There are many methods currently producing high modulus and high strength films and fibers in industry. This publication examines the results of a hot nip drawing process to produce high modulus PP films at a relative...
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There are many methods currently producing high modulus and high strength films and fibers in industry. This publication examines the results of a hot nip drawing process to produce high modulus PP films at a relatively rapid production rate. The effects of both temperature and rate of draw on the drawn material will also be examined.
Fabrication discontinuities in weldments pose a serious engineering problem for structural applications involving cyclic loading. Often, the discovery of fabrication discontinuities through nondestructive inspection c...
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: The ultimate crystalline modulus of poly(oxymethylene) was estimated by using the Raman longitudinal acoustic mode and small-angle X-ray scattering. In this paper we emphasize the sensitivity of the calculated modul...
The drawing of polymers into high strength films or tapes is an important process in industry. A method of local heating and drawing of plastic sheets into high strength films is discussed, and the preliminary results...
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The drawing of polymers into high strength films or tapes is an important process in industry. A method of local heating and drawing of plastic sheets into high strength films is discussed, and the preliminary results of this new technology are presented.
Areas under the linear tan δ–temperature (tA) and linear loss modulus–temperature (LA) curves of the polyacrylate and polymethacrylate homologous series and their interpenetrating polymer networks (IPNs) were inves...
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Areas under the linear tan δ–temperature (tA) and linear loss modulus–temperature (LA) curves of the polyacrylate and polymethacrylate homologous series and their interpenetrating polymer networks (IPNs) were investigated. For poly(methyl acrylate), LA values are independent of crosslinking level through 25%, but tA decreases. With increasing side group length, on the other hand, tA remains nearly independent of side group length for both homologous series, having values near 50 and 65 (units of K) for the acrylate and methacrylate series, respectively. However, LA decreases steeply with increasing side group length. A phenomenological treatment of areas is presented in order to explain tA and LA behavior semiquantitatively. Both tA and LA exhibit areas characteristic of the structure of the particular polymers. The homopolymer LA areas are additive in determining the area under the corresponding curve for the IPN. This suggested a group contribution analysis for LA, where each moiety contributes specific values to the area.
The exposure of dielectrics to moisture in the presence of an electrical field can result in the growth of water trees possibly leading to premature failure (1). Although investigated extensively, the mechanisms of in...
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The exposure of dielectrics to moisture in the presence of an electrical field can result in the growth of water trees possibly leading to premature failure (1). Although investigated extensively, the mechanisms of initiation and growth of water trees remain unclear. In relation to this, the mode of water transport through treed polymeric materials is a subject of considerable controversy. It has been suggested that the voids constituting the water trees are interconnected by channels which develop under the influence of electrical stress and collapse due to surface tension once the field is removed (2). If this is the case, one must consider the possibility that the observed stress dependence of the rate of water-tree growth is controlled by the effect of the stress of the rate of water transport through a damaged dielectric. To date, all work dealing with fluid transport studies show no indication of the existence of these channels. However studies were carried out either with undamaged materials (3) or without an applied field (4,5).
The miscibility of blends of poly(butylene terephthalate) and poly(bisphenol A-carbonate) was investigated using differential scanning calorimetry. Contrary to previously reported data, PBT and PC were found to be alm...
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The miscibility of blends of poly(butylene terephthalate) and poly(bisphenol A-carbonate) was investigated using differential scanning calorimetry. Contrary to previously reported data, PBT and PC were found to be almost completely immiscible over the entire compostion range studied. The minor change in Tg's observed for samples quenched form the melt can be attributed to transesterification at elevated temperatures. The melting behavior and normalized enthalpy of fusion are somewhat dependent on composition but the behavior is erratic.
Interpenetrating polymer networks (IPN's) can be defined as a combination of two polymers in network form, at least one of which was synthesized and/or crosslinked in the immediate presence of the other. Historica...
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Interpenetrating polymer networks (IPN's) can be defined as a combination of two polymers in network form, at least one of which was synthesized and/or crosslinked in the immediate presence of the other. Historically, the science of IPN's began with the papers of J. R. Millar in 1960 on homo‐IPN's made from polystyrene, but the first recorded publication is a patent by J. W. Aylsworth in 1914. This latter system was based on phenol‐formaldehyde for one network, and sulfur cured natural rubber for the other network. Early academic laboratories interested in IPN's include the Frisch team at Detroit and SUNY, who soon added their former student, Danny Klempner, and Yuri Lipatov's team at the Ukranian SSR Academy of sciences in the USSR, as well as the author's laboratory. More recent academic teams interested in IPN's include Douglas Hourston at the University of Lancaster, England; Robert Cohen at MIT; S. C. Kim at the Korea Advanced Institute of science and Technology, Seoul, Korea; G. Meyer and J. M. Widmaier in Strasbourg, France; and many others. Numerous industrial laboratories are interested, noting that about 90 U.S. patients have been granted, most of them in the past ten years. Systems of special interest include the new thermoplastic IPN's, which are really hybrid materials between polymer blends and IPN's, and the IPN‐based RIM (reaction injection molding) materials. Other materials include the sequential IPN's and the SIN's, which have both polymers simultaneously polymerized, and the latex IPN's, which often exhibit core‐shell characteristics.
Considering the practical importance of fatigue in determining material usefulness, we have undertaken a program to elucidate the influence of semicrystalline morphology on fatigue. This note reports some of our initi...
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Considering the practical importance of fatigue in determining material usefulness, we have undertaken a program to elucidate the influence of semicrystalline morphology on fatigue. This note reports some of our initial findings. The polymer used in this study was Pro-fax 6523 polypropylene (PP).
An expression is presented which relates the experimentally observed melting point depression in crystallizable, compatible polymer blends to changes in lamellar thickness and thermodynamic considerations. Considering...
An expression is presented which relates the experimentally observed melting point depression in crystallizable, compatible polymer blends to changes in lamellar thickness and thermodynamic considerations. Considering a given crystallization temperature, this relationship suggests that one should observe a depressed blend melting point, despite an increase in lamellar thickness over the pure crystallizable material. Possible explanations for the melting point elevation observed in some compatible blends are discussed.
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