression for the fractional decrease in length of a crosslinked, aligned α‐helical structure when it is converted to the random coil form. The assumptions made are that the crosslinkages undergo little lateral displacement and that the volume remains constant. The expression so obtained is \documentclass{article}\pagestyle{empty}\begin{document}$l/l_{0} = {{\left\{ {23.7n - 17.3 - [10\sqrt {l//l_0 } - 7]^2 } \right\}^{1/2} } \mathord{\left/ {\vphantom {{\left\{ {23.7n - 17.3 - [10\sqrt {l//l_0 } - 7]^2 } \right\}^{1/2} } {1.5n}}} \right. \kern-\nulldelimiterspace} {1.5n}} $\end{document} where l is the supercontracted length of the polypeptide fiber, l0 is its original length and n is the number of amino acid residues between crosslinkages.
Crosslinkages in wool fibers and their relationship to the two‐stage supercontraction of wool fibers in solutions of LiBr
Authors: Crewther W. G.
Published: April 2003

Rupture of a large proportion of the disulfide bonds of wool by reduction and methylation has no effect on the extent of total supercontraction in solutions of LiBr at 98.5°C. Reduction and methylation of the disulfide bonds increases the extent of the first stage and decreases the extent of the second stage of supercontraction. No two‐stage phenomenon is then observed at the normal extent of the first stage of supercontraction. The relationship between the extent of the first stage of supercontraction and the content of residual disulfide bonds is that predicted by the statistical mechanical theory for a structure containing acid‐labile crosslinkages at equal intervals of about 35 residues and disulfide crosslinkages at equal intervals of about 20 residues along the α‐helices of the aligned structures. This is compared with the half‐cystine content of the low sulfur protein fraction of the wool; approximately 1 residue in 18. Conversion of the disulfide bonds of wool into SCH2CH2S crosslinkages causes a decrease in the extent of the second stage and total supercontraction but does not affect the extent of the first stage. The relationship between the extent of total supercontraction, and the content of dithioethylene crosslinkages is almost identical with that observed for the first stage and disulfide content in S‐methyl wool samples. The disulfide and sulfydryl contents of wool are not altered by supercontraction at pH 6. It is concluded that the first stage of supercontraction of wool fibers in solutions of LiBr is due to the conversion of aligned α‐helices into an elastomeric form, the extent of the first stage being restricted by disulfide and acid‐labile crosslinkages. Further contraction occurs during the second stage as a result of sulfydryl‐disulfide interchange reactions which eliminate the restrictive influence of the disulfide bonds. The final extent of supercontraction is limited by acidlabile crosslinkages.
Low temperature solution polycondensation of piperazine polyamides
Authors: Morgan Paul W. , Kwolek Stephanie L.
Published: April 2003

A simple process is described for the preparation of condensation polymers from diamines and diacid halides, which comprises reacting equivalents of the intermediates at about room temperature in an inert solvent together with an acceptor for the by‐product acid. This first paper of a series discusses the formation of polyamides from piperazines and aliphatic and aromatic diacid chlorides. Examples are poly(sebacyl piperazine) and poly(terephthaloyl dimethylpiperazine). Such variables are discussed as types of acid acceptors, solvents, reactant balance, interfering reactions, and the mechanism of the reaction. Some of the polymers are described briefly in terms of melt temperature, solubility, and molecular weight‐viscosity relationships.
Amine acid‐acceptors for the preparation of piperazine polyamides by low‐temperature solution polycondensation
Authors: Morgan Paul W. , Kwolek Stephanie L.
Published: April 2003

Polyamides from 2,5‐dimethylpiperazine and terephthaloyl and sebacyl chlorides, having high molecular weight, were prepared in a single solvent system in the presence of various amine acceptors. Strongly basic, hindered secondary amines were fair acceptors, but tertiary amines were preferred. The tertiary amines performed well when the pKa in water was equal to or greater than the pKa of the amine group on the end of a polymer chain. The polycondensations were affected adversely by acid chloride‐tertiary amine reactions, by precipitation of diamine salts, and under some conditions by precipitation of polymer.
Electron spin resonance of irradiated solution‐crystallized polyethylene
Authors: Salovey R. , Yager W. A.
Published: April 2003

