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  • 1
    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: This article presents crystallization kinetics studies on a cocrystallizing polymer highdensity polyethylene (HDPE)/linear lowd-ensity polyethylene (LLDPE) blend. The nonisothermal crystallization exotherms obtained by differential scanning calorimetry (DSC) were analyzed to investigate the effect of cocrystallization on kinetics parameters, namely the Avrami exponent and activation energy. The regular change of Avrami exponent with blend composition from a value of about 3 corresponding to HDPE to a value of 2 corresponding to LLDPE is observed. A sheaf-like crystalline growth with variation of nucleation depending on blend composition is concluded from these results of DSC exotherm analysis in conjunction with the small-angle light scattering observations. The observed variation of activation energy of crystallization with blend composition suggests the role of interaction of side chains and comonomer units present in the LLDPE. © 1994 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 56 (1995), S. 169-175 
    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: Blends of poly(ethylene terephthalate-co-p-oxybenzoate) (PET-PHB) with poly(ethylene terephthalate) (PET) have been studied in the form of as-spun and drawn fibers. Mechanical properties of drawn blend fibers (DR-6.0) up to 10 wt % liquid crystalline polymer (LCP) component exhibit significant improvement in modulus and strength. With the addition of 10 wt % LCP content in PET matrix, the modulus increases from 11.78 to 17.72 GPa, and the strength increases from 0.76 to 1.0 GPa in comparison to the PET homopolymer. With further addition of LCP content, the properties drop down. Scanning electron microscopy studies of drawn blend fibers show that up to 10 wt % LCP content the blends contain the LCP domains in the size range of 0.07-0.2 μm and are well distributed in the PET matrix. © 1995 John Wiley & Sons, Inc.
    Additional Material: 2 Ill.
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  • 3
    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: Poly(ethylene terephthalate) (PET) and bisphenol-a-polycarbonate (PC) are known to form a miscible blend whereas ternary blends of PET, PC, and polypropylene (PP) form two phases. This is based on the considerations of various chemical events which may occur in these systems. The role of ester-carbonate interchange reactions during melt mixing and fabricating is found to be unimportant. Differential scanning calorimetric analysis of the ternary blends shows that there appears to occur an exothermic transition in the heating mode of the instrument. This exothermic event was found to be suppressed considerably by incorporating suitable additives into the system. Degradation reactions studied by thermogravimetric analysis and a dilute solution viscometric technique reveal that there exists some kind of interaction among the components even with the immiscible PP component.
    Additional Material: 9 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 1766-1773 
    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: Moldability and mechanical properties of polyethylene terephthalate (PET) under normal molding conditions were found to improve significantly when it was blended with bisphenol-A-polycarbonate (PC) and polypropylene (PP) to form ternary polymer blend systems. DSC results of these blends revealed that the PET and PC components formed a miscible blend while PP being incompatible with them, formed a separate phase. PP was also found to form a sleeve around the PET-PC miscible phase and, thereby, showed a skin-core type of morphology. Variations of mechanical properties with varying amounts of PP was measured keeping the ratio of PET and PC constant. Tensile and flexural properties of the blends decrease with the amount of PP. Notched impact strength increases up to a certain level of PP and then decreases, while the unnotched values decrease gradually. The effect of annealing on the mechanical properties of these blends have been discussed on the basis of the increased crystallinity of some of the components.
    Additional Material: 9 Ill.
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  • 5
    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: Fibers prepared from poly(ethylene terephthalate) (PET) and poly(butylene terephthalate) (PBT) blends show a sharp decrease in tensile strength and modulus when blends are on the verge of phase segregation. The modulus values differ for homopolymers for their differences in chain configuration and methylene groups and that of the blends are in proportion. The experimental strength values are higher than the predicted values according to Paul's model for incompatible polymers. At 90/10 PET/PBT blend, the modulus is high, which may be a relative factor to the smaller crystal size of the components.
    Additional Material: 8 Ill.
