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  • 1
    Electronic Resource
    Electronic Resource
    Chemical interactions in blends of bisphenol A polycarbonate with tetraglycidyl-4,4'-diaminodiphenylmethane epoxy (1995)
    s.l. : American Chemical Society
    Macromolecules 28 (1995), S. 6779-6786 
    Details
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ma00124a012
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  • 2
    Electronic Resource
    Electronic Resource
    Sub-Tg molecular relaxation and enthalpy relaxation behavior in amorphous glassy poly(ether imide) (1997)
    Springer
    Journal of polymer research 4 (1997), S. 213-219 
    Details
    ISSN: 1572-8935
    Keywords: Physical aging ; PEI ; Enthalpy relaxation ; Sub-Tg molecular relaxation ; Dynamic mechanical analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Physical aging behavior of glassy, amorphous poly(ether imide) (PEI) at a high aging temperature range (15 ∼ 25 °C below the polymer Tg of 215 °C) was investigated. A quantitative modeling approach was utilized to describe the aging process of PEI. The experimental data of enthalpy of relaxation for constructing the models were obtained using differential scanning calorimetry (DSC). At relatively low aging temperatures, the enthalpy of relaxation simply increases linearly with the logarithm of time. At high temperatures another parameter accounting for distribution is needed for better description. Furthermore, the sub-Tg molecular chain relaxation of aged PEI was characterized using dynamic mechanical analysis (DMA). Physical aging significantly suppressed the β chain relaxation but not the γ-relaxation, suggesting that the chain segmental motion for the β-relaxation is the one responsible for chain conformation changes reaching an equilibrium glassy state.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s10965-006-0027-x
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  • 3
    Electronic Resource
    Electronic Resource
    Reversibility of thermodynamic lower critical solution temperature phenomenon in miscible poly(ε-caprolactone)/poly(benzyl methacrylate) (1998)
    Springer
    Journal of polymer research 5 (1998), S. 205-211 
    Details
    ISSN: 1572-8935
    Keywords: Polycaprolactone ; Poly(benzyl methacrylate) ; Miscibility ; LCST ; Reversibility ; Binodal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Differential scanning calorimetry and optical microscopy were performed to examine the reversibility of phase separation at above the lower critical solution temperatures in a miscible poly(ε-caprolactone) (PCL)/poly(benzyl methacrylate) (PBzMA) blend system. Upon heating, phase separation occurred via a binodal nucleation and growth (NG) mechanism at above 240 °C, which is a lower critical solution temperature (LCST). The pattern of phase domains suggests that the phase separation was meta-stable. Interestingly, the LCST phase separation was found to be readily reversible to original homogeneity upon cooling at regularly accessible rates. A major factor may be that the temperature window between the LCST curve and blend Tg curve is wide, resulting in a convenient temperature range for the polymer chains to kinetically reorganize to a state favored by the thermodynamic conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s10965-006-0058-3
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  • 4
    Electronic Resource
    Electronic Resource
    A differential scanning calorimetry study on poly(ethylene terephthalate) isothermally crystallized at stepwise temperatures: multiple melting behavior re-investigated (1996)
    Springer
    Colloid & polymer science 274 (1996), S. 309-315 
    Details
    ISSN: 1435-1536
    Keywords: Multiple melting ; DSC-crystallization ; poly(ethylene terephthalate) ; lamellar thickness
    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 The multiple melting behavior of poly(ethylene terephthalate) (PET) was investigated with differential scanning calorimetry (DSC) by examining PET samples having been subjected to special schemes of crystallization and annealing treatment at multiple descending temperatures. Upon such step-wise annealing in decreasing temperatures, the existence of doublet melting peaks in addition to a series of multiple minor peaks in the PET has been demonstrated using carefully designed thermal schemes. Using the Hoffman theory, multiple lamellae populations, might be suggested to be simultaneously present in the PET subjected to such thermal treatments. However, direct experimental evidence has yet to be provided. The low-temperature minor crystals simply melt during normal scanning without having time enough to reorganize into higher-melt crystals. Nevertheless, the effect of scanning on non-isothermal crystallization does exist but is primarily confined to the temperature range much below the main melting region where the crystallization of polymer chains can progress at a reasonable rate. At higher temperatures near the main melting region, annealing for extended times is required in order to result in relative changes of the melting endotherms of the upper and lower peaks in the main melting doublet. In all we have shown that interpretations of the multiple melting phenomenon in semicrystalline polymers can be better refined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00654051
