Showing papers in "Journal of Polymer Science Part A-2: Polymer Physics in 1967"
229 citations
TL;DR: In this paper, a detailed structure analysis of polyoxymethylene molecule was carried out by the method of three-dimensional Fourier synthesis, where diffraction data were measured on a highly ordered polyoxylene sample prepared from a single crystal of tetraoxane by solid-state radiation polymerization.
Abstract: Detailed structure analysis of the polyoxymethylene molecule was carried out by the method of three-dimensional Fourier synthesis The diffraction data were measured on a highly ordered polyoxymethylene sample prepared from a single crystal of tetraoxane by solid-state radiation polymerization By assuming the anisotropic thermal factors for the oxygen and carbon atoms and taking into account the contribution of the hydrogen atoms, good agreement between the observed and calculated structure factors was obtained; the R factor is 88% The distance between the oxygen atom and the helix axis r(O) = 0671 A is slightly shorter than r(C) = 0691 A The bond distance CO = 1421 A, the angle ∠COC = 112°24′, and ∠OCO = 110°49′ All the internal rotation angles of the skeletal bonds are 78°13′ It is deduced from the experimental results that each crystallite of polyoxymethylene is composed of only one type of helix, right-handed or left-handed
67 citations
TL;DR: In this article, the effect of structural isomerisms in the form of a vinyl side group and cyclization on the wettability of polydimethylsiloxane was investigated.
Abstract: Data on wettability of elastomers should be considered basic to the understanding of all phases of elastomer adhesion. However, no such data in the form of critical surface tensions were available for elastomers other than polydimethylsiloxane. For this study, 18 elastomers were selected to determine the effects of functional groups, of geometrical and structural isomerisms, of copolymerization, and of the induced orientation upon wettability. Most results support the constitutive law of wettability established by Shafrin and Zisman. The effect of structural isomerisms in the form of a vinyl side group and cyclization is discussed. An equation for the calculation of critical surface tension of a copolymer or of a mixture of isomers is proposed as follows:
where Ni is the mole-fraction of the individual monomer in the copolymer and is the critical surface tension of each homopolymer. Most elastomer adhesion studies conducted in the past were concerned with the diffusion theory of adhesion. This study further supports the conclusion on the role of diffusion and adsorption in adhesion advanced in Part I, especially with respect to the physical state of polymer at the time of application. The wettability data in this study could shed some light upon major basic mechanisms involved in elastomer reinforcement.
50 citations
49 citations
TL;DR: Polarized infrared measurements were made on polymer samples to obtain the structural changes occurring during the orientation process as discussed by the authors, and the absorbances of the infrared bands were measured by determining the three components of the absorbance.
Abstract: Polarized infrared measurements were made on polymer samples to obtain the structural changes occurring during the orientation process. The absorbances of the infrared bands were measured by determining the three components of the absorbance. Two components were obtained directly with plane-polarized light while the third is obtained by tilting the sample and extrapolating. Corrections were made for machine optics polarization, sample birefringence, polarizer inefficiency, anisotropy of the index of refraction, and scattering from the film surface. Data are reported for polyethylene obtained from cold-drawn specimens as a function of draw temperature. Polyethylene exhibits no strain-induced crystallization as a result of the chain-alignment process. Annealing of the drawn samples reperfects the distorted crystals.
41 citations
TL;DR: In this paper, the effect of long-chain branching on the size of low-density polyethylene molecules in solution is demonstrated through solution viscosity and molecular weight measurements on fractionated samples.
Abstract: The effect of long-chain branching on the size of low-density polyethylene molecules in solution is demonstrated through solution viscosity and molecular weight measurements on fractionated samples. These well-characterized fractions are analyzed by gel permeation chromatography (GPC), and it is shown that the separation of the polymer molecules by this technique is sensitive to the presence of long-chain branching. By using fractions of branched polyethylene possessing differing degrees of branching, one observes that a single curve is adequate in relating elution volume to molecular weight. This calibration curve is applied in the GPC analysis of a variety of commercial low-density polyethylene resins and it is shown, by comparison with independent osmometric and gradient elution chromatographic data, that realistic values for molecular weight and molecular weight distribution are obtained. The replacement of molecular weight M by the parameter [η]M as a function of elution volume, leads to a single relationship for both linear and branched polyethylenes. This indicates that GPC separation takes place according to the hydrodynamic volumes of the polymer molecules. The comparison of data for polyethylene and polystyrene fractions suggests that this volume dependence of the separation will be observed for other polymer–solvent systems.
