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  • 1
    Electronic Resource
    Electronic Resource
    Cooperative cavitation in rubber-toughened polycarbonate (1995)
    Springer
    Journal of materials science 30 (1995), S. 587-595 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Particle cavitation in the stress-whitened zone ahead of a semicircular notch in polycarbonate blended with a core-shell rubber was characterized by transmission electron microscopy. Cavitation of rubber particles at five locations in the stress-whitened zone was correlated with the local stress and strain history. It was found that cavitation initiated some distance ahead of the notch when a mean stress condition was met. Initially, only a fraction of the particles cavitated and these were randomly distributed. Single cavitated particles grew into cavitated domains by cooperative cavitation of nearby particles until cavitation was arrested when shear yielding of the matrix provided an alternative mechanism for relief of strain energy. Far from the notch, where the stress state approached uniaxial tension, cavitated domains grew into linear arrays of cavitated particles. A mechanism of cooperative crazing in microlayer composites of polycarbonate and styrene/acrylonitrile copolymer was adapted to cooperative cavitation of core-shell rubber particles. It was proposed that cooperative cavitation of nearby particles occurred by impingement of a small plastic zone that formed at the equator of a cavitated particle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00356315
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  • 2
    Electronic Resource
    Electronic Resource
    Core-shell structured latex particles. III. Structure-properties relationship in toughening of polycarbonate with poly(n-butyl acrylate)/poly(benzyl methacrylate-styrene) structured latex particles (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 58 (1995), S. 419-425 
    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 performance of the designed structured core-shell latex particles in toughening polycarbonate (PC) matrix was examined. Izod impact testing of the PC-core-shell latex blends were used to evaluate the influence of parameters related to the core-shell latex particles on toughening polycarbonate. Among these parameters are the particle size and levels of crosslinking of the core rubber particles, composition and molecular weight of the shell polymer, and weight ratio of shell to core polymers as well as the particle morphology. In this work, core-shell structured latex particles with thinner shells of higher molecular weight polymers were found to improve the impact resistance of polycarbonate. The role of chain entanglements in increased adhesion between the discrete rubbery phase and the continuous glassy matrix and the importance of surface-to-surface interparticle distance for toughening at various temperatures are discussed. © 1995 John Wiley & Sons, Inc.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1995.070580220
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  • 3
    Electronic Resource
    Electronic Resource
    Comparison of some butadiene-based impact modifiers for polycarbonate (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 53 (1994), S. 513-525 
    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 relationship of blend morphology to deformation mechanisms and notched Izod impact strength was studied with three butadiene-based impact modifiers for polycarbonate (PC). The impact modifiers were a linear polybutadiene (PB), a styrene-butadiene-styrene block copolymer (SBS), and a structured latex particle having a PB core and methyl methacrylate/styrene shell (MBS). The particle-size distribution in the blends was determined from transmission electron micrographs (TEM). Fractographic analysis combined with TEM examination of thin sections from impacted specimens provided insight into the failure mechanisms. Good impact was achieved with PC/MBS blends when cavitation of the core-shell particles relieved triaxiality and enabled the matrix to fracture by the plane stress ductile tearing mode that is characteristic of thin PC. The best impact properties were obtained with PC/SBS blends when the modifier was dispersed as aggregates of small particles. Cavitation at the weak internal boundaries relieved triaxiality, but subsequent coalescence of cavitated particles during ductile drawing of the matrix created critical size voids and the resulting secondary cracks reduced the toughness of the blend. In general, PB did not significantly enhance the impact strength of PC. © 1994 John Wiley & Sons, Inc.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1994.070530506
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  • 4
    Electronic Resource
    Electronic Resource
    Deformation of rubber-toughened polycarbonate: Macroscale analysis of the damage zone (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 52 (1994), S. 177-193 
    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: Two commercial core-shell rubbers were used as impact modifiers for polycarbonate (PC). Specimens with a single semicircular edge notch were stretched uniaxially in order to study the prefracture damage evolution of blends under a triaxial tensile stress state. The irreversible deformation of modified PC included a cavitation mechanism in addition to the three shear modes of unmodified PC. At the macroscopic level, the cavitation condition could be described by a mean stress concept. The corresponding critical volume strain for cavitation in PC blends was determined to be independent of rubber content but differed for the two impact modifiers. The critical volume strain for cavitation was used as an index of cavitation resistance for the impact modifiers. The effect of rubber content and temperature on Izod impact strength of the PC blends was also reported. From the relationship between the cavitation resistance and the Izod impact strength, it was proposed that impact modifiers with a higher cavitation resistance impart better toughness to blends with PC. © 1994 John Wiley & Sons, Inc.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1994.070520206
