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  • 1
    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: A study of simultaneous acoustic and rheometric (dynamic mechanical) measurements of the epoxy curing process is undertaken to assess the validity of using acoustic cure-monitoring sensors for process control. Our results demonstrate that the acoustic technique provides a sensitive means for monitoring the cure of neat epoxy over the entire cure cycle. The acoustic modulus calculated from the shear velocity qualitatively tracks the mechanically measured dynamic modulus and correctly ranks the stiffness of two epoxy compositions. When the frequency difference is accounted for, using time-temperature superposition of the dynamic mechanical measurements, quantitative agreement between the acoustic and mechanical moduli for fully cured epoxy resins is also quite good.
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  • 2
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 467-474 
    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: The grafting of maleic anhydride (MAH) on high density polyethylene in a counter-rotating twin screw extruder has been studied. As the reaction kinetics appear to be affected by mass transfer, good micro mixing in the extruder is important. Due to the competing mechanisms of increasing mixing and decreasing residence times at increasing screw speed, and due to the complicated reaction scheme, various non-linearities exist that are prohibitive for simple optimization rules. The interaction diagram presented in this paper for a twin screw extruder as a MAH grafting reactor can be used for better understanding of the influence of the extruder parameters on the reaction process.
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  • 3
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 488-493 
    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: Gear pump assisted extrusion is becoming popular in the plastics processing industries. The growth has been tremendous since 1980. In this study, the benefits of gear pump assisted extrusion, especially in single screw applications, is critically reviewed, and a method of predicting the operational conditions of the gear pump assisted extrusion system is discussed. Further, shortening the length to diameter ratio of the extruder in gear pump assisted extrusion was analyzed and found to produce a reduction in energy consumption, provided melting is completed.
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  • 4
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992) 
    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
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  • 5
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 506-515 
    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: Internal stresses in injection-molded parts are the result of thermal, flow, and pressure histories. Internal stresses can be roughly divided into thermal and flow-induced stresses. In this paper, a modified layer-removal method is presented to determine thermal stress distributions in injection-molded flat plates. With this method, the curvature of a rectangular specimen is determined after the removal of a layer from one surface. This curvature is converted into a stress via a mathematical relation, originally derived by Treuting and Read. By determining the local curvatures after successive layer removals, stress distributions along the flow path were obtained within a single specimen. Validation of this modified layer-removal method is described. A good reproductibility was obtained. The method can be regarded as semi-quantitative. Flat plates were injection-molded from three amorphous polymers: polystyrene, polycarbonate, and a polyphenylene ether/high-impact polystyrene blend. In general, the flat-plate cross-section shows a three-region stress distribution with a tensile stress region both at the surface and in the core of the flat plate and an intermediate region with compressive stresses. The modified layer-removal method was used to determine influences of mold temperature, annealing treatment, and pressure history on the thermal stress distributions. Increasing mold temperature results in a decreasing overall stress level, while the compressive stress region shifts to the surface. An annealing treatment significantly reduces the overall stress level, without affecting the stress pattern. Stress distributions along the flow path were influenced by the varying pressure histories from the entrance to the end of the mold cavity. The various features of the stress profiles are explained by the influence of the pressure decay rate in the injection-molding process.
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  • 6
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 529-534 
    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: The network formation processes for imidazole-cured epoxy resins were examined by relating the reaction chemistry and the physical properties during cure. Network formation models were developed based on kinetic studies and the laws of conditional probability. These models were used to predict the weight-average molecular weight, the gel point, and the sol fraction as a function of the resin composition and the processing conditions. Rheological and extraction experiments were conducted to confirm the model results and to develop criteria for identifying the gel point.
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  • 7
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 535-541 
    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: The kinetics of cyclotrimerization and the thermal stability of bisphenol Abased cyanate ester resin systems were determined using Fourier transform infrared spectroscopy, differential scanning calorimetry, and thermogravimetry. The bisphenol A dicyanate was cured with 4 phr nonylphenol and with the octoates of zinc and manganese, and cobalt acetylacetonate at concentrations ranging from 0 to 750 ppm metal. An empirical rate law was used to predict the cyanate concentration profiles. The observed reaction rate showed a first-order dependenće on the initial metal concentration and a second-order dependence on the cyanate concentration in the kinetically controlled regime. For the uncatalyzed systems, the kinetics was described by a second-order autocatalytic model. The thermal stability of the network was found to be dependent on the catalyst concentration for the zinc catalysts. For the samples cured with manganese, no effect of concentration on the thermal stability was observed.
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  • 8
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 558-566 
    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: Ar+ irradiation and annealing at an elevated temperature are used to improve the adhesion of deposited Cr thin films by vacuum evaporation onto polyimide (PI) substrates. The Ar+ ions of 50 and 200 keV and various Ar+ doses ranging from 1 × 1013 to 2 × 1016 ions/cm2 are chosen for the experiments, after many preliminary trials. The surface analyses are conducted employing Rutherford Backscattering Spectroscopy (RBS), Fourier transform infrared spectrometry (FTIR), X-ray photoelectron spectroscopy (XPS), and Scanning electron microscopy (SEM). Ar+ irradiation produces an interfacial layer of about 100 Å (10 nm) thick in which Cr particles and PI molecules are physically mixed and chemically bonded. The chemical bonds of Cr—O and a trace of Cr≡C are observed by XPS and FTIR. Impact-wear tests are also conducted in order to determine the effects of the Ar+ irradiation on the wear property of a Cr/PI system. A significant increase in the property is observed and the increase appears to be a function of the degree of adhesion of the Cr film to the PI substrate.
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  • 9
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    Polymer Engineering and Science 32 (1992), S. 581-581 
    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
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  • 10
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 582-585 
    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: Deep penetration welding of polymers can be carried out at high speed with relatively low laser power. This results from an efficient coupling CO2 laser radiation to polymers that leads to volume heating. A brief review of energy coupling and heat transfer effects in polymers under CO2 laser welding conditions is given. Some examples of low power (10 to 100 watt) CO2 welding of polypropylene and polyethylene at depths of up to 1.5 cm are discussed.
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  • 11
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992) 
    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
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  • 12
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 206-212 
    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: Coat-hanger dies are commonly used for the extrusion of plastic sheets and films. To describe the flow of a molten polymer through a coat-hanger die, a two-dimensional approach is necessary. Moreover, the thermal effects, which play an important role in the flow distribution, have to be taken into account. In this paper, two numerical models for the simulation of coat-hanger dies are described and compared. These models differ mainly in the simplifying assumptions used and in the treatment of the thermal problem. The simulations obtained with the two models were compared with each other and with experimental data. The discrepancies between the two models can be explained by the different theoretical treatments.
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  • 13
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    Polymer Engineering and Science 32 (1992), S. 213-220 
    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: A general computation of multilayer coextrusion flow in a flat die geometry is presented. For any given number of layers of different polymers, characterized by their thermal and rheological behaviors, the model permits computation of velocity and temperature fields along the flow in constant or slightly varying geometries. The influence of different operating parameters (wall regulation temperature, flow rate, initial temperatures) on the interface positions and temperature evolutions is evaluated. Theoretical predictions of interface positions are in agreement with experiments carried out on an industrial multimanifold flat die.
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  • 14
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    Polymer Engineering and Science 32 (1992), S. 221-230 
    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: A critical part of any master model used to simulate or control a composite material manufacturing process is the description of resin flow through the fiber bed. We present here a review of both theoretical and experimental studies of fluid flow through porous media, including fiber beds. For the practical porosity range of interest in continuous fiber composites processing (0.3〈 ∊ 〈 0.6), the permeability cannot be accurately described using the Blake-Kozeny-Carman equation, even though the flow is Newtonian at very low Reynold's number. For aligned fiber situations, the Kozeny constant, k, deviates radically from theory, depends on bed nonuniformities, and is only constant over very narrow porosity ranges. Thus, one cannot experimentally determine k at high porosities and use this value to describe low porosity situations. Theoretical attempts, based on perfectly spaced and aligned arrays of cylinders, adequately describe the transverse permeability of ideal fiber beds in the high porosity range, but do not succeed at porosities below 0.6. For axial flow through aligned fiber beds, the theory yields permeabilities much lower than are experimentally observed throughout the entire porosity range. For randomly arranged fibers, random cylinder theory also predicts permeabilities that are significantly lower than are measured.
