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Influence of preheating and post-curing on a novel fiber-reinforced composite post material

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posted on 31.10.2018 by Letícia Nunes de ALMEIDA, Gustavo Adolfo Martins MENDES, Isabella Negro FAVARÃO, Amanda Vessoni Barbosa KASUYA, Marcela Gonçalves BORGES, Murilo de Sousa MENEZES, Rodrigo Borges FONSECA

Abstract The aim of this study was to investigate the influence of preheating and post-curing methods on diametral tensile strength (DTS), flexural strength (FS), knoop microhardness (KHN), and degree of conversion (DC) of an experimental fiber-reinforced composite (FRC). Specimens (30 wt% of 3-mm-short E-glass fiber, 22.5 wt% of methacrylated-based resin and 47.5 wt% of filler particles) were subjected to: P – photocuring at 1500 mW/cm2 for 40 s (control); P/M – photocuring and microwave post-curing (540W/5 minutes); P/A – photocuring and autoclave post-curing (120°C/15 minutes); PH-P – preheating (60°C) and photocuring; PH-P/M – preheating, photocuring and microwave post-curing; and PH-P/A – preheating, photocuring and autoclave post-curing. Specimens for DTS (Ø 3 x 6 mm) and FS (25 x 2 x 2 mm) were tested at Instron 5965. KHN employed a 50g load for 30s. DC was measured using FTIR spectroscopy. Statistical analysis employed: factorial analysis, normality test, one-way ANOVA and Tukey’s HSD test, independent T-test and the Dunnett test. Interaction between factors was not significant (P>0.05). Preheating promoted significantly higher values of FS and KHN (p = 0.0001). Post-curing promoted significantly higher values for KHN (p = 0.0001). For DTS (p = 0.066) and DC (p= 0.724) no statistical difference was found between groups. SEM images showed that preheating promoted better interaction between glass fibers and resin matrix. Preheating increased FS, KHN and DTS, and post-curing increased KHN. DC was not affected by both methods. Preheating and post-curing methods can be used to improve some mechanical properties of FRCs’ but degree of conversion remains unaffected.

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