If films containing oriented lamellae of solution crystallized polyethylene are rotated in the external magnetic field, marked anisotropy in electron spin resonance is noted. When the magnetic field is perpendicular to the chains the spectrum consists of ten lines with a hyperfine component separation of 15 gauss. When the magnetic field is parallel to the chains, the spectrum is a sextet with a splitting of 34 gauss. These splittings are in fairly good agreement with the studies of McConnell et al. on irradiated malonic acid single crystals. The high resolution and stability of electron spin resonance spectra of irradiated polyethylene crystallized from solution suggest greater perfection of crystalline order than in elongated fibers. Moreover, the results on solution crystallized polyethylene indicate that the alkyl radicals are formed at random in the crystalline matrix.
Effect of copper on the autoxidation of cellulose suspended in sodium hydroxide solution
Authors: Michie R. I. C. , Neale S. M.
Published: April 2003

A kinetic study has been made of the depolymerization of cotton cellulose immersed in aerated solutions of sodium hydroxide and in solutions of sodium hydroxide containing dissolved copper. In absence of (added) copper the reaction rate is proportional to the thermodynamic molal activity of the sodium hydroxide over the concentration range 2–14N. Addition of copper causes an increase in the rate but to an extent which depends on the alkali concentration; with constant copper concentration and with increasing alkali concentration the rate now passes through a maximum at approximately 6N sodium hydroxide. The decrease in rate above 6N alkali has been ascribed to the increasing importance of oxygen solubility and of diffusion which become rate determining factors at the higher alkali concentrations. In 4N sodium hydroxide and at low copper concentration diffusion is taken to be unimportant; under these conditions the rate is proportional to the concentration of copper in the solution external to the cellulose but is relatively insensitive to the total amount of copper absorbed by the cellulose. However, it has previously been shown that the overall absorption of copper is probably due to contributions from two different sorbing sites in the cellulose anhydroglucose unit. The rate is found to be approximately proportional to the calculated extent of absorption by the site postulated to form the less stable complex with copper. There is some indication that copper bound in this latter position is responsible for the catalytic depolymerization.
Main‐chain degradation and thermal stabilization of polyoxymethylene by ionizing radiation
Authors: Torikai Sadao
Published: April 2003

Polyoxymethylene dihydrate was irradiated in vacuum and in air at room temperature by γ‐rays from Co60, and the change of its thermal stability was examined. The logarithm of viscosity number decreased linearly with the logarithm of dose both in vacuum and in air. The decomposition curve of irradiated polyoxymethylene in vacuum at 200°C. can be divided into two components. The percentage of stable polymer of the irradiated polyoxymethylene dihydrate increased with decreasing solution viscosity, attained a value of 80–95%, and was expressed approximately as function of η/η0. In case of irradiation in air, the stabilization was often invalidated by oxygen. The after‐effects of irradiation on the stabilization could not be detected under the irradiation conditions examined in the present study. In decomposition in vacuum at 250°C., the irradiated polyoxymethylene dihydrate showed a curve of three components. It seems certain that the irradiated polyoxymethylene dihydrate consists mainly of three kinds of polymer differing in their thermal stabilities. The most stable polymer comprises about one‐fourth of total stable polymer. These facts might be explicable with the formation of formyloxy and methoxy endgroups by the disproportionation reaction of radicals produced primarily by main chain scissions. The inclusion of stable polymer before irradiation was noted in the case of the polyoxymethylene produced in the post‐polymerization of irradiated solid formaldehyde.
Effect of molecular weight and its distribution on stretching of polyacrylonitrile gel
Authors: Kobayashi Hidehiko , Sasaguri Kiichiro , Fujisaki Yoshisato , Amano Toshihiko
Published: April 2003

The present studies were designed to secure information about the effect of molecular weight and its distribution on the hot‐stretchability (defined as maximum hot draw ratio possible without breakage under given condition) of the coagulated gel obtained by extruding a concentrated solution of polyacrylonitrile dissolved in 70% nitric acid into dilute nitric acid solution. After washing, the coagulated threads thus obtained were stretched at 100–140°C. In the case of fractionated polyacrylonitrile, the results obtained under the above conditions showed a maximum hot‐stretchability at M = 80,000. Below this point, hot‐stretchability was lowered with decrease of molecular weight. For polymers having a molecular weight larger than this value, it was also depressed as molecular weight increased and approached a certain value. For whole polymers, hot‐stretchability distribution curves obtained from molecular weight distribution curves by substituting molecular weight with corresponding hot‐stretchability were studied. It was found that the maximum stretchability of a whole polymer was the weight average value of those of its constituent polymer species. The effect of molecular weight of the polymer on the mechanical properties of fibers and their fine structure was investigated by means of tensile and x‐ray measurement.
Diffusion and sorption of vapors in ethylene–propylene copolymers. I. Equilibrium sorption
Authors: Frensdorff H. K.
Published: April 2003

