bluuebunny/crossref_metadata_2025 huggingface dataset:
A kinetic analysis of swelling of rat tail tendon
Authors: Elden Harry R. , Feldman Marsha
Published: April 2003

Interaction of water with connective tissue is an important biophysical process. The chemical and physical morphology of tendons is a complex syncitium of collagen (procollagen + collastromin), mucopolysaccharide (aqueous phase + dense phase), and water (free and bound). It is proposed that a kinetic analysis of swelling of tendons might add new facts concerning the properties of the above tissue system. The present study shows that although diffusion may be the transport basis for swelling, there exists an anomalous dependence of diffusion on time of swelling. It is proposed that the velocity of swelling (dW/dt) is equal to a term Ks(A/W − BW), the latter embodying a specific rate constant Ks, a driving factor A, and a retardation factor B which relates transitory tendon weight W to the initial weight W0, the equilibrium weight W∞ and time t. When this equation is integrated, a working expression is obtained that agrees satisfactorily with experimental data. It is supported further by theories of swelling of anisotropic gels. Data plotted in the form of log (W2∞ − W2)/(W2∞ − W20) versus t showed good agreement with linearity required by the above rate equation. Longitudinal stress decreased swelling ratio W∞/W0, but sped up attainment of equilibrium.
Molecular weight distribution of linear polyethylene by sedimentation velocity analysis
Authors: McCormick H. W.
Published: April 2003

The molecular weight distribution of high density polyethylene and polymethylene has been measured by analysis of sedimentation velocity experiments carried out at high temperatures. The solvent, α‐bromonaphthalene, produced less sensitivity of flotation to molecular weight than could be expected for a highly desirable but presently impossible θ‐solvent. The molecular weight distributions obtained by this method are compared with those obtained by solution precipitation fractionation procedures.
Copolymerization of α‐pyrrolidone and ϵ‐caprolactam
Authors: Kobayashi Fumio , Matsuya Koichi
Published: April 2003

Copolymerization of α‐pyrrolidone and ϵ‐caprolactam has been carried out in the presence of sodium and acetyl compounds. A large amount of both catalysts is necessary to obtain a comparatively good yield. Infrared absorption measurement was adopted to obtain the polymer composition. The compositions of unreacting monomer were determined by equation: D958/D994 = 0.501(CclCpy), where D958 and D994 are optical densities at 958 and 994 cm.−1, which are characteristic absorptions of ϵ‐caprolactam and α‐pyrrolidone, respectively, and Ccl and Cpy, are concentrations of monomers in weight. The polymer composition was calculated from this composition of residual monomers. The polymerization was followed by this analysis and it was found that the α‐pyrrolidone polymerized a t the early stage of reaction while ϵ‐caprolactam reacts with a steady rate. Higher temperature made this phenomenon distinguishable and the degradation of α‐pyrrolidone was observed. The optimum temperature for polymerization was 90–110°C. The stability of α‐pyrrolidone anion explains these phenomena, as this anion promotes alkaline‐salt formation and degradation and reduces the chain numbers. The prepared copolymers have low melting points and good solubilities which vary according to composition. The melting point of the copolymer whose composition is 1 mole caprolactam: 1 mole pyrrolidone is as low as 140°C. and this polymer shows good solubility in ethanol. Apparent monomer reactivity ratios indicate that the copolymers formed are block copolymers.
Activity coefficients of small ions in ion‐exchange resins
Authors: Lakshminarayanaiah N.
Published: April 2003

Crosslinked phenol sulfonic acid resins in the form of rods have been prepared. Anion uptake by these resins in equilibrium with aqueous solutions of NaCl, NaBr, Na2CO3, and Na3C6H5O7 at 30°C. in the concentration range 0.001–3.0N, their density, water content, and exchange capacity have been determined. From these data, activity coefficients of small ions in the resin phase have been calculated and compared with the values derived by the existing theories of Mackie and Meares, and Lazare et al. The agreement between the observed and calculated values is not satisfactory.
Static electricity in polymers. II. Chemical structure and antistatic behavior
Authors: Shashoua Victor E.
Published: April 2003

From studies of the rate of buildup and decay of positive and negative charges on the surfaces of vinyl and condensation polymers, a number of general observations were obtained correlating the polymer chemical structure with antistatic behavior. Polymers with functional groups such as COONa, SO3Na, HCONCH3, CONEt2, P (NMe2)3, and imidazole were found to have good antistatic properties. These functional groups were more effective in improving the antistatic properties of polymers when they were used as side chain substituents than when they were employed as part of the main polymer chain. A number of highly water‐sensitive and water‐soluble polymers were found to have extremely poor antistatic properties, indicating that there is no direct correlation of antistatic properties with hydrophilic character. A new parameter, the charge selective power of a substance, was devised to describe the charge polarity preference of a given substance. It is defined by the equation: σ = (τ+ – τ–)/τRMS, where τ+ is the halflife of charge decay for positive charge, τ− is the halflife of charge decay for negative charge, and τRMS is the root‐mean‐square halflife of charge decay. The charge selective power of a substance was found to correlate well with the assignments of substances in the tables of triboelectric series. The effect of impurities on charge decay properties and the charge selective power of polymers was found to be extremely important in influencing antistatic behavior. The synthesis of the following polymers with specific functional groups is described: polyvinylpentamethyl phosphoramide; the poly‐N‐dimethylurea derivative of polymethylolacrylamide; poly(N‐acrylyl morpholine); poly( N‐acrylyl pyrrolidine).
Radiation damage in oriented polyamides
Authors: Kashiwagi Michio
Published: April 2003

