Thermal stability and crystallization of poly(aryl ether ether ketone)

Studies on the reprocessability of poly(ether ether ketone) (PEEK)

“…This is consistent with the observations of Jonas and Legras (1991), who concluded that the crystallisation onset temperature was independent of an isothermal treatment time in the temperature range 400°C to 420°C. It is therefore reasonable to conclude that a hold time of 20 minutes at 385°C, as used in this experiment,…”

“…The enthalpies of crystallisation in both graphs show no significant change indicating that the amount of crystalline material remains the same independent of the percentages of virgin/1 st regrind mixes and number of processing cycles. Jonas and Legras (1991) showed that PEEK maintained at 385°C still retained numerous crystallisation nuclei; therefore the samples in our experiment may have maintained a high population of nucleants. If the degree of crystallisation remains fairly constant, it would be expected that tensile properties should also remain stable, as indicated in past studies.…”

“…Studies on the effect of thermal history on PEEK crystallisation behaviour (and therefore resulting mechanical properties), have shown that the quality and quantity of the crystalline regions depend on the cooling kinetics and can be altered by the presence of inclusions such as fibres (Sarasua et al, 1996), or by self-nucleation (Jonas and Legras, 1991). Jonas & Legras (1991) also examined the degradation, in terms of branching, induced when held in the molten state, and found that the structural defects created by branching reduced the crystallinity, whilst the restricted molecular mobility associated with increased molecular weight decreased the crystallisation rate. Bakar et al (1999) reported a 2% drop in the crystallinity of pure PEEK for every 10°C rise in melt processing temperature, although this effect was absent in composites containing 5% or 10% hydroxyapatite.…”

High performance PEEK/carbon nanotube composites compatibilized with polysulfones-I. Structure and thermal properties

“…Since its commercialization, PEEK has been used in a wide range of applications, from medicine to the electronics, telecommunication and transport industries (automobile, aeronautic and aerospace) [10]. Over the last decades many studies have been reported on the structural [11], mechanical [12] and thermal [13] characterization of this linear aromatic polymer, albeit only a few papers deal with such composites made of a PEEK matrix; the most relevant are those published by Shaffer et al [14], working with vapor-grown carbon nanofiber/PEEK composites, Deng et al [15], dealing with multi-walled carbon nanotube (MWCNT)/PEEK nanocomposites, and Song et al [16], who prepared sandwich like SWCNT paper/PEEK composites. Recently, our group reported the synthesis and characterization of PEEK/SWCNT composites [17].…”

Anisotropic linear thermal expansivity of poly(ether-ether-ketone)

“…Although the morphological, mechanical and thermal properties of PEEK have been reported in details [9][10][11], there have been few reports on linear thermal expansivity (a) of PEEK [12,13]. The a is a significant thermal property and depends on the backbone chemistry, morphology, crystallinity and molecular orientation of the polymers [14].…”