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  • 6
    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: Binary blend of high-density polyethylene (HDPE) and linear low-density polyethylene (LLDPE), prepared by melt mixing in an extruder, in the entire range of blending ratio, is studied for crystallization behavior by differential scanning calorimetry (DSC) and X-ray diffraction measurements. Cocrystallization was evident in the entire range of blend composition, from the single-peak character in both DSC crystallization exotherms and meltingendotherms and the X-ray diffraction peaks. A detailed analysis of DSC crystallization exotherms revealed a systematic effect of the addition of LLDPE on nucleation rate and the subsequently developed crystalline morphology, which could be distinguished in the three regions of blending ratio, viz, the “HDPE-rich blend,” “LLDPE-rich blend,” and the “middle range from 30-70% LLDPE content.” Variations in crystallinity, crystallite size, and d spacing are discussed in terms of differences in molecular structure of the components.
    Additional Material: 6 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 27 (1982), S. 3211-3218 
    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: A large number of nylon 6 fiber samples with varying internal structure were obtained by changing draw ratios, drawing temperature, and quenching immediately after drawing. Modulus of these samples is analyzed by Takayanagi model and fraction of tie chains is obtained. It is observed that the modulus of these samples is directly proportional to the fraction of tie chains.
    Additional Material: 2 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 31 (1986), S. 2145-2155 
    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: Blends of small percentage of plastic grade polypropylene with fiber grade polypropylene are studied in unoriented and oriented states. A 3% blend sample has a higher spherulitic growth rate, and improved mechanical behavior in drawn fiber state as compared to the parent sample. These changes are related to the presence of bimodal and trimodal crystal texture of polypropylene in the blend, respectively. At a higher blend percent, specifically at 10 and 15%, the mechanical properties of the drawn fiber are inferior and these are related to partial phase segregation of the components.
    Additional Material: 7 Ill.
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  • 9
    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 binary blend of high-density polyethylene (HDPE) and linear low-density polyethylene (LLDPE) in the range of composition from 100% HDPE to 100% LLDPE has been investigated for tensile and flexural properties and the morphology in the deformed state on tensile fracture. Tensile properties (initial modulus, yield stress, and elongation-at-yield, ultimate tensile strength and elongation-at-break, and work of yield and work of rupture) and flexural properties (flexural modulus and flexural yield stress) are studied as a function of blend composition. Behavior, in terms of these properties, is distinguishable in three zones of blend composition, viz. (i) HDPE-rich blend, (ii) LLDPE-rich blend, and (iii) the middle zone. In zones (i) and (ii), the variations of these properties are more or less linear, whereas in the middle region [i.e., zone (iii)], there is a reversal of trends in variation or sometimes a behavior opposite to the expected one. The results are explained on the basis of the effects of cocrystallization and the presence of octene-containing segments in the amorphous phase. Scanning electron micrographs of the tensile fracture surfaces are presented to illustrate the occurrence of transverse bands interconnecting the fibrils.
    Additional Material: 7 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 47 (1993), S. 857-866 
    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: Thermotropic copolyesters PET/60 PHB and PET/80 PHB fibers are melt spun at different extrusion temperatures and at different draw-down ratios. The flow behavior of PET/60 PHB is studied at different temperatures and shear rates. The melt of (PET/60 PHB) at temperatures above 265°C exhibit low viscosity and low activation energy of flow. The modulus and strength for both PET/60 PHB and PET/80 PHB fibers increase with the increase in extrusion temperature and draw-down ratio in the ranges studied. High birefringence, indicating the presence of mesophase is observed between 265 and 300°C on a hot stage polarizing microscope. X-ray diffraction patterns show that the molecular orientation increased with increasing draw-down ratio. Scanning electron microscopy of these fibers shows a well-developed highly oriented fibrillar structure. Superior mechanical performance of fibers spun at around 275°C are attributed to the presence of nematic mesophase in the polymer melt. © 1993 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
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