A high-viscosity solvent-free cardanol modified epoxy hardener HW-541 with good chemical resistance Epoxy hardener HW-541 is a solvent-free phenalkamine epoxy curing agent with very high bio-content. It has excellent rapid cure properties, even at low temperatures with long pot life, and provides good adhesion on wet or otherwise unprepared surfaces. HW-541 can also be used in potable water applications and industrial adhesives. 1. The physical and chemical properties