Foam dressings are manufactured as either a polyurethane or silicone foam. They transmit moisture vapor and oxygen and provide thermal insulation to the wound bed. Polyurethane foams consist of two or three layers, including a hydrophilic wound contact surface and a hydrophobic backing, making them highly absorbent. They facilitate uniform dispersion of exudate throughout the absorbent layer and prevent exterior leakage (strike-through) due to the presence of a semipermeable backing. Foams are useful for both primary and secondary dressings.
Resource:
https://www.ncbi.nlm.nih.gov