Oriented polyamides were irradiated with 1.5‐M.e.v. electrons and the paramagnetic resonance was examined to determine the radical species. The spectrum is composed of two radical species which decay at different rates. The predominant radical has a spectrum with three main lines (intensity ratio; 1:2:1), each split into two. The doublet splitting changes with the rotation of the magnetic field, while the triplet splittings undergo slight change. The spectrum indicates that the radical is of an unpaired electron interacting with one σ‐proton and two equal π‐protons. In addition, the width of the individual lines is broad (half width = ca. 18 gauss) and it is presumably due to the ill‐resolved hyperfine structure of NH group. These confirm that the radical is CONHCHCH2 as indicated by the findings of Burrell on irradiated amides. The other radical has a five‐line spectrum, which indicates that the radical may be of the type resulting from a CC bond scission, although not fully investigated.
A general kinetic scheme for ziegler‐type polymerizations
Authors: Reich Leo , Stivala S. S.
Published: April 2003

A general kinetic scheme is postulated for Ziegler‐type polymerizations. The scheme may be used to explain either qualitatively or quantitatively the dependence of rate on monomer, alkyl, and metal halide concentrations, and on catalyst ratio. Molecular weight and temperature considerations are discussed in the light of the general kinetic scheme. Dual active sites, upon which monomer molecules may be adsorbed and oriented in a unique manner and which could explain the stereospecific polymerization of α‐olefins as well as the activities of Ziegler‐type catalysts are also discussed.
Molecular configuration of branched macromolecules
Authors: Notley N. T.
Published: April 2003

Macromolecules with very long backbone and a multiplicity of side chains have been prepared. Polystyrene with stearylamido and polystyrene with laurylamido side chains were obtained by the copolymerization of p‐vinylstearanilide and of p‐vinyllauranilide with styrene. Polymers were made suitable for configurational studies by repetitive precipitation fractionation. Light‐scattering and viscosity studies on dilute solutions indicated however that the effect of side chains on molecular volume was secondary in importance to the effect of variations in fractionation efficiency. Hydrogen succinate side groups on secondary cellulose acetate were obtained by a reaction on the polymer which was demonstrated to be nondegradative. A series of polymers was obtained with the same backbone molecular weight and varying substitution. A steric parameter was derived from viscosity measurements in acetic acid and its dependence on increasing extent of succinylation showed a progressive stiffening of the cellulose chain.
On the fractionation of polypropylene by coacervation
Authors: Redlich O. , Jacobson A. L. , McFadden W. H.
Published: April 2003

In the development of a method for the molal weight fractionation of polypropylene some solubility data were collected. Consistent fractionation results were obtained. The size of the fractions (several grams) was sufficient for the investigation of the influence of the molal weight and its distribution on various properties.
The nature of active components in catalytic systems prepared from TiCl3, monoalkylaluminum dihalides, and electron‐donor substances, in the polymerization of propylene
Authors: Zambelli A. , Dipietro J. , Gatti G.
Published: April 2003

The reaction of two molecules of AlRCl2 with an electron donor molecule D, gives rise to the practically quantitative formation of AlR2Cl and AlCl3.D. This can explain the catalytic activity in the stereospecific polymerization of propylene to isotactic polymer of the systems prepared from violet TiCl3, AlRCl2, and an electron‐donor substance. These systems have the same degree of stereospecificity as the systems consisting of AlR2ClTiCl3 (violet).
Homogeneous anionic polymerization. I. Molecular weights of polystyrene initiated by sodium naphthalene
Authors: Morton Maurice , Milkovich Ralph , McIntyre D. B. , Bradley L. J.
Published: April 2003

A study has been carried out on the molecular weight distributions of polystyrene initiated by sodium naphthalene in tetrahydrofuran solution. Stringent high‐vacuum techniques were used in order to minimize initiator destruction or chain termination. Molecular weights were measured by osmotic pressure, dilute solution viscosity, light scattering and sedimentation equilibrium. In general, the molecular weight distributions found were quite narrow, as predicted, and corresponded to a stoichiometry of one polymer chain for two initiator molecules. However, the breadth of the distribution was very sensitive to experimental conditions, the M̄w/M̄n values found ranging from 1.1 to 1.5. At the higher molecular weights, there was some indication of a chain transfer reaction, leading to a lower molecular weight than expected, as well as a broadening of the distribution. This transfer reaction did not appear to be due to any transfer step between the short‐lived radical‐anions and the solvent.
Homogeneous anionic polymerization. II. Molecular weight of polystyrene initiated by lithium alkyls
Authors: Morton Maurice , Rembaum A. A. , Hall J. L.
Published: April 2003

A study has been carried out on the molecular weights and their distribution for polystyrene prepared by means of ethyl and butyl lithium initiators, using benzene and tetrahydrofuran as solvents. Stringent high vacuum techniques were employed in order to minimize any destruction of initiator or termination of growing chains in these anionic polymerizations. Under these conditions, it was found that the stoichiometry corresponded to the formation of one chain from each initiator molecule. Furthermore, the molecular weight distribution could be made very narrow (M̄w/M̄n = 1.05 – 1.1) in these cases, where the initiation reaction was very rapid compared to the propagation step. In the case of the benzene systems, the initiation reaction was too slow, leading to a broadening of the molecular weight distribution, and this could be circumvented by a “seeding” technique whereby all the chain anions were pre‐initiated before the main polymerization took place. The alkyl lithium initiators were found to react rapidly with THF at room temperature, but the styryl lithium apparently did not.
Effect of solid polymer interaction on transition temperature and diffusion coefficients
Authors: Kumins Charles A. , Roteman Jerome
Published: April 2003

