Enhancing the mechanical performance of poly(ether ether ketone)/zinc oxide nanocomposites to provide promising biomaterials for trauma and orthopedic implants

Abstract

Poly(ether ether ketone)/zinc oxide (PEEK/ZnO) composites were manufactured by using the injection molding technique. Before blending with the PEEK resin matrix, some ZnO nanoparticles were modified by γ-aminopropyltriethoxylsilane (APTES). The effect of surface modification of ZnO nanoparticles by amino groups and Si-O bonds was investigated. PEEK/ZnO composites were characterized by scanning electron microscopy (SEM), thermogravimetric analysis, and X-ray diffraction. The scanning electron micrographs showed that ZnO nanoparticles were encapsulated in the PEEK phase; within this phase, the nanoparticles were homogeneously dispersed. Mechanical and tribological properties were measured by tensile strength, flexural strength, coefficient of friction, and wear rate. It was shown that the interfacial compatibility between ZnO nanoparticles and PEEK matrix was significantly enhanced due to the amino and Si-O bonds decorated on the ZnO nanoparticles. More importantly, the thermal stability of PEEK improved upon the incorporation of ZnO nanoparticles into this matrix. Cell viability studies with mouse osteoblasts demonstrated that cell growth on PEEK and PEEK/ZnO was significantly enhanced. On the basis of the obtained results, PEEK/ZnO composites are recommended as promising candidates for orthopaedic materials and trauma implants.

Fig. 1. The preparation flow chart of PEEK composite.

Scheme 1. Preparation of modified zinc oxide nanoparticles.

Fig. 2. Spectra of ZnO, functionalized ZnO, and APTES.

Fig. 3. XRD patterns of ZnO and PEEK composites.

Fig. 4. Non-isothermal DSC cooling (a) and heating (b) scans of PEEK and the PEEK–ZnO nanocomposites with different nanoparticle loadings.

Fig. 5. TGA curves obtained under a nitrogen atmosphere for PEEK and the corresponding nanocomposites.

Fig. 6. DTG curves of PEEK and its composites.

Fig. 7. TMA curves of PEEK and PEEK composites.

Fig. 8. Comparison of the mechanical properties of PEEK–ZnO nanocomposites with different nanoparticle loadings: (a) strain at break; (b) tensile strength; (c) Young's modulus; (d) flexural strength. The pink and blue bars correspond to composites reinforced with ZnO or m-ZnO.

Fig. 9. The curves of the friction coefficients of PEEK and its composites.

Fig. 10. Tribological properties of PEEK–ZnO nanocomposites and PEEK: (a) friction coefficient; (b) wear rate.

Fig. 11. Typical SEM micrographs of surface (a) ZnO and (b) m-ZnO.

Fig. 12. TEM images of PEEK/ZnO (a) 5 wt% ZnO/PEEK (b) 5 wt% m-ZnO/PEEK.

Fig. 13. Worn surfaces of PEEK and PEEK composite materials, (a) PEEK, (b) 5 wt% ZnO/PEEK, (c) 5 wt% m-ZnO/PEEK, (d) 7.5 wt% m-ZnO/PEEK.

Fig. 14. Mouse osteoblasts on membranes of PEEK and PEEK/ZnO composites after 3 days, (A) PEEK without cell, (B) cell on microslide, (C) cell on PEEK, (D) cell on PEEK/2.5 wt% ZnO, (E) cell on PEEK/5.0 wt% ZnO, (F) cell on PEEK/2.5 wt% m-ZnO, (G) cell on PEEK/5.0 wt% m-ZnO, (H) cell on PEEK/7.5 wt% m-ZnO, (I) cell on PEEK/10 wt% m-ZnO.

Fig. 15. MTT results for MC3T3-E1 on membranes of PEEK and PEEK/ZnO composites after 3 days of cell culture (*P 0.05), blank: PEEK, 1: PEEK/2.5 wt% ZnO, 2: PEEK/5.0 wt% ZnO, 3: PEEK/2.5 wt% m-ZnO, 4: PEEK/5.0 wt% m-ZnO, 5: PEEK/7.5 wt% m-ZnO, 6: PEEK/10 wt% m-ZnO.

Fig. 16. Differentiation of MC3T3-E1 on PEEK and PEEK/ZnO composite membranes after 1, 3, 5, 7, and 9 days of cell culture (*P < 0.05), blank: PEEK, 1: PEEK/2.5 wt% ZnO, 2: PEEK/5.0 wt% ZnO, 3: PEEK/2.5 wt% m-ZnO, 4: PEEK/5.0 wt% m-ZnO, 5: PEEK/7.5 wt% m-ZnO, 6: PEEK/10 wt% m-ZnO.