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  • 5
    Electronic Resource
    Electronic Resource
    Reaction-induced phase separation in a semiinterpenetrating network of reactive ternary blends (1996)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 34 (1996), S. 781-788 
    Details
    ISSN: 0887-624X
    Keywords: DGEBA epoxy ; polycarbonate (PC) ; PMMA ; reactions ; IPN ; ternary polymer blends ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Morphology and reaction mechanisms were probed on a model reactive ternary blend system of polycarbonate (PC), poly(methyl methacrylate) (PMMA), and diglycidylether of bisphenol-A (DGEBA) epoxy by using differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR). Molecular interactions/reactions between the components in the blends after heating treatments are discussed. It was found that reactions took place among the components and that an interpenetrating network was built. The possible reaction mechanisms and the resulting structures after the heating treatments were probed. In the blends, PC and DGEBA reacted to form a network, while PMMA remained free. The semiinterpenetration, however, did not result in a network interlocked into a homogeneous state. The single Tg of the heated ternary DGEBA/PC/PMMA blends actually did not reflect a homogeneous interpenetrating network. Due to relatively small PMMA domains, the ternary blend network exhibited a single Tg. Upon etching the PMMA domains from the blend by acetone, a clearly interpenetrating network of reacted PC and epoxy was exposed and confirmed. The reactions leading to such a morphology are discussed with experimental evidence. © 1996 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Morphology and glass transition behavior of polycarbonate-phenoxy system: Effects of trans-reactions in domain interface regions (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 35 (1997), S. 97-103 
    Details
    ISSN: 0887-624X
    Keywords: phenoxy ; polycarbonate (PC) ; exchange reactions ; morphology ; polymer blends ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Effects of trans reactions on the morphology, glass transition, and phase behavior in a classical blend system of a poly(hydroxyl ether bisphenol-A) (phenoxy) with bisphenol-A polycarbonate (PC) were investigated by differential scanning calorimetry (DSC) and optical microscopy. Although two Tgs were observed in the as-prepared PC/phenoxy blends, an apparently single, but broadened, Tg was found in the blends after heating at high temperatures, typically 200-250°C for short times. The optical microscopy results indicated that same scales of heterogeneity did exist in post-heated PC/phenoxy blends as well as unheated blends. Explanations were provided. After heating-induced interchange reactions (—OH and carbonate), randomly linked polymer chains might form at the numerous interfaces of the mutually occluded/included micro-domains. The majority of the chains in the micro-domains are forced to relax in coordinated motion modes after heating, thus showing a single Tg. A mechanism of trans reactions in interfacial regions was briefly discussed in supplement to earlier reports in the literature. © 1997 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Instrumented impact evaluation of a toughened carbon fiber epoxy composite (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 129-136 
    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: Instrumented impact testing and analysis were performed on an interlaminartoughened carbon fiber epoxy composite (Toray 3900-2/T800H) and a conventional (untoughened) epoxy composite (Fiberite 934/T300). Severity of impact was varied by using a wide range of impact energy. The effect of difference in the tup of the impact instrument was discussed. The residual compressive strengths after compact (CAI's) were measured by using a universal mechanical tester. The impact damage and delamination resistance of the toughened and conventional composites were quantitatively compared. At the same impact energy, the extent of damage was much less severe and the CAI was higher for the toughened composite. Relationships between the CAI's, the state of impact damage, and impact energy were investigated. Impact damage mechanisms for these two composites were not exactly the same. The impact damage of the conventional composite exhibited much greater extents of delamination. By contrast, interlaminar delamination in the toughened composite was found to be significantly suppressed, and the impact damage was more dominated by controlled matrix cracking/fiber damage, instead of catastrophic delamination. As a result, the CAI's of the toughened composite exhibited a monotonous decrease with increase in the impact energy and in the linear dimension of extents of damage.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760350202