39 citations
TL;DR: In this paper, the elastic and photoelastic properties of polyethylene networks were studied at high temperatures, i.e., in the molten state, and the equilibrium swelling was also measured in several solvents.
Abstract: Polyethylene networks were prepared by γ-irradiation of linear polyethylene, both molten and crystalline. The elastic and photoelastic properties of the networks were studied at high temperatures, i.e., in the molten state. The equilibrium swelling was also measured in several solvents. Values of the crosslinking efficiency G of γ-radiation, the molecular, weight Me between entanglements, the optical anisotropy α of the equivalent random link, and the polymer-solvent interaction parameter μ are deduced. Samples prepared by irradiation in the amorphous state showed markedly non-Gaussian elastic behavior. The presence of a large non-Gaussian term in the optical anisotropy is also deduced. The value of α obtained for swollen samples, which showed substantially Gaussian elastic behavior, was 3.9 × 10−24 cm.3, about one-half of that obtained for dry samples. It corresponds to an equivalent random link of only about 5 CH2 units, on the basis of Denbigh's values for bond polarizabilities. The samples prepared by irradiation in the crystalline state showed lower values for α, which also depended upon the degree of crosslinking. This is attributed to the nonrandom chain configurations prevailing at the time of crosslinking. The same samples were found to show more nearly Gaussian elastic behavior, which is attributed to the same cause.
37 citations
TL;DR: The length of the span of the terephthaloyl residue in poly(ethylene Terephthalate) guarantees independence of the conformations of successive repeating units of the chain this article.
Abstract: The length of the span of the terephthaloyl residue in poly(ethylene terephthalate) guarantees independence of the conformations of successive repeating units of the chain. Interactions within units of the chain are amenable to interpretation by comparisons with related polymers; cis and trans conformations of the terephthaloyl residue are given equal weighting. The mean-square dimension ratio (〈r2〉0/M)∞ estimated on this basis is in substantial accord with the value deduced from experiments.
37 citations
TL;DR: In this paper, the infrared absorption spectra of selected crystalline and non-crystalline bands of linear polyethylene was studied and it was shown that the non-caulfield regions in these cases and the pure melt are structurally similar.
Abstract: The infrared absorption spectra of selected crystalline and noncrystalline bands were studied in bulk-crystallized specimens of linear polyethylene which encompassed the extremely wide density range of 0.92–0.99 g./cm.3. The analysis of the data obtained at room temperature yield degrees of crystallinity by infrared methods which are in very good accord with the values deduced from the density measurements. Studies of the infrared spectra as a function of temperature give fusion curves which are in agreement with those obtained by thermodynamic methods. However, in order to obtain these latter results cognizance must be taken of the large negative temperature coefficient of the specific extinction coefficients of the crystalline bands from room temperature to the melting point. The necessary data to account for this phenomena were obtained from studies of the spectra of the n-paraffin, C94H190, where molecular crystals are formed. Analysis of the two gauche bands, at 1352 and 1303 cm.−1, which are assigned to the noncrystalline regions demonstrate that for bulk-crystallized samples of lowest densities the intensity ratio at room temperature is identical to that expected from the pure melt at this temperature. The conclusion is thus reached that the noncrystalline regions in these cases and the pure melt are structurally very similar. For samples of higher density, where the crystallite size is comparable to the extended chain length, the intensity ratio of the two gauche bands is altered. This change could reflect a change in the sequential distribution of gauche bonds. This intensity ratio for crystals formed from dilute solution is very similar to that for the high-density bulk-crystallized material and indicates a similarity in structure of the noncrystalline regions in the two cases.
36 citations
36 citations
TL;DR: In this paper, the α, β, and γ transitions at temperatures between −200 and +100°C were determined from damping and shear modulus data, and compared with their fluorine containing analogs.
Abstract: The α, β, and γ transitions at temperatures between −200 and +100°C. of crosslinked aromatic and aliphatic epoxy polymers were determined from damping and shear modulus data, and compared with their fluorine containing analogs. Loci of segmental relaxation are suggested at various temperatures, and similarities between aliphatic and fluorocarbon segments, and polyethylene and polytetrafluoroethylene are discussed. Two systems of structurally similar monomers 2,2,3,3,4,4-hexafluoropentane diglycidyl ether-1,5 and 1,4-butane diglycidyl ether, and 2,2-bis(4-glycidyl phenyl ether)hexafluoropropane and 2,2-bis(4-glycidyl phenyl ether) propane were polymerized with the aid of two diamine curing agents, namely, ethylenediamine and m-xylylenediamine. Polymers of the aromatic diepoxides showed transitions with peaks at −56°C. and above +70°C. Three main peaks were registered for the aliphatic and fluorocarbon diepoxides: at −125 and at −100°C., at −56°C., and at 0°C. It is suggested that the Tg is affected by an interdependence of relaxation of all components of the polymer main chain.
