Polyethylene: (PE) Closed-cell, water resistant, more rigid than polyurethane, high strength and durability, shock absorbing, vibration dampening. Available in cross-linked, as well as laminated up to 6" Used for end caps and inserts.
Polyurethane: (PU) Open-celled, flexible, non-abrasive. Available in convoluted (egg crate), antistatic and fire resistant grades. Available in a wide range of densities and compressions to handle different loads.
Types of polyurethane foam:
-Polyether: Low cost, all-purpose
-Polyester: Higher tensile strength than polyether