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  • 5
    Electronic Resource
    Electronic Resource
    Deformation of rubber-toughened polycarbonate: Microscale and nanoscale analysis of the damage zone (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 55 (1995), S. 1691-1702 
    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: Deformation of polycarbonate (PC) impact-modified with a core-shell rubber (MBS) was examined at the microscale and nanoscale. The stress-whitened zone (SWZ) that formed ahead of a semicircular notch was sectioned and examined in an optical microscope and transmission electron microscope. At the microscale, the texture of the SWZ consisted of fine shear lines that formed when cavitation of the rubber particles relieved triaxiality and enabled the PC matrix in the SWZ to deform in shear. Examination of thin sections from the SWZ in the transmission electron microscope revealed nanoscale deformation of the rubber particles. When the particle concentration was low (2%), only random cavitation of rubber particles was observed. At higher particle concentrations (5 and 10%), cooperative cavitation produced linear arrays of cavitated particles. The matrix ligaments between cavitated particles were strong enough that they did not fracture; higher strains were accommodated by particle cavitation and matrix extension in the regions separating the arrays. The cavitated arrays were also observed in the damage zone that accompanied the fracture surface of specimens impacted at -20°C. Cooperative cavitation may have implications for the impact strength of blends with higher concentrations of rubber particles. The possibility that particle-particle interactions facilitate cavitation and promote matrix shear deformation is especially relevant to low-temperature impact strength. © 1995 John Wiley & Sons, Inc.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1995.070551209
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  • 6
    Electronic Resource
    Electronic Resource
    Core-shell structured latex particles. I. Copolymerization of styrene/benzyl methacrylate as a choice for shell material and characterization of poly(n-butyl acrylate) core latex particles (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 58 (1995), S. 385-399 
    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: Composition, molecular weight, and microstructure of the “shell” polymer in core-shell structured latex particles, designed for toughening polycarbonate matrix, should be controlled for enhanced miscibility between the shell polymer and the matrix. Various “shell polymer” systems based on styrene (St) and benzyl methacrylate (BM) were synthesized. Reactivity ratios were determined for (St) and (BM). Chain transfer efficiency studies revealed the susceptibility of styrene to transfer to a chain transfer agent. Benzyl methacrylate was found to have steric and stability factors hindering its tendency to chain transfer with various chain transfer agent. Miscibility tests between P(St/BM) and polycarbonate (PC) indicated different degrees of miscibility, depending upon polymerization conditions. Factors other than molecular weight, such as branching and crosslinking, were found to play a role in the miscibility. Monodisperse poly(n-butyl acrylate) (PBA) seed latex particles of variable degree of crosslinking and particle size were successfully synthesized by batch emulsion polymerization. © 1995 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1995.070580218
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  • 7
    Electronic Resource
    Electronic Resource
    Core - shell structured latex particles. II. Synthesis and characterization of poly(n-butyl acrylate)/poly(benzyl methacrylate - styrene) structured latex particles (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 58 (1995), S. 401-417 
    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 synthesis of structured latex particles involved the preparation of a slightly crosslinked poly(n-butyl acrylate) (PBA) seed and a poly(benzyl methacrylate-styrene) [P(BM-St)] shell. It was found that structured core-shell latex particles prepared by semicontinuous monomer addition yielded better coverage of the seed particles than those polymerized by batch and that poly(benzyl methacrylate) yielded better coverage than polystyrene (PS). Polymerizations in the presence and absence of a chain transfer agent indicated that the presence of isooctyl mercaptopropionate (IOMP) causes the second-stage monomer to polymerize as an isolated, single patch of shell material. In the absence of IOMP, smaller patches of shell material are spread throughout the PBA seed surface. The different morphologies obtained under different polymerization conditions were attributed to thermodynamic and kinetic factors such as polymer-polymer interfacial tensions and viscosity effects. © 1995 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1995.070580219
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