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  • 1
    Electronic Resource
    Electronic Resource
    Equilibrium and non-equilibrium melting of branched polyethylene relating to defect incorporation within crystals (1987)
    Springer
    Colloid & polymer science 265 (1987), S. 239-245 
    Details
    ISSN: 1435-1536
    Keywords: Branchedpolyethylene ; equilibriummelting point ; enthalpy offusion ; surface free energy ; kinks ; chain defects
    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 New equilibrium melting point data, for polyethylene containing chain defects, are tested in the light of random copolymer predictions. A simplified expression for the melting point depression of random copolymers containing small amounts of non-crystallizable units is derived. Non-equilibrium melting data for rapidly quenched polyethylene samples are also reported. The fusion enthalpyΔH∘(X), and the surface free energyσ e for crystals containing defects are evaluated using crystallinity, equilibrium meltingtemperatures and X-ray long period data. It is shown that increasing defect penetration within crystals induces a decrease ofΔH∘(X) withX in accordance with theoretical predictions. Finallyσ e is, similarly, shown to decrease with increasing number of chain defects attached to the crystal surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01412713
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  • 2
    Electronic Resource
    Electronic Resource
    Microhardness-structure correlation of iPP/EPR blends: influence of molecular weight and EPR particle content (1998)
    Springer
    Colloid & polymer science 276 (1998), S. 786-793 
    Details
    ISSN: 1435-1536
    Keywords: Key words Microhardness ; poly(propylene) ; ethylene-co-propylene rubber ; blends ; surface free energy
    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 influence of molecular weight on the mechanical properties of isotactic poly(propylene) (iPP) and iPP blended with ethylene-propylene copolymers has been investigated by means of the microhardness technique. The hardness (H) of iPP is shown to slightly decrease with increasing molecular mass, within the range of molecular weights investigated. The H-decrease is correlated to a loss of crystallinity as the average molecular weight increases. On annealing, the mechanical properties are enhanced as a consequence of an increase in both, the degree of crystallinity and the crystalline lamellar thickness. A value of H ∞ c for iPP crystals of infinite thickness in the α-form is proposed for the first time. The inclusion of EPR particles in the iPP matrix softens the material. This result could be explained in terms of an increase in the basal surface free energy of the iPP crystals with increasing amount of rubber content.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003960050311
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  • 3
    Electronic Resource
    Electronic Resource
    Influence of molecular weight on the microhardness of poly(ethylene terephthalate) (1998)
    Springer
    Colloid & polymer science 276 (1998), S. 138-143 
    Details
    ISSN: 1435-1536
    Keywords: Key words Poly(ethylene terephthalate) ; microhardness ; crystallinity ; high molecular weight
    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  Poly(ethylene terephthalate) (PET) was annealed in vacuum at different temperatures (190–260 °C) for different times (10 min–24 h) in order to examine the mechanical properties (microhardness) of PET samples with a wide range of molecular weights (10 000–120 000). Short annealing times result in a twofold decrease in mol. wt. due to hydrolytic decomposition. However, long annealing times give rise to a substantial molecular weight increase. It is found that microhardness (H) rises linearly with the degree of crystallinity obtained during up-grading of mol. wt. and its extrapolation leads to H-values of completely crystalline PET, H PET c=405 MPa for samples with conventional mol. wt. and of 426 MPa for samples with mol. wt. higher than 30 000. It is shown that the increase of mol. wt. for each set of samples with a given range of degree of crystallinity also causes a slight increase of H. The influence of mol. wt. upon hardness is discussed in the light of the changes in the physical structure (crystallinity, crystal thickness) which is formed at given heat treatment conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003960050221
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  • 4
    Electronic Resource
    Electronic Resource
    Physical aging in poly(ethylene naphthalene-2,6-dicarboxylate) in relation to sorbed water, enthalpic relaxation, and mechanical properties (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 33 (1995), S. 1653-1661 
    Details
    ISSN: 0887-6266
    Keywords: physical aging ; poly(ethylene naphthalene-2,6-dicarboxylate) ; water sorption ; microhardness ; excess enthalpy ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Amorphous poly(ethylene naphthalene-2,6-dicarboxylate) (PEN) films (∼ 220 μm thick), stored in ambient atmosphere for different periods of time and after annealing at different temperatures below Tg = 123°C, for different times, have been investigated by infrared spectroscopy (FTIR), microhardness, and differential scanning calorimetry (DSC). FTIR spectroscopy and weight measurements reveal the presence of water which is easily removed by annealing of the films. Films again recover their initial weight and absorption bands after 1-2 days storage in ambient atmosphere. Samples annealed at different temperatures Ta for different times ta show an increasing microhardness for relatively short times of ta. The microhardness passes through a maximum at an annealing time depending on Ta, and it decreases toward values somewhat larger than the initial ones. The changes observed in the microhardness and in the values of the excess enthalpy with storage time of the samples at room temperature depend on the physical aging as well as on the content of water of PEN films. © 1995 John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1995.090331111
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