It has been shown that a nonreinforcing solid such as titanium dioxide can radically alter the glass transition temperature of the model polymer, poly(vinyl chloride–vinyl acetate) copolymer after being mechanically incorporated within it. The Tg values were either higher or lower than that of the original unfilled polymer, depending on the volume fraction of the solid. The magnitude of these changes is in some cases as great as 49°C. This phenomenon was explained on the basis of adsorption of the acetate radicals on the surface of the solid and the breaking of interchain hydrogen bonds. The changes in segmental mobility of the polymer as indicated by the variation in Tg were also verified by gaseous diffusion studies.
Radiation‐induced graft polymerization of styrene to nylon
Authors: Odian George , Sobel Marjorie , Rossi Albert , Klein Robert , Acker Terese
Published: April 2003

It was observed in the gamma radiation‐induced graft polymerization of styrene to nylon that dilution of the styrene with methanol greatly accelerates the rate of styrene grafting. The compositions of the solutions absorbed by the nylon on equilibration with the various methanol—styrene solutions were determined. These results showed that the concentration of styrene available for the grafting reaction is much greater when the styrene—methanol solutions are employed than when undiluted styrene is employed. It was found that the values of k/kt for these graft polymerizations are increased by a factor of 105 compared to the corresponding value in homopolymerization. These increases in the k/kt term are ascribed to the greater viscosity of the medium in which the grafting reaction takes place and to the immobilization of the graft polymer chains by the Trommsdorff‐type effect of methanol. A discussion is presented of the applicability of steady‐state kinetics, as well as of the various competing reactions, in the graft polymerization.
Polymerization of phosphonitrilic chloride trimer at high pressures and temperatures
Authors: Soulen J. R. , Silverman M. S.
Published: April 2003

Polymerization of phosphonitrilic chloride trimer at pressures of 10 kbars and above has shown that increasing pressure favors the formation of the rubbery high polymer thermodynamically, but slows its rate of formation. There appears to be no difference in hydrolytic or thermal stability between elastomer formed under high pressure conditions and that obtained by the more usual polymerization at 1 atm.
Polymer NMR spectroscopy. VIII. The influence of the pH of the polymerization medium on the stereochemical configuration of polymethacrylic acid
Authors: Bovey F. A.
Published: April 2003

It is shown that when methacrylic acid is polymerized in an aqueous system, the stereochemical configuration of the polymer, deduced by observation of the high resolution NMR spectra of polymethyl methacrylate samples prepared by methylation, is markedly influenced by the pH of the system. Syndiotactic propagation is favored at higher pH, presumably because coulombic repulsion between negatively charged monomer and negatively charged growing polymer radicals increases the free energy of activation for isotactic monomer placement.
Gas transmission in irradiated polyethylene
Authors: Bixler Harris J. , Michaels Alan S. , Salame Morris
Published: April 2003

The transmission of helium, nitrogen, methane and propane was studied in samples of a high pressure, branched polyethylene (46% crystalline) irradiated to a dose in air of 108 roentgens from a Co60 source. By using a time‐lag apparatus the permeability, diffusion, and solubility constants were measured in the temperature range 0‐55°C. These data were compared with those obtained in samples of the above polymer beforeirradiation. Infrared analysis indicates that oxidation, unsaturation, and croaslinking had resulted from irradiation of the polymer. Because of a possible gradient in chemical composition through the irradiated films, the usual analysis of the time‐lag data may not have been applicable to the present work. The apparent diffusion and solubility constants were, however, qualitatively consistent with the anticipated effects of the chemical and physical changes resulting from irradiation. The apparent solubility constants were uniformly higher by 40% in the irradiated film as compared to the values in the unirradiated films. No reduction in crystallinity was observed upon irradiation, so this increase was ascribed to the effect of chemical composition changes. A thermo‐dynamically consistent increase in the apparent heats of solution was also observed. The apparent diffusion constants were lower in the irradiated samples with the fractional reduction increasing with gas molecular diameter. The reduction for helium was 30%, while that for propane was 54%. The apparent energies of activation for diffusion showed no significant change upon irradiation. Arguments are presented to indicate that the reduced apparent diffusion constants apparently arose from the mild cross‐linking which had occurred in the amorphous phase. Comparisons are made between the gas transmission data obtained in the unirradiated samples with those for other high pressure, branched polyethylenes studied in this laboratory in light of a simple model for gas flow in the crystalline‐amorphous matrix.
Depolarization measurements of polymer solutions at high dilutions. Part II
Authors: Kalpagam V. , Rao M. Ramakrishna
Published: April 2003

