摘要:

AbstractThe small‐angle x‐ray scattering (SAXS) patterns of a number of linear polyethylene (PE) and polyoxymethylene (POM) samples have been measured and compared to the intensity functions of one‐dimensional paracrystalline lattices. It was found that the ratio of the angular positions of the second and first scattering maxima (θ2/θ1) is generally less than or equal to 2.0, implying that the paracrystalline lattice statistics are symmetric or moderately skewed to larger periods. The Bragg spacing (“long period”) of such samples is within 3% of the identity period of the macrolattice. With quenched POM the ratio θ2/θ1is substantially larger than 2.0, which indicates either extremely asymmetric lattice statistics or coexisting structures within the material. From consideration of the reduced widths of the first scattering maxima, it was found that some broadening is present in addition to that from the paracrystallinity. This excess broadening could result from a finite lattice length of ∼1000 Å. The need for careful experimental technique for obtaining the actual position of the scattering maximum is emphasized. In addition, it is demonstrated that the scattering curve and the correlation function of the system yield essentially the same apparent st

ISSN:0098-1273    

DOI:10.1002/pol.1973.180110601

出版商:John Wiley&Sons, Inc.    

年代:1973

数据来源: WILEY

摘要:

AbstractThe scattering from a two‐dimensional spherulite is calculated on the basis of an assembly of anisotropic rods imbedded in an isotropic matrix and arranged in a spherulitic distribution. Provided the dimensions of the rods are small compared with the wavelength of the light, the scattering from such an assembly is shown to be identical with that from an internally uniform spherulite. The effective polarizabilities of this uniform spherulite in the radial and tangential directions are equal to the average polarizabilities in these directions of the constituent rods together with their surrounding

ISSN:0098-1273    

DOI:10.1002/pol.1973.180110602

出版商:John Wiley&Sons, Inc.    

年代:1973

数据来源: WILEY

摘要:

AbstractThe possibility of constructing zero‐shear viscosity master curves valid for the entire range of concentration for a large number of polymer solutions in different solvents independent of molecular weight and the nature of the solvent is considered. The results obtained show that the parameters characterizing the individual macromolecular chain., viz., the dimensions of the polymer coil and the rheological effectiveness of segmental interactions, are significant in determining the viscosity of polymer solutions from very dilute to highly concentrated ones. The relation between the parameter of rheological interaction and characteristics of polymer solutions such as the flexibility of the polymer chain and the Flory‐Huggins parameter is discussed. This permits one to separate the influence of the energy and entropy factors on the concentration dependence of zero‐shear visc

ISSN:0098-1273    

DOI:10.1002/pol.1973.180110603

出版商:John Wiley&Sons, Inc.    

年代:1973

数据来源: WILEY

摘要:

AbstractThe crystal structure of nylon 12 prepared by polymerization of dodecalactam has been determined by x‐ray diffraction. Nylon 12 fiber exhibits only the γ form as its stable crystal structure. The unit cell of nylon 12 was determined with the aid of the x‐ray diffraction pattern of a doubly oriented specimen. The unit cell is monoclinic witha= 9.38 Å,b= 32.2 Å (fiber axis), c = 4.87 Å and β = 121.5° and contains four repeating monomer units. The chain is planar zigzag for the most part but is twisted at the position of amide groups, forming hydrogen bonds between neighboring parallel chains. The chain conformation is similar to that of the γ form of nylon 6 proposed by Arimoto. It was deduced from the calculations that there are two chain conformations statistically coexistent according to the direction of twisting. In each conformation, hydrogen bonds are formed between parallel chains to make pleated sheetlike structures. The sheets are nearly parallel to (200) and in the sheet the directions of the neighboring chains are antiparallel, as is the case wi

ISSN:0098-1273    

DOI:10.1002/pol.1973.180110604

出版商:John Wiley&Sons, Inc.    

年代:1973

数据来源: WILEY

摘要:

AbstractThree different polyolefins, a linear polyethylene, an isotactic polypropylene, and an isotactic polybutene‐1, were melt‐spun into filaments. The degree of orientation of the filaments was measured by polarized‐light microscopy, x‐ray diffraction, and a retraction technique, and the results were then related to the melt‐draw ratio. The increase in the elastic deformation ratio of polymer chains by spin‐stretching, estimated by thermal retraction at a temperature aboveTm, was monotonic with respect to the melt‐draw ratio. On the other hand, as‐spun filaments of polyethylene and polypropylene were characterized by a plateau in birefringence over the range of melt‐draw ratios from 8 to 80. The change in orientation functions for crystals in these filaments was similar to the change of birefringence. On the other hand, the birefringence and the crystalline orientation functions for polybutene‐1 increased smoothly with increasing melt‐draw ratio. The most highly melt‐drawn filaments of these polymers had a strongly oriented structure, corresponding to that in high

ISSN:0098-1273    

DOI:10.1002/pol.1973.180110605

出版商:John Wiley&Sons, Inc.    

