Silicon-based preceramic polymers and their uses in polymer composites: synthesis, characterization and processing

Dönmez Karadal, Sibel
The objectives of this study are to synthesize poly(dimethylsilane) (PDMS) preceramic polymer and to investigate its effect on morphology, flame retardant and mechanical properties of polypropylene (PP) based composites. There are mainly two parts in this thesis. In the first part, PDMS was synthesized by electrochemical polymerization of dichlorodimethylsilane, which was dissolved in 1,2 dimethoxyethane (DME) solvent consisting of tetrabutyl ammonium perchlorate (TBAP), as supporting electrolyte. PDMS was obtained in powder form and characterized with Fourier transform infrared, ultraviolet-visible and proton nuclear magnetic resonance spectroscopic analyses, thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). Since PDMS has some impurities coming from TBAP and DME, alternatively, the PDMS synthesis was done by electrochemical reduction of dichlorodimethylsilane without using solvent and/or supporting electrolyte for seven days. PDMS was produced as pure and characterized with the same methods used for previous synthesis. In the second part of this thesis, PP based composites with additives were prepared by using a twin-screw extruder and injection molding machine and were characterized with limiting oxygen index (LOI), horizontal burning, TGA, differential scanning calorimetry (DSC), tensile and impact tests and SEM analysis. Triphenyl phosphate, boron phosphate, magnesium hydroxide, intumescent flame retardants (IFR) (melamine phosphate (MP) and pentaerythritol (PER)), antimony trioxide and poly(methylsilsesquioxane) were additives used in this study other than PDMS. According to LOI test results, the highest LOI value among the PDMS composites was obtained in 1% PDMS, 14.25% MP and 4.75% PER (w/w) containing composite as 24%, whereas the LOI value of neat PP was measured as 17.5%. It was determined that elastic moduli of all the composites studied were higher than neat PP.


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Citation Formats
S. Dönmez Karadal, “Silicon-based preceramic polymers and their uses in polymer composites: synthesis, characterization and processing,” M.S. - Master of Science, Middle East Technical University, 2011.