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Influence of molecular weight on the microhardness of poly(ethylene terephthalate) (1998)

Vanderdonckt, C. ; Krumova, M. ; Baltá Calleja, F. J. ; [et al.]

Springer

Colloid & polymer science 276 (1998), S. 138-143

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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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Physical aging in poly(ethylene naphthalene-2,6-dicarboxylate) in relation to sorbed water, enthalpic relaxation, and mechanical properties (1995)

Rueda, D. R. ; Varkalis, A. ; Viksne, A. ; [et al.]

Bognor Regis [u.a.] : Wiley-Blackwell

Journal of Polymer Science Part B: Polymer Physics 33 (1995), S. 1653-1661

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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.