Depolarization measurements of transversely scattered light were determined for well fractionated samples of poly(methyl methacrylate) in methyl ethyl ketone and a critical consolute mixture of methyl ethyl ketone and isopropanol (1 : 1 by volume). ρu and ρv in methyl ethyl ketone decrease with increasing concentration and tend to become constant above a certain critical concentration, while in the critical consolute mixture, the values decrease steadily with increasing concentration. The ρh values increase with increasing concentration in methyl ethyl ketone, while in the critical consolute mixture they are independent of concentration; this indicates that the size does not change in critical consolute mixture. The individual components Hv and Vv are analyzed for the poly(viny1 acetate) and poly( methyl methacrylate) systems studied by plotting Hv,/C and Vv,/C versus concentration. The observed discrepancies from Doty's predictions are explained.
Viscosities of dilute solutions of polymethyl methacrylate
Authors: Moore W. R. , Fort R. J.
Published: April 2003

Viscosities of dilute solutions of six fractions of polymethyl methacrylate in the molecular weight range of 48,000–400,000 have been obtained with benzene, toluene, chloroform, tetrachloroethane, and n‐amyl methyl ketone as solvents at different temperatures in the range 25–60°C. There is evidence for association of polymer in amyl methyl ketone, and degradation in tetrachloroethane is possible at higher temperatures. Variations of [η] and of k′ with solvent agree generally with those observed by other workers. Where comparison is possible, values of K and a in the expression [η] = KMa are also in general agreement with other values. Values of K′ in the Flory equation [η] = K′M1/2/α3 may possibly vary with solvent, and it is suggested that in cases where solvation of polymer occurs, the chains may be prevented from adopting the unperturbed configuration adopted in less polar solvents. [η] increases with increase of temperature in all cases but that of tetrachloroethane, but there appears to be a maximum value near 53°C. with both benzene and amyl methyl ketone. The variation of the exponent a with temperature is similar to that of [η]. In the cases of benzene and chloroform, the temperature coefficient of [η] seems to be primarily due to changes in the value of the swelling factor α, but in other cases changes in the value of (r̄02/M) are important, r̄02 being the mean square unperturbed end‐to‐end distance of the polymer chains.
Éatude de l'influence du tetrahydrofurane sur la radioreticulation du chlorure de polyvinyle
Authors: Wippler C. , Gautron R.
Published: April 2003

In this paper an attempt was made to explain the crosslinking mechanism of PVC, when irradiated in the presence of tetrahydrofurane. Taking into account several experimental results, a very likely conclusion seems to be that a bridge between two PVC molecules consists in a THF molecule, of which the ring has been opened by the combined effects of the irradiation and of the chlorine or hydrochloric acid evolved from the PVC.
Syndiotactic polyvinyl formate and derived polyvinyl alcohol
Authors: Rosen Irving , McCain G. H. , Endrey A. L. , Sturm C. L.
Published: April 2003

A study was made of the effect of polymerization temperature on the syndiotacticity of polyvinyl formate. Vinyl formate was polymerized with ultraviolet light initiation in the temperature range from −20 to +30°C. The value of (Ep — Et)/2 obtained, 4.5 kcal./mole, is characteristic of those values obtained by other workers for the free radical‐initiated polymerization of vinyl acetate. A linear relationship was found to exist between the viscosities of the polyvinyl formates and those of the derived polyvinyl alcohols. The degree of polymerization of polyvinyl formate may be calculated from the equation: [η] = 4.42 × 10−3 DP0.63. The low temperature polymerization of vinyl for‐ mate results in more syndiotactic polymer, as shown by x‐ray diffraction. Polyvinyl for‐mate obtained at more elevated polymerization temperatures did not demonstrate the same degree of order. No difference was found between the infrared spectra of the polyvinyl formates. The polyvinyl alcohol derived from polyvinyl formate polymerized at low temperatures (0 to −35°C.) exhibits water resistance and forms a colored iodine complex similar to that obtained with the syndioactic polyvinyl alcohol derived from polyvinyl trifluoroacetate. Conventional polyvinyl alcohol and that derived from polyvinyl acetate polymerized at −30°C. do not exhibit the same properties. Minor differences in the 1,2‐glycol content in the various polyvinyl alcohols do not account for the differences in the observations. The amount of head‐to‐head addition in various vinyl aliphatic esters seems to be related to the inductive strength of the acid portion of the ester. No difference was found between the crystallinities of the various polyvinyl alcohols, as measured by film density. Heat treatment increases the crystallinities about the same amount, but the water resistance of the stereoregular materials remains higher. From the good correlation between the observations made on polyvinyl formate and the derived polyvinyl alcohol, it is concluded that syndiotactic polyvinyl formate, and hence syndiotactic polyvinyl alcohol, is obtained by the low temperature free radical‐initiated polymerization of vinyl formate. Increased syndiotacticity is more readily obtained in polyvinyl formate than in polyvinyl acetate, indicating the greater influence of inductive effect compared with the steric effect in controlling stereoregularity during free‐radical propagation.
Polyethers. XI. Polymerization ofDL‐propylene oxide with optically active catalyst systems
Authors: Chu Nan Shieh , Price Charles C.
Published: April 2003

The polymerizations ofL‐propylene oxide by aluminum isopropoxide–zinc chloride, ferric chloride–propylene oxide, and diethylzinc–water catalysts have been studied further and analyzed in terms of the source of stereocontrol in producing isotactic crystalline polymer. The polymerization ofDL‐propylene oxide by optically active complexes of the above catalysts with poly(L‐propylene oxide) and with a catalyst formed from triisobutylaluminum andL‐propylene glycol failed to produce any evidence for stereopreference by the catalysts for theL‐ orD‐molecules.
Copolymerization studies. III. Reactivity ratios of model ethylene copolymerizations and their use in Q–e calculations
Authors: Burkhart R. D. , Zutty N. L.
Published: April 2003