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  • 8
    Electronic Resource
    Electronic Resource
    On the multiple melting behavior of polymorphic syndiotactic polystyrene and its behavior in a miscible state (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2041-2049 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Differential scanning calorimetry (DSC) and X-ray diffraction analysis were performed to study the multiple melting behavior and crystal forms of neat syndiotactic polystyrene (s-PS) in comparison with its miscible blends with amorphous atactic polystyrene (a-PS) or poly(2,6-dimethyl-p-phenylene oxide) (PPO). For neat s-PS annealed at 242 to 250°C, three melting peaks of changing intensity were observed (labeled I, II, and III from low to high temperature), while if annealed at high temperatures (254°C or higher) only two melting peaks were left. The missing peak was determined to be Peak-III for s-PS annealed at high temperatures. For the s-PS/a-PS or s-PS/PPO blends, two melting peaks were observed, and the missing peak is Peak-II. The missing Peak-II in the blend systems is attributed to the β-modification. Apparently, the condition of s-PS being compatible with a-PS or PPO is unfavorable for generating the β-modification upon melt crystallization. This study also showed that Peak-I is associated with the β-modification. Peak-III may be associated with the less stable β′ form, which can be transformed to the β form upon annealing at high temperatures. For the s-PS/a-PS or s-PS/PPO blends upon annealing at higher temperatures, Peak-III quickly decreases, leaving only a single melting peak (Peak-I) for the blends. The phenomenon of the decrease of Peak-III crystals in the blend is similar to that for neat s-PS annealed at high temperatures.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Miscibility and cure kinetics studies on blends of bisphenol-A polycarbonate and tetraglycidyl-4,4′-diaminodiphenylmethane epoxy cured with an amine (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 33 (1995), S. 2235-2244 
    Details
    ISSN: 0887-6266
    Keywords: TGDDM epoxy ; polycarbonate ; blends ; cure kinetics ; miscibility ; thermosets ; thermoplastics ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Differential scanning calorimetry (DSC) has been applied to characterize the glass transition behavior of the blends formed by bisphenol-A polycarbonate (PC) with a tetrafunctional epoxy (tetraglycidyl-4,4′-diaminodiphenyl methane, TGDDM) cured with 4,4′-diaminodiphenylsulphone (DDS). A rare miscibility in the complete composition range has been demonstrated in these blends. Additionally, the blend morphology was examined using scanning electron microscopy (SEM) and a homogeneous single-phase PC/epoxy network has been observed in the blends of all compositions. Moreover, polycarbonate incorporation has been found to exert a distinct effect on the cure behavior of the epoxy blends. The cure reaction rates for the epoxy-PC blends were significantly higher due to the presence of PC. In addition, the cure mechanism of the epoxy blends was no longer autocatalytic. An n-th order reaction mechanism with n = 1.2 to 1.5 has been observed for the blends of DDS-cured epoxy with PC of various compositions studied using DSC. The proposed n-th order kinetic model has been found to describe well the cure behavior of the epoxy/PC blends up to the vitrification point. © 1995 John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1995.090331608
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  • 10
    Electronic Resource
    Electronic Resource
    Preparation of crosslinked epoxy microparticles via phase inversion (1996)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 34 (1996), S. 2591-2598 
    Details
    ISSN: 0887-6266
    Keywords: epoxy microspheres ; phase inversion ; DGEBA ; PMMA ; blends ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) studies have been performed to reveal a crosslinked epoxy nature of the spherical particles formed in cured epoxy/DDS/PMMA blends. An interesting phase inversion phenomenon was observed in cured DGEBA/DDS/PMMA blends, which occurred at a relatively low thermoplastic composition of 20 phr PMMA in blends. A unique method of preparing crosslinked epoxy spheres of controlled sizes based on cure-induced phase inversion is described in this report. Several factors have been found to affect the geometry of the formed epoxy spheres. The volume fraction of PMMA in the blends strongly dominates the influence. With the increase of PMMA volume fraction in the blends, the spheres not only become smaller in sizes, but also more regular in the spherical geometry due to less impingement. The crosslinking density (DDS phr in the blends) has been found to influence the average sizes of the spheres. The cure temperature has relatively limited effects only when the PMMA loadings in the blends are relatively small. Various potential applications for the epoxy microspheres may be investigated in future studies. © 1996 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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