Scholarly Publications - Chemistry

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Browsing Scholarly Publications - Chemistry by Author "Akaltan, F."

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    Characterization of denture acrylic resin surfaces modified by glow discharges
    (Sage Publications, Inc., 1997) Süzer, Ş.; Özden, N.; Akaltan, F.; Akovali, G.
    Resin samples prepared by compression molding using a poly (methyl methacrylate) (PMMA) denture base material were exposed to radio-frequency (rf) glow discharges to improve the wettability of the material. Fourier transform infrared (FT-IR) reflectance, X-ray photoelectron spectroscopy (XPS), and contact-angle measurements have been employed to characterize the changes introduced by the glow discharge plasma. FT-IR measurements cannot detect any modification. XPS reveals an increase in the O/C atomic ratio. Contact angles of the plasma-treated samples are always lower when compared with untreated ones. The increased O atomic concentration is attributed to formation of -COH groups on the surface during plasma treatment. The O/C atomic ratio decreases upon heating the samples in vacuum to 100 °C for 1-2 min and exposing the samples to liquid CH2Cl2 for 1-2 min. Exposure to distilled water for prolonged periods causes a slight decrease during the initial 1-20 days but levels off to a constant value up to a period of 60 days. Plasma treatment seems to offer a durable increase in the wettability for these materials left in air or distilled water.
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    Time-related wettability characteristic of acrylic resin surfaces treated by glow discharge
    (Elsevier, 1999-12) Özden, N.; Akaltan, F.; Süzer, Şefik; Akovali, G.
    STATEMENT OF PROBLEM: Adhesion and cohesion have important roles in denture retention, and attempts have been made to improve the wettability of the acrylic resin material by surface treatments. PURPOSE: This study examined the initial and subsequent wettability of an acrylic resin denture base material treated under air or argon plasma atmosphere before and after exposure to air or distilled water. MATERIAL AND METHODS: Acrylic resin specimens were treated with plasma under air or argon atmosphere and were either exposed to air or distilled water for up to 60 days. Wettability characteristics of the acrylic resin specimens were determined by contact-angle measurements after 2 hours and after 60 days. Surface composition of the specimens also was analyzed with x-ray photoelectron spectroscopic (XPS) measurements. RESULTS: Statistically significant difference was found between control and each of the plasma treatment groups (P <.05). Although the storage condition and storage period caused statistically significant difference on contact angle values (P <.05), atmosphere type did not have any effect on the results (P >.05). XPS spectra of the plasma-treated specimens differed from control specimens only in the O1s region with a narrower and more intense peak that could be assigned to -COH groups. During 60 days of exposure, the O/C atomic ratios decreased within the first 2 weeks but settled to 0.40 and 0. 32 up to 60 days compared with 0.26 for untreated control specimens. CONCLUSION: Glow discharge plasma altered the surfaces of the acrylic resin and increased thc wettability as shown both by XPS and contact-angle measurements, and plasma treatment seemed to offer a durable (at least up to 60 days) wettability.