TL;DR: In this article, single-crystal preparations of polyethylene were treated with the selective oxidizing agent, fuming nitric acid, and the degraded products were examined as regards layer thickness, chemical and weight changes, recrystallization and annealing treatments, and by broadline NMR, as part of a systematic investigation aimed at clarifying the nature of disordered material in single crystals.
Abstract: Single-crystal preparations of polyethylene were treated with the selective oxidizing agent, fuming nitric acid. The degraded products were examined as regards layer thickness (by low-angle x-ray studies), chemical and weight changes, recrystallization and annealing treatments, and by broadline NMR, as part of a systematic investigation aimed at clarifying the nature of disordered material in single crystals. It emerges that there is a disordered-mobile region along the fold surface of the crystals in agreement with other parallel works along similar lines. In a more detailed analysis we can now decompose the nitric acid attack into components affecting the basal and side surfaces, respectively. Taking into account the recrystallization–annealing observations, we infer that the fold surface is heterogeneous with folds of more than one kind. These results were combined with a preliminary molecular weight distribution study by gel permeation chromatography. Taking into account all the available evidence, we are led to suggest a composite structure where surface looseness, coresponding to long loops and hairs, is superimposed on the more regular folded surface. This model is in the process of being tested. The problems concerning the assignment of a value to the amount of surface looseness are being discussed. In addition, a discontinuity in the thermal behavior of the crystals between 75 and 80°C. has been detected.
TL;DR: In this article, the authors used the horizontal shift along the abscissa of the master curve of the zero-shear viscosity of polyvinyl acetate and polystyrene under a wide range of molecular weight M and concentration c dependencies.
Abstract: Molecular weight M and concentration c dependencies of the zero-shear viscosity (η) were measured over wide ranges of M and c for concentrated solutions of linear and branched poly(vinyl acetate) as well as of polystyrene under θ conditions. The log η versus log M and log η versus log c curves for a given system can be superposed by the horizontal shift along the abscissa, giving smooth master curves. From the shift factors the ratio of two exponents β and α, which appear in the following equation, can be evaluated: η = K′(cρ)αMβ, where ρ is the density of the solution and K′ is a constant at constant temperature. The evaluated values of β/α for the systems under θ conditions are equal to or very close to 0.50 as was anticipated from the previous work. The above superposition method was also applied to available viscosity data, and it was found that β/α had a good correlation with a in [η] = KMa. This indicates that the individual molecules in concentrated solutions maintain the same individuality as in dilute solutions, and might be a positive support to the packed sphere model proposed previously by the authors. The effect of solvent on the molecular weight and the concentration dependencies of viscosity was also discussed.
TL;DR: In this article, the results of detailed measurements of osmotic pressure, light scattering, and viscosity of polyvinyl chloride solutions were used to establish the molecular weight dependence of [η] and A2, to estimate the unperturbed dimensions of the poly(vinyl dioxide) molecule, and to analyze critically the [−]−M correlations published hitherto.
Abstract: The results of detailed measurements of osmotic pressure, light scattering, and viscosity of poly(vinyl chloride) solutions are used to establish the molecular weight dependence of [η] and A2, to estimate the unperturbed dimensions of the poly(vinyl chloride) molecule, and to analyze critically the [η]–M correlations published hitherto.
TL;DR: In this article, Bohn et al. measured the thermal expansion and dielectric relaxation of polyacrylonitrile at frequencies from 30 cps to 3 Mc/sec.
Abstract: Thermal expansion and dielectric relaxation of polyacrylonitrile were measured in the temperature range from −75 to 152°C. at frequencies from 30 cps to 3 Mc./sec. The thermal expansion curve and the temperature dependence of logarithmic relaxation time both show an inflection at 85°C. An x-ray study by Bohn reveals that this inflection comes from the thermal expansion of the paracrystalline phase of this polymer, and consequently the transition at 85°C. and the associated relaxation are ascribed to molecular motion in the paracrystalline phase. The relaxation strength increases with increasing temperature above this point. The transition is caused by freezing of the bending vibration of chains whereas the relaxation results from rotational vibration. The length of segments in this phase is roughly estimated to be ca. 100 A. by comparing the observed relaxation strength with the theory developed on the basis of the above considerations.