Equilibrium sorption of cyclohexane, n‐hexane, carbon tetrachloride, n‐pentane, benzene, trichlorotrifluoroethane, and methylene chloride in ethylene‐propylene copolymers at 10°, 23°, and 40°C. has been measured. These penetrants range from most soluble to least, in the order given. The propylene content of the copolymer has very little effect on equilibrium sorption, and the heats of dilution are small. The concentration dependence of the results is discussed in terms of the Flory‐Huggins equation. Correlation between sorption and solubility parameter is considered.
Diffusion and sorption of vapors in ethylene–propylene copolymers. II. Diffusion
Authors: Frensdorff H. K.
Published: April 2003

The diffusion rates of methylene chloride, benzene, n‐pentane, n‐hexane, and cyclohexane in a copolymer of 51 mole‐% propylene and 49% ethylene at 23°C. and penetrant concentrations of up to 10 vol.‐% have been measured, as have the rates of benzene diffusion in copolymers containing 31–100% propylene units at 10, 23, and 40°C. Integral diffusion coefficients were calculated from the initial diffusion rates; differential diffusion coefficients from the final rates. Comparison of the two types of diffusion co‐efficients leads to the conclusion that their concentration dependence flattens out at the very lowest penetrant concentrations. The diffusion coefficients fall and the activation energies rise as the propylene content of the copolymers increases. Diffusion in low‐propylene copolymers occurs at rates comparable to those in natural rubber, while the rates in atactic polypropylene are slower by about an order of 1 magnitude. Even so, the latter are about 10 times faster than in polyisobutylene.
Cationic polymerizations of 3‐methylbutene‐1. II. Polymerizations at extremely low temperatures
Authors: Kennedy J. P.
Published: April 2003

The cationic polymerization of 3‐methylbutene‐1 has been studied at extremely low temperatures e.g., −130°C. and below. Practically no polymerization occurs, even at high catalyst concentrations, and the system lies “dormant” at −150°C. The molecular weight‐conversion curve obtained with AlCl3 is a straight line which can be extrapolated through the origin. The slope of this line is determined by monomer concentrations. Higher molecular weights are obtained at the same conversion with higher monomer concentrations. With boron trifluoride catalyst, the linear part of the curve does not extrapolate back through the origin. Product molecular weights were higher in ethyl chloride than in pentene with BF3 at the same conversion level at −130°C.
Preparation and reactions of p‐cyanostyrene–styrene copolymers
Authors: Beckerbauer Richard , Baumgarten Henry E.
Published: April 2003

Copolymers of p‐cyanostyrene and styrene were prepared by heating p‐iodostyrenestyrene copolymers with cuprous cyanide in N‐methylpyrrolidinone. The p‐cyanostyrene copolymers could not be hydrolyzed to the benzoic acid derivative but were converted to the methyl p‐vinylbenzoate‐styrene copolymer by reaction with methanol and hydrogen chloride. This methyl ester copolymer was partially hydrolyzed to the free acid. A p‐cyanostyrene(11%)‐styrene copolymer was treated with n‐butyl and methyl Grignard reagents to yield the corresponding n‐butyl‐ and methyl‐p‐styryl‐ketone copolymers. In the reaction with n‐butylmagnesium chloride, the intermediate n‐butyl‐p‐styrylketimine copolymer was isolated.
Crosslinked and noncrosslinked diisocyanate‐linked elastomers containing substituted urea groups
Authors: Havlik A. J. , Smith Thor L.
Published: April 2003

