摘要:

AbstractThe sorption behavior of particulate‐filled resin composites is discussed and related to several different models. A thermodynamic analysis of the sorption is presented in the form of a cycle for the changes in Gibbs free energy. From such an analysis it is possible to set up a scale of relative adhesion between filler and resin matrix. It is shown that the scale depends on the sorbate, but use of this scale will rate the adhesion between resin and filler in the correct relative orde

ISSN:0098-1273    

DOI:10.1002/pol.1973.180111101

出版商:John Wiley&Sons, Inc.    

年代:1973

数据来源: WILEY

摘要:

AbstractIt has been recently discovered that polymers craze at low temperatures in the presence of nitrogen or argon. A quantitative theory has been developed which explains (1) the critical temperature above which the phenomenon disappears, (2) the critical stress for nucleating a craze, (3) the effect of strain rate on the yield point and size of crazes, (4) the drop in the load during craze yielding, and (5) the increase in strength of the polymer in N2or Ar at high strain rates so that the ultimate strength may exceed that in He or vacuum. The crazing action of the gases is described qualitatively at the molecular level.

ISSN:0098-1273    

DOI:10.1002/pol.1973.180111102

出版商:John Wiley&Sons, Inc.    

年代:1973

数据来源: WILEY

摘要:

AbstractA new crystal modification was found in poly(ethylene oxide) stretched about two‐fold after necking at room temperature. An x‐ray diffraction analysis indicated that the planar zigzag molecule passes through a triclinic unit cell with parameters α = 4.71 Å,b= 4.44 Å,c(fiber axis) = 7.12 Å, α = 62.8°, β = 93.2°, and γ = 111.4°. The space group isP1−Ci1. Packing of the molecule is very similar to that of monoclin

ISSN:0098-1273    

DOI:10.1002/pol.1973.180111103

出版商:John Wiley&Sons, Inc.    

年代:1973

数据来源: WILEY

摘要:

AbstractMeasurements of apparent viscosity, normal stress coefficient, and storage and loss moduli have been used to determine the characteristic relaxation time. The ratio of the characteristic relaxation time θincorresponding to a given deformation rate ˙γ to that of the initial state θeis found to be a function of ˙γθin. For a wide range of polymeric systems, the ratio of normal stress to the initial high elasticity modulus and to the high elastic deformation γeare the same function of ˙γθin. It has been established that γe, like other viscoelastic characteristics of polymer systems, is determined by the relaxation properties and their variation due to deformation. The dependence of γeon θe/θinis common to a wide range of polymeric systems. The generalized characteristics were independent of the nature of the polymeric chain, molecular weight, molecular weight distribution, temperature, polymer concentration in solution, and solvent type. These results allow us to describe approximately normal stresses and high‐elastic deformations as functions of shear rate and storage and loss moduli as functions of frequency, if we know θinthe relation between shearing stre

ISSN:0098-1273    

DOI:10.1002/pol.1973.180111104

出版商:John Wiley&Sons, Inc.    

年代:1973

数据来源: WILEY

摘要:

AbstractAn attempt was made to evaluate stresses on chemical bonds in axially stressed polymers from the shift of skeletal vibration frequencies in chain molecules. The maximum stress on chemical bonds was found to be at least ten times the average stress on the specimen.

ISSN:0098-1273    

DOI:10.1002/pol.1973.180111105

出版商:John Wiley&Sons, Inc.    

年代:1973

数据来源: WILEY

摘要:

AbstractBased upon the high‐temperature solid‐state dielectric behavior of H‐Film and supporting evidence from infrared spectroscopy, heat capacity, thermal expansion, and dynamic mechanical measurements, it is concluded that the actual chemical structure of H‐Film is far more complex than previously expected. The very unusual thermal properties of this polymer, such as lack of a glass transition temperature, its extreme insolubility, and high dielectric losses above 250°C with only weakly corresponding mechanical losses, suggest that in addition to the pyromellitimide repeat unit, a significant part of the structure consists of amide groups, probably in the form of cr

ISSN:0098-1273    

DOI:10.1002/pol.1973.180111106

出版商:John Wiley&Sons, Inc.    

