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  • 1
    Electronic Resource
    Electronic Resource
    Monofilament drawing device for in situ x-ray scattering studies of orientation development in polymeric fibers (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 2652-2657 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The physical properties of polymer fibers are directly related to the development of orientation in the draw zone under extensional conditions. Although the final properties and microstructure of fibers can be evaluated after processing is completed, it is desirable to understand the development of orientation during drawing independently from the effects superimposed by subsequent unit operations. In situ x-ray scattering measurements of the extrudate in the draw zone provide an ideal means of accomplishing this goal. Depending on the polymeric system to be studied, rotating anode or synchrotron-based x-ray sources may be required, making portability of the fiber drawing device highly desirable. This paper describes an easily transportable in situ x-ray filament drawing device, and discusses typical data obtained using the device to produce filaments from a liquid crystalline nematic solution of poly(cis-benzoxazole) in polyphosphoric acid. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1145604
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  • 2
    Electronic Resource
    Electronic Resource
    Deuteron NMR analysis of the molecular origin of the thermal relaxations in polycarbonates (1988)
    s.l. : American Chemical Society
    Macromolecules 21 (1988), S. 2058-2063 
    Details
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ma00185a030
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  • 3
    Electronic Resource
    Electronic Resource
    Treatment of SANS data from hot stretched polystyrene chains (1990)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 23 (1990), S. 1-5 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The small-angle neutron scattering technique is applied to a hot stretched 5% perdeuterated polystyrene sample in order to investigate the residual macromolecular orientation at various length scales. The observed orientation is left over after fast quenching (in ice water) of the hot stretched sample. Previous investigations focused on how much polymer chains follow the external stretching. It is found that, even when macromolecules follow the external stretching affinely on the average, they do not deform uniformly. Moreover, over the time scale of the temperature quench, small chain portions relax more rapidly than large ones.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889889008484
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  • 4
    Electronic Resource
    Electronic Resource
    The inclination angle of nonisotropic inhomogeneities determined by SANS (1986)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 19 (1986), S. 320-323 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The angle between the axis of symmetry of nonisotropic inhomogeneities and the surface of a bulk sample is sometimes unknown. This angle may be determined by fitting small-angle neutron scattering (SANS) data taken at two or more different sample inclination angles. The feasibility of this technique is verified by analyzing SANS data taken at different tilt angles from a well characterized hot-stretched (partially deuterated) polystyrene sample.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S002188988608929X
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  • 5
    Electronic Resource
    Electronic Resource
    Modes of deformation in rubber-modified thermoplastics during tensile impact (1991)
    Springer
    Journal of materials science 26 (1991), S. 6249-6259 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Real-time small-angle X-ray scattering (RTSAXS) studies were performed on a series of rubber-modified thermoplastics. Scattering patterns were measured at successive time intervals as short as 1.8 ms and were analysed to determine the plastic strain due to crazing. Simultaneous measurements of the absorption of the primary beam by the sample allowed the total plastic strain to be computed. The plastic strain due to other deformation mechanisms, e.g. particle cavitation and macroscopic shear deformation was determined by the difference. Samples of commercial thicknesses can be studied at high rates of deformation without the inherent limitations of microscopy and its requirement of thin samples (i.e., plane strain constraint is maintained on sample morphology). Contrary to the conclusions drawn from many previous dilatation-based studies, it has been demonstrated that the strain due to non-crazing mechanisms, such as rubber particle cavitation, and deformation of the glassy ligaments between rubber particles, occurs before that due to crazing mechanisms. Crazing accounts for at most only half of the total plastic strain in HIPS (high impact polystyrene) and ABS (rubber-modified styrene-acrylonitrile copolymer) materials. The proportion of strain attributable to crazing can be much less than half the total in thermoplastic systems with considerable shear yield during plastic deformation. The predominant deformation mechanism in polycarbonate-ABS blends is shear in the PC (polycarbonate) with associated rubber gel particle cavitation in the ABS. This cavitation means that there appears to be a direct relationship between gel particle rubber content in the ABS and toughness of the blend. The mechanism is the same whether the tensile stress is in the direction parallel or perpendicular to the injection-moulded orientation, with simply less total strain being reached before fracture in the weaker perpendicular direction. Crazing, although the precursor to final fracture, occurs after the predominant mechanism and contributes only a few per cent to the total plastic deformation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00551868
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  • 6
    Electronic Resource
    Electronic Resource
    Modes of deformation in rubber-modified thermoplastics during tensile impact (1991)
    Springer
