PURHarze

PURHarze, or polyurethane resins, are a class of polymers formed by the reaction of polyols with di- or polyisocyanates to produce urethane linkages. They exhibit a broad range of mechanical properties and can be tailored for coatings, foams, adhesives, sealants, and composites.

They are commonly formulated as two-component systems (2K PUR) consisting of a polyol or prepolymer component and an isocyanate component, or as one-component systems that cure on exposure to moisture or heat. Waterborne PURs reduce volatile organic compound (VOC) content. Other variants are solvent-borne, solvent-free, or reactive and designed for particular processing methods such as spraying, casting, laminating, or dipping.

PURHarze offer characteristics including strong adhesion to diverse substrates, good chemical and abrasion resistance, and tunable hardness and elasticity. Thermal stability and weathering resistance can be optimized through formulation. Applications span industrial coatings, wood finishes, automotive and aerospace coatings, rigid and flexible foams for insulation, adhesives for wood and composites, sealants for construction, and elastomeric materials.

Processing requires attention to pot life, mixing ratios, and curing conditions. Because isocyanates can cause sensitization and respiratory issues, appropriate ventilation, personal protective equipment, and training are essential. Environmentally, regulations address VOC content, exposure limits, and substance restrictions (such as REACH in the EU). End-of-life options include mechanical and chemical recycling of PUR foams and energy recovery where feasible.