Ureahartsit

Ureahartsit, commonly referred to as urea resins, are a family of thermosetting polymers derived from urea and formaldehyde, often with melamine as a component (melamine–urea–formaldehyde resins). They form by condensation of urea with formaldehyde under acidic or basic conditions, creating crosslinked networks that cure with heat. The most common subtype is urea–formaldehyde (UF) resin; when melamine is included, the material is called MUF resin and generally has improved moisture resistance and heat stability.

Ureahartsit are widely used as binders and adhesives, particularly in wood-based panels such as particleboard, medium-density fibreboard (MDF), and plywood, where they provide high bonding strength at relatively low cost. They are also used as sand binders in foundry molding and in certain coatings and papers. Variants and refinements aim to reduce formaldehyde emissions and improve moisture resistance, contributing to regulations that favor low-emission binders.

A key consideration is formaldehyde release, especially under humid or hot conditions. This has driven development of lower-emission UF formulations, as well as alternative resins like phenol–formaldehyde and melamine–urea–formaldehyde systems. Ureahartsit remain a major class of amino resins due to their balance of cost, performance, and processing ease, although environmental and health concerns continue to shape their use.