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  • 15
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    Polymer Engineering and Science 32 (1992), S. 240-253 
    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: A method is presented for measuring three-dimensional fiber orientation in fiber-reinforced polymers and placing confidence limits on the results. The orientations of individual fibers are determined from the elliptical intersections between the cylindrical fibers and a polished section. This can be done using either manual digitization or automated image analysis. Volume averages for the sample are computed using an orientation-dependent weighting function that corrects for the bias of an area-based sample. Equations are developed for nonuniform fiber lengths, using both number-average and weight-average measures of orientation. Sources of systematic, measurement, and sampling error are discussed and equations for sampling error and the propagation of measurement error are derived. The results use a second-rank tensor to characterize fiber orientation, but the error analysis can be applied to any type of orientation parameter. We implement the technique using manual digitization of optical micrographs. Our implementation accurately measures samples with known orientation, and produces identical results from two perpendicular sections of a glass fiber/nylon injection-molded sample.
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  • 16
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    Polymer Engineering and Science 32 (1992), S. 273-279 
    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: We have studied the impact strength, by Charpy and Izod tests, of blends of polyamide 6 with different rubbers, 10 wt% of each, or rubbers and glass fibers (8.5 wt% and 15 wt% respectively). The rubbers are from three different families: (i) a nonreactive cross-linked terpolymer, methyl methacrylate/butadiene/styrene (17/64.5/18.5); (ii) two block copolymers compatible with the matrix, poly(tetramethylene glycol)/polamide 12 (70/30 or 34/66); and (iii) two polymers containing reactive functionality, a terpolymer ethylene/ethyl acrylate/maleic anhydride (68/30.5/1.5) and a copolymer ethylene/acrylic acid (90/10). The classification of additives in regard to improved impact depends on the procedure used for the impact strength measurement, particularly on whether the samples are notched or unnotched. The results are discussed in relation to the dimensions and the adhesion of the rubber particles. The level of adhesion has been estimated from observations in scanning electron microscopy of cavities due to pullout nodules and of nonextracted rubber after treatment in boiling xylene. Strong variations in the morphologies are found, depending on the chemical nature of the rubber. The crystalline state of the polyamide in the blends has also been evaluated from differential scanning calorimetry.
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  • 17
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    Polymer Engineering and Science 32 (1992), S. 287-297 
    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: Sheet composites of polypropylene and poly(ethylene terephthalate) were produced by melt consolidation of alternating layers of polymer films and random glass fiber mats. The composites had a nominal glass content of 50 wt% (∼30 vol%). The sheets were stamped into a complex part from which test specimens were machined, and mechanical properties determined. Flexural strengths as high as 159 MPa were recorded for polypropylene composites and 313 MPa for poly(ethylene terephthalate) composites. The flexural modulus of the polypropylene composites reached 9.1 MPa, whereas the modulus of the stiffest poly(ethylene terephthalate) composite was 15 GPa. The impact properties of the composites were equally high. Polypropylene composites absorbed up to 257 J/cm during an instrumented falling dart impact test. Poly(ethylene terephthalate) composites absorbed as much as 116 J/cm in the same test.
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  • 18
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    Polymer Engineering and Science 32 (1992) 
    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
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  • 19
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    Polymer Engineering and Science 32 (1992), S. 298-304 
    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: The fiber straightening pre-tension applied during the sample preparation of single fiber composites is suggested here to significantly affect the number of fragments as well as the value of the Kelly-Tyson interface shear strength obtained from single filament composite tests. This implies that fragmentation tests performed under seemingly identical conditions, but in which the fiber pre-tension is not accurately controlled during sample preparation, might yield widely differing experimental results. We present and discuss a new set of experimental results dealing with fiber pre-tension effects in carbon/epoxy single fiber composites.
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  • 20
    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: Surface-induced transcrystallization in fibers has been reported in some advanced polymer composites. It is believed that transcrystalline interphase may affect stress transfer efficiency between the reinforcing fiber and the matrix. In this study, attempts were made to examine the effects of transcrystallinity on composite performance, particularly on fiber-matrix interfacial bond strength, and to investigate possible attributes of transcrystallization. Three polymer resins, poly(etherketoneketone) (PEKK), poly(etheretherketone) (PEEK), and poly(phenylenesulfide) (PPS), and four types of fiber, polyacrylonitrile (PAN)-based AU-4 (untreated AS-4) carbon, pitch-based carbon, poly (p-phenylene terephthalamide) (PPDT) aramid, and E-glass were used. It was found that PPDT aramid and pitch-based carbon fibers induce a transcrystalline interphase in all three polymers because of an epitaxial effect. Under certain conditions, transcrystallization was also observed in PAN-based carbon and E-glass fibers, which may be partially attributed to the thermal conductivity mismatch between the fiber and the matrix. Plasma treatment on fiber surface showed a negligible effect on inducing transcrystallization, whereas solution-coating of PPDT on the fiber surface showed a positive effect. The Microdebonding test, which measures the interfacial bond strength between the fiber and the matrix, consistently showed more than 40% increments for various single filament systems with transcrystalline interphase versus without. However, the effects of transcrystallinity on the interfacial bond strength appeared to decrease as the fiber content increased in composites.
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  • 21
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    Polymer Engineering and Science 32 (1992), S. 475-480 
    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: An approach to formulation is presented that is based on a statistical experimental design package for use on a personal computer. The total level of phosphite + hindered phenol, and the ratio of phosphite to hindered phenol are used as experimental variables. The approach was tested on extrusions of polypropylene using melt flow retention and yellowness index as observed variables. A quadratic model gave a satisfactory fit to the data for both variables. Contour plots are presented of the performance of the systems for two commercially available hindered phenols and two polypropylene samples. The largest difference between the resins is in the degree of color generation on extrusion. For both hindered phenols, a resin made using “3rd generation” or “high activity” catalyst gave lowest color development on extrusion. There were also small differences in the response of the melt flow of the resins to phosphite level.
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  • 22
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    Polymer Engineering and Science 32 (1992), S. 481-487 
    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: The consumption of hot-fillable poly(ethylene terephthalate) bottles is extremely large and is still increasing in Japan. This type of bottle is generally manufactured by the heat-set method using hot molds after stretch-blow molding. In this study, the method is simulated using a setting application in which sheets can be stretched constraining their sizes on a hot aluminum block. The crystallinities of the sheets are found to depend on the thermal history, i.e., the duration and temperature of the heat-set cycle. Heat-setting mitigates thermal-shrinkage of the sheets which is due to the increase in crystallinity or in the tense segments in the amorphous region. The structure of the heat-set sheet varies depending on the original stretched sheet. For a sample of low draw ratio, the crystallinity does not increase because of the heat-set. For a sample of medium draw ratio, the crystallinity increases greatly and the tense segments in the amorphous region also increase because of heat-set. For a sample of high draw ratio, the crystallinity increases a little but the numbers of the crystallite and tense segments in the amorphous region do not change with the heat-set.
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  • 23
    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: The dynamic behavior of the solution polymerization of styrene in a continuous stirred tank reactor is analyzed with a mixture of tert-butyl perbenzoate and benzoyl peroxide as an initiator system. In the modeling of the reactor, a viscosity dependent reactor wall heat transfer coefficient is used to account for the changing heat transfer efficiency as monomer conversion and polymer molecular weight increase. The steady state and bifurcation behaviors have been investigated with the reactor residence time, initiator feed composition, initiator concentration, feed solvent volume fraction, and coolant temperature as bifurcation parameters. Unlike the reactors with constant heat transfer coefficient, the present system exhibits relatively simple steady state and dynamic bifurcation behaviors. Oscillatory behavior is observed only when the solvent volume fraction in the feed exceeds 0.2. The dynamic simulation of the reactor also indicates that a feedback temperature controller may fail to maintain the reactor temperature when the heat transfer coefficient changes as a result of process disturbances.