Monomer reactivity ratios for the copolymerization of ethylene (M2) with n‐butyl acrylate, vinyl chloride, vinyl acetate, and vinyl fluoride have been measured at 1000 atm. The respective values and the experimental temperatures are r1 = 11.9, r2, = 0.03, 70°C.; r1 = 3.6, r2 = 0.24, 90°C.; r1 = 1.08, r2 = 1.07, 90°C.; r1 = 0.16, r2 = 4.39, 160°C. Price Q and e values for ethylene calculated from these reactivity ratios, uncorrected for differences in reaction pressure, are 0.03 and −0.43, respectively. New Q and e values (Q0 and e0) for these four comonomers were calculated on the basis of ethylene rather than styrene as the reference monomer. Assuming that the Q0 and e0 values for ethylene are 1.0 and zero, respectively, the monomer's Q and e0 value are as follows: n‐butyl acrylate, 33.3, + 1.02; vinyl chloride, 4.2, + 0.37; vinyl acetate, 0.93, ∼0; vinyl fluoride, 0.25, + 0.6. These Q0 and e0 values give calculated reactivity ratios which are in reasonable agreement with experimental ones. Good agreement is also obtained when the r2 value for the vinyl acetate/ethylene copolymerization is compared with the directly determined rate constant ratio for the addition of an ethyl radical to ethylene and to vinyl acetate, respectively, calculated from previously published data.
Diffusion‐controlled polymerization of some alkyl methacrylates
Authors: North A. M. , Reed G. A.
Published: April 2003

A study has been made of the nonstationary‐state free‐radical polymerization of methyl, n‐butyl, isobutyl, and 3,5,5‐trimethylhexyl methacrylate in mixed solvents of varying viscosity. It has been found that the termination reaction is diffusion controlled over the complete viscosity range in each case. Values of the ratio kt/kp have been obtained for each monomer in ethyl acetate solvent. The relative decreases in this ratio as the size of the alkyl group increases have been compared with decreases calculated (a) on the basis of translational diffusion of macroradicals controlling termination, (b) on the basis that segmental diffusion of the radical chain end in the coiled polymeric free radical is the rate‐controlling process in termination. Although it has been necessary to consider an oversimplified model of segmental diffusion, the calculated dependence of kt on the size of the alkyl group is in accord with that observed experimentally, whereas decreases calculated on the basis of translational diffusion do not agree with those observed. The results are interpreted as signifying that segmental diffusion of the radical chain end is the rate‐determining step in the termination of the free‐radical polymerization of the alkyl methacrylates, and as providing a simple method of calculating the relative values of the diffusion‐controlled termination rate constant for the polymerization of different monomers.
Syntheses of polyanhydrides. XII. Crystalline and high melting polyamidepolyanhydride of methylenebis(p‐carboxyphenyl)amide
Authors: Yoda Naoya
Published: April 2003

The acid‐catalyzed condensation of formaldehyde and aromatic nitrile has been investigated. Methylenebis(p‐carboxyphenyl)amide was synthesized in 90% yield by the interaction of p‐cyanobenzoic acid with formaldehyde under the influence of conc. sulfuric acid. Polycondensation of methylenebis(p‐carboxyphenyl)‐amide was carried out with acetic anhydride at 260–365°C. under vacuum and under a N2 atmosphere. The linear crystalline polyamidepolyanhydride thus obtained has a melting point at 325–330°C. and exhibits excellent stability towards thermal and hydrolytic degradation. It was confirmed from the experimental evidence that the introduction of the amide linkage in the main chain of the polymer increases the melting temperature of crystallite owing to the formation of intermolecular hydrogen bonds within the molecule of polyanhydride repeating unit. The molecular structure was inferred on the basis of infrared spectra and the x‐ray diffraction pattern of the polyamidepolyanhydride. The correlation between cohesion energy per chain unit and crystalline melting temperature of various aromatic and aliphatic polyanhydrides is discussed in detail.
Oxidative crosslinking of polyethylene by ultraviolet light
Authors: Cotten G. R. , Sacks W.
Published: April 2003

The mechanism of weathering damage in polyethylene films was studied by measurement of molecular weight (by intrinsic viscosity), content of xylene‐insoluble fraction (gel), and carbonyl group concentration (by infrared analysis) in exposed samples. Results obtained indicate that both chain scission β and crosslinking α occur simultaneously. The effect of thickness and crystallinity of the polyethylene films suggest that the ratio β/α may be dependent upon the oxygen concentration at the site of reaction and, therefore, the rate of penetration of oxygen through the film, at constant intensity of absorbed light. The chain scission reaction appears to be favored in highly crystalline regions.
Inhibition kinetics of the polymerization of styrene. II. Investigations on the effect of s‐trinitrobenzene
Authors: Tüdös Ferenc , Kende Imre , Azori Mária
Published: April 2003