    Journal of materials science 26 (1991), S. 6249-6259 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Real-time small-angle X-ray scattering (RTSAXS) studies were performed on a series of rubber-modified thermoplastics. Scattering patterns were measured at successive time intervals as short as 1.8 ms and were analysed to determine the plastic strain due to crazing. Simultaneous measurements of the absorption of the primary beam by the sample allowed the total plastic strain to be computed. The plastic strain due to other deformation mechanisms, e.g. particle cavitation and macroscopic shear deformation was determined by the difference. Samples of commercial thicknesses can be studied at high rates of deformation without the inherent limitations of microscopy and its requirement of thin samples (i.e., plane strain constraint is maintained on sample morphology). Contrary to the conclusions drawn from many previous dilatation-based studies, it has been demonstrated that the strain due to non-crazing mechanisms, such as rubber particle cavitation, and deformation of the glassy ligaments between rubber particles, occurs before that due to crazing mechanisms. Crazing accounts for at most only half of the total plastic strain in HIPS (high impact polystyrene) and ABS (rubber-modified styrene-acrylonitrile copolymer) materials. The proportion of strain attributable to crazing can be much less than half the total in thermoplastic systems with considerable shear yield during plastic deformation. The predominant deformation mechanism in polycarbonate-ABS blends is shear in the PC (polycarbonate) with associated rubber gel particle cavitation in the ABS. This cavitation means that there appears to be a direct relationship between gel particle rubber content in the ABS and toughness of the blend. The mechanism is the same whether the tensile stress is in the direction parallel or perpendicular to the injection-moulded orientation, with simply less total strain being reached before fracture in the weaker perpendicular direction. Crazing, although the precursor to final fracture, occurs after the predominant mechanism and contributes only a few per cent to the total plastic deformation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02387801
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  • 7
    Electronic Resource
    Electronic Resource
    SANS from hot-stretched polystyrene revisited (1991)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 29 (1991), S. 1607-1612 
    Details
    ISSN: 0887-6266
    Keywords: neutron scattering (SANS) from hot stretched polystyrene ; polystyrene, hot stretched, SANS study of ; chain deformation in hot stretched polystyrene, SANS study of ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Small-angle neutron scattering (SANS) has been used to investigate macromolecular orientation of uniaxially hot-stretched partially deuterated polystyrene. Principle radii of gyration and degree of eccentricity were measured over a range of hot-stretch temperatures, strain rates, and external draw ratios (EDR). Results show affine deformation for EDR 〈4 and an increase in the degree of local molecular orientation with increasing rate of strain and decreasing stretching temperature. It also is found that although the macromolecules follow the external stretching affinely on average, they do not deform uniformly.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1991.090291306
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  • 8
    Electronic Resource
    Electronic Resource
    In situ X-ray scattering studies of lyotropic liquid crystalline PBO and PBZT monofilament drawing (1994)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 32 (1994), S. 2567-2573 
    Details
    ISSN: 0887-6266
    Keywords: poly(cis-benzoxazole) ; poly(trans-benzothiazole) ; lyotropic ; liquid crystalline ; monofilament ; x-ray scattering ; compressive strength ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The results of a series of novel synchrontron-based in situ x-ray scattering experiments of monofilament fiber drawing from lyotropic solutions of poly(cis-benzoxazole) (PBO) and poly(trans-benzothiazole) (PBZT) are reported. The purpose of the study is to determine orientation and microstructure development in the draw zone as a function of shear rate in the capillary die, and spin draw ratio (SDR). The transition of the extrudate from opaque to the transparent is complete at about a SDR = 3 and f of 0.9. The filament orientation parameter (f) was found to depend strongly on spin draw ratio, but not shear rate. The orientation was found to increase down the extrudate toward completion of the draw down as one proceeds further from the die face up to an extrudate length of 3.8 cm. Coherence lengths on the order of 19 nm (axial), and 4.5 nm (lateral) have been observed. These “microdomain” sizes are consistent with the “crystallite” sizes typically observed in coagulated fiber. The occurrence of these microdomains in the draw zone as a precursor to the microfibrillar structure is believed to be the origin of low filament compressive strength. © 1994 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1994.090321602
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  • 9
    Electronic Resource
    Electronic Resource
    Physical aging in thermosets of differing degrees of cure - master curve generation and the relation to mechanical properties (1988)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 28 (1988), S. 1-5 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Physical aging of a thermoset system based on bisphenol-A epoxy (DERTrademark of The Dow Chemical Company. 383) and tetrabromobisphenol-A cured with sulfanilamide and diaminodiphenylsulfone was studied as a function of cure history. Changes in the dynamic mechanical spectra for the thermoset system were correlated to changes in relative toughness associated with physical aging as determined by plane-strain biaxial tension-compression yield measurements. It was found that master curves, generated by using tan δ data obtained in the β relaxation temperature regime, are well related to the corresponding changes in mechanical properties and, hence, have predictive value. Relative toughness decreases and compressive yield increases with decreasing tan 5 because of decreased molecular segmental mobility. The relative extent of physical aging for the as-cast thermosets was shown to be linearly related to the cure time.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760280102
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  • 10
    Electronic Resource
    Electronic Resource
    Coagulation of poly(p-phenylene benzobisoxazole) in polyphosphoric acid using aqueous and nonaqueous solutions (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 33 (1995), S. 1621-1626 
    Details
    ISSN: 0887-6266
    Keywords: poly(p-phenylene benzobisoxazole) ; PBO ; polyphosphoric acid ; diffusion ; fluorescence microscopy ; aqueous coagulants ; nonaqueous coagulants ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Diffusion of aqueous and nonaqueous coagulants into lyotropic/nematic solutions of poly(phenylene benzobisoxazole) in polyphosphoric acid using fluorescence microscopy is reported. The fluorescence microscopy technique offers advantages in that the experiment is independent of the coagulant and the experiments can be performed in a front surface mode so that optically thin samples are not required. The diffusion process is modeled as Case II diffusion as described by Crank and Park. The apparent diffusion coefficients are found to range from ∼ 2 × 10-6 cm2/s to ∼ 2 × 10-7 cm2/s for aqueous and nonaqueous coagulants. The apparent diffusion coefficients can be varied by several orders of magnitude (e.g., down to ∼ 3 × 10-10 cm2/s) by varying the concentration of polyphosphoric acid in the coagulant. © 1995 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1995.090331106
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