In my first year as a plant engineer, I approved a $3,200 order of silicone gaskets for an oil-lubricated compressor. I honestly thought silicone was the premium answer to everything: it resists heat, cold, ozone, and looks trustworthy on paper. The oil turned those gaskets into a swollen mess within six weeks. The nitrile replacements cost less, survived, and are still running. I still kick myself for choosing a 'premium' material without checking what it hates most: petroleum oil.

Since then, I have worked on hundreds of sealing and cushioning projects, including Momentive silicone products. Along the way, I made a second expensive mistake: I used polyethylene foam where polyurethane resin foam was needed. The difference became obvious after a few months of compression. This guide covers the practical differences between silicone vs nitrile and polyethylene foam vs polyurethane resin foam from someone who has thrown away enough bad parts to know better.

What you are actually comparing

First, silicone vs nitrile is an elastomer decision. Both bend, stretch, and seal, but their chemical backbones lead to very different service limits. Nitrile, also called NBR, is the petroleum-resistant workhorse. Silicone is the wide-temperature, weather-resistant specialty.

Polyethylene foam and polyurethane resin foam belong to a different category. You use them for padding, gasket backing, vibration isolation, acoustic absorption, and thermal insulation. From the outside, they both look like soft foam sheets. The reality is not that simple: polyethylene foam is usually closed-cell, lightweight, waterproof, and inexpensive. Polyurethane resin foam is more elastic, more durable under repeated loads, and often better for structural cushioning.

Temperature behavior

Silicone vs nitrile

Typical published ranges for standard nitrile compounds are roughly -30°C to +120°C. Silicone compounds are commonly rated from about -60°C to +200°C, sometimes higher. If your application is in a hot chamber and has no petroleum fluids, silicone is hard to beat. If the application is oil mist at 100°C, nitrile is the better choice despite silicone's temperature advantage. My expensive compressor gasket proved this the hard way.

Polyethylene foam vs polyurethane resin foam

Standard polyethylene foam begins to soften and creep around 60-80°C, depending on density and whether it is cross-linked. Many flexible polyurethane resin foam formulations are rated to around 100°C. For a pad between a hot pump and a mounting plate, choose polyurethane resin foam if you expect sustained heat. I learned this when a PE foam pad deformed under a small transformer enclosure during its first summer.

Fluid and weather resistance

Nitrile vs silicone

Nitrile is famous for resisting mineral oils, diesel, gasoline, and many hydraulic fluids. Silicone swells badly in non-polar hydrocarbons. Silicone's strength is different: it resists ozone, UV, and weathering far better than nitrile does. If you expose a nitrile O-ring outdoors in direct sun, you will probably see cracