When it comes to engineering foam products for packaging, manufacturing, or specialty applications, performance matters. The right foam isn’t just about appearance or initial feel — it’s about how it behaves under stress, how it recovers, and how it performs over time.
At Sterling Manufacturing & Distributing, we work with clients in industries from electronics to industrial equipment, creating foam solutions that meet exact specifications. That means knowing and testing for the properties that determine whether a foam product will stand up to its intended use.
Below, we take a closer look at six important terms from our foam glossary that relate to performance and testing. Understanding these can help you make better choices for your application — and ensure your products are protected, comfortable, or durable as needed.
Definition: The amount of return to the original dimensions and properties of a flexible polyurethane foam (FPF) sample after a deforming force is removed.
Why It Matters:
Recovery is all about “bounce back.” In packaging, you want foam that can absorb impact during shipping but quickly return to its shape to protect the product again if another jolt occurs. In seating or bedding, good recovery means the material won’t develop permanent indentations that affect comfort.
Example Application:
For a medical device case, recovery is critical — the foam must return to its precise cutouts so the equipment remains secure after repeated handling. Sterling tests recovery to ensure the foam performs consistently in real-world conditions. Note that “slow recovery” or “memory foams” are characterized by viscoelasticity; regular FPFs recover instantly, while memory foams recover more slowly.
Definition: The number of pounds of force necessary to indent an FPF sample by 25 percent of its original height. Surface firmness is often referred to as Indentation Force Deflection (IFD) or Indentation Load Deflection (ILD).
Why It Matters:
Surface firmness impacts both feel and function. A foam that’s too soft may not offer adequate support; one that’s too firm may not provide the cushioning or fit required. In packaging, this property can be the difference between a product arriving safely or sustaining damage from excessive movement.
Example Application:
In protective foam inserts for electronics, the right surface firmness ensures the product is held snugly without being overly compressed, which could stress delicate components.
Definition: A test procedure (ASTM D3574) that measures the surface resilience of FPF by dropping a standard steel ball from a set height onto a FPF sample and recording the percentage it rebounds.
Why It Matters:
Resilience affects how a foam responds to impact or sudden compression. High rebound can indicate a springy, energetic feel, while lower rebound might be preferred for shock absorption.
Example Application:
For sports equipment padding, higher ball rebound may be desirable to maintain responsiveness. For protective shipping foam, lower rebound can help dissipate impact energy rather than returning it to the object.
Definition: The ratio of a foam’s ability to support force at different levels of indentation — calculated as the ratio between the Indentation Force Deflection (IFD) at 65 percent and 25 percent compression.
Why It Matters:
This property tells you how the foam supports weight as it’s compressed. A higher compression modulus generally means more support at deeper compressions, which can prevent “bottoming out” in seating or packaging applications.
Example Application:
In industrial equipment packaging, a higher support factor ensures that heavy machinery parts won’t compress the foam too far, maintaining consistent cushioning throughout transport.
Definition: The mass per unit volume of foam, measured in pounds per cubic foot (pcf) or kilograms per cubic meter (kg/m³).
Why It Matters:
Density is one of the most critical foam properties because it affects strength, durability, and performance. However, density alone doesn’t determine firmness — two foams can have the same density but very different feel and support characteristics depending on formulation.
Example Application:
A high-density foam might be specified for repeated-use protective cases, while a lighter-density foam might be chosen for one-time-use packaging to save weight and cost.
Definition: A permanent loss of initial height in a foam sample after compression, caused by collapse of the cell structure.
Why It Matters:
A low compression set means the foam maintains its shape and cushioning ability over time. A high compression set could mean the foam flattens or loses resilience quickly, compromising protection or comfort. Compression set is usually measured as a percent of permanent deformation per standardized testing protocol (e.g., after 22 hours at 70°C).
Example Application:
In reusable shipping containers, a low compression set is essential, so the foam continues to provide consistent protection after multiple trips.
While each of these properties tells you something about foam performance, they rarely operate in isolation. For example:
This is why choosing the right foam often involves balancing multiple factors based on the intended application.
Sterling Manufacturing & Distributing doesn’t just supply foam — we engineer solutions. Our Design & Testing department works with you to:
Whether we’re fabricating EPS packaging inserts, designing polyurethane foam cushioning, or creating multi-layer composites, our goal is to deliver consistent, reliable performance you can count on.
Understanding these foam testing and performance terms is the first step toward selecting the right material for your application. The next step is partnering with a manufacturer who knows how to apply them in real-world scenarios.
At Sterling, we combine decades of experience with in-house testing capabilities to ensure every foam product we make meets the highest standards. From initial design to finished product, we’re here to help you protect what matters most.
Ready to discuss your next project? Contact Sterling Manufacturing & Distributing today to request a sample box and learn how we can create a custom foam solution for your needs.