Organo-titanates and zirconates coupling agents in polymer composites: A review

Abstract

Organometallic coupling agents play a crucial role in polymer blends and composites by enhancing the compatibility between different polymers or improving interfacial adhesion between polymers and reinforcement agents or fillers. These agents facilitate chemical bonding, improving mechanical properties, dispersibility, and moisture resistance. While conventional coupling agents, such as silanes, are widely used across various applications, they present limitations, including susceptibility to hydrolytic degradation in aqueous environments and reduced bonding efficiency with non-silica or non-hydroxyl-bearing compounds. This poses challenges in developing composites with long-term hydrolytic stability, a key objective in polymer materials research. Hence, pursuing hydrolytically stable composites remains critical in polymer materials research. In contrast, organometallic compounds such as titanate coupling agents improve the bonding between inorganic materials—such as carbon, graphite, calcium carbonate (CaCO₃), hydroxyapatite, and metal oxides—and polymer matrices. While the effect of these coupling agents on the physical and mechanical properties of dental prostheses have been thoroughly reviewed, few attempts have addressed these coupling agents’ applications in polymer compounds/composites. This paper aims to review the application of organometallic compounds such as titanate and zirconate coupling agents in polymer blends and composites to highlight and identify gaps in the earlier research work and provide resourceful data for future research. The review offers insights and valuable data to advance the knowledge of polymer composites, particularly in tailoring an enhanced interfacial bonding for long-term performance under harsh environmental conditions.