A study was made of the preparation and properties of diisocyanate‐linked elastomers prepared from polyoxypropylene glycol (POPG), toluene‐2,4‐diisocyanate (TDI), and toluene‐2,4‐diamine (TDA). The chemical structure and gelation of a series of prepolymers were investigated first. Next, many series of elastomers were prepared at 60°C. in open molds and at 110°C. in closed molds from mixtures in which values of the ratio of isocyanate groups to the sum of the hydroxyl groups and amino groups (R1) and the ratio of the amino groups to hydroxyl groups (R2) were systematically varied. Cure at 60°C. gave tough, noncrosslinked elastomers, the properties apparently resulting from interchain attractive forces, while cure at 110°C. gave covalently crosslinked elastomers having rather similar properties. Glass‐transition temperatures increased linearly with the concentration of substituted urethane groups but were independent of the concentration of substituted urea groups. An explanation for the surprising behavior is presented. The noncrosslinked elastomers were soluble in N,N‐dimethylacetamide (DMA) and similar solvents. Intrinsic viscosities in DMA were found to increase with R1 at constant R2. Young's modulus, tensile strength, and ultimate elongation were determined between −23 and 82°C. At elevated temperatures, the crosslinked elastomers showed near‐equilibrium moduli, while the noncrosslinked ones did not. The number of chains per milliliter for the crosslinked elastomers was calculated from the quantities of excess isocyanate and urea hydrogens, along with an assumed topology for the network. The moduli for both types of elastomers were related to chemical composition. Various relationships between the ultimate properties and equilibrium moduli were evaluated. Extensions up to 5000% with elastic recoveries of better than 90% were noted.
Estimation of copolymer reactivity ratios: An example of nonlinear estimation
Authors: Behnken D. W.
Published: April 2003

The first portion of the paper consists of a brief statement of the statistical procedures involved in obtaining efficient estimates of parameters from experimental data, determining their precision, and selecting optimum experiments. Emphasis is primarily directed toward models in which the parameters appear in a nonlinear fashion. Some of the difficulties and pitfalls which are encountered are discussed; primary among these are the problems arising from linearization schemes and transformations affecting the error structure. References are given which supplement the necessarily cursory discussion given here. Utilizing this background, the second half applies itself to the problem of estimating the reactivity ratios in the copolymer equation. Approximate and exact estimation schemes are described which both guarantee most efficient use of the data and allow objective probabilistic statements to be made about the reliability of the estimates. A graph is presented which allows the experimenter to select the two initial feed ratios for his experiments which provide the most information for the estimation scheme. Use of the graph presumes that order of magnitude estimates of the reactivity ratios can be made in advance. A sequential scheme can be followed when prior information is lacking or is not very precise. When more than two different initial feed ratios are to be used, the optimum ratios for two‐point experiments give a good indication of the proper range to cover.
Phase changes in fibrous macromolecular systems and associated elasticity. Model phase diagrams
Authors: Ciferri A. , Smith K. J.
Published: April 2003

In order to illustrate the concepts of solid–solid and solid–melt first‐order transitions and associated elasticity for an ideally homogeneous fiber where different conformational arrangements of the macromolecules in the crystalline state are possible, phase diagrams were arbitrarily constructed on the basis of reasonable estimates of the variables involved. With some limitations, these diagrams illustrate several situations which might be expected to occur in real systems and the conditions under which one crystalline modification can be expected to be stable or metastable and under which a transition to another crystalline form or to the amorphous rubbery state can be observed. The variables which determine the state of the system were considered to be the external tensile force and temperature, pressure being regarded as a constant. Thermodynamic concepts and relationships used under such conditions were only a generalization of those established by Flory and Gee. Large changes of length of the fiber were assumed to occur during the reversible phase changes. A unified schematic picture of the elastic behavior of a fiber in its different physical states (single phase: crystalline or amorphous; two co‐existing phases: crystal–crystal or crystal–amorphous) is afforded by the construction, on the basis of the phase diagram, of stress–strain isotherms, length–temperature curves at constant load, and stress–temperature curves at constant length.
Photoelastic properties of tightly crosslinked networks
Authors: Blumstein Alexandre
Published: April 2003

The photoelastic properties of tightly crosslinked networks formed from expoxy resins were investigated in the rubbery and in the glassy states. The following resins were used: bisphenol–diepoxy, resorcinol–diepoxy, and trisphenol–triepoxy resins. The anisotropy Δa of the links, the degree of crosslinking N, and the rigidity of the network were varied independently and the variation of the stress‐optical constant with these parameters measured at different temperatures. The results indicate the strong influence of a parameter g depending upon the interactions between the links of the network. g and Δa contribute to the value of the stress‐optical constant in opposite directions and can partially compensate each other. If this parameter is introduced in order to account for the interchain interactions, the theory of rubber photoelasticity can account qualitatively for the photoelastic behavior of these networks.
Polyurethane sulfides containing cyclohexane ring in the polymer chain
Authors: Iwakura Yoshio , Sakamoto Munenori , Awata Yasuhira
Published: April 2003

