Ultra-high-molecular-weight polyethylene fiber reinforced dental composites: Effect of fiber surface treatment on mechanical properties of the composites

Objectives. Poor interfacial adhesion between the fibers and resin matrix in the ultra high molecular weight polyethylene (UHMWPE) fiber reinforced composites (FRCs) is the main drawback of the composites. This study aims to evaluate the effect of corona and silane surface treatment of the fibers on the mechanical properties of the UHMWPE FRCs. Methods. UHMWPE fibers were exposed to corona discharges for different periods of time (0 s, 5 s, 7 s). The surface characteristics of the UHMWPE fibers were investigated by attenuated total reflectance Fourier transformed infrared spectroscopy (ATR-FTIR), atomic force microscopy (AFM), scanning electron microscopy (SEM) and nanoindentation technique. The flexural strength and flexural modulus of the FRCs made of the treated fibers were determined on 2 mm x 2 mm x 25 mm specimens. The fracture toughness (the critical stress intensity factor, K-IC) of the composites was also evaluated using a three-point single edge notch beam (SENB) bending technique. Statistical analysis of the data was performed with ANOVA and the Tukey's post-hoc test. The fiber-resin interface and the fracture surface were investigated using SEM. Results. The change in the surface mechanical properties and chemistry of the corona treated UHMWPE fibers were monitored. The fibers exposed to corona for 5s showed higher surface nanohardness. In the FRCs, the specimens reinforced with 5s corona treated silanized fibers showed higher mechanical properties (flexural modulus, flexural strength, and fracture toughness), SEM images revealed a better adhesion between the resin and fibers after 5s fiber corona treatment and silanization. Significance. Corona and silane treatment of UHMWPE fibers provide dental FRCs with improved mechanical properties. (C) 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.