On the synergistic effect of sulfonic functionalization and acidic adhesive conditioning to enhance the adhesion of PEEK to resin-matrix composites

Abstract

ObjectiveThe objective of this study was to evaluate the combined effect of the sulfuric acid etching and an acidic adhesive conditioning on the shear bond strength of PEEK to a resin-matrix composite. Materials and methodsForty PEEK specimens were assigned randomly to 4 groups for H2SO4 etching followed by universal adhesive (pH at 2.5) conditioning for 0, 1, 3, and 5 min. Thirty PEEK specimens were divided into 3 groups for only acidic adhesive conditioning for 0, 1, 3, and 5 min. After the light-curing of the adhesive, a nanohybrid resin composite was applied onto the surfaces and then light-cured following the manufacturer`s guidelines. All specimens were stored in distilled water at 37 °C for 24 h mechanical testing. Shear bond strength tests were performed using a universal testing machine. Surfaces were analyzed by SEM, light interferometry, FTIR, and liquid contact angle measurement. Statistical analysis was performed by one-way ANOVA and Tukey’s post hoc tests (p < 0.05). ResultsNo adhesion was achieved between untreated PEEK a resin-matrix composite, regardless of the adhesive conditioning time points. Shear bond strength of H2SO4-etched PEEK to resin-matrix composite increased with time (0 mmin. 4.95 ± 2.86 MPa < 1 min: 9.35 ± 2.26 MPa < 3 min: 17.84 ± 2.82 MPa < 5 min: 21.43 ± 5.00 MPa). SEM images revealed a significant modification of PEEK surface topography after the H2SO4 etching. SignificanceThe acidic adhesive was unable to modify the untreated PEEK surface to establish an effective adhesion although a synergistic effect was noticed when the universal (acidic) adhesive was applied over a H2SO4-etched PEEK surface, thus improving the PEEK to resin-matrix composite adhesion.