Memory/Visco foam is polyurethane with additional chemicals increasing its viscosity and density. It is often referred to as visco-elastic polyurethane foam. It is also referred to as low resilience polyurethane foam (Such as in some laptop sleeves (see LRPu). In some formulations, it is firmer when cooler. Higher-density memory foam reacts to body heat, allowing it to mold to a warm human body in a few minutes. A lower-density memory foam is pressure-sensitive and molds quickly to the shape of the body. less more