Preparation and characterization of silane-terminated hybrid polyurethane coatings

In this thesis study, the synthesis and characterization of hybrid polyurethane coatings terminated with silane-functionalized end groups were carried out. The main objective of the study was to investigate the effect of silane types with different structural properties on polyurethane prepolymers and final product to optimize the rheological, chemical, and mechanical performance of the resulting coating materials. First, the prepolymer was synthesized by reacting an IPDI-based isocyanate with a polyol, followed by modification of the end groups using various amino-functional silanes. During the reactions, the %NCO values were monitored by titrimetric analysis, aiming for complete closure of the NCO groups after silane addition. FT-IR spectroscopy was used to characterize the prepolymers and silane-terminated products, investigating the presence of NCO and Si-O-Si bonds. Furthermore, viscosity measurements revealed the decisive effect of the silane structure on the product rheology. An inverse relationship was observed between NCO content and viscosity, determining the optimum %NCO level to be in the range of 1–2%. Within this range, the product retained its processability and did not lose its mechanical properties. When comparing various silane types, systems modified with N-(n-butyl)-3-aminopropyltrimethoxysilane (BAPTMS) have demonstrated the best performance due to low crosslinking, suitable viscosity, and high reaction yield. Other silane types, however, exhibited high viscosity and processability issues due to excessive cross-linking and gelation tendencies. In conclusion, this study demonstrates that determining the appropriate silane type and reaction conditions in the synthesis of silane-terminated hybrid polyurethane coatings plays a critical role in controlling the final product properties. The results obtained directly contribute to industrial applications aimed at improving the performance of polyurethane-based coatings. Keywords: Silane, Polyurethane, Prepolymer, Hybrid, Coating