TL;DR: In this paper, the temperature dependence of x-ray small-angle scattering from fractionated linear polyethylene crystallized from the melt was determined experimentally over a range of temperatures from room temperature to the melting point.
Abstract: The temperature dependence of x-ray small-angle scattering from fractionated linear polyethylene crystallized from the melt was determined experimentally over a range of temperatures from room temperature to the melting point. It was found in general that only the most intense of the several small-angle peaks exhibited a thermally dependent behavior. Below the crystallization temperature this peak increased in intensity with temperature, at constant peak position. Recrystallization was manifest in a discontinuous shift of the peak. During isothermal crystallization, the peak intensity first increased, then decreased, with time. It is concluded from supplementary electron microscopy and from the behavior of the peak that its position reflects the period of stacking of lamellae and that its intensity is controlled primarily by the thickness of the layer separating lamellae. The reversible peak intensity effect is attributed to an entropydriven growth of the interlamellar layer at the expense of the crystalline lamellae. The intensity effects observed during crystallization are associated with the primary and secondary phases of crystallization. Lamellar surface free energies were computed from melting point observations and were found to increase with molecular weight.
TL;DR: In this article, a generalization of the theory of rate processes for an arbitrary strain tensor is proposed and discussed, and the components of the deformation and the work done by the deviator of the stress during the elementary flow process are evaluated.
Abstract: The theory of rate processes has been applied by Eyring to the plastic flow of solids, but he considers only the case of simple shear. Some assumptions concerning a generalization of this theory for an arbitrary strain tensor are here proposed and discussed. The components of the deformation and the work done by the deviator of the stress during the elementary flow process are evaluated. According to these results, it can be proved that the yield condition of Huber, Hencky, and von Mises is valid when there is no hydrostatic stress. The discrepancy between the yield stresses corresponding to tensile and compressive tests is explained by the influence of the hydrostatic component and evaluated by taking account of the amount of free volume required for an elementary jump. The calculated value agrees with the experimental data. Measurements of the inclination of Luder's bands and deformation components on poly(vinyl chloride) flat bars strained by tensile tests are in good agreement with the proposed theory.
TL;DR: In this article, a drawing of linear polyethylene at 60°C to an extension ratio of ten drastically reduces the sorption and diffusion of n-pentane, benzene, methylene chloride, and tetrachloroethylene.
Abstract: Drawing of linear polyethylene at 60°C. to an extension ratio of ten drastically reduces the sorption and diffusion of n-pentane, benzene, methylene chloride, and tetrachloroethylene. Methylene chloride was chosen for more detailed study. The sorption is of the normal Fickean type. It is also fully reversible in the temperature range between 25 and 45°C. if the sorbed amount is kept to below 0.5%. At higher concentrations the sample relaxes so that sorption irreversibly increases. The reversible sorption per gram of amorphous component is about 1/6 of that in undrawn polyethylene. The diffusion constant has a larger temperature and concentration dependence than in the undrawn material. At zero concentration the activation energy for diffusion is 34.4 kcal./mole and the diffusion constant at 25°C. is 8 × 10−11 cm.2/sec. as compared with 14.4 kcal./mole and 1.5 × 10−8 cm.2/sec. in undrawn PE. Cold drawing reduces the sorption sites without changing their energy content, but drastically cuts down diffusion and increases the activation energy. A smaller part of the increase of the latter is a consequence of the lower enthalpy of the amorphous material and a larger part is probably due to the increased distance between sorption sites.
TL;DR: In this article, the relationship between the optical anisotropy of high polymeric materials in bulk and the orientation of structural units within the materials was described in general by using several types of mean values of the orientation distribution function of three Eulerian angles, under some assumptions about the symmetry of the function being applicable for most of the industrial products.
Abstract: The relationship between the optical anisotropy of high polymeric materials in bulk and the orientation of structural units within the materials was described in general by using several types of mean values of the orientation distribution function of three Eulerian angles, i.e., the orientation factors, under some assumptions about the symmetry of the function being applicable for the most of the industrial products. A newly defined biaxial orientation factor, Fθηi = 〈sin2 θj cos 2ηj〉, where θj and ηj are the polar and azimuthal angles of the jth axis within the structural unit with respect to the bulk axes, may relate the biaxial orientation of the structural units to the dichroic orientation factors, which are measurable optical anisotropic indices of the bulk materials. Some applications of the results to the birefringence and infrared and dye dichroism are also discussed.
TL;DR: The relationship between molecular weight distribution and structure in polymerizations with long-chain branching was reviewed and extended in this paper, where an experimental examination of intrinsic viscosity in polydisperse, trifunctionally branched systems was carried out in three systems: a theta-solvent, a good solvent, and one that was intermediate in solvent interaction.