Polyurethane sulfides of high molecular weight containing trans‐1,4‐cyclohexylene groups were successfully obtained by both methods of polymerization, polyaddition of trans‐1,4‐cyclohexylenebis(N,N‐ethyleneurethane) or trans‐hexahydro‐p‐xylylenebis(N,N‐ethyleneurethane) with polymethylene dimercaptans and polycondensation of bis(chloroformates) with polymethylenebis(β‐aminoethyl thioethers) prepared by reaction of ethylenimine with polymethylene dimercaptans. Comparison of physical properties of the polymers prepared by both methods of preparation indicated that (1) polymer repeating units of polyaddition and polycondensation products were quite equivalent; (2) polycondensation polymers had chloroformyl groups as terminal groups.
Hydration and ion binding of polyelectrolytes
Authors: Ikegami Akira
Published: April 2003

The counterion binding of polyelectrolytes has been investigated with special attention to the change of the structure of water in the neighborhood of charged polymer skeleton induced by the binding. The molar volume change due to this structural change of water was obtained by the method of refractivity measurement. Systems employed were polyacrylic acids neutralized to varying degrees by tetra‐n‐butyl‐ammonium hydroxide or sodium hydroxide in the presence and absence of simple low molecular salts such as NaCl and BaCl2. The results indicate that there are two regions of water around the polyion. In the first “intrinsic” hydration region, water molecules are oriented to individual charged groups. In the second region, water molecules are rearranged by the cooperative action of two or more charged groups on the polyion. The binding of Ba++ or La+++ to the polyion destroys not only the second region but also the first intrinsic region. On the other hand, Na+ ions are bound only in the second region without effect on the first region. The amount of bound Na+ ions estimated by refractivity measurement changes with the charge density of the polyion, showing the characteristic feature as a condensation phenomenon.
Rheo‐optical properties of polymers. V
Authors: LeGrand D. G.
Published: April 2003

A theory of the rheo‐optical properties of polyerystalline polymers has been developed. It is based on a model similar to that used by Debye for his theory of dielectric relaxation. Using the theory, sized of crystals in various types of polyethylene are calculated from rheo‐optical data and compared with results obtained by x‐ray techniques.
Rheo‐optical properties of polymers. VI. Dynamic birefringence
Authors: LeGrand D. G.
Published: April 2003

In previous papers we have presented data on the dynamic birefringence and light scattering from polyethylene. New studies of the dynamic birefringence of polytetrafluoroethylene, silicone rubber, polycarbonate, polymethyl methacrylate, and polyethylene as a function of frequency and temperature have been made. The results are presented and interpreted in terms of various proposed theories. The relationships between the mechanical and optical relaxation spectrum are discussed.
Linear free energy relationship in the diffusion of gases through polymer films
Authors: Kwei T. K. , Arnheim W. M.
Published: April 2003

The general correlation between ΔH†/T and log D0 in the diffusion of gases through polymers is discussed in terms of a linear free energy relationship. It is shown that the diffusion constant D can be expressed as log D = kα + constant, where k is a parameter characteristic of the diffusing gas and α is a parameter characteristic of the polymer. The relationships between structural characteristics of gases and polymers and the respective parameters k and α are discussed. The possible application of similar linear free energy relationships for the purpose of expressing the permeability constant (P) and the solubility coefficient (S) is also suggested.
Mechanism of the mechanical degradation of cellulose
Authors: Ott Ronald L.
Published: April 2003

From electron spin resonance spectra of a ball‐milled cellulose sample, it was established that the mechanical degradation of air‐dry cellulose was characterized by the formation of free radicals. It was shown that iodine increased the rate of mechanical degradation, presumably by preventing the recombination of at least some of the radicals formed during grinding. Since no difference in iodine consumption during grinding was observed between air‐dry and oven‐dry cellulose samples, it was concluded that heterolytic cleavage of cellulose molecules did not occur. The formation of benzyl iodide and cyclohexyl iodide was observed when cellulose was ground with iodine in toluene and cyclohexane, respectively. It is possible that either chain transfer reactions between cellulose radicals and solvent molecules account for the halogenation of the solvent or that the halogenation is due to a hypoiodite structure formed by the reaction of cellulose alkoxy radicals with iodine.
Copolymerization of diethyl phosphonoalkyl acrylates
Authors: Overberger C. G. , Sarlo E.
Published: April 2003

