Polyurethane vs Polyethylene Foam: Which One Protects Your Product
Both materials show up constantly in protective packaging, and they get mixed up often. The short version: polyurethane is soft and open cell, polyethylene is firm and closed cell. That single difference drives almost everything else.
Polyethylene foam (PE)
Closed cell structure, meaning the cells are sealed off from each other. That makes it firmer, more structured, and much better at resisting water and chemicals. It holds its shape under load rather than wrapping around the product.
Strengths: moisture and chemical resistant, durable, holds up under repeated use, common in die cut inserts and rigid case foam
Tradeoffs: less able to conform to irregular shapes, firmer cushioning response
Polyurethane foam (PU)
Open cell structure, meaning air moves through it. That makes it soft, flexible, and good at conforming around irregular shapes. It compresses easily under light to moderate loads and gives a gentle, wrapping kind of cushioning.
Strengths: flexible, conforms to product shape, strong shock and vibration absorption, comfortable fit around delicate or irregular items
Tradeoffs: absorbs moisture more readily, generally not the first choice in wet or humid environments
How to pick
If the product is delicate, irregularly shaped, or needs a soft custom fit, polyurethane is usually the better starting point. If the product needs to survive moisture, chemical exposure, or repeated handling in a rigid case, polyethylene tends to win.
A lot of packaging setups actually use both, polyethylene for the outer structure and polyurethane for the inner cushioning layer. If you are not sure which combination fits your product, that is a conversation worth having before you commit to tooling.