When you’re choosing foam for a case insert or a custom-packaged product, the decision usually comes down to two materials: polyethylene (PE) and polypropylene (PP). Both protect parts from shock and vibration. Both can be fabricated in multiple ways. They aren’t interchangeable, though. Each material behaves differently under load, stress, moisture, and long-term use.
This guide breaks down the traits that matter most in protective packaging so you can choose the right foam for your application.
PE foam is a closed-cell polyethylene material. It’s flexible, strong, and reliable for repeat impacts. This is the material most engineers reach for when they need cushioning that survives shipping and handling.
Key traits
PE is the backbone of industrial packaging because it handles the everyday chaos of transit without deforming permanently.
PP foam is a closed-cell polypropylene material. It’s stiffer than PE and has a higher temperature tolerance. It also rebounds faster, which can matter for parts that move, snap, or lock in place.
Key traits
PP works well when the packaging needs structure in addition to protection.
Here’s how the two materials behave in the real world.
PE offers softer energy absorption. It spreads impact across a larger area, which keeps fragile or sensitive parts safer. PP is firmer, so the force transfers more directly unless you increase thickness.
If your part can’t take a hit, PE usually wins.
Related Content: What Is a Cushioning Curve? Designing Better Foam Packaging
PE resists permanent dents under repeated loads. PP snaps back quickly but can crease if overstressed because of its rigidity.
If your packaging will be reused or handled many times, PE provides more consistent long-term protection.
PP tolerates higher temperatures. PE works fine in typical shipping conditions but isn’t ideal for environments with sustained heat exposure.
If your product sees heat or is stored near equipment that warms up, PP may perform better.
Both materials come in many densities, but PE has more availability in the mid-range densities used for protective packaging. This makes it easier to dial in the exact cushioning curve you need.
Related Content: Does Higher Density Mean More Firmness for Packaging Foam?
PE is generally more cost-effective. PP can be slightly more expensive because of how it’s manufactured and the specialized use cases.
Choose PE when you need:
PE is the standard for electronics, medical devices, instruments, consumer goods, and anything fragile enough to need reliable cushioning.
Choose PP when you need:
PP is popular for automotive components, industrial tools, precision equipment, and reusable containers that need structure more than softness.
For most protective packaging applications, PE foam is the better choice. It provides safer impact absorption, fewer permanent dents, and more predictable results across a wide range of densities and part types.
PP shines in projects that need stiffness, heat resistance, or structural support. It’s not as commonly used for cushioning, but works well for certain engineered fits.
Every product behaves differently under load, shock, and vibration. Density, geometry, and handling conditions all play a role. The best way to make the right choice is through a quick engineering review.
Foam Industries can run impact testing, review your drawings, and recommend the right material based on your part, your shipping environment, and your budget.
Foam Industries is a custom protective packaging company specializing in foam – with additional wood and plastic fabrication services. Our custom foam fabrication services are ideal for any type of packaging, display, or support service needed – from design to finished product.