Poly Foam 

A polyurethane foam mattress (or PU) is also known as polyfoam. This is the most common type of mattress foam. It is often used as an upper comfort layer in innerspring mattresses. However, a big block of the foam can be used by itself as a polyurethane foam mattress.
At this point you may be wondering if polyurethane foam is similar to memory foam. In terms of feel, it is quite different. Both have polyurethane in them though. The main difference between polyurethane foam and memory foam is that memory foam contains additional chemicals which increase its density and viscosity. So they are chemically related, but feel vastly different to each other. PU foam is a lot more ‘bouncy’ or springy than memory foam.
Polyurethane foam is made entirely synthetically. There is no such thing as a natural PU mattress, in contrast to latex which can be 100% natural.