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  • 24
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    Polymer Engineering and Science 32 (1992), S. 586-592 
    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: Thin microtomed samples from hot-tool butt welds of polypropylene pipes are subjected to uniaxial tensile stress using a specially built instrumented microtesting machine. The deformation of the interface between the weld and the bulk polymer is measured by an optical method. An analysis of these measurements is carried out using the finite element method, and contours of the effective stress are obtained. There is a steep stress gradient at the junction of the weld flash and the bulk polymer, although the stress concentration factor is relatively low. The stress is essentially constant in the bulk polymer apart from the region near the weld zone. Tests on samples without the weld flash show that the maximum stress occurs within the weld zone. This is consistent with long-term tests on larger samples, where the fracture is found to initiate within the weld. The method of analysis enables the stress-strain response of the weld material to be determined.
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  • 25
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    Polymer Engineering and Science 32 (1992), S. 600-611 
    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: Ultrasonic welding of oriented polypropylene (OPP) using tie-layer materials has been examined. The thermal cycle at the joint interface was evaluated using a high speed data acquisition system, and concurrent changes in horn displacement (penetration) and the output power were monitored. The model explaining process operation involves four phases, i.e., I-where heating occurs because of the stresses generated in asperities on the contacting surfaces; II-where the whole tie-layer reaches the melting point; III-where the polymer melt is subjected to intense heating from viscous dissipation and is squeezed out; and IV-where the joint cools after welding. In the early stages of ultrasonic welding the heat generated at asperities on the contacting surfaces leads to melting of the tie-layer/oriented polypropylene interface within 50 ms. The tie-layer heats up because of a combination of viscoelastic dissipation and heat conduction from the oriented polypropylene/tie-layer interface, and the rate of temperature rise at the midline of the tie-layer is in the range 200°/s to 400°/s. The reduction in thickness of the test specimens (penetration) is negligible up to the time when the tie-layer melts completely, and then changes rapidly when the melted polymer at the joint interface is squeezed out. The influence of machine parameters (amplitude and contact pressure) and of tie-layer Melt Flow Index is also examined. The total time required for completion of the welding process decreases when the amplitude and applied pressure are increased. The use of low Melt Flow Index tie-layers produces peak temperature as high as 600° at the bondline, and little material is ejected during the ultrasonic welding operation.
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  • 26
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    Polymer Engineering and Science 32 (1992), S. 810-822 
    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: This work presents an analytical technique to describe the orientation behavior of short fibers in arbitrary two-dimensional homogeneous flows. It is shown that the fiber orientation, specified by a unit vector, can be analytically calculated at any instant using any initial orientation and flow kinematics. The rotation of a fiber with the bulk fluid deformation is expressed in terms of orientation vector components by utilizing an equivalent strain tensor calculated from the fluid kinematics. This technique is then used to evaluate the orientation behavior of a large number of fibers starting from different initial orientations, representing an orientation state. The orientation distribution function is generated statistically by considering the frequency distribution curve of the orientation of the large number of fibers. It is shown that using a combination of analytical solutions and statistical methods provides a convenient description of fiber orientation behavior. The accuracy of the generated orientation distribution function is found to be dependent on the number of fibers used in the analytical solution. The statistical orientation distribution function is compared with the exact solutions for certain homogeneous flows and found to be in close agreement.
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  • 27
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    Polymer Engineering and Science 32 (1992), S. 836-840 
    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: A commercial epoxy resin, consisting of a mixture of diepoxides based on diglycidyl ether of bisphenol-A (DGEBA) and containing an epoxidized polypropylene glycol as reactive diluent, was characterized by 1HNMR, FTIR, SEC, and chemical analysis. The kinetics of the cure with ethylenediamine (EDA) was catalyzed by the (OH) groups present in a large amount in the commercial formulation. A second order kinetic behavior gave an accurate fitting of results obtained by different experimental techniques (DSC in dynamic and isothermal modes and SEC in the pregel stage). The activation energy was E = 59.1 kJ/mol (14.1 kcal/mol), in very close agreement with values reported for the catalytic mechanism of the DGEBA-EDA polymerization. From the gel conversion and the critical stoichiometric ratio for samples containing an epoxy excess it was found that the average functionality of epoxidized species was f = 1.58.
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  • 28
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    Polymer Engineering and Science 32 (1992), S. 841-844 
    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: Elastic moduli of injection molded blends of polycarbonate with poly(styrene-co-acrylonitrile) (SAN) have been obtained at temperatures between the glass transition temperatures of the two components. When compared with compression molded blends as a function of composition, the moduli were found to differ by as much as a factor of three at intermediate compositions. The variations are ascribed to differences in connectivity between minor component particles. The morphologies of these materials have been modeled using percolation concepts to quantify continuity of the individual phases. The effects of phase continuity resulting from composition as well as dispersed phase shape differences were evaluated. It was found that shape per se has only a minor effect on percolation. However, shape as reflected in the size of dispersed particles relative to the extent of the domain in which they reside is primary for developing a model for continuity of the phases. An empirical relation for percolation in finite domains was devised from Monte Carlo simulations. Modulus values calculated from these continuity considerations agree well with the observed data.
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  • 29
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    Polymer Engineering and Science 32 (1992), S. 854-860 
    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: The morphology, rheology, and mechanical properties of blends of polysulfone (PSF) with up to 65% of a wholly aromatic liquid crystalline polymer (LCP) were investigated. In injection molded specimens a skin-core morphology was observed with the LCP minor phase oriented in the skin and globular in the core. Scanning electron microscopy of fractured surfaces showed sharp phase boundaries, suggesting low interfacial adhesion. The neat PSF and blends with low amounts of LCP exhibited a low shear Newtonian plateau not observed in the blends with high LCP levels. The addition of LCP to PSF resulted in an increase in stiffness, a small increase in tensile strength, and a significant improvement in processability.
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  • 30
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    Polymer Engineering and Science 32 (1992), S. 861-867 
    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: Commercial polysulfone/polycarbonate (PSU/PC) polymer blends were reprocessed up to five times to determine the influence that reprocessing has on their structure and physical properties. All the high strain properties, mainly ductility, significantly decreased under harsh processing conditions, such as five cycles at 320°C. The results of reprocessing the blends at 320°C have been compared with results at a lower temperature and also with those of the separate components with the aim of clarifying the origin of the degradation. These results plus Fourier transform infrared spectroscopy (FTIR), dynamic mechanical analysis, and melt flow index measurements (MFI) indicate that the presence of the two polymers together clearly decreases the resistance to degradation of each component. Moreover, degradation under the stated conditions is mainly thermal and does not change the chemical nature of the blends. However, a clear decrease in molecular weight was observed both by viscosimetry and MFI measurements as was a shift to higher temperatures of the low temperature secondary transition of both PC and PSU. Both molecular weight and secondary transition changes usually deteriorate mechanical properties but not in the degree observed here. This probably means that the fine and difficult-to-observe structure of the blend has also changed.
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  • 31
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    Polymer Engineering and Science 32 (1992), S. 886-893 
    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: Dynamic mechanical thermal analysis (DMTA), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM) concurrently show that polycarbonate (PC)/poly(methyl methacrylate) (PMMA) blends have a two-phase structure. The differences between the Tgs of parent polymers and the Tgs of conjugate phases, determined by both DMTA and DSC, indicate a limited miscibility of components and allow the approximate composition of conjugate phases to be calculated. The Flory-Huggins interaction parameter calculated by using these data assumes values about 0.035 ± 0.010. Phase inversion occurs in an interval close to the 50/50 composition, though the molar masses and melt viscosities of the polymers were rather different. Partial miscibility of components ensures interfacial adhesion capable of sustaining the stress transfer between phases up to fracture. Yield stress of the blends is very close to values foreseen by the rule of mixtures. A specific feature of the blends studied is that the addition of 10 to 20 vol% of PMMA to PC increases the strain at break and work to fracture, which are rather low for the PC used. The enhanced capability of the blends to absorb mechanical energy is probably linked to plastic deformation of the dispersed PMMA.