年代:1973

数据来源: WILEY

摘要:

AbstractThe polymerization ofp‐xylylene was followed with a newly designed differential thermal analysis system at temperatures between −196°C and −20°C. It was found that at the lower temperatures the monomer condenses first to the crystalline monomer before simultaneous polymerization and crystallization. At the higher temperatures, polymerization and crystallization are successive. The data are in agreement with the morphology and crystal structure data derived in Part I of this series of papers on crystallization during polymerization of poly‐p

ISSN:0098-1273    

DOI:10.1002/pol.1973.180110606

出版商:John Wiley&Sons, Inc.    

年代:1973

数据来源: WILEY

摘要:

AbstractAn attempt to interpret the prominent dielectric relaxations of poly(γ‐benzyl L‐glutamate) and poly(γ‐methyl L‐glutamate) in terms of their structures was made by applying the barrier theory of Hoffman. Potential energy maps for the rotation of the polar side group, which are required in this application, were calculated by taking account of molecular environment of the polar side group. The dichroic ratios from infrared measurements were satisfactorily calculated, based on the maps. This provides evidence that the maps are reliable. In applying the barrier theory, it was modified by the assumption that the conformations of the side groups are distributed according to the Boltzmann law. On the basis of the maps, the magnitude of the dielectric absorption and the mean relaxation time were calculated in terms of the modified barrier theory; these were in fairly good agreement with the experime

ISSN:0098-1273    

DOI:10.1002/pol.1973.180110607

出版商:John Wiley&Sons, Inc.    

年代:1973

数据来源: WILEY

摘要:

AbstractThe hydrodynamic volume concept can be used effectively with gel‐permeation chromatographic (GPC) and viscosity data to estimate the molecular weight of a variety of polymers. Agreement is within ±5–10% of the absolute values and thus is satisfactory for many purposes. An iterative computer technique and a method developed by Funt and Hornof for analyzing GPC–viscosity data were found to be equivalent with respect to estimating the molecular weights for the five cases studied. The latter is easily employed but restricted to the case where the sample of interest and the GPC calibration standards have approximately equal Mark‐Houwink parameters. Since GPC measurements are commonly performed in thermodynamically good solvents, the general applicability of the method is not impaired. Using the unperturbed dimensions of the polymer chain to estimate the molecular weight of a variety of polymers was not as satisfactory as the above techniques. This approach generally gave biased molecular weight values (consistently low or consistently high). Agreement with the absolute values ranged from 10 to 30%. We therefore believe that either of the techniques based on the hydrodynamic volume concept can be used more effectively to estimate the molecular weight of a series of polymers than the treatment based on the unperturbed d

ISSN:0098-1273    

DOI:10.1002/pol.1973.180110608

出版商:John Wiley&Sons, Inc.    

年代:1973

数据来源: WILEY

摘要:

AbstractPoly(p‐phenylene pyromellitamic acid)s were synthesized over the weight‐average molecular weight range 8,000 to 22,000. The polymers were recovered as amorphous powders composed of 3–4 × 1–2 μ platelets 0.1–0.2 μ thick containing 20–30% associated solvent. Consumption of reactants and attainment of the ultimate molecular weight of the polymer were found to occur within the first few minutes of reaction. The polymers were characterized by scanning electron microscopy; ultraviolet, visible, near‐infrared, and infrared spectroscopy; x‐ray analysis; viscometry; and light‐scattering photometry. The intrinsic viscosity–molecular weight relation for the polymer in DMF was\documentclass{article}\pagestyle{empty}\begin{document}$ [\eta ] = 25.2 \times 10^{ - 4} \bar M_w^

ISSN:0098-1273    

DOI:10.1002/pol.1973.180110609

出版商:John Wiley&Sons, Inc.    

年代:1973

数据来源: WILEY

摘要:

AbstractThe Polarized lower‐frequency infrared spectra (800–33 cm‐1) of nylon 66 (α form), nylon 77 (γ form), and nylon 6 (both α and γ form) have been examined. The spectral changes which occur on complex formation of the polyamides with iodine‐potassium iodide solution and on subsequent iodine desorption have been studied in relation to the changes in the polymer structures. On the basis of these results, most of the stronger bands have been reasonably assigned to the vibrations characteristic of the amide group and the methylene chain of the polyamides, and some new structure–frequency correlations have been established for

ISSN:0098-1273    

DOI:10.1002/pol.1973.180110610

出版商:John Wiley&Sons, Inc.    

年代:1973

数据来源: WILEY