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  • Polymer and Materials Science  (12)
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  • 1
    Electronic Resource
    Electronic Resource
    Multicomponent latex IPN materials. I. Morphology control (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 35 (1997), S. 2193-2206 
    Details
    ISSN: 0887-624X
    Keywords: multicomponent ; latex ; interpenetrating polymer networks ; IPN ; core/shell ; morphology ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of novel structured latex particles with interpenetrating polymer network (IPN) cores and glassy SAN shells were developed in an attempt to investigate the feasibility of these polymers as both toughening and damping agents in thermoplastics. The IPN cores were composed of one impact part (polybutadiene based) and one damping part (acrylic based, with Tg around +10°C). The particle morphologies of these polymers were determined by TEM. The glass transitions and mechanical behavior of the polymers were characterized from DMS. The effect of different components on the final core/shell particle morphologies and mechanical properties was studied. The mechanical behavior of core/shell particles with IPN cores was also compared with that of separate core/shell and multilayered core/shell particles. In addition, normal core/shell synthesis (rubbery part first then the glassy part) and inverted core/shell synthesis (glassy part first then the rubbery part) were performed to provide another access for morphology control. It was found that the core/shell latex particles with poly(butyl acrylate) based copolymers are more miscible than poly(ethylhexyl methacrylate)-based copolymers. The high grafting efficiency of poly(butyl acrylate) plays an important role in governing phase miscibility. The latex particles synthesized by the inverted core/shell mode showed higher miscibility than the normal synthesized ones. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 2193-2206, 1997
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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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
    Toughening polycarbonate with core-shell structured latex particles (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 62 (1996), S. 2005-2013 
    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 toughness as a function of temperature of polycarbonate modified by blending with core-shell structured latex particles was evalated. Comparisons were made among a commercial core-shell latex (MBS), other core-shell (CS) latexes that incorporated a single component rubbery core, and a new class of interpenetrating polymer network (IPN) core-shell latexes with two elastomers in the core. Notched tensile tests differentiated among the blends in terms of their toughness. The most effective modifier at low temperatures was the commercial MBS latex. The CS latexes produced blends that were only slightly less tough than the MBS blends despite better dispersion of MBS and better adhesion to the matrix. The IPN blends were the least tough at low temperatures; however, at 25°C, a blend with IPN had the highest impact strength. Differences between CS and MBS blends were attributed to differences in the percent of butadiene-containing rubber and the chemical nature of the shell. A comparison among the CS latexes showed that increasing the acrylonitrile content of the shell increased the toughness, and increasing the rubber content or the gel fraction of the core increased the toughness. © 1996 Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 5
    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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  • 6
    Electronic Resource
    Electronic Resource
    Investigation of the miscibility of polycarbonate-poly(ethyleneterephthalate) blends: Solid-state 1H-NMR T1 relaxation time measurements, transmission electron microscopy, and structure-properties relationship (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 52 (1994), S. 1431-1445 
    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: Solid-State 1H-NMR measurements of T1 relaxation times performed on polycarbonate-poly(ethyleneterephthalate) (PC-PET) blends point out the presence of two separate domains with apparent dimensions of about 80 nm. The variation of PET domain relaxation time with the increase of PC content is explained in terms of an interface in which parts of the PC molecules are finely dispersed into the PET matrix. Relaxation parameters and compositions match very well an equation that quantitatively describes a three-phase model formed by two domains separated by an interface of mixed components. Micrographs obtained by transmission electron microscopy (TEM) clearly reveal the presence of two separate domains with a phase inversion at 40/60 wt% composition. PET domains, although larger than expected from NMR analysis, are characterized by a dispersion of small PC particles that are considered responsible for the observed diffusion of magnetization from PET to PC domains. The partial miscibility seems to be physical in nature rather than due to transesterification processes between the components, as stem from 1H-NMR spectra in solution of PET and PC-PET blends. T1 relaxation times measured in the same way on totally immiscible PC-PA-6 blends, support, by contrast, the NMR interpretation of PC-PET results. The mechanical properties of PC-PET blends exhibit ductile behavior throughout the entire range of composition. This indicates that PC and PET are mechanically compatible. This is also in agreement with the isothermal crystallization data for PET at various compositions of PC-PET. These results are in agreement with the existence of a partial miscibility between PET and PC. © 1994 John Wiley & Sons, Inc.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1994.070521009
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  • 7
    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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  • 8
    Electronic Resource
    Electronic Resource
    Interfacial aspects of latex ipns for toughening polycarbonate. I. Synthesis and characterization (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 58 (1995), S. 375-384 
    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: Core/shell structured latex particles with an interpenetrating polymer network (IPN) core(polymer A and polymer B) and glassy shell (polymer C) were synthesized by emulsion polymerization techniques. Polymer A was poly(butadiene-stat-styrene) (90/10) (P(Bd/S)). Polymer B was either poly(butyl acrylate-stat-methyl methacrylate) (60/40) or poly(butyl acrylate-stat-styrene) (60/40) prepared by a sequential IPN technique to form the cores. The glass transition temperatures, Tg, of polymer A and polymer B were around -70 and 10°C, respectively. The shell, polymer C, poly(styrene-stat-acrylonitrile) (72/28), was polymerized with grafting onto the IPN core by a semicontinuous process. The particle size and particle size distribution were measured by light-scattering, capillary hydrodynamic fractionation, and transmission electron microscopy. The glass transition temperatures were determined by differential scanning calorimetry. The polymer A (particle sizes between 200-270 nm) with different gel fractions was used to characterize the effect of gel fraction on IPN morphology. A core/shell type phase separation was observed for IPN particles when using a polymer A with 〉 90% gel fraction. A distribution of polymer B domains in polymer A was obtained when using polymer A with a 40% gel fraction. A good coverage of polymer C on the IPN core particles was obtained at a core/shell ratio of one to one. A broad glass transition range for the core/shell structured latex particles was observed. In article II of this series, these latex particles will be used to toughen such engineering thermoplastics as polycarbonates to understand the particular toughening theories of these polymers. © 1995 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1995.070580217
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  • 9
    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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  • 10
    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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