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  • 32
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    Polymer Engineering and Science 32 (1992), S. 894-902 
    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: In this work, blends of polycarbonate and a high density polyethylene were investigated through their morphology, mechanical properties, and the effect of compatibilizers: a copolymer styrene-butadiene-styrene and an ionomer. Blending was performed in the melt state at 220°C, and the concentration of the compatibilizers was varied from 1% to 5% by weight. In the case of the copolymer modified blend, the results showed no change in the mechanical properties compared to the neat blend, whereas the morphology showed that the copolymer might interact with only one phase. For the ionomer, the addition of 1% increased the Young's modulus and the tensile strength of the blend. For the morphology, a large change in the size of the dispersed phase (polyethylene) is observed. This was attributed to the compatibility of the ethylene group of the ionomer with the minor phase, and the reaction between the carbonate group of polycarbonate (PC) and the acid group of the ionomer. An investigation on the binary blends of PC and the ionomer showed the occurrence of a chemical reaction that might be of a transesterification type. Differential scanning calorimetry and Fourier transform infrared techniques were used to characterize these blends.
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    Polymer Engineering and Science 32 (1992) 
    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
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  • 34
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    Polymer Engineering and Science 32 (1992), S. 921-923 
    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: The melt flow index and oxidation induction period of low-density polyethylene crosslinked with dicumyl peroxide (DCP) in the presence of tetrakis (methylene β-3, 5-di-butyl-4-hydroxypheny1)-propionate methane (Antioxidant 1010) were determined. The results suggest that there is a negative synergism between this crosslinking agent and antioxindant. Part of the antioxidant terminated the chain propagation by trapping radicals, and thus reduced the efficiency of crosslinking. The antioxidant efficiency was also reduced owing to meaningless consumption.
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  • 35
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    Polymer Engineering and Science 32 (1992), S. 909-919 
    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: Fractography has been used in the post-failure analysis of single edge notched specimens of injection molded blends of polycarbonate (PC) and acrylonitrile-butadiene-styrene terpolymer (ABS). The mode of ductile tensile fracture of single edge notched specimens depended on comosition. Plane stress shear tearing was observed in the composition range PC/ABS 90/10 to 70/30 by weight where PC was the continuous phase. Intermediate compositions, PC/ABS 60/40 to 40/60, had a co-continuous or almot co-continuous phase morphology; these blends fractured by mixed mode pop-in, where a tunneling center crack relieved the triaxiality and permitted plane stress shear lips to form near the edges. Herringbone fracture, a plane strain mode characterized by discontinuous crack growth, was observed when ABS was the continuous phase, PC/ABS 30/70 to 10/90. An S-shaped relationship was observed between the ductile-to-brittle transition temperature and the composition. Addition of ABS to PC increased ductility up to PC/ABS 70/30 and 60/40, which were the most ductile compositions. Further addition of ABS decreased the ductility, and the least ductile compositions were PC/ABS 30/70 and 10/90.
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  • 36
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    Polymer Engineering and Science 32 (1992), S. 1086-1096 
    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: A finite element algorithm developed previously has been successfully extended to the study of nonlinear time-dependent problems. Nonlinear viscoelastic and viscoplastic models have been used to study the time-dependent deformation and failure of high density polyethylene (HDPE). Two classes of nonlinear models have been identified; those that allow stress redistribution with time under specified traction boundary conditions, and those that do not. The implications of using viscoelastic vs. viscoplastic models, as well as the specific mathematical form of the constitutive equations selected for use, have been studied. Strains predicted using the FE algorithm have been compared with experimental measurements for (i) a HDPE plate with a hole and (ii) a double edge notch HDPE specimen, both under remote tension. Excellent agreement was obtained between numerical predictions and the experimental values.
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  • 37
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    Polymer Engineering and Science 32 (1992), S. 1105-1113 
    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: The influence of sample thickness on fatigue crack propagation rates in injection molded nylon 66 was determined by preparing 12.7 mm thick plaques along with more conventional 3.0 mm thick samples. Initial results suggested a large effect of thickness as the crack propagation rates were accelerated in the thicker samples and the stress dependence was also increased. Since the calculated thickness for a plane stress to plane strain transition in nylon 66 is 9.0 mm, it was thought that these results were related to the stress state at the crack tip. However, a more thorough study of the thicker plaques has now demonstrated that neither the magnitude nor the stress dependence of the fatigue crack growth rates is necessarily changed under plane strain conditions as similar results can be obtained for thick and thin plaques. It is suggested that the earlier results were confounded by a previously unrecognized processing history effect which does accelerate fatigue fracture. The latter effect is shown by thermal analysis and optical microscopy to be related to a rearrangement of the polymer network during melt processing.
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  • 38
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    Polymer Engineering and Science 32 (1992), S. 1114-1125 
    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: Fatigue crack propagation rates in injection molded nylon 66 were previously shown to be strongly affected by prior processing history. To provide a physical basis for the observed acceleration in crack growth rates, microtomed sections were cut through the tips of stable fatigue cracks and examined by optical microscopy. A reduction in spherulite size occurs with reprocessing along with an accompanying decrease in the amount of deformation at the crack tip. For the initially processed nylon 66 this deformation consists of a vast array of independently initiated craze-like zones. Patchy type regions observed on the fatigue fracture surface are similar in size to the initially formed crazed zones. Crack advance occurs by the breakdown and coalescence of the crazed regions via matrix shearing. The extensive damage zone is believed to result in a reduction in stress intensity at the crack tip thereby reducing the crack propagation rates. For the reprocessed nylon 66, one observes fewer crazes and a sharper fatigue crack tip with a consequent acceleration in crack propagation rates and a smoother fracture surface.
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  • 39
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    Polymer Engineering and Science 32 (1992), S. 1126-1137 
    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: Brittle failure, a significant design issue for plastic components subject to impact loads, is especially catastrophic when the material is normally ductile. Such behavior is not adequately understood relative to the micromechanisms, controlling parameters, and design consequences in plastics. Previous work has identified the process of crazing as being relevant to these failures in thermoplastics. The relationship between crazes generated through mechanical loading and subsequent brittle failure of amorphous thermoplastics is discussed and the hypothesis that the craze event is a necessary but insufficient condition for brittle failure is employed. Emphasis is focused upon the engineering prediction of craze formation and its use as a conservative brittle failure criteria for defining geometric details to prevent brittle failure. First, a series of experiments using one geometry is applied to study the concept of crazing as a precursor to brittle fracture in the two amorphous polymers polycarbonate and polyetherimide. Second, three-dimensional finite element analyses are used to assess the effects of changes in geometric detail upon the continuum stress state and eventual failure of the specimen for these two materials.
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    Polymer Engineering and Science 32 (1992), S. 1138-1146 
    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: The compressive-stress strain response of polyurethane foam under uniaxial compressive impact loading has been studied. The development of a uniaxial constitutive model from strain rate controlled compression tests is detailed. Density and temperature functions have been added to the integral power model proposed by Schwaber, Meincke, and Nagy. The model assumes that the effects of density, temperature, strain and strain rate on stress are separable functions. The model correlated well with actual static compression tests and was used successfully to predict the impact response of energy absorbing polyurethane foam under uniaxial compressive loading.
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    Polymer Engineering and Science 32 (1992) 
    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
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    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
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    Polymer Engineering and Science 32 (1992), S. 1163-1173 
    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: This paper exmines the influence of process variables on final thickness distributions for vacuum-formed thermoplastic parts. The process variables investigated include evacuation rate, sheet surface temperature, mold temperature, and material slip over the mold surface. The experimental data presented include, in addition to thicknesses, sheet surface temperature obtained via infrared thermography. A finite element program to model the vacuum-forming process is discussed, and the wall thickness distribution predicted by this program for a vacuum-formed part is compared with the results of the experiments.