Diethylphosphonomethyl acrylate, diethylphosphonomethyl methacrylate, and 1‐diethylphosphonoethyl acrylate were copolymerized by radical catalysis with methyl methacrylate and, in one case, methyl acrylate. The reactivity ratio values indicate that the phosphorous‐containing monomers enter into the copolymer somewhat less readily than methyl acrylate or methyl methacrylate. Both electronic and steric effects may be operative.
Cold‐drawing of acetone‐crystallized polyethylene terephthalate
Authors: Blakey P. R. , Sheldon R. P.
Published: April 2003

The room‐temperature cold‐drawing behavior of acetone‐crystallized polyethylene terephthalate film has been compared with that of amorphous and heat‐crystallized film. X‐ray diffraction photographs give good resolution in the case of the acetone‐crystallized sample with evidence of molecular orientation in every case. The order of the magnitudes of the yield stresses is acetone‐crystallized < amorphous < heat‐crystallized. Heating of the drawn samples produces disorientation for the amorphous drawn film with an improved resolution of the diffraction photograph for the heat‐crystallized film. It is suggested that the results are in agreement with a picture of a drawing mechanism involving molecular mobility in the amorphous regions and that acetone influences the yield stress by lowering the softening temperature.
Aliphatic polyhydrazides: A new low temperature solution polymerization
Authors: Frazer A. H. , Wallenberger F. T.
Published: April 2003

High molecular weight polyhydrazides have been prepared by a new low temperature polymerization technique from equimolar amounts of a dihydrazide and a dicarbonyl chloride in dialkyl amide solvents. All‐aliphatic polyhydrazides were insoluble in dimethyl sulfoxide, had polymer melt temperatures ranging from 200 to 300°C. Films could be pressed and fibers could be pulled from the melt. Aliphatic‐aromatic and oxalic‐aromatic polyhydrazides which undergo dehydration at different rates had polymer melt temperatures ranging from 250 to 300°C. and inherent viscosities ranging from 0.3 to 1.5. They were soluble in dimethyl sulfoxide, a solvent from which tough films could be cast.
Clay‐catalyzed reactions of olefins. I. Polymerization of styrene
Authors: Bittles James A. , Chaudhuri A. K. , Benson Sidney W.
Published: April 2003

Qualitative observations are reported on the polymerization of styrene with acid clay cracking catalysts. Molecular weights were 500–2000, depending on solvent, catalyst quantity, monomer concentration, and temperature, monomer conversions approached 100%. The reaction rate is rapid at 0°C. and at ambient temperatures and is severely inhibited by water and other proton acceptors. The polymer was structurally the same as polystyrene and contained saturated endgroups formed by solvent termination and by a competitive cyclization reaction. The chain termination products and polymer end‐groups were identified.
Die sekundäre keimbildung bei polyäthylen‐sphärolithen
Authors: Heber I.
Published: April 2003

The growth of two dimensional polyethylene spherulites has been followed in the range of 115° to 125°C. The radial growth velocity vr has been assumed to be determined by the rate of formation of secondary nuclei on the nuclei on the spherulite border. Thus the nucleation theory gives the expression

The critical free energy ΔF* has been calculated for rectangular nuclei ΔF* = x(4σeσe/Δf). This nucleus according to the calculation consists of a single layer of attached chain segments. Specific surface tensions σe/σs of the critical nucleus derived from the radial growth rate on the base of the theory agree with the values obtained for polyethylene single crystals with folded chains. On the base of the known folding length in polyethylene the secondary nucleus consists of three closely arranged folded chain segments 100 A. in length. The satisfactory agreement between the values derived from growth rates of two‐dimensional spherulites and the results obtained on polyethylene single crystals confirms the assumption that the growth velocity of spherulites is determined by the rate of formation of secondary nuclei on their surface.
Density of polyethylene
Authors: Mortimer George A. , Hamner William F.
Published: April 2003

