A Novel Class of Cost Effective and High Performance Composites Based on Terephthalate Salts Reinforced Polyether Ether Ketone

Abstract

Poly(ether ether ketone) (PEEK)-based nanocomposites have been realized with incorporation (0-30 wt %) of anhydrous calcium terephthalate salts (CATAS), synthetized by reaction of terephtalic acid with the metal (Ca) oxide, by means of a melt processing. Their structure, morphology, thermal, and mechanical properties have been investigated. Scanning electron microscopy observations confirmed homogeneous dispersion of nanometer-sized fillers and a toughened fracture morphology even at the higher content, while thermal characterization confirmed an unvaried thermal stability and unmodified crystalline structure of the reference PEEK matrix. A negligible nucleating effect was evidenced, while a blocking effect of the amorphous phase fraction provide composites with increased stiffness, confirmed by enhanced values of G' and shifts of glass transition peak to higher temperatures, for restriction in chain mobility imposed by CATAS. The proposed solutions aimed to enlarge the application range of high performance costly PEEK-based composites, by using thermally stable nanofillers with limited costs and easily controllable synthesis phase.

Keywords: calcium terephthalate salts; high performance nanocomposites; poly(ether ether ketone), PEEK.

Figure 1

Chemical structure of calcium terephthalate salts before (left) and after (right) thermal treatment (evidence of structural rearrangement with indication of bond length) reprinted from [16].

Figure 2

Field emission scanning electron microscope (FESEM) micrograph of calcium terephthalate trihydrate salts (CATS) (a) and thermogravimetric/derivative of mass loss (TG/DTG) curves for CATS (b); FESEM micrograph of CATAS (calcium terephthalate anhydrous salts)(c) and TG/DTG curves for CATAS (d).

Figure 3

Fourier transform infrared (FT-IR) (a) and X-ray diffraction (XRD) (b) spectra of CATS and CATAS.

Figure 4

FESEM micrographs of neat PEEK and PEEK nanocomposites with 10, 20, and 30 wt % of CATAS at different magnification.

Figure 5

(a) XRD patterns; (b) TG/DTG curves; (c) G’ and (d) G” curves; (e) complex viscosity; and (f) storage (open symbol) and loss moduli (closed symbol) at 400 °C for PEEK and PEEK_CATAS nanocomposites at different CATAS content.

Figure 6

Differential scanning calorimetry (DSC) scans: (a) first heating; (b) cooling; (c) and (d) second heating scan (arrow for double melting peaks in (c) and zoom for T_g in (d)) of PEEK and PEEK composites at different CATAS content (symbols every 1000th points).