Abstract: The relationships between molecular weight distribution and structure in polymerizations with long-chain branching were reviewed and extended. Results were applied to an experimental examination of intrinsic viscosity in polydisperse, trifunctionally branched systems. Several samples of poly(vinyl acetate) were prepared by bulk polymerization under conditions of very low radical concentration. The relative rate constants for monomer transfer, polymer transfer, and terminal double-bond polymerization were established from the variation of Mn and Mw with the extent of conversion. Average branching densities were then calculated for each sample and ranged as high as 1.5 branch points/molecule. Intrinsic viscosities [η]B were measured in three systems: a theta-solvent, a good solvent, and one that was intermediate in solvent interaction. These results were compared with calculated viscosities, [η]L, which would have been observed if all the molecules had been linear. The values of [η]B/[η]L were substantially the same in all three solvents. The variation of this ratio with branching density was compared with the theory of Zimm and Kilb as adapted to polydisperse systems. Discrepancies were noted, and the adequacy of present model distribution functions for branched polymers was questioned.
TL;DR: In this paper, the segmental motion of the chain end in dilute solution was studied by the fluorescence polarization method on the fluorescent polyacrylamide conjugates thus obtained.
Abstract: Polyacrylamide having a fluorescent residue at the chain end was prepared by polymerization of acrylamide in the presence of a fluorescent dye. The segmental motion of the chain end in dilute solution was studied by the fluorescence polarization method on the fluorescent polyacrylamide conjugates thus obtained. The linear relation between 1/p and T/η0 held for every sample studied in aqueous media, where p is the degree of polarization of the fluorescence, T is the absolute temperature, and η0 is the viscosity of the medium. The mean relaxation time 〈ρ〉 of the conjugate was evaluated from these data as a function of the molecular weight of the conjugate. The value of 〈ρ〉 increased slightly with molecular weight, varying from 3.3 × 10−9 to 7 × 10−9 sec. The absolute values of 〈ρ〉 and its molecular weight dependence suggest that 〈ρ〉 represents the mean rotational relaxation time for the cooperative motion of about ten monomeric units at the chain end. The effect of the mean extension of polymer chain on the segmental motion was found to be negligible.
TL;DR: In this article, the authors identify three distinct types of polymer adhesion on the basis of the physical state of adhesive and adherend: (1) Rubbery polymer-rubbery polymer (R-R adhesion), (2) Rubber polymer-glassy polymer (G adhesion) and (3) rubbery polymer nonpolymer (S adhesion).
Abstract: It is possible to identify three distinct types of polymer adhesion on the basis of the physical state of adhesive and adherend: (1) rubbery polymer–rubbery polymer (R–R adhesion); (2) rubbery polymer–glassy polymer (R–G adhesion); (3) rubbery polymer–nonpolymer (R–S adhesion). Limitations of the diffusion and adsorption theories and their conflicting results are discussed within the framework of the proposed classification. By defining the physical state of the polymer as an adhesive or as an adherend, it is possible to eliminate many of the discrepancies commonly noted in attempted application of the diffusion and adsorption theories. As predicted by the Bueche-Cashin-Debye equation, the diffusion of a polymer into another should be greatly reduced as it changes from the rubbery to the glassy state. For this reason, diffusion, which depends to a great extent on the physical state of the polymer, is actually a limited, selective process. Assuming a 1013 poise bulk viscosity at glass temperature, self-diffusion constants of forty polymers were calculated to be 10−21cm.2/sec. or 10−5A.2/sec. This slow rate of diffusion is unmeasurable and insignificant. Adsorption, which is less dependent on the physical state of the polymer, is more frequently encountered.
TL;DR: In this paper, the effect of microstructure on crystallizability of polyoctenamers prepared by R3Al-WCl6 catalyst was studied, and it was shown that poly octenamer with a broad range of transvinylene content do crystallize.
Abstract: The effect of microstructure on crystallizability of polyoctenamers prepared by R3Al-WCl6 catalyst was studied. The results indicate that polyoctenamers with a broad range of trans-vinylene content do crystallize. The measured melting points are dependent on the trans-vinylene content. From the dependence of melting temperature on copolymer composition, a value of 73 ± 2°C. for the melting point and a molar heat of fusion ΔHu of 3520 cal./mole are calculated for 100% trans-polyoctenamer. From the melting point depression in the presence of diluent, a value for ΔHu of 4800 cal./mole is obtained.