Preparation of polybenzoxazine-EPDM rubber based hydrophobic nanocomposite materials

The aim of this thesis is to prepare a hydrophobic nanocomposite with Polybenzoxazine (PBZ) and ethylene-propylene-diene-monomer rubber (EPDM) filled by nano titanium dioxide (TiO₂) and polytetrafluoroethylene (PTFE/Teflon). In this work, the first step in the process is to synthesize fluorine-containing PBZ. Fluorine is intended to contribute to hydrophobicity of the PBZ. PBZ was synthesized by ring-opening polymerization, catalyzed by dimethyl amino ethanol (DMAE) base catalyst using benzoxazine monomer obtained from 4-hydroxy benzaldehyde, 2-(trifluoromethyl)aniline and paraformaldehyde. In order for the PBZ polymer to be ring-opening polymerization to take place, the reactants were magnetically mixed in an oil bath at 100 °C for 24 hours. As a result of polymerization, a hard brittle, light-yellow color solid polymer was obtained. Since the synthesized PBZ is a hard and brittle polymer on its own, it is necessary to get help from another polymer to improve the elasticity for polymer nanocomposite samples. Thus, it was prepared a blend with PBZ and EPDM rubber. Polymer nanocomposite samples with weigh ratios of 40% EPDM and 40% PBZ blend matrix, 10% nano TiO2 and 10% PTFE additives were prepared. Since at least one of the fillers must be nano-sized in order to meet the condition of being a nanocomposite, 0-20 nanometer TiO2 additive is used. Both nano TiO2 and PTFE additives helped to prepare a hydrophobic polymer nanocomposite. Since one of the matrix components is EPDM rubber, some of the samples were cross-linked with 0.1% sulfur by weight to perform the vulcanization step, which is an important step in the use of rubber material. Polymer nanocomposite samples prepared with and without sulfur were heated and cured with temperatures of 25 °C, 100 °C, 150 °C and 180 °C, respectively. The effect of sulfur and curing temperature on the hydrophobicity of polymer nanocomposite samples was studied. The EPDM-PBZ nanocomposites were also characterized by UV-vis., TGA-DTA, SEM, SEM-EDX, FTIR, contact angle measurement characterizations. The contact angle was noted as 101.1° for PBZE1-EPDM-PTFE-Nano TiO2 nanocomposite sample. According to the UV results, the samples showed wide range abroad absorption peaks. According to all test results, the preparation of a hydrophobic polymer nanocomposite was successful. It was observed that the additives were homogeneously distributed in the matrix, there was no agglomeration. When the prepared polymer nanocomposites were compared to whether they were hydrophobic or not, it was clearly seen that the temperature and the curing process by cross-linking with sulfur increased the hydrophobicity in the samples. In particular, the EPDM-PBZ polymer nanocomposite sample with sulfur, vulcanized at 150 °C presented better hydrophobic features with a contact angle of 110°.