年代:1973

数据来源: WILEY

摘要:

AbstractSpecimens of poly(vinylidene fluoride), crystal form II, annealed at different temperatures between 130 and 180°C were characterized by specific volume measurements, differential scanning calorimetry (DSC), and electron micróscopy. The degree of crystallinity calculated from the specific volume changed only by 15% i.e., from 50% to 65%. On the other hand, the melting behavior changed with annealing conditions. When a specimen was annealed above 170°C, two endothermic peaks appeared on either side of the annealing temperature. Results from DSC measurements made at different heating rates and electron microscopy showed that the two endotherms were caused by a bimodal distribution of lamellar thicknesses. The equilibrium melting point was found to be 210°C from the linear relation of the melting point and the annealing temperature. The equilibrium enthalpy and entropy of fusion were found to be 1.6 keal/mole and 3.3 eu/mole of repeat units by measurement on polymer–diluent mixtures. The surface free energy was found to be 5.1 kcal/mole of lamellar sequences from the plot of melting point versus reciprocal lamellar thickness obtained by electron microscopy. From a plot of enthalpy of fusion versus reciprocal lamellar thickness the surface enthalpy was found to be 20 keal/mole of lamellar sequences. These data lead to the estimate that a chain fold consists of about 30 repeat

ISSN:0098-1273    

DOI:10.1002/pol.1973.180111107

出版商:John Wiley&Sons, Inc.    

年代:1973

数据来源: WILEY

摘要:

AbstractRelative tilt between two similar thin crystals may result in the formation of a moiré pattern in the electron image. Patterns hitherto interpreted as being parallel moirés or rotation moiré obtained from overlapping solution‐grown polymer crystals are reconsidered, and it is shown that in some cases a tilt model is more acceptable. The general features of tilt moiré patterns predicted for crystals of this kind are discussed and compared with micrographs appearing in the literature. Methods of distinguishing tilt moiré patterns are indicated, though it is admitted that such experiments would be difficult to complete in the time limited by destruction of the crystal structure under the action of the electron beam. Extinction contours may also sometimes be confused with long‐period tilt moiré patterns, and again careful experimentation is required for accurate identification. The model of the structure of solution‐grown polyethylene crystals inferred from a tilt moiré interpretation of many of the electron image fringe patterns found in the literature is consistent with that derived from o

ISSN:0098-1273    

DOI:10.1002/pol.1973.180111108

出版商:John Wiley&Sons, Inc.    

年代:1973

数据来源: WILEY

摘要:

AbstractA series of energy calculations have been carried out in order to describe the epitaxial crystallization of polyethylene from solution in terms of molecular interactions. The total energy has been computed as the sum of electrostatic, dispersion, and repulsion contributions. The potential energy associated with a section of a planar‐zigzag polyethylene chain has been determined for various orientations and positions above three different planar alkali halide substrates. Inspection of the energy surfaces as a function of the spatial degrees of freedom reveals that the minimum energy orientation of the chain is that for which it is parallel to the substrate [(001) cleavage plane] and aligned in the 〈110〉 direction on the surface, a result in accordance with available experimental evidence. Specifically, the chain preference is to position itself along rows of positive ions, whereas alignment along rows of negative charge appears energetically unfavorable. The mode of chain orientation is virtually independent of lattice matching criteria. Dispersionrepulsive forces have been found to be most sensitive to orientation and greater in magnitude than the electrostatic f

ISSN:0098-1273    

DOI:10.1002/pol.1973.180111109

出版商:John Wiley&Sons, Inc.    

年代:1973

数据来源: WILEY

摘要:

AbstractLexan polycarbonate specimens in the form of tubes were deformed in torsion. The deformation occurs by the nucleation and growth of discrete shear bands. Shear bands are initially formed at the upper yield point. Development of the bands is accompanied by a drop in the stress to a lower yield point. At the lower yield point the strain inside the bands is approximately 70% and remains constant thereafter. Further deformation occurs by growth of the bands until they cover the entire sample. When the direction of twisting is reversed after the shear bands are formed, the deformed material untwists uniformly, without deformation in the previously undeformed material, and the stress required for untwisting the deformed material is lower than the stress required to propagate the band into undeformed material.

ISSN:0098-1273    

DOI:10.1002/pol.1973.180111110

出版商:John Wiley&Sons, Inc.    

年代:1973

数据来源: WILEY