The kinetics of the polymerization of styrene initiated by azo‐bis‐isobutyronitrile was investigated in the presence of s‐trinitrobenzene (TNB). According to the experimental results, the TNB behaves like a weak inhibitor and is transformed into a retarder during the inhibition period. The kinetic laws of this case of inhibition are not known from literature. Therefore, the fundamental kinetic relations of inhibition accompanied by retardation were elaborated. The kinetic equations for the rate of the inhibited polymerization and for the consumption of the inhibitor were deduced. A method was elaborated for the calculation of the length ti of the inhibition period from the apparent inhibition period t' to be determined by extrapolation from the measured dilatometric data. The experimental results obtained with TNB at 40, 50, and 60°C. can be well interpreted by the deduced kinetic relations. According to the computations, the number of macroradicals deactivated by one TNB molecule amounts to 3.14 ± 0.1 at 40°C., 2.98 ± 0.1 at 50°C., and 2.89 ± 0.2 at 60°C. It is pointed out that this surprising value of the stoichiometric coefficient cannot be interpreted by trivial considerations. Finally, the relative reactivity of the TNB compared to that of the monomer as well as the dependence of this reactivity on temperature were determined.
Molecular interpretation of glass temperature depression by plasticizers
Authors: Dimarzio Edmund A. , Gibbs Julian H.
Published: April 2003

The view that the glass transition is basically thermodynamic in nature is used to derive an expression for glass temperature depression by plasticizers. The second‐order transition temperature is given as that temperature at which the configurational entropy first becomes zero as we cool the polymer–diluent system. The concentration of plasticizer, size of the plasticizing molecule, and its flexibility are found to be the main determinants of glass temperature depression. Available experimental data confirm the predictions of the theory, and it is thereby concluded that the thermodynamic view is sufficient to explain glass temperature depression. It is pointed out that data exist which contradict the free volume theory, as applied to glass temperature depression.
Dynamic shear behavior of poly(γ‐benzyl L‐glutamate), poly(D,L‐propylene oxide), and poly(ethyl vinyl ether)
Authors: Saba R. G. , Sauer J. A. , Woodward A. E.
Published: April 2003

The dynamic mechanical properties in shear have been studied for poly(γ‐benzyl‐L‐glutamate), poly(D,L‐propylene oxide), and poly(ethyl vinyl ether) in the 95–100° to 240–340°K. region by use of a torsional pendulum in free decay at frequencies of 0.05–1 cycles/sec. Poly (γ‐benzyl L‐glutamate) exhibits a prominent loss maximum at 288°K. (0.18 cycles/sec.) attributed to reorientational motions principally of the side chains. For poly(D,L‐propylene oxide) two loss peaks are found at ∼120°K. (0.59 cycles/sec.) and 211°K. (0.37 cycle/sec.), being attributed to motion in the amorphous regions of a small (3–4) and large number of segments, respectively. In the case of poly(ethyl vinyl ether) the principal dispersion region is found at ≳230°K., while a secondary loss maximum is located at ∼100°K. This behavior is similar to that reported for polypentene‐1 and polybutene‐1, except that the two motional processes are shifted to lower temperatures.
Thermodynamic properties of rodlike polyelectrolyte solutions in the presence of salts
Authors: Oosawa Fumio
Published: April 2003

A theoretical foundation is given to the experimentally established relation called the additivity law, according to which the thermodynamic and transference properties of linear polyelectrolyte solutions with low molecular salts are described as a superposition of the effects of ions from polyelectrolytes and those from low molecular salts. By employing a cylindrical free volume model for a solution of thin and long rodlike polyelectrolytes and analyzing the Poisson‐Boltzmann equation it is found that the electrostatic free energy is expressed in a special form as a function of the geometry of the system. On the basis of this expression of the free energy, the additivity law is derived by a thermodynamic treatment without an approximate procedure to solve the Poisson‐Boltzmann equation. The additivity is a property not accidental but essential to rodlike polyelectrolytes. The same method is applicable to analysis of the interaction between two parallel rodlike polyions in the presence of low molecular salts.
Stereoregularity in polyvinyl alcohols and esters
Authors: Cooper W. , Johnston F. R. , Vaughan G.
Published: April 2003

From solution properties and x‐ray crystallinities of polyvinyl esters and alcohols derived from several vinyl esters polymerized at different temperatures, it is considered that polyvinyl haloacetates are more regular in structure than polyvinyl acetate, but this regularity has not been proved to result from increased syndiotacticity. It has been found that the crystallinities of polyvinyl trifluoroacetates prepared from vinyl‐acetate via polyvinyl alcohols are comparable with those prepared directly from vinyl trifluoroacetate at similar polymerization temperatures. The x‐ray diffraction patterns of polyvinyl acetate prepared from the monomer and of acetylated polyvinyl alcohol obtained by hydrolysis of polyvinyl trifluoroacetate are identical. Likewise, those of polyvinyl alcohols derived from several different vinyl esters cannot be distinguished from one another. Polyvinyl acetates prepared at high and low temperatures and prepared from the trifluoroacetate all hydrolyze in alkaline solution at substantially the same rate. The significant finding in this investigation is that whereas polymerization temperature has a marked effect on the crystallinity of polyvinyl trifluoroacetate, it has little influence on the water solubility of the polyvinyl alcohols. Water solubility is determined by the structure of the monomer from which the polyvinyl alcohol was obtained.
Polybenzimidazoles. II
Authors: Vogel Herward , Marvel C. S.
Published: April 2003

