Morphology and dynamical mechanical properties of poly ether ketone ketone (PEKK) with meta phenyl links

Abstract

Poly ether ketone ketone (PEKK) with different proportion of meta phenyl links were investigated by combining differential scanning calorimetry and dynamic mechanical analysis. The influence of the Terephthalyl/Isophthalyl isomers (T/I) ratio on the vitreous phase is mild, the shift of the glass transition is limited to a few degrees and the vitreous G′ is only sensitive to the content of the crystalline phase. Contrarily, the increase of meta isomers is responsible for a significant decrease of the melting temperature (Tm) by 60 °C, which considerably facilitates processing. The modification of interchain interactions in the crystalline phase might be implied. A series of thermal protocols evidenced that the difference of crystallization behavior is also dependent upon the T/I isomer ratio. A time and temperature dependence of annealing on the double melting behavior of PEKK was observed. Regarding the mechanical behavior, the observed reinforcing effect due to the crystalline phase was more prominent in the rubbery state than in the glassy state. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43396.

Isothermal crystallization kinetic modeling of poly(etherketoneketone) (PEKK) copolymer

“…We observed that w 1 is closed to 1 for low temperatures and then decreases to values lower than 0.5 for temperatures above 260 C. This shows that the formation of the secondary crystallization is promoted for low degree of supercooling. This observation has also been reported by few authors [18,39] with the increase of a first endothermic peak which occurs 10 C above the annealing temperature attributed to the melting of the secondary crystallization. In fact, for high annealing temperatures, the diffusion process is very important with a high mobility of the chains allowing the enhancement of the crystalline phase by the growth of a second crystalline structure within lamellae.…”

“…This is due to a lowering of the macromolecular chains regularity with the T/I ratio which decreases the crystalline phase compactness [9]. PEKK 60/40 has a T g about 156 C and a T m about 300 C [18], which is lower than the one for PEEK (around 340 C [2]). This is quite interesting for processing regarding part manufacturing costs and possible degradation at high temperature.…”

“…Isothermal crystallization mechanisms of PEKK 60/40 have been studied by Gardner et al [9] and Cort es et al [18]. After annealing, they observed an additional endotherm during the melting which occurs about 10 C above the annealing temperature.…”

“…At last, PEKK 60/40 crystallizes less and slower than PEEK because ketone linkages are stiffer than ether linkages. The maximum crystallinity varies between 22% and 27% and it does not crystallize for cooling rates above 10 C.min À1 [18].…”

Dynamic rheological behavior of poly(ether ketone ketone) from solid state to melt state

“…reported the evolution of melting and crystallization behavior of PEKK upon the influence in meta links content. We recently published a combined study by differential scanning calorimetry and dynamic mechanical analysis (DMA) in the solid state of PEKK with different thermal history and T / I ratio (80/20, 70/30, 60/40) . In the vitreous state, very few works concern sub‐glass relaxations of PEKK.…”