1. What are the density and ILD/IFD (firmness) values, and what is the difference between them?
Density (commonly 40-80 kg/m3 or 2.5-5 PCF) determines durability and resistance to sagging; the higher the density, the longer the service life. ILD/IFD (Indentation Load Deflection) determines the soft or firm feel and is a separate matter from density, so a high-density foam can still be soft.
2. Will it sag quickly? Is it pure material or filler-extended? What is the service life?
Cheap memory foam with added fillers deforms permanently within six months to a year, while premium pure polyurethane material can last 7-10 years or even longer. A rebound rate of 95-98% or higher after roll packing and transport is a common acceptance criterion.
3. How is the heat dissipation? Does it feel hot and stuffy?
The biggest weakness of regular memory foam is its closed-cell structure, which tends to trap heat.