Research Information System
Thesis Type: Postgraduate
Institution Of The Thesis: Gazi Üniversitesi, Fen Bilimleri Enstitüsü, Turkey
Approval Date: 2011
Student: ULYA AKARSU
Supervisor: NURSEL DİLSİZ
Abstract:Surface modification of nanoparticles has influence on improvement of biodegradable polymer matrices nanocomposites. To improve the properties of nanocomposite and uniform dispersion of nanoparticles in matrix can be performed by surface modification of nanoparticles. In this study, the surface of TiO2 nanoparticles was modified by two different surface modification methods. Nanoparticles grafted with lactic acid containing (LA-g-TiO2) and propionic acid-n-hexylamine containing (AA-g-TiO2) and non-grafted nanoparticles (TiO2) were added to the poly(lactic acid) (PLA) matrix via solvent casting method. Chemical structure of nanocomposites was examined by Attenuated Total Reflectance (ATR) and Fourier Transform Infrared (FTIR). Thermal stability was indicated by Differential Scanning Calorimeter (DSC) and Thermogravimetric Analysis (TGA). Mechanical properties were measured by Dynamical Mechanical Analysis (DMA). Surface topography was investigated by Atomic Force Microscopy (AFM). The contact angle measurements were carried on Drop Shape Analysis (DSA). It was determined that these two different surface modification methods were achieved successfully by exploring ATR spectrums. TGA results showed that thermal stability of nanocomposites containing LA-g- TiO2 (LA-g-TiO2/PLA) was improved. Thermal degradation temperature of 1 wt.% PLA/LA-g-TiO2 was obtained 20 ºC higher than püre PLA. DSC curves showed that glass transition and melting temperatures of nanocomposites were independent of loading of AA-g-TiO2 and LA-g-TiO2 nanoparticles. DMA results demonstrate that the most efficient bonding and compatibility were seen in PLA/LA-g-TiO2 nanocomposite. AFM micrographs of the nanocomposites suggest that grafted TiO2 nanoparticles were homogeneously dispersed in polymer matrices. Contact angle measurements demonstrate that nanocomposites were gained hydrophilic character by adding TiO2 nanoparticles into PLA films. Contact angles of nanocomposites which contain 0.5 wt.% TiO2 and AA-g-TiO2 nanoparticles shifted to low values (64.6º and 65. 6º, respectively) when compared with pure PLA (82.6º). The results showed that grafted nanoparticles played an important role in improving thermal and mechanical properties of the nanocomposites.