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    Polymer Engineering and Science 32 (1992), S. 1350-1357 
    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: The dynamic creep behavior of a filled poly(dimethylsiloxane) elastomer was studied under cyclic stress. The stress level was chosen such that the increase in the internal temperature was small and that microcracks were not observed. This work has demonstrated that cyclic stress in combination with high temperature accelerates the degradation of the elastomer. The results suggest that because of the applied force, breaks in the load-bearing chains of the network occur. These breaks, while relieving the mechanical stress, create highly reactive ionic fragments. It is believed that because of the subsequent reactions of the ionic fragments, changes in the specific gravity, storage modulus, effective crosslink density, and length of the sample (creep) are observed. The observed decrease in the storage modulus is thought to occur because of the reaction of the ionic fragments with moisture, which results in the formation of silanol chain ends that reduce the effective crosslink density. The results also show that contrary to the prediction of the Boltzmann's Superposition Principle, the rate of creep is greatly enhanced when the sample is subjected to a sinusoidally varying dynamic load as compared to a comparable static load. The polymer weight loss was found to be linear with time and strongly dependent on the level of applied dynamic and static force. In addition, the weight loss and rate of creep were also found to be strongly dependent upon temperature.
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  • 45
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    Polymer Engineering and Science 32 (1992), S. 1358-1365 
    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: Interest in the development of polymeric materials for high temperature, electronic and microelectronic applications has led to an increasing number of new polymers. Many of these polymers have complex organic ring structures and semirigid backbones, characteristics that have posed some difficulties for structural analysis. The purpose of this paper is to test and compare two practical nondestructive optical techniques, polarized optical microscopy and polarized refractometry, for the determination of three-dimensional surface and bulk anisotropy in these advanced materials. The optical techniques are first tested on a series of optically homogeneous uniaxially oriented isotactic polypropylene films and then applied to the analysis of high refractive index Kapton (PMDA-ODA) polyimide films. The study includes a test of the validity of the compensator method, including the effect of fringe jumping, the use of polymer retarders, and the tilting technique of Stein.
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  • 46
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    Polymer Engineering and Science 32 (1992), S. 1372-1378 
    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: Polymer coatings are widely used to protect glass from indentation damage. A model for the strength degradation that occurs when a sharp indenter penetrates through the coating is developed by accounting for the indentation load shared by the coating and substrate. This model accounts for the additional load supported by the coating due to the pile-up of coating material underneath the indenter. The model predicts the strength degradation as a function of indentation load, coating and substrate hardnesses, and coating thickness. Comparison of the model to experimental data for a wide range of polymer coatings (two epoxies, epoxy acrylate, and urethane acrylate) on soda-lime glass substrates shows good agreement.
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  • 47
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    Polymer Engineering and Science 32 (1992), S. 1500-1508 
    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: Novolak resins provide the best overall performance for “g” and “i”-line photoresists. There is a continuing need for advanced novolak designs that will provide improved lithographic, thermal, and etch characteristics that may be reproducibly synthesized. A novolak synthesis process was developed using the solution condensation technique. Cresol mixtures with m-cresol and 3,5-xylenol at specific ratios provide reproducible novolaks with controlled molecular weights. In order to achieve high thermal and etch performance, while retaining photospeed and resolution characteristics, three basic approaches were investigated: (1) increase in molecular weight, which produces novolaks with Tg ranging from 120 to 130°C with relatively slow dissolution rates; (2) incorporation of multi-hydroxyphenols such as resorcinol to tailor the dissolution rate, resolution, thermal, etch, and adhesion characteristics; (3) partial esterification of multi-hydroxy novolaks giving a Tg range of 140 to 150°C. Lithographic evaluation of the novolak resins was performed by formulating with a 2,1,4-diazonaphthoquinone (DNQ) sensitizer. Results on resin synthesis, molecular weights, lithographic, thermal, and etch characteristics are discussed.
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    Polymer Engineering and Science 32 (1992), S. 1511-1515 
    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: The quantum yield for acid generation from alkyl and arylsulfonic acid esters of pyrogallol was measured in resist films composed of a sulfonate, tBOC-BA, and novolak resin. It was found that the quantum yield increases with decreasing molecular size of the sulfonyl group, which can explain the differences in sensitivity of the resist systems. Methanesulfonic acid esters of various phenol derivatives were synthesized to see the effect of backbone structure on the efficiency of acid generation. The sensitivity measurement of resists containing these sulfonates indicates that the number of sulfonyloxy groups bonded to a benzene ring is important. The higher number of the sulfonyloxy groups gives a higher efficiency of acid generation.
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    Polymer Engineering and Science 32 (1992), S. 1516-1522 
    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: t-Butyloxycarbonyl (t-BOC) blocked compounds based on the protection of phenolic groups, e.g. poly-4-hydroxystyrene derivatives, Bisphenol A type dissolution inhibitors, or onium salt photoacid generators, have found widespread research interest for photoresist systems with excellent photosensitivity and high resolution power. We have made an extension of this approach using new phenol type polymers. This contribution presents first details on the chemistry of these systems and results of their lithographic evaluation as positive tone photoresists for deep UV applications.
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    Polymer Engineering and Science 32 (1992) 
    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
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    Polymer Engineering and Science 32 (1992), S. 1557-1557 
    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
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    Polymer Engineering and Science 32 (1992), S. 1545-1549 
    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: The multiple interference effect is one of the major causes of the fluctuation in critical dimension control (CD) and in mark detection for alignment. Suppressing this effect is critical for future photolithography. We propose a new photolithography technique called anti reflective coating on resist (ARCOR), which improves linewidth accuracy and overlay accuracy by suppressing multiple interference. ARCOR consists of relatively simple processes: A clear antireflective film is spun onto the resist prior to the mark detecting for alignment and exposure. The film is subsequently removed and the resist developed in the conventional way. ARCOR differs from ARC, which suppresses the reflection at the resist/substrate interface. ARCOR suppresses the reflection at the air/resist interface. ARCOR allows mark detection and exposure without light intensity-loss and multiple interference. The experiments mainly examine polysiloxane and perfluoroalkylpolyether as ARCOR materials. It is shown that linewidth accuracy can be improved from 0.3 to 0.03 μm. The signal-to-noise ratio of the alignment signal is drastically improved, and the overlay error is about half that of the conventional method. ARCOR is also effective for directly measuring the reflectivity at the resist/substrate interface, which is a key parameter of the multiple interference effect and the halation. Using ARCOR and a thin resist film, the measured ratio of reflected light to incident light indicates the reflectivity at the resist/substrate interface. Because, the probe light does not reflect off the resist surface and the intensity-loss at the resist surface is suppressed. With perfluoroalkylpolyether film, the measurement error is ∼ 1.5%.
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    ISSN: 0933-5137
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    Materialwissenschaft und Werkstofftechnik 23 (1992) 
    ISSN: 0933-5137
    Keywords: Chemistry ; Polymer and Materials Science
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    Materialwissenschaft und Werkstofftechnik 23 (1992), S. 66-66 
    ISSN: 0933-5137
    Keywords: Chemistry ; Polymer and Materials Science
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    Materialwissenschaft und Werkstofftechnik 23 (1992), S. 74-76 
    ISSN: 0933-5137
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Materialwissenschaft und Werkstofftechnik 23 (1992), S. A24 
    ISSN: 0933-5137
    Keywords: Chemistry ; Polymer and Materials Science
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    Materialwissenschaft und Werkstofftechnik 23 (1992), S. 82-94 
    ISSN: 0933-5137
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: It is assumed that the plane in which the maximum variance of the equivalent stress appears is critical for a material and the fatigue fracture should be expected in this plane. The equivalent stress is calculated according to the fatigue criterion of maximum shear and normal stresses in the fracture plane. It was demonstrated that for each stationary random stress state there is one or more critical planes where the fatigue fracture plane can be expected. The variance method together with the discussed fatigue criterion give good results for three analysed types of carbon steels under multiaxial cyclic loadings.
