Effects of surface treatments on the adhesion between PEEK and silicone polymer

Polyetheretherketone (PEEK) material can be used as a prosthetic scaffold to repair bone defects, but the inert surface of PEEK limits the application of this polymer material on prosthetic scaffolds.

The purpose of this in vitro study was to investigate the effects of different surface treatments on the bond strength between PEEK and medical-grade silicone polymer.

Forty PEEK specimens were randomly assigned to 1 of 5 groups. The experimental groups consisted of D-PEEK, B-PEEK, S-PEEK, and BS-PEEK, which were sequentially treated with DMSO, sodium borohydride (NaBH₄), 98% concentrated H₂SO₄, and a combination of concentrated sulfuric acid and sodium borohydride, respectively. Group P-PEEK served as the untreated control. Scanning electron microscopy was used to observe the PEEK surface morphology, and X-ray photoelectron spectroscopy was performed to analyze changes in the surface functional groups before and after the modification. Each treated PEEK group was bonded to medical-grade silicone polymer using silicone adhesive (n=8), and adhesion strength was assessed with a universal testing machine. One-way analysis of variance tests was used to analyze the data (α=.05).

Surface etching was evident in the B-PEEK, S-PEEK, and BS-PEEK groups; visible pores appeared on the S-PEEK and BS-PEEK surfaces. The root mean square values of the bond strength deviations between PEEK and silicone polymer showed significant differences among the various groups (P<.001), with the BS-PEEK group exhibiting the highest mean ±standard deviation bond strength (2.58 ±0.46 MPa). Significant differences in contact angles were found among the various groups (P<.001), with S-PEEK exhibiting the highest surface energy (42.6 ±2.1 mN/m). No surface modifications showed cytotoxicity.

Sulfonation and NaBH₄ treatments significantly enhance the adhesion strength between silicone polymer and PEEK. Sulfonation followed by NaBH₄ treatment produces a substantial increase in bond strength between silicone polymer and PEEK.