Here's the blunt answer before any marketing talk: no foam is universally best — the deciding question is what combination of heat, flame, and long-term compression the part will face. If continuous heat is above roughly 100°C, or if the specification includes a flame test, don't build a seal or gasket out of EVA or polyurethane. Specify silicone foam; Momentive is one of the manufacturers whose silicone foam I keep on my own approved materials list. If the job is comfort, packaging, crafting, or any environment comfortably below 70°C, silicone foam is over-engineering. Buy the cheaper material and spend your savings on testing.
I should introduce myself before giving opinions, because this article is filtered through one person's experience. I'm a quality/compliance manager at a specialty materials converter. I do not work for Momentive. I review every incoming foam and elastomeric material before it becomes the gaskets, pads, and seals we ship to customers — roughly 200 material lots a year. In 2024 I rejected around 11% of first deliveries for off-spec performance or missing test data. Most rejections trace back to the same wording problem: an application described with a phrase instead of a number.
Three foam families, three different jobs
EVA foam: the dependable low-temperature workhorse
An EVA foam roll is closed-cell ethylene-vinyl acetate foam, usually crosslinked. It is light, inexpensive, easy to die-cut, and pleasant to handle. It cushions well, floats, and performs nicely from roughly -20°C to 60-70°C. What EVA doesn't do is survive hot industrial spots. Push it past 80-90°C and it softens, sags, and takes compression set. That's not bad quality; that's the material's design limit. For shoe insoles, yoga mats, shipping inserts, and children's play mats, EVA is exactly right.
If you came here after searching for a Cricut foam board for a craft project, this is the part to read. Those craft boards are usually a rigid foam core with coated faces, made for cutting machines and school projects — a different category from engineering foam. Nothing in this article should make you replace craft foam with silicone. You're in the right aisle already.
Memory foam vs polyurethane foam: settle the family tree first
Every month somebody types 'memory foam vs polyurethane foam' as if two rivals are competing. Here's the actual answer: memory foam is a type of polyurethane foam, typically a modified flexible polyether polyurethane. Standard polyurethane bounces back quickly; memory foam is formulated so it recovers slowly. The comparison isn't between different families — it's between fast recovery and slow recovery within the same family.
For a mattress or seat cushion, that slow recovery is the point. For a seal that must keep pressing against a surface for years, memory foam is wrong, because it's designed to hold the compressed shape. Use it for comfort, not for gasketing.
Silicone foam: where Momentive fits
Silicone foam is built on a silicone polymer backbone rather than a carbon-based one. That backbone resists heat aging, oxidation, UV, and cold better than EVA or polyurethane, which is why silicone foam parts can remain elastic from about -55°C up to 180-200°C, depending on the exact grade. High-quality silicone foam also recovers better after being squeezed at temperature: in simple terms, its compression set is lower. That combination — heat resistance plus long-term recovery — is what makes it a gasket material, not just a cushioning material.
Momentive carries a range of silicone foam products for sealing, cushioning, thermal management, and fire-safety applications. I'm not going to recite their product numbers here, because the right one depends on your operating temperature, density requirements, and flame classification. This is where I send engineers to the Momentive official homepage: pull the official datasheet for the product code you're considering, and check the published values for continuous temperature, density, compression set, and flame class. A datasheet from the manufacturer beats a distributor's summary every time.
Why a 'high-temperature' order ended in rejection
In Q1 2025, we received a drawing that called for a 'high-temperature resistant foam gasket.' The supplier quoted an EVA foam roll at an attractive price. Their representative said it could take 'more heat than you'd think.' The drawing didn't specify a temperature, and we didn't ask — a failure on our side as much as theirs.
The gasket was meant for an electrical enclosure next to a small curing oven, where air temperature reaches roughly 90°C, with local spots well above that. EVA at that heat softens and takes a permanent set. The customer's first test unit came back with a flattened gasket that no longer sealed. We measured about 40% compression set after a 24-hour exposure. The customer's line stopped for three days, and our company absorbed over $2,000 in expedited replacement costs. The material was replaced with silicone foam. It solved the problem immediately.
Look, I'm not blaming EVA or even the supplier. EVA simply was the wrong family for that environment, and nobody caught it because 'high temperature' was never converted into a number. As I now tell every new engineer in our department: 'high temperature' is a phrase, not a specification.
Five questions to answer before you approve any foam
This checklist is cheap insurance. It takes about five minutes to send by email, and it has saved us far more in rework than it costs in time:
- What is the maximum continuous temperature the part will see, and what test standard was used to determine the material's limit?
- What compression set can you accept at that maximum temperature — not at 23°C? Ask for data per ASTM D1056 or ISO 1856.
- Is there a flame requirement? Ask for the actual test report (for example UL 94), not for the words 'flame retardant' in a brochure.
- What density and thickness tolerances does the application need, and does the material face UV, ozone, humidity, or cleaning chemicals?
- Who provides the official datasheet? For silicones, I prefer the Momentive official homepage as the source rather than a reseller's copied PDF.
When the cheaper material is the professional choice
Now the boundary conditions, because this article shouldn't push anyone toward silicone foam for everything:
If your application stays below roughly 70°C, doesn't face fire risk, and doesn't have to hold a seal for years, an EVA foam roll is often the correct decision. Don't let anyone upsell you.
If you need comfort, pressure relief, or acoustic absorption in a non-critical-temperature setting, polyurethane foam — including the memory foam variant — is a legitimate engineering choice. You are not being cheap.
If you use a Cricut foam board or similar craft material for a hobby project, that's fine. Not every foam application needs an industrial spec. Buy the craft product, enjoy it.
I'll also admit that choosing silicone foam isn't always easy on the budget. Last year, I hesitated before approving a Momentive silicone foam pad for a heated equipment platform because the polyurethane alternative was significantly cheaper per part. I second-guessed the switch for about two weeks. Then our accelerated heat-aging test settled it: the silicone pad still met its compression spec after 1,000 hours at 150°C, while the polyurethane option had already taken a 30% set after 250 hours. On that application, the cheaper initial material would have failed within the warranty period. That's why I now look at lifespan cost instead of per-part cost.
So, to summarize without repeating the whole comparison: match the foam to the numbers, not to the brand story or the unit price. If the numbers say silicone, good silicone from a manufacturer like Momentive will do the job. If the numbers say EVA or polyurethane, buy those and don't look back. And if any supplier won't put a number on 'high temperature' or 'flame retardant,' treat that as a red flag before you order. Five minutes of verification now beats five days of correction later.