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    Materialwissenschaft und Werkstofftechnik 23 (1992), S. 197-200 
    ISSN: 0933-5137
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: A Laser-Interferometer for Non-contacting Measurements of Displacements in the Range of NanometersA prototype laser-interferometer with a computer-aided control and evaluation system was developed and attached to a commercial tensile testing equipment for testing. With microhardness indentations as markers it is possible to determine displacement changes with a resolution of about one nanometer. The capabilities of this test system are demonstrated e.g. by measurements of the static Young's modulus, the determination of the crack opening behaviour and the coefficient of thermal expansion of Cu-specimens.
    Notes: Ein Laser-Interferometer mit einem rechnergestützten Auswerteverfahren wurde in einer Prototypentwicklung an eine kommerzielle Zugprüfmaschine angepaßt und erprobt. Mit Hilfe von als Meßmarken dienenden Mikrohärteeindrücken erlaubt dieses Meßsystem. Abstandsänderungen mit einer Auflösung von etwa 1 Nanometer zu bestimmen. Die Funktionsfähigkeit dieser Meßanordnung wird an Beispielen der E-Modulmessung der Bestimmung des Rißöffnungsverhaltens und des Wärmeausdehnungs-koeffizienten von Cu-Proben demonstriert.
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    Materialwissenschaft und Werkstofftechnik 23 (1992), S. A62 
    ISSN: 0933-5137
    Keywords: Chemistry ; Polymer and Materials Science
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    Materialwissenschaft und Werkstofftechnik 23 (1992), S. 249-249 
    ISSN: 0933-5137
    Keywords: Chemistry ; Polymer and Materials Science
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    Materialwissenschaft und Werkstofftechnik 23 (1992), S. A6 
    ISSN: 0933-5137
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Materialwissenschaft und Werkstofftechnik 23 (1992), S. 283-286 
    ISSN: 0933-5137
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Mercury Penetration Technique and Grain Size Analysis of ConcreteThe paper describes the behaviour of hardened cement paste and concrete under high velocity water jet attack. Using mercury penetration technique and grain size analysis method, the failure performance is identified as a fracture mechanical one. The behaviour of the materials is influenced due to aggregate grains.
    Notes: Der Beitrag beschreibt das Verhalten von Zementstein und Betonen bei der Beanspruchung durch Flüssigkeisstrahlen hoher Geschwindigkeit. Mittels Quecksilberporosimetriemessungen und Korngrößenanalysen wird festgestellt, daß der Versagensvorgang bruchmechanisch orientiert ist und daß das Verhalten deutlich durch die Zuschlagstoffkörner beeinflußt wird.
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    Materialwissenschaft und Werkstofftechnik 23 (1992), S. A80 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Materialwissenschaft und Werkstofftechnik 23 (1992), S. A80 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Materialwissenschaft und Werkstofftechnik 23 (1992), S. 117-123 
    ISSN: 0933-5137
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Oberflächenbehandlung von Al2O3 mit CO2-LaserPoröse und dichte Al2O3-Keramik wurde mit infrarotem Laserlicht oberflächenbehandelt. Hierbei wurden die Leistungsdichte der Laserstrahlung in weiten Grenzen variiert und unterschiedliche Vorheiztemperaturen benutzt. Die Bildung von Rißnetzwerken und die Tiefe der geschmolzenen Zonen wurde in Abhängigkeit von verfahrensparametern ermittelt.Die Untersuchungen zeigen, daß eine Kornvergrößerung in der Aufschmelzzone nicht vermieden. aber die Rißbildung durch Optimierung der Laserparameter und Vorheizen effektiv herabgesetzt werden konnte. Die Oberfläche der porösen Keramik konnte durch infrarote Laserstrahlung erfolgreich versiegelt werden.
    Notes: Laser surface melting of porous and dense compact Al2O3 ceramics was studied by using a wide range of laser power densities and different preheating temperatures. Tendency for cracking and depth of melted zone were measured as a function of operating conditions.The experiments showed that grain growth in the laser treated zone could not be avoided but tendency for cracking was substantially reduced by optimizing laser parameters and preheating procedure. Surfaces of porous ceramic were successfully sealed by infrared laser light.
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    Keywords: Chemistry ; Polymer and Materials Science
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    Description / Table of Contents: Fatigue crack propagation under in phase mixed mode I+II loadingStress intensity factors of kinked cracks are calculated by using the boundary-element-method (BEM). The results are compared to some analytical solutions. Referred to the crack deflection angles. The results of BEM calculation agree well with NUISMER's criterion and in addition with the experimental results.The growth rates of kinked cracks are compared to purely mode I loaded cracks. At R = 0.6 the crack growth rates don't show any difference. At R = 0.1 the angled cracks show slower growth rates. The reason is a significant II*-induced crack closure. When referring the crack growth rates to ΔKeff, there is almost no difference between the propagation rates of angled cracks and straight cracks. This is in good agreement with the results, achieved at R = 0.6.
    Notes: Die Spannungsintensitätsfaktoren KI* und KII* abgelenkter. kurzer Zusatzrisse werden mit Hilfe der Boundary-Element-Methode (BEM) berechnet und mit den Ergebnissen analytischer Ansätze verglichen. Die BEM Simulation liefert bezüglich der erwarteten Rißablenkwinkel ähnliche Ergebnisse wie der Ansatz von NUIS-MER bzw. wie das Tangentialspannungskriterium. Die experimentellen Ergebnisse stimmen mit denen der numerischen Simulation gut überein.Die Fortschrittsraten abgelenkter Risse werden mit denen von rein Modus I belasteten Rissen verglichen. Bei einem Spannungsverhältnis R = 0.6 ist kein signifikanter Unterschied feststellbar. Bei R = 0.6 weisen die abgelenkten Risse kleinere Fortschrittraten auf. Die Ursache dafür ist II*-induziertes Rißschließen. Bezogen auf ΔKeff, zeigt sich bei R = 0.1 kein nennenswerter Unterschied zwischen den Mixed-Mode und Modus I Rissen. Diese Beobachtung deckt sich mit den Ergebnissen, die bei R = 0.6 erzielt wurden.
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    Materialwissenschaft und Werkstofftechnik 23 (1992), S. 151-156 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Materialwissenschaft und Werkstofftechnik 23 (1992), S. A46 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Materialwissenschaft und Werkstofftechnik 23 (1992), S. 179-179 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Materialwissenschaft und Werkstofftechnik 23 (1992), S. 179-179 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Materialwissenschaft und Werkstofftechnik 23 (1992) 
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    Materialwissenschaft und Werkstofftechnik 23 (1992), S. 216-216 
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    Materialwissenschaft und Werkstofftechnik 23 (1992) 
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    Materialwissenschaft und Werkstofftechnik 23 (1992), S. 217-223 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: On Alternating Bending Machine WEBI's Suitability for Determination of Fatigue CharacteristicsAlready in 1966, experimental investigations revealed that the flat bending torsion testing machine „FLATO“ (Schenck, Darmstadt) doesn't keep constant its torsional moment amplitude in case of specimen's fatigue softening or hardening, respectively. Thus. conclusions concerning the material's fatigue characteristics drawn from such experimental results might therefore be seriously false. Furthermore, also the alternating bending testing machine „WEBI“ (Schenck, Darmstadt) shows an equivalent behaviour concerning its bending moment amplitude. For this reason. the main findings of a comprehensive experimental study carried out on WEBI with an unalloyed steel C 45 (0.45 mass perccnl C) in different heat treatment conditions are reported in this paper.
    Notes: Bei zwangsangetriebenen Schwingprüfmaschinen bestimmter Bauart kommt es im Falle zyklischer Ent- oder Verfestigung des geprüften Werkstoffes zu Veränderungen bezüglich deren Beanspruchungscharakteristik. Schon 1967 werden derartige Verände-rungen von technologisch und damit gleichermaßen anwendungsorientiert bedeutsamer Größenordnung im Zuge von Untersuchungen auf einer Flachbiege-Torsions-Maschine („FLATO“) aufgezeigt. Die vorliegende Arbeit berichtet über eine entsprechende Experimentalstudie auf einer Wechselbiegemaschine („WEBI“). Die Ergebnisse erhärten den Vorbehalt gegen die Verwendung von Prüfmaschinen dieses Bauprinzips zur Ermittlung von Ermüdungskennwerten, sofern diese Maschinen nicht durch zusätzliche, derzeit (noch) nicht handelsübliche Kontroll- bzw. Regeleinrichtungen ergänzt werden.
