Why is water the main carrier liquid in many modern coatings?

Water has become the predominant carrier liquid in modern surface coatings primarily due to environmental regulations.1

Historically, many coatings relied on organic solvents to dissolve polymers and facilitate application. However, these solvents are classified as volatile organic compounds (VOCs), which are released into the atmosphere during application and curing. Because these substances contribute to the formation of air pollution and ozone at low elevations, their use has been subject to increasingly strict legislative controls since the 1960s.23

In contrast, water presents no pollution hazard by itself. It is widely used as a carrier for latex coatings and as a partial solvent for water-reducible systems. While organic cosolvents are sometimes added to these systems to ensure proper polymer solubility, the shift toward water-based carriers remains a critical strategy for complying with environmental standards.21