The density of polyethylene produced by free‐radical‐initiated batch polymerization at elevated pressures and temperatures was found to be determined by the amount of short‐chain branching and the molecular weight. The short‐chain branching was shown to depend solely upon the pressure and temperature of polymerization. This branching increased as the pressure was reduced or as the temperature was increased. The molecular weight was shown to have an important influence on the density at much higher molecular weight levels than previously reported (up to 50,000 Mn). The density increased as molecular weight decreased. At a constant polymerization pressure and temperature, the type and amount of initiator and chain‐transfer agent had no effect on short‐chain branching. Inasmuch as the type and amount of these substances do have an effect on molecular weight, they did affect density indirectly through the molecular weight. An equation relating the density, molecular weight, and polymerization pressure and temperature is given.
Random degradation of chain polymers accompanied by partial dissolution of the degraded material
Authors: Mejzler D.
Published: April 2003

Some processes of random degradation of chain polymers in suspension are accompanied by the dissolution of the part of the degraded material having the shortest chain lengths. The molecular weight determinations are then usually made not on the total degraded material, but only on its undissolved part. It is shown that if any two of the following three experimentally determinable values are known: (1) weight fraction of undissolved degraded material, (2) number‐average DP of undissolved degraded material, (3) weight‐average DP of undissolved degraded material, the following parameters may be calculated: (1) the third experimental value; (2) the extent of degradation of the total degraded material and, therefore, the true values of the number‐average and weight‐average DP of the total material; (3) the maximum chain length of the degraded material in solution; (4) the number‐average and the weight‐average DP of the dissolved part of the degraded material; (5) the respective number fractions of the dissolved and undissolved chains in the degraded material. The calculations are carried out for the two conventional models of random degradation, that of Kuhn and that of Montroll‐Simha. For the former model, simple approximate formulas are also given, which yield solutions with a satisfactory accuracy.
Critical analysis of molecular weight distributions derived from fractionation data. I. Column elution
Authors: Kotliar A. M.
Published: April 2003

The evaluation of broad molecular weight distributions, based on the fractionation data obtained by column elution techniques and the Schulz‐Dinglinger approximation, is critically analyzed employing an electronic computer and a solubility function based on the Flory‐Huggins theory. The results, based on Schulz and Wesslau type distributions, show that although some characteristic features may be established, the determined values of the distribution parameters may be greatly in error.
Diffusion and viscosity of polyvinyl acetate‐diluent systems
Authors: Kishimoto Akira
Published: April 2003

The diffusion coefficient of methanol in polyvinyl acetate (PVAc) and the steady flow viscosity of the PVAc‐diethyl phthalate (DEP) system have been studied. In diffusion studies the sorption and permeation of methanol vapor in the polymer were measured over a temperature range above and below Tg of the pure polymer. The mutual diffusion coefficient, D, was estimated from the rates of absorption and desorption from and back to nonzero initial and final concentration, and also from the steady state permeability. The D derived by different methods agreed within experimental error. By using the equation of Frisch, the time lag for permeation was calculated as a function of penetrant concentration from the D data. The calculated values were larger than the observed ones at temperatures slightly above and below Tg, but when the temperature was well above Tg both values agreed with each other. At temperatures below Tg anomalous permeation curves which could not be fully explained at the present stage appeared. In viscosity studies measurements were made over the complete range of DEP composition at temperatures from 10 to 100°C. by using four different experimental techniques. The plot for the logarithm of the viscosity against weight fraction of polymer at a fixed temperature was convex upward at low concentration and then became concave upward at high concentration. In the intermediate region an inflection point appeared. Experimental data for the thermodynamic diffusion coefficient of methanol in PVAc and the isothermal viscosity data for the system PVAc‐DEP have been analyzed in terms of the free volume theory presented previously. It was found that experimental data were well represented by the theory.
Temperature dependence of birefringence in irradiated polyethylene
Authors: Keneally E. , Gard J. , Adler G.
Published: April 2003

The birefringence of irradiated polyethylene was observed as a function of temperature. The data are consistent with a mechanism in which crosslinking limits the growth and annealing of crystallites. Crosslinks formed in material which was oriented at the time the crosslinks were formed, results in an oriented gel. This effect explains the birefringence and the persistence of nucleation sites at high temperatures.
Role of organic diluents in a sol‐phase polymerization
Authors: Guha T. , Biswas M. , Konar R. S. , Palit S. R.
Published: April 2003