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    Materialwissenschaft und Werkstofftechnik 23 (1992), S. A66 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Materialwissenschaft und Werkstofftechnik 23 (1992), S. 243-249 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: Thin, adherent and stable polymeric films of 4-(2-pyridylazo)resorcinol (abbreviated as PPAR) were prepared by oxidative polymerization in 0.2 M NaOH solutions. PPAR films deposited on GC electrodes were found to inhibit the electron transfer reactions of the couple [Fe(CN)6]3-/4-. The redox behaviour of CuCl2 in 0.5 M KCl at bare and PPAR-covered GC electrodes was studied by cyclic voltammetry, RDE voltammetry and chronoamperometry. At PPAR-covered electrodes the peak potential of deposition of Cu occurs at ≃ 260 mV more cathodic potential than bare electrodes whereas the redox peaks of Cu2+/1+ and the oxidation of Cu → Cu1+ occur at the same potentials. Catalysis of thc redox processes of the couple Cu2+/1+ at PPAR-covered electrodes is attributed to incorporation of the redox species by chelation and electrostatic attraction. The diffusion coefficient of Cu2+ species (D = 0.29 × 10-5cm2 S-1) at PPAR-covered electrodes was found to be less than at bare electrodes (D = 0.95 × 10-5 cm2 S-1) whereas the effective bulk concentration (CO* = 28 mM) is higher than the used concentration: 10 mM.
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    Materialwissenschaft und Werkstofftechnik 23 (1992), S. 299-304 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: Untersuchungen an Flachzugproben und Behältern aus Vergütungs- und Feinkornbaustählen mit etwa halbelliptischen Oberflächenrissen haben gezeigt. Daß die Versagensspannung nach Verfahren des plastischen Versagens konservativ ermittelt wird. Während sie nach dem Ansatz von Harrison und dem Fließkriterium von Mises - unabhängig von der Rißtiefe - im Mintel um etwa 10% unterschätzt wird, bewerten die anderen untersuchten Verfahren (Mattheck, Chell) deutlich konservativer. Der Grad der Unterschätzung wächst von etwa 30 bzw. 40% bei mittleren Rißtiefen bis zu 70% bei tiefen Rissen. Für einseitigen Wasserstoffangriff auf der Rißausgangsseite ergaben sich i.a. die gleichen konservativen Bewertungen wie bei Luftumgebung.Die Untersuchung hat weiterhin gezeigt, Daß die Versagensspannung von Fluchzugproben unter Luft- und Wasserstoff-Atmosphäre mit etwa konstanter Rißtiefe mit guter Genauigkeit berechnet werden kann, wenn im Restquerschnitt der Mittelwert zwischen Streckgrenze und Zugfestigkeit als Fließspannung angesetzt wird.Es ist für ähnliche Bauteile zu erwarten, daß die erarbeiteten Ergebnisse auf Werkstoffe mit vergleichbaren Rißzähigkeits- und Festigkeitseigenschaften übertragbar sind.
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    Materialwissenschaft und Werkstofftechnik 23 (1992), S. 315-315 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Materialwissenschaft und Werkstofftechnik 23 (1992) 
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    Materialwissenschaft und Werkstofftechnik 23 (1992), S. 343-351 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: In total strain-controlled tests without mean strain the cyclic deformation behaviour of unalloyed normalized steels with carbon contents 0,1 ≤ C ≤ 1,05 (wt.-%) is characterized by pronounced softening and slight hardening processes. With increasing carbon content the cyclic deformation curves are shifted to higher stress amplitudes. Cyclic stress strain curves of unalloyed steels determined in tests without mean load are independent of the testing procedure. With increasing carbon content the number of cycles for εa,e = εa,p (transition point) of strain-controlled SN-curves is shifted to smaller values.
    Notes: Das Wechselverformnungsverhalten unlegierter normalisierter Stähle mit Kohlenstoffgehalten 0,1 ≤ C ≤ 1.05 (in Masse-%) ist in totaldehnungskontrollierten mitteldehnungsfreien Versuchen durch ausgeprägte zyklische Entfestigungs- und schwache Verfestigungsvorgänge gekennzeichnet. Die zyklischen Spannungs-Dehnungskurven werden mit wachsendem Kohlenstoffgehalt zu größeren Spannungsamplituden verschoben. Die mittelspannungsfrei ermittelten zyklischen Spannungs-Dehnungskurven unlegierter Stähle sind unabhängig von der Versuchsführung. Die Übergangslastspielzahl, bei der in der Dehnungswöhlerlinie εa,e = εa,p wird, verschiebt sich mit wachsendem Kohlenstoffgehalt zu kleineren Werten.
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  • 82
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    Materialwissenschaft und Werkstofftechnik 23 (1992), S. 375-377 
    ISSN: 0933-5137
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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    Materialwissenschaft und Werkstofftechnik 23 (1992), S. A98 
    ISSN: 0933-5137
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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    Materialwissenschaft und Werkstofftechnik 23 (1992), S. 379-384 
    ISSN: 0933-5137
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Das Diffusionsschweißen von Metall-Keramik-Verbindungen kann sowohl rnit Hilfe konventioneller Diffusionsschweißanlagen als auch unter Anwendung der Heißisostatischen Preßtechnik durchgeführt werden. Der Einsatz der HIP-Technologie ermöglicht die Herstellung verschiedenartiger Werkstoffverbunde. Aufgrund der unterschiedlichen Eigenschaften der metallischen und keramischen Grundwerkstoffe werden die Schweißverbindungen in der Regel mit Hilfe von Zwischenschichten hergestellt. Lediglich bei Keramiken, die ein den Metallen ähnliches Ausdehnungsverhalten aufweisen, können Direktschweißungen durchgeführt werden. Voraussetzung für alle Werkstoffverbundsysteme ist die Entwicklung einer entsprechenden Schweißtechnologie, deren Parameter bestimmend sind für Art, Ausdehnung und Zusammensetzung der Reaktionszone, und die damit die Verbindungsgute der Diffusionsschwingungen entscheidend beeinflussen.
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    Materialwissenschaft und Werkstofftechnik 23 (1992), S. A110 
    ISSN: 0933-5137
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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    Materialwissenschaft und Werkstofftechnik 23 (1992), S. 419-419 
    ISSN: 0933-5137
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 87
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    Particle and Particle Systems Characterization 9 (1992), S. 125-137 
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The possibilities and limitations of photon correlation spectroscopy (PCS) as a practical tool for particle sizing are reviewed. In this part the most frequently used methods of data analysis are briefly surveyed. The practical performances for the determination of particle size distributions were evaluated by a comparative study with different kinds of users (industrial and academic research groups and manufacturers). The PCS results were also compared with electron microscopy (EM) and static light scattering (SLS) results. Thereby it was confirmed that the amount of reliable information that can be obtained by PCS about particle size distributions with measuring times of the order of minutes is limited by the ill-conditioning of the data inversion procedure, among other factors. Nevertheless, the information obtained from the PCS measurements agrees essentially with the EM and SLS results.
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    Particle and Particle Systems Characterization 9 (1992), S. 144-150 
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Beam shape coefficients, gnm, are at the core of the generalized Lorenz-Mie theory describing the scattering of a shaped beam by spheres. A decrease in computation times is essential for systematic applications of the theory. This paper introduces a new formulation to compute beam shape coefficients, gnm, in the framework of the localized approximation and discusses symmetry relations between the coefficients. The new formulation permits computation times to be decreased by one to two orders of magnitude.
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    Particle and Particle Systems Characterization 9 (1992), S. 154-155 
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
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    Particle and Particle Systems Characterization 9 (1992), S. 151-153 
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Experiments on the suspension polymerization of styrene were conducted at various stabilizer concentrations, dispersed phase hold-up fractions, impeller types and impeller speeds. The experimental final particle size distributions obtained were almost always described by the upper limit number distribution. Plots of the maximum diameter, amax, and the mean diameters, a21 and a10, vs. the Sauter mean diameter, a32, gave straight lines with slopes of 1.24, 0.99 and 0.97, respectively.
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    Particle and Particle Systems Characterization 9 (1992), S. 171-175 
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The size distributions of four samples of quartz dust, suspended in liquids of different refractive index (RI), were determined using a Malvern 2600 laser particle sizing instrument. As the relative RI, between particle and suspension media, approached unity the instrument over-estimated the mean particle size for the three finest quartz samples. An under-estimated mean particle size was recorded for the largest quartz sample indicating the complex nature of light scattering by small particles under conditions of low relative RI.A regime of relative refractive index is determined within which particle size analysis using laser diffraction, invoking anomalous diffraction theory, becomes prone to large errors and this range is compared with the van de Hulst criterion.
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    Particle and Particle Systems Characterization 9 (1992), S. 176-185 
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Phase-Doppler experiments applied to optically absorbent (homogeneous and inhomogeneous) liquids are described. Simultaneous size and velocity measurements of single droplets were executed at three off-axis angles ψ. These angles were found to be suitable for the evaluation of the phase-Doppler technique by Mie theory. Both the sizes of the monodisperse droplets and their absorption properties were varied. At least with respect to homogeneous liquids, comparison of the droplet diameters obtained by phase-Doppler measurement and by photography (reference technique) showed good agreement. Concerning the optical properties of inhomogeneous liquids, additional phase-Doppler measurements were carried out using an alternative device based on a laser diode and photodiodes. The longer wavelength λ (830 nm instead of 488 nm) reduced the influence of the inhomogeneities on the droplets' scattering behaviour and thereby improved significantly the phase-Doppler results. It is concluded that phase-Doppler anemometry is suitable for the sizing of optically absorbent droplets of real process fluids. Such droplets result from atomization processes often used in various branches, such as the chemical, pharmaceutical and food industries (production of powders and granules, "spray drying"), automotive engineering (dispersing fuels for combustion) and agriculture (crop spraying). Mie scattering theory is a powerful aid for describing the scattering behaviour of dispersed droplets of real process fluids with more complicated optical properties compared with water, i.e. the behaviour of optically absorbent homogeneous liquids, and for determining the necessary parameters of the optical set-up.
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    Particle and Particle Systems Characterization 9 (1992), S. 207-207 
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
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    Particle and Particle Systems Characterization 9 (1992), S. 231-236 
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The topical problem of pulsed recording of light-scattering particles in a flux has been studied. Along with the determination of the sizes of particles, this problem involves the simultaneous evaluation of their material composition. Such a task arises in analysing multi-component disperse systems. It is shown that it can easily be realized if the particle materials differ appreciably in absorption coefficients and closeness of their refractive indices to that of the dispersion medium. This is connected with the significant difference of the spatial distribution of the scattered light. A simple method for solving such a problem has been designed with regard to the peculiarities of recording weak light fluxes and the necessity for real-time optical measurement processing.
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    Particle and Particle Systems Characterization 9 (1992), S. 213-222 
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Modern image analysis equipment has now made it possible to obtain detailed intensity profile information about objects imaged under the optical microscope. If the object contrast is generated by light absorption alone then the image profile of the object is a square wave and the size information is contained in the fundamental frequency of the Fourier components of that square wave. The period of the fundamental frequency lies very close to the intensity midpoint of the image profile. As long as the microscope objective numerical aperture (NA) is high enough to pass this fundamental the object can be sized to an accuracy which is chiefly dependent upon the signal to noise ratio of the system and independent of classical notions of microscope resolution.Thus for latex particle metal replicas it was possible to determine the diameter to a precision which was typically on the order of 13% of the classical Sparrow limit of resolution for the objective employed.By sizing the same particle replica with objectives of different NA it was demonstrated that the size obtained was independent of the objective NA used as long as the replica diameter was above the Sparrow limit. This is in accordance with optical theory.About mid-summer the Goldstein "Zernike" program became available to us through the kindness of Dr. Goldstein. With this program it was possible to model the effect of optical path difference. Unlike particle replicas, most real objects generate object profiles that are a function of refractive index difference and thickness or path difference in addition to object size and transmittance. Although the "Zernike" program can accommodate path differences, it assumes that the object has negligible thickness-an assumption not merited by most real microscopic objects.Although exact quantitative agreement could not always be obtained with reasonable assumptions, the predictions of the "Zernike" program nevertheless could help to define sample preparation conditions which enabled high accuracy sizing to be performed.This work thus demonstrates that an extremely high degree of accuracy and precision in particle sizing is available from the optical microscope which is independent of classical notions of microscope "resolution". The major requirements are that the objective NA be sufficiently high enough to pass the Fourier components which contain the size information and that features in the image can be identified which contain the size information.
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    Particle and Particle Systems Characterization 9 (1992), S. 237-251 
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The application of the singular value analysis and reconstruction method (SVR) and of the Contin method for the collective analysis of multi-angle noisy photon correlation data sets was investigated. Provided the data are sampled equidistant in time and by proper tuning of the sampling time to the scattering angle, a collective multi-angle SVR analysis is feasible. For homogeneous spherical particles such an analysis does not require any prior knowledge of the angular dependence of particle scattering power (e.g. Mie scattering). SVR allows the information content to be separated from noisy intensity autocorrelation data. It is illustrated that the multi-angle SVR analysis enhances the recovery of the information content. Moreover, SVR can be used as a fast and accurate preprocessor for extracting the field autocorrelation function for a subsequent Contin analysis whereby prior knowledge of particle scattering power as a function of scattering angle is used as a constraint. Compared with the data analysis of multi-angle time-averaged scattered intensity measurements, the information that can be extracted from multi-angle PCS data in comparable accumulation times is poorer.
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    Particle and Particle Systems Characterization 9 (1992), S. 259-263 
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An unexpectedly large additional three phase locking region, the outlaw area has been found where three phase, locked particle may be formed. This implies that in some ores, the number of three phase locked particles may be an order of magnitude larger than expected. The size of this outlaw region is sensitive to the angle at which the three phases meet. Since these higher order locked particles behave differently in separation circuits, it is proposed that in characterizing a solid or ore rock, these angles between the interfacial planes be both measured and included in a Textural Transform.
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    Particle and Particle Systems Characterization 9 (1992), S. 1-8 
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A new computer-aided image analysis procedure for characterizing the number and sharpness of potential cutting facets on the profiles of the image of an abrasive fineparticle is described. In the method, the digitized profile is explored by a running chord generating procedure which generates what is described as the facet signature of the profile. This signature can be processed at different threshold levels to recognize facets of the profile having different levels of sharpness as defined by the acute angle of the facet. Several different ways in which data from the procedure could be used to describe a population of polishing powder fineparticles are outlined. The potential use of the new descriptive characterization procedures for following the physical changes in the powder corresponding to the degeneration in performance of a polishing powder during use is outlined. The possible use of the new methodology to describe the health hazards of angular shaped dust fineparticles and flake type fillers (such as mica) in composite material technology is outlined.
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    Particle and Particle Systems Characterization 9 (1992), S. 9-18 
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Two dimensional images are often used as a basic for calculating shape descriptors of particles. An edge roughness descriptor, the fractal dimension, can be found from a Richardson plot of measured perimeter versus the measuring step length. Data Scatter on these plots is shown to be related to the incipient formation of polygonal harmonics, which are regular polygons formed during a structured walk around the image edge. This relationship was verified using both computer generated fractal images and real particle outlines.
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    Particle and Particle Systems Characterization 9 (1992), S. 28-30 
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A single parameter, denoted as the "aggregation probability", is introduced to represent the average potential of clustering in a suspension in which the aggregates are undergoing random and simultaneous coagulation and breakup by means of mechanical stirring. The parameter may be useful for obtaining quick estimates of the equilibrium cluster size distributions in such systems.
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