A polybenzimidazole has been prepared from 3,3′‐diaminobenzidine and phthalic anhydride which has a high molecular weight and very good heat stability. Replacement of the hydrogen atoms on the nitrogen of the imidazole nuclei in a polybenzimidazole does not improve the heat stability as indicated by the properties of poly‐2,6‐(m‐phenylene)‐3,5‐diphenyldiimidazobenzene. Polybenzimidazoles with aliphatic units have been prepared from 3,3′‐diaminobenzidine and the diphenyl ester of succinic and glutaric acids. The diphenyl esters of oxalic and malonic acids did not yield polymers presumably because cyclic amides were formed. Further hydrolytic stability tests on polybenzimidazoles have been reported. Some model compounds have been prepared for comparison of their melting points and absorption spectra with those of the corresponding polymer.
Reaction of polymeric radicals with organometallic compounds
Authors: Huff T. , Perry Eli
Published: April 2003

The reactivities of polystyryl, polymethyl methacrylyl and polyacrylonitryl radicals with thirteen organometallic substrates were measured and correlated at 60°C. The organometallics chosen were saturated, aliphatic derivatives of elements from Groups 2b, 3a, 4a, and 5a of the Periodic Table. Correlation was accomplished by the method proposed by Bamford, Jenkins, and Johnston. The correlation based on the above three monomers allowed the prediction of the chain transfer constant C of four of the tested substrates with an untested radical, the polymethyl acrylyl, with an accuracy of better than 101. Since the correlation was based on absolute values of C which covered the range of 106 and which were accurate to within 100.8, it was concluded that the correlation was a valid one and was useful for predictive purposes. Values of C for untested substrates can be predicted with only a low order of accuracy because data are not available on the polarizability of most compounds. The introduction of oxygen into the vicinity of the metal–carbon bond reduces the values of C drastically and confirms that C is very sensitive to polar factors. There appears to be a correlation between β (the polarizability of the substrate) and β (the intrinsic reactivity of the substrate) within a given group of the Periodic Table. The fact that there is not a general correlation between α and α for the whole Periodic Table suggests that the mechanism of the transfer reaction is different from group to group.
Apparatus for measuring the dynamic tensile modulus of thin polymeric films
Authors: Hansen Orin C. , Fabry Thomas L. , Marker Leon , Sweeting Orville J.
Published: April 2003

A method and apparatus have been developed specifically for the determination of the dynamic tensile modulus of thin polymeric films. A weight is attached to a 2 × 60‐mm. strip of film, the upper end of which is clamped to a phonograph recording head. The recording head is used to set the system into either longitudinal or transverse vibration. The cross‐sectional area of the film is determined in place from the length, the density, and the transverse resonant frequency (the Vibroscope principle). The modulus is found from the dimensions of the specimen and the longitudinal resonant frequency. The apparatus has been used to study the moduli of a series of polymeric packaging films, the dependence of the modulus of polyethylene film on the angle between the long axis of the specimen and the machine direction, the gage dependence of the stiffness of polyolefin films, and the relationship between the modulus and the moisture and glycerol contents of cellophane.
High frequency titrations of polydicarboxylic acid copolymers: Polyitaconic acid‐Co‐styrene and polymaleic acid‐Co‐styrene
Authors: Drougas J. , Timnick A. , Guile R. L.
Published: April 2003

A useful method, more rapid and more accurate than elemental analysis, has been developed to determine the composition of copolymers of itaconic anhydride and maleic anhydride with styrene. The method involves a high frequency titration of the sample. The method can also be used to detect traces of acidic impurities in polymers and in the identification of mixtures of similar acidic copolymers. Titration indicates that the acid segments in the copolymers of itaconic acid–styrene, maleic acid–styrene, and the homopolymer polyitaconic acid act as dibasic acids. The method appears to have a sensitivity that permits identification and approximate resolution of two carboxylate species in the same polymer.
Radiation degradation of polymethacrylates. Dose rate and medium effects
Authors: Shultz A. R. , Roth P. I. , Berge J. M.
Published: April 2003

γ‐Irradiations of polymethyl methacrylate (PMMA) powders confirm observations in literature that air retards the radiation‐induced molecular weight lowering of this polymer. The energy absorptions per scission Ed are 91 e.v. in air at 0.117 Mreps/hr., 76 e.v. in air at 0.70 Mrep/hr., and 56 e.v. in vacuum at 0.117 Mrep/hr. γ‐Radiation degradation of PMMA solutions (5 gm. PMMA/100 ml. solvent) in butanone and in ethyl acetate gave apparent energies per scission of 63 e.v. and 26–30 e.v., respectively. The latter low value is not understood. Poly‐n‐butyl methacrylate (PNBMA) displays considerable sensitivity to air and dose‐rate effects during γ‐irradiation. Apparent energy absorptions per main‐chain scission observed for γ‐irradiated PNBMA powder are: Ed = 454 e.v. in air at 0.117 Mrep/hr. and Ed = 226 e.v. in vacuum at 0.117 Mrep/hr. The latter value is far above the Ed (146 e.v.) observed for electron‐irradiated PNBMA film. To decrease possible chain recombination and/or polymer–polymer crosslinking reactions degrassed solutions of 4.5, 10.0, and 55 wt.‐% PNBMA in ethyl acetate were γ‐irradiated. Apparent Ed values of 74 e.v., 74 e. v., and 226 e. v., respectively were found. Thus, the more dilute solutions give PNBMA scission energies near that of bulk PMMA. The 55 wt.‐% PNBMA solution gives a scission energy indistinguishable from that of bulk PNBMA under the same irradiation conditions. Competitive crosslinking and main‐chain scission are postulated for electron‐irradiated poly‐n‐alkyl methacrylates. The energy per main‐chain scission is assumed constant for all the homologes. The ratio of crosslinked units to chain scissions, α/β, is then found to increase linearly with (n−1), where n is the number of carbon atoms in n‐alkyl groups of the side chain. This scheme yields a consistent explanation of the radiation response of the lower members of the poly‐n‐alkyl methacrylate homologous series. A comparison of light‐scattering Mw and solution viscosity (Mw)v molecular weight changes did not reveal the concurrent crosslinking in PNBMA films undergoing chain scission by 1 m.e.v.‐peak electron irradiation. Some inquiry is made into the theoretical sensitivity of this comparison method.
Degradation of a polycarbonate by ionizing radiation
Authors: Golden J. H. , Hazell E. A.
Published: April 2003

