Piezoelectric composites of PZT ceramics and several semi-crystalline polymers have been produced by embedding slender PZT rods (4 volume percent) in the polymers. The observed dielectric constants were considerably l...
Piezoelectric composites of PZT ceramics and several semi-crystalline polymers have been produced by embedding slender PZT rods (4 volume percent) in the polymers. The observed dielectric constants were considerably lower than that of pure PZT. The hydrostatic piezoelectric voltage coefficients of the composites were larger than PZT, even though the composite hydrostatic piezoelectric strain coefficients were lower. Composite figures of merit ranged from one-third to six times that of PZT.
Lead zirconate–titanate (PZT)/polymer composites have been prepared by in situ polymerization of styrene and methyl methacrylate around aligned, thin PZT rods. Hydrostatic piezoelectric coefficients (d̄ h and ḡ g h )...
Lead zirconate–titanate (PZT)/polymer composites have been prepared by in situ polymerization of styrene and methyl methacrylate around aligned, thin PZT rods. Hydrostatic piezoelectric coefficients (d̄ h and ḡ g h ) measured by a dynamic technique yielded figures of merit (d̄ h ḡ h ) roughly four times that of homogeneous PZT for as‐polymerized composites. When these composites were annealed at a temperature slightly below the glass transition temperature of the matrix polymer and repoled, d̄ h ḡ h increased nearly twofold due primarily to a reduction of the composite dielectric constant. The piezoelectric response was found to be essentially independent of frequency from 30 to 160 Hz.
Small‐angle neutron scattering, SANS, stands forth as one of the most important of the new tools for evaluating polymer chain conformation and morphology. This paper reviews the SANS literature through 1982, with a f...
Small‐angle neutron scattering, SANS, stands forth as one of the most important of the new tools for evaluating polymer chain conformation and morphology. This paper reviews the SANS literature through 1982, with a few early 1983 references added. The theory of SANS is outlined and compared to light scattering. SANS values of polymer molecular weights and radii of gyration obtained in the bulk state were found to be in agreement with values obtained from dilute solutions by light scattering. In each case, deuterated fractions of polymer were inserted into the hydrogeneous matrix, or vice versa, to provide contrast. Several new research areas are then discussed, including unidirectional stretching of elastomers, stress‐relaxation, polymer‐polymer miscibility, crystallization from the melt compared with crystallization from dilute solutions, nonclassical aggregation during bulk polymerization of thermoset systems, morphology of polymer blends, block copolymers and ionomers, the core‐shell structure of latexes and polymer blocks, and grafts as surfactants in emulsions and latexes. Much new and sometimes unexpected information is being provided by the SANS research now in progress.
Annealing studies of the calcium salt of an ethylene-methacrylic acid copolymer are reported. Fourier-transform infrared spectroscopy and differential scanning calorimetry were applied to the investigation of the effe...
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Annealing studies of the calcium salt of an ethylene-methacrylic acid copolymer are reported. Fourier-transform infrared spectroscopy and differential scanning calorimetry were applied to the investigation of the effect of polyethylene crystallization on ionic structure as a function of annealing temperature and time. The spectroscopic changes observed in the spectra of the calcium salt annealed at 80°C differ from those seen in the spectra of the calcium salt annealed at room temperature. These changes are interpreted in terms of the multiplet-cluster model and the effect of the polyethylene-type crystallinity on the ionic microstructure.
Chain lengths have been calculated from the peak positions of the longitudinal acoustic modes (LAM) of polyethylene single crystals grown at several different temperatures. The data are consistent with other experimen...
作者：
RUNT, JRIM, PBPolymer Science Program
Department of Materials Science and Engineering The Pennsylvania State University Pennsylvania 16802 University Park United States
The development of poly(ϵ-caprolactone) (PCL) crystallinity in poly(ϵ-caprolactone)/poly(styrene-co-acrylonitrile) blends of 20% by weight PCL was studied for samples prepared under a variety of conditions. Solution c...
A systematic study of the sodium and calcium salts of an ethylene–methacrylic acid copolymer is reported. Fourier-transform infrared spectroscopy (in the midinfrared region) is applied to the characterization of stru...
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A systematic study of the sodium and calcium salts of an ethylene–methacrylic acid copolymer is reported. Fourier-transform infrared spectroscopy (in the midinfrared region) is applied to the characterization of structural changes as a function of temperature and time of annealing. In the spectra of calcium ionomers, bands associated with carboxylate dimers are identified and assignments of specific spectral features to multiplets and clusters are discussed. The spectroscopic changes observed in the spectra of sodium ionomers differ somewhat from their calcium counterparts in that a single infrared band attributed to isolated carboxylate groups is observed. Assignments of specific bands to multiplets and clusters can, however, be made in a manner consistent with the interpretation of the spectra of calcium ionomers.
A set of isothermally melt-crystallized polyethylene samples was examined using small-angle x-ray scattering (SAXS). Time and temperature of crystallization were the variable parameters used to create the set of sampl...
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A set of isothermally melt-crystallized polyethylene samples was examined using small-angle x-ray scattering (SAXS). Time and temperature of crystallization were the variable parameters used to create the set of samples. Following background subtraction, desmearing, and application of the Lorentz factor to the raw SAXS data it is possible to see many orders of reflection. This suggests that much higher degrees of order are present in isothermally melt-crystallized samples than had previously been thought possible. A combination of SAXS and DSC data indicates that there is no evidence for isothermal thickening in these samples. This study, coupled with data obtained from PE single crystals, produced information concerning the extrapolation of single-crystal data to fit bulk systems. In addition, the equilibrium melting point T determined is somewhat lower than previously claimed. This study also suggests that the surface energy of the mature crystals is always lower than that of the nucleated state and/or the nucleation factor K σ en increases with decreasing supercooling.
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