Novel solutions in polyurethane coatings

Abstract

Polyurethane-based materials are among the most versatile and strategically significant classes of polymers in the coatings and specialty chemicals industries. Their segmented molecular architecture, consisting of hard and soft domains connected through urethane linkages, enables precise tailoring of mechanical, thermal, interfacial, and barrier properties. As a result, polyurethane coatings are widely employed in industrial and protective coatings, corrosion protection, adhesives, elastomers, functional textiles, and advanced composite systems. However, increasing regulatory pressure, sustainability requirements, and application-driven performance demands are reshaping conventional polyurethane chemistry and driving the development of novel coating architectures. Restrictions on volatile organic compounds (VOCs) and growing concerns regarding isocyanate exposure have accelerated the transition toward environmentally responsible technologies. The motivation for this Ph.D. thesis arises from the growing demand for multifunctional, durable coating systems that perform reliably across diverse application domains. Among emerging approaches, organic-inorganic hybrid coatings represent a powerful strategy for combining complementary functionalities within a single material platform. Silicone-polyurethane hybrids, in particular, exploit the low surface energy, flexibility, and thermal stability of polydimethylsiloxane (PDMS) together with the mechanical strength, adhesion, and film-forming ability of polyurethane. Such systems have demonstrated enhanced hydrophobicity, lubricity, washing durability, and resistance to environmental stress. Importantly, the performance of silicone-polyurethane coatings is highly dependent on the mode of silicone incorporation, whether as a modifier within the polyurethane backbone or as a polyurethane segment integrated into a silicone-dominated architecture. A systematic evaluation of these structural approaches, especially across different application domains, remains limited in the literature. Functional textile finishing represents one of the important application area where durability, moisture management, and resistance to repeated laundering are essential. Modern textile coatings are expected to deliver comfort-related properties such as controlled wetting, moisture transport, and softness while maintaining long-term performance. Conventional silicone finishes often suffer from migration or removal during washing, leading to a loss of functionality. Consequently, polymer-bound or hybrid systems that ensure semi-permanent fixation to fiber surfaces are increasingly sought. Beyond technical textile, one of the important functional coating research area is corrosion. Recent research trends in corrosion protection emphasize environmentally friendly inhibitor systems, hybrid barrier coatings, and self-healing or stimuli-responsive architectures. Integrating such functionalities into waterborne and hybrid polyurethane systems presents a promising route toward sustainable, high-performance anticorrosion coatings. However, correlating polymer architecture, microstructure, and functional performance especially when hybrid systems are employed remains a complex and underexplored challenge. Polymeric inhibitor systems are still developing area for saline environments. Protective coatings serve as the primary defence against corrosion by providing barrier properties, strong adhesion to metal substrates, and, in advanced systems, active inhibition or self-regulating functionality. Within this broad scientific and technological context, the present thesis aims to develop and systematically investigate novel polyurethane-based coating systems capable of addressing both textile functionalization and corrosion protection requirements. The study focuses on two chapters: In the first part, three polyurethane-based coating systems, PDMS-modified polyurethane (PDMS-m-PU), polyurethane-modified silicone (PU-m-PDMS), and a reference pure blocked polyurethane were successfully synthesized using controlled prepolymer and blocking-deblocking strategies. Their chemical structures were verified by FTIR and 1H NMR, 13C NMR analyses, confirming urethane formation, effective siloxane incorporation, and complete consumption and blocking of free isocyanate groups. Deblocking mechanisms were characterized by thermal analysis. The synthesized polymers were applied to 100% cotton woven and 100% polyester knitted fabrics, where SEM-EDX analyses confirmed homogeneous coating distribution, durable retention on fiber surfaces, and overall moisture management (OMM) values of approximately 0.8 or higher. The second focus of the polyurethane coating is corrosion. This study highlights that over 95% inhibition efficiency is possible in 3.5% NaCl Solution with a novel polymeric inhibitor. A novel polymer was synthesized by modifying Poly(styrene-co-maleic anhydride) with TRIZMA. This polymer was successfully integrated into a VOC-compliant waterborne polyurethane matrix. Electrochemical and surface analysis confirmed its high efficiency and film formation mechanism. Overall, this work provides fundamental insight into advanced polyurethane chemistry while offering practical guidance for the design of next-generation, multifunctional coatings suitable for both functional textiles and corrosion protection in demanding industrial environments.