The effect of organic solvents on the rate of heterogeneous aqueous polymerization initiated by the K2S2O8Na2S2O4 redox pair has been studied. The separating polymer phase remains in colloidal dispersion, the stability of which is partly due to charge and partly due to hydration. Both the water‐miscible and water‐immiscible organic liquids decrease the rate of polymerization, the limiting conversion, and the molecular weight of the polymers. It has been suggested that the water‐miscible organic liquids preferentially solvate the latex particles and thereby decrease the hydration stability and monomer concentration in the latex particles, whereas the water‐immiscible organic liquids decrease the monomer concentration in the latex particles due to the partition of the monomer between the aqueous and the nonaqueous phases. Thus the fall in the rate and molecular weight of the polymers may be ascribed to the increase in the termination rate by the faster coagulation of the latex particles and dilution of monomer concentration at the reaction site.
Role of organic diluents in a precipitative aqueous polymerization
Authors: Konar R. S. , Guha T. , Palit S. R.
Published: April 2003

The effect of organic liquids on the rate of heterogeneous aqueous polymerization initiated by the KMnO4H2C2O4 redox pair has been studied. The separating polymer phase is a precipitate under experimental conditions. The rate of polymerization, the limiting yield, and the molecular weight of the polymers were found to decrease in presence of organic liquids. This behavior has been ascribed to (1) the increase in the termination rate due to the swelling of the precipitated polymer particles containing trapped radicals and (2) the fall in the monomer concentration at the reaction site.
Molecular weight distribution and viscosity of multichain polymers in ε‐caprolactam polymerization
Authors: Manabe Tomonobu
Published: April 2003

The molecular weight distribution is calculated on the basis that x − 1 indistinguishable monomer units are distributed in f unnumbered branches with no restrictions on the number per branch. The weight fraction of single‐ and multi‐chain polymer mixture of polymerization degree x is for f = 2,

and for f = 3,

where, p is the extent of reaction, Q the number of equivalents that reacts with one mole of monomer, and L the number of equivalents of unreacted groups per mole of monomer. When the limiting viscosity number [η] and the melt viscosity μ are expressed as the function of the (fractionated) degree of polymerization x: [η] = Kv xα and μ = Kμ xβ, the solution and the melt viscosities are expressed as follows:

The relation among the number‐average, viscosity‐average, weight‐average and melt viscosity‐average degree of polymerization is discussed. The relation between the solution and the melt viscosities is also discussed.
Photosensitized polymerization of acrylic monomers. III. Kinetics of polymerization of acrylamide in the absence of oxygen
Authors: Toppet S. , Delzenne G. , Smets G.
Published: April 2003

Acrylamide polymerizes at 25°C. in aqueous solution by photosensitization with eosin, in absence of any reducing agent and of oxygen; a strong photoreduction of the dyestuff proceeds simultaneously. The photopolymerization has been followed gravimetrically, while the rate of photoreduction was followed colorimetrically. The rate of photoreduction is proportional to the absorbed light intensity. The rate constants are proportional to the monomer concentration when this concentration is lower than 0.42 mole/l.; above this value they are independent from it. The rate of photopolymerization is proportional to the square root of the eosin concentration when this concentration is ≤ 10−6 mole/l.; above this value, the rate becomes independent of the eosin concentration. With respect to the monomer the order of reaction varies from 1.5 to 1.85 when the eosin concentration is 0.4 × 10−6 and 6 × 10−6 moles/l., respectively. With respect to the light intensity, the order of reaction is 0.35 when the monomer and eosin concentrations are respectively, 2.8 moles/l. and 0.4 × 10−6 moles/l. The kinetics of photoreduction are interpreted on the basis of a reaction between the excited triplet state of the dye and the monomer, and a kinetic scheme is presented. The kinetics of photopolymerization are explained by a termination process between a growing chain and a primary radical, besides the usual termination process between two growing chains.
Les polymeres à l'interface eau–air
Authors: Jaffe J. , Loutz J.‐M.
Published: April 2003

Even at high superficial dilution (π < 40 mdyne/cm.−1) it is impossible to determine the molecular weight of a flexible polymer. Using statistical equations containing an adjustable parameter it can be accounted for the compression isotherms. This parameter corresponds not to an experimental relation, and is without any physical significance. The polymeric layers can be described by Singer's equation, if one attributes to the term x the significance of an experimental parameter.