The degradation of a polycarbonate by electron irradiation in oxygen and in vacuum has been examined. It was found that the polymer undergoes chain scission and that crosslinking apparently did not occur, the molecular weights of irradiated specimens were therefore determined from the intrinsic viscosity of methylene chloride solutions. From the relationship of molecular weight to radiation dose the value ofG(scissions per 100 e.v. of energy absorbed) was found to be 0.14 in oxygen and 0.09 in vacuum. The effect of both molecular weight and radiation dose on the mechanical properties of polycarbonate irradiated in vacuum was studied. Conventional tensile properties were examined, and fracture energies were also obtained by use of a tensile impact apparatus based on the flywheel principle which was used to strain the speciments at 340 in./sec. With increase in radiation dose the maximum yield strength and extension fall slowly at first and then rapidly at a dose of approximately 100 Mrad. The elastic modulus is, however, virtually unaffected by irradiation and the attendant changes in molecular weight. The fracture energy falls steadily with radiation dose, and from the results a linear relationship,F= 0.0044Mv− 59, between fracture energyFand molecular weightMvhas been obtained over the range examined, the energy, becoming immeasurably small at molecular weight below 13,500. The results suggested that in this case fracture energy was a better measure of residual strength after irradiation than other tensile properties. The chemical changes caused by radiation lead to greatly enhanced ultraviolet light absorption with a maximum at 305 mμ and a shoulder at 320 mμ. The absorption (E; 1%, 1 cm.), in oxygen and in vacuum was shown to be a linear function,E= 0.020R+ 0.32 of the radiation doseR. The changes in the infrared spectrum, in particular the carbonyl absorption, of irradiated specimens have been discussed. Mass spectrographic measurements showed that degradation proceeded with evolution of H2, CO, and CO2, both in oxygen and in vacuum.
Thermodynamic properties of polymethyl methacrylate and methyl methacrylate
Authors: Warfield R. W. , Petree M. C.
Published: April 2003

From published data the entropy, enthalpy, and Gibbs free energy of polymethyl methacrylate (PMMA) have been calculated over the temperature range 0–260°K. These functions have also been calculated for methyl methacrylate over the range 0–210°K. The entropy of polymerization at 210°K. was found to be 9.63 cal./mole°K. and the free energy of polymerization was found to be −11.8 kcal./mole. The thermodynamic function Cp/T versus T as calculated for PMMA exhibits a maximum at 70–100°K. The number of classically vibrating units per repeating unit of PMMA at 260°K. is 6.38, and the difference Cp–Cv is found to be 0.014 cal./g.°K.
Orientation and strength of branched polymer systems
Authors: Hsiao C. C. , Wu T. S.
Published: April 2003

A previous theory is simplified and extended to analyze the effect of macromolecular orientation on the tensile strength of a branched polymer solid. The analytical result is then compared with some known experimental data for oriented polymethyl methacrylate.
Diffusion of benzene in polyacrylates
Authors: Kishimoto A. , Enda Y.
Published: April 2003

An investigation has been made of the sorption and permeation of benzene vapor in polymethyl acrylate and polyethyl acrylate over relatively wide ranges of temperature and concentration. The mutual diffusion coefficients were estimated from the rates of absorption and desorption, and the steady‐state permeability. The diffusion coefficients determined by the different methods agreed within experimental error, suggesting that the sorption processes for these systems are controlled by truly Fickian diffusion mechanism. By using the equations of Frisch, the time lags for permeation have been calculated as a function of concentration from the diffusion coefficient data, and compared with the observed values. The calculated values agreed with the observed ones, indicating that the nonstationary state of permeation is controlled by a purely Fickian diffusion mechanism. Experimental data for the thermodynamic diffusion coefficients DT of benzene in PMA and PEA have been analyzed in terms of a simple free volume theory previously developed. It is found that, in all cases examined, the derived relation fits well experimental data. Three temperature‐dependent parameters involved in the theory are evaluated, and their variation with temperature are discussed.
Growth and morphology of single crystals of cellulose triacetate
Authors: Manley R. St. John
Published: April 2003

Single crystals of cellulose triacetate were prepared by supercooling dilute solutions in mixtures of nitromethane and n‐butanol. The crystals are approximately square in shape and thicken by spiral growths centered on screw dislocations. The chain molecules are perpendicular to the lamellae which are about 180 A. thick. In spite of their stiffness the molecules appear to assume folded configurations in the lamellae. Various morphological features of the crystals are described and discussed.