Effects of pressure on poly(ether‐ether‐ketone) (PEEK) sintering mechanisms

ABSTRACT This study deals with the understanding of the sintering mechanisms that occur during consolidation of an ultra‐high‐performance polymer: poly(ether‐ether‐ketone). In particular, we investigated the effects of uniaxial pressure during spark plasma sintering (SPS) processing. Glass‐transitio...

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Bibliographic Details
Published in:Journal of applied polymer science 2019-06, Vol.136 (24), p.n/a
Main Authors: Sébileau, Jean‐Charles, Lemonnier, Sébastien, Barraud, Elodie, Vallat, Marie‐France, Carradò, Adele, Nardin, Michel
Format: Article
Language:English
Subjects:
chain ends
Chain mobility
Chemical Sciences
Cohesion
Consolidation
Degree of crystallinity
Grain boundaries
Healing
Materials science
Molecular chains
Molecular conformation
Plasma sintering
poly(ether‐ether‐ketone)
Polyether ether ketones
polymer sintering
Polymers
pressure effect
Pressure effects
Scanning electron microscopy
sintering mechanisms
Spark plasma sintering
Transition temperature
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Summary:ABSTRACT This study deals with the understanding of the sintering mechanisms that occur during consolidation of an ultra‐high‐performance polymer: poly(ether‐ether‐ketone). In particular, we investigated the effects of uniaxial pressure during spark plasma sintering (SPS) processing. Glass‐transition temperature (Tg) measurements under loading, stress–strain curves and scanning electron microscopy analysis allowed us to determine the role of pressure intensity and temperature of application on macromolecular chain mobility in both the bulk and the surface of the particles. First, a loss of chain mobility in the bulk of the particles was observed under high pressure. Second, it was shown that high pressure applied at low temperature leads to friction effects between the particles which enhances chain mobility in the particle shell through a local melting phenomenon. These experimental conditions favor the healing of particles and high cohesion was then observed in the resulting sintered samples. The level of friction is enhanced when pressure is applied at a low temperature since the powders are still in a glassy state. Finally, the achievement of cohesive grain boundaries was found to be related to the location and conformation of chain ends. Good healing between particles can only occur if a sufficient number of chain ends are available at the surface of the particle shell. We showed that the native powder state plays a significant role. The direct use of as‐received powder leads to final material exhibiting good cohesion whereas pretreatments of the native powder are highly detrimental. It should be noted that this processing does not affect the high initial degree of crystallinity because no bulk melting is observed during consolidation by sintering. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47645. Influence of location and conformation of chain ends on polymer cohesion (compression test).
ISSN:0021-8995
1097-4628
DOI:10.1002/app.47645