| Organic silicone resins are used for the formulation of heat-resistant and anticorrosion coatings. Because of their high cost, copolymers of siloxanes such as acrylate siloxanes, urethane siloxanes, and epoxy siloxanes are used for paint formulation as an alternative. Epoxy siloxanes and urethane siloxanes, known as inhibitive coatings, are both characterized by high thermal stability, weather and ultraviolet resistance, color stability, good protective and anticorrosion properties. Introduction of anticorrosion and heat-resistant pigments in such binders leads to the formulation of paints that can be used as primer with excellent properties. The nature of binder, pigments, extenders as well as the application process play significant role in overall properties of formulated paint. However, a clear relationship is difficult to establish between the properties of the paints and the content or the heating process. Hence, it is worth to evaluate the relationship between heat-resistant, mechanical, protective and anticorrosion properties of such paint systems and its components for their specific use.In this thesis, in order to evaluate and compare heat-resistant, mechanical and anticorrosion properties of epoxy siloxane and urethane siloxane paints containing the same anticorrosion and heat-resistant pigments, a well-known industrial epoxy siloxane binder referred to as HG-43was first formulated into paints, and then compared with two different urethane siloxane paints based on binders obtained by different synthesis methods. Thus, this work is summarized as follows:(1) Firstly, commercial epoxy siloxane binder, HG-43, has been formulated into paints. Traditional anticorrosion inhibitive and barrier protective pigment such as zinc phosphate, micaceous iron oxide and aluminum oxide have been used as the main variables for paint formulation. Titanium dioxide and mica have been also used. Nano-silicon dioxide was added to the formulation. Formulated HG paints heated at different temperatures and times showed that they have good impact resistance up to50kg·cm at180℃for three days of exposure. Moreover, impact resistance of the paint system HG-3rich in micaceous iron oxide was remained unchanged at300℃for five hours of exposure. Using thermogravimetric analysis (TGA) in inert gas, thermal resistance and stability of formulated paints was studied. HG-4rich in aluminum oxide showed excellent thermal resistance. The residual weight of HG-4is67.71%at800℃and its weight loss at300℃for five days of exposure is4%. Scanning electron microscopy (SEM) of the surface of paints did not show any defect. Furthermore, pigment particles were uniformly dispersed. However, at high temperatures up to300℃, the surface of HG paints showed some defects. HG paints immersed in different chemicals for seven days showed excellent chemical resistance, particularly HG-1containing almost the same quantity of all pigments. Electrochemical impedance (EIS) evaluation of protective and anticorrosion properties of HG paints showed that they resist to corrosion for21days of immersion in3.5%wt NaCl solution. Moreover, HG-1containing all pigments at the same quantity showed the best protective and anticorrosion properties. HG paint systems served as reference paints.(2) Secondly, a new urethane siloxane binder synthesized by crosslinking functionalized silicone resin with specially synthesized organoalkoxysilane has been formulated into paints. This silicone resin urethane binder that was called SRU-4contains70%of siloxane. SRU-4was formulated into paint by the same pigments and extenders used in the formulation of HG-43. The evaluation of the properties of SRU paints by the same method and techniques used for HG paints showed that SRU paints have better mechanical, adhesion, chemical, thermal and anticorrosion properties than HG paints. Particularly SRU-4C rich in micaceous iron oxide showed excellent impact resistance at300℃for five days and at350℃for four days. Urethane siloxane paints based on crosslinked binder showed excellent adhesion and flexibility at350℃for10hours of heating. SRU-4D rich in aluminum oxide showed the best thermal resistance in inert gas and oxygen. SRU paints showed excellent chemical resistance. SRU-4A containing all pigments at the same quantity exhibited the best chemical resistance. It showed also improved protective and anticorrosion properties. With the aim to improve heat-resistance of SRU paints, the paint was formulated into two-layer paints. For the topcoat silicon nitride and glass-spheres were used in combination with aluminum oxide while different undercoats were formulated with micaceous iron oxide, zinc phosphate or their mixtures. The two-layer paints showed improved thermal and anticorrosion properties. AG-3having a combination of micaceous iron oxide and zinc phosphate in the undercoat showed excellent protective and anticorrosion properties. This paint also showed the best chemical resistance.(3) Finally, another urethane siloxane binder obtained by sol-gel process of traditional alkoxysilanes and the same specially synthesized organoalkoxysilane used in previous urethane siloxane binder was formulated to paints. This siloxane urethane-urea that was referred to as SPUU-2contains90%of siloxane. One-layer SPUU paints showed excellent mechanical and adhesion properties. SPUU-2C rich in micaceous iron oxide showed excellent impact resistance, flexibility and adhesion for four days of heating at350℃. Thermal properties of one-layer SPUU paints were better than that of one-layer and two-layer SRU paints. SPUU-2A containing all pigments at the same quantity showed4.6%of weight loss at300℃for5days. They also exhibited better protective and anticorrosion properties than that of SRU paints. SPUU-4A showed the best protective and anticorrosion properties. Using the same heat-resistant pigments, i.e. silicon nitride and glass-spheres, formulated SPUU-2binder to two-layer paints exhibited the best thermal, protective and anticorrosion properties. The weight loss of BG-3containing micaceous iron oxide and zinc phosphate in the undercoat showed4.2%of weight loss at300℃for five days. It also showed the best chemical, protective and anticorrosion properties. BG-1having micaceous iron oxide as major component of undercoat showed the best mechanical properties. |
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