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  • Chemistry  (16)
  • distributions of distances  (1)
  • liquid modifier  (1)
  • 1
    Electronic Resource
    Electronic Resource
    The role of the liquid interface agent in mechanical properties improvement of modified chalk filled polyolefins (1982)
    Springer
    Colloid & polymer science 260 (1982), S. 652-662 
    Details
    ISSN: 1435-1536
    Keywords: filled polyolefins ; mineral fillers ; liquid modifier ; polymer-filler interactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract On the basis of the experimental results described in detail in the following sections an explanation of the mechanism of liquid modifier in chalk filled PP action was proposed. After concluding that liquid modifier does not change the sample morphology and crystallinity it was stated that it facilitates filler particles translocation in polymer matrix during deformation. Such translocations are the necessary condition for saturation of volume increase of the sample due to void formation in the process of polymer filler separation preserving the sample from its premature fracture. The most important physicochemical parameter of liquid modifier seems to be its molecular weight. This parameter determines liquids ability to migrate in micropore structure arising under stress and thus to act as a cracking agent. The possibility of the importance of more efficient heat dissipation in the sample was shown indicating the role of better thermal contacts in the sample in the case of modified chalk used as a filler. Such picture of mechanism of liquid modifier action leads also to two important conclusions: Due to polymer filler separation by means of liquid layer no further filler particles surface processing, as in some cases, is needed. The method of modification can be easily generalized for other polymers especially other polyolefins [19], [20] as physicochemical requirements for liquid are known.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01414651
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  • 2
    Electronic Resource
    Electronic Resource
    Statistical approach to the description of spherulite patterns. Two-and three-dimensional cases (1983)
    Springer
    Colloid & polymer science 261 (1983), S. 1-8 
    Details
    ISSN: 1435-1536
    Keywords: Primary nucleation ; spherulitic pattern ; distributions of distances ; statistical approach
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A new statistical approach was applied for the description of spherulite patterns for athermal and thermal type of primary nucleation. The two-and three-dimensional cases were treated in the same way. The analytical expressions were developed for spherulite boundary and inner point distances distributions. It was shown that in the case of the thermal nucleation the nuclei distance are correlated although they were nucleated in a random way. The results were confirmed by the data from computer simulation. The analysis of the theoretical formulas showed that the spherulite pattern remains unchanged if the primary nucleation density is constant (the growth rate can vary) in the case of the athermal nucleation. In the case of the thermal nucleation if the ratio of the nucleation rate and growth rate does not change (both can vary but the ratio must remain constant) the spherulite pattern is not modified.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01411511
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  • 3
    Electronic Resource
    Electronic Resource
    Low-density polyethylene filled with chalk and liquid modifier (1981)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 26 (1981), S. 4047-4058 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    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: Based on the concept of introducing a liquid layer between the polymer and filler, a composition containing low-density polyethylene, chalk, and oligomer of ethylene oxide was proposed. Compositions containing up to 50% chalk modified with ethylene oxide exhibit typical thermoplastic behavior, i.e., neck formation and plastic deformation. They also show high-impact strength and other good properties. On the basis of mechanical data, the main action of the ethylene oxide oligomer in the system is to inhibit crack generation and propagation.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1981.070261207
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  • 4
    Electronic Resource
    Electronic Resource
    High orientation of toughened chalk-filled isotactic polypropylene: Preparation and properties (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 1217-1227 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Chalk-filled isotactic polypropylene (iPP) toughened by modifying the interfaces with liquid oligomer of ethylene oxide was subjected to high deformation at elevated temperature. Oriented chalk-filled material exhibits interesting properties: high concentration of open interconnected pores, high elastic modulus, high tensile strength, ability to absorb large quantities of liquids, white color and roughness of the surface. A continuous process for the production of oriented, toughened, chalk-filled isotactic polypropylene is described. The stretching ratios which can be achieved range from 4 to 8 for modified chalk concentrations with compositions of 60 and 40 wt%, respectively. Solid state extruded, toughened, chalk-filled iPP prepared for comparison exhibits similar morphology and properties as drawn toughened chalk-filled iPP although it contains much less voids.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760321707
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  • 5
    Electronic Resource
    Electronic Resource
    Stability of spherulite growth rate (1990)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 28 (1990), S. 1813-1821 
    Details
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Spherulite growth rates in thin films of isotactic polypropylene, poly (methylene oxide), and poly (ethylene adipate) have been studied by light microscopy. The growth rate of the parts of spherulites formed from pockets of occluded melt is decreased drastically. The decrease is associated with the negative pressure buildup inside the pockets due to the density change as the melt is converted to spherulites. Material subjected to negative pressure shows a higher melting point of 3-4'C if the pressure is released prior to melting. Slight periodic changes of the growth rate were detected during crystallization of banded spherulites. No changes in growth rate were observed for two spherulites about to impinge or for spherulites growing near a solid obstacle.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1990.090281012
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  • 6
    Electronic Resource
    Electronic Resource
    Crystallization of isotactic polypropylene and high-density polyethylene under negative pressure resulting from uncompensated volume change (1993)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 31 (1993), S. 1285-1291 
    Details
    ISSN: 0887-6266
    Keywords: crystallization ; isotactic polypropylene ; high-density polyethylene ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The melting behavior of spherulites in thin sections of isotactic polypropylene bulk samples and high-density polyethylene thin films crystallized isothermally at various temperatures has been studied by polarized light microscopy. The regions around cavities and multiple boundary points between spherulites have higher melting temperatures than the other parts of spherulites crystallized in Regime III. The increase in melting temperature is explained as a result of crystallization under negative pressure arising locally in pockets of occluded melt due to density change during spherulitic crystallization. The negative pressure lowers locally the equilibrium melting temperature and therefore decreases the undercooling, which results in an increase in lamellar thickness. Sectioning of bulk samples releases frozen negative pressure and reveals the increase in melting temperature of those parts of spherulites that were crystallized at lower undercooling. © 1993 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1993.090311003
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  • 7
    Electronic Resource
    Electronic Resource
    Spherulite nucleation in blends of isotactic polypropylene with isotactic poly(butene-1) (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 54 (1994), S. 1513-1524 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    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 phase morphology and the influence of composition on the primary nucleation of isotactic polypropylene in isotactic polypropylene/isotactic poly(butene-1) (iPP/iPB) blends were investigated by electron and light microscopy and small-angle light scattering. It was found that iPP and iPB are miscible but the thermal treatment induces partial phase separation of components and the formation of iPP-rich and iPB-rich phases. The complete phase separation needs high temperatures and/or a long time of melt annealing. In samples crystallized isothermally at low undercooling the heterogeneous primary nucleation in blends is depressed as compared to plain iPP. In blends the less active heterogeneities lose their activity because of an increase of the energy barrier for critical size nucleus formation due to phase separation of blend components during crystallization. For the same reason the rate of homogeneous nucleation in blends decreases, as observed in samples crystallized at very high undercooling. At very high undercooling iPP and iPB are able to crystallize with similar rates, which results in the formation of a fraction of iPB spherulites in addition to iPP spherulites. Consequently the number of spherulites in the blend is larger than that in plain iPP, in spite of the decrease in the homogeneous nucleation rate of iPP in the blend. © 1994 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1994.070541016
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  • 8
    Electronic Resource
    Electronic Resource
    Spherulite growth in isotactic polypropylene-based blends: Energy and morphological considerations (1984)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 24 (1984), S. 1155-1165 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The kinetics of isothermal crystallization of polymer blends in which the matrix is a crystallizable polymer is considered. It is shown that depending on the difference in interfacial energies the inclusions are rejected or engulfed by the growing spherulite. Other factors influencing rejection, engulfing, and/or deformation of dispersed particles of the second polymer are the viscosity of the melt, the spherulite growth rate, and the size of dispersed particles. If the difference in interfacial energies is positive, then rejection or engulfing requires additional work to be done by the crystallization front. This dissipation of energy decreases the spherulite growth rate. It is estimated that the rejection of the second component is the most important phenomenon in the crystallization of blends. The spherulite growth rate of isotactic polypropylene in blends with low-density polyethylene and several elastomers was studied as a function of crystallization temperature and concentration. The comparison of growth rate data with morphological changes occuring during crystallization of blends studied shows very good agreement with the theoretical predictions based on energetics considerations.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760241502
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  • 9
    Electronic Resource
    Electronic Resource
    Acoustic emission during crystallization of polymers (1990)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 28 (1990), S. 1171-1186 
    Details
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Ultrasonic emission was found to accompany spherulitic crystallization of polymers from the melt. The source of acoustic waves was identified as an abrupt negative pressure release in regions of melt occluded by spherulites (weak spots) in the course of crystallization. The buildup of a negative pressure in occluded areas is a result of a density change during crystallization. When the level of stress approaches the limit related to melt cohesion, cavitation occurs, the stress is released, and acoustic wave is emitted. On the basis of a statistical approach to the description of spherulitic structure formation, it was predicted that most acoustic events should occur at a high degree of conversion - close to the end of crystallization. The ultrasonic emission was found during isothermal crystallization of isotactic polypropylene and poly(methylene oxide). In the case of Nylon 6, acoustic emission was attributed to environmental stress cracking and degradation. No acoustic events were recorded during crystallization of high-density polyethylene and during similar thermal treatment of a series of noncrystallizable polymers. Addition of a nucleating agent to crystallizable polymers drastically reduces the acoustic emission during crystallization, which indicates that the spherulite size is one of the most important parameters. Depending on the size and geometry of weak spots, melt properties, and mechanical properties of spherulites, the stress in weak spots is either released by cavitation or remains frozen in the material. It was found that the time distribution of acoustic emission is located between the time distributions of the formation of weak spots and the formation of quadruple boundary points between spherulites.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1990.090280714
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  • 10
    Electronic Resource
    Electronic Resource
    Polyacrylamide gels filled with ferromagnetic anisotropic powder: A model of a magnetomechanical device (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 58 (1995), S. 1007-1013 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    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 concept of a magnetomechanical system able to show permanent magnetization if compressed or to deform in a uniform magnetic field, is presented. The system design is based on polyacrylamide gel filled with demagnetized hard ferrite particles. The ferrite filled gel is deformed by plane strain compression and magnetized while compressed. The orientation of individual magnetized particles was randomized upon compression release. Such samples exhibit no magnetic moment if decompressed and produce magnetic field intensity from 3 to 30 G if compressed. The samples exposed to external uniform magnetic field show macroscopic contraction or expansion of up to 40% of the initial dimensions. The most efficient ferrite was neodymium ferrite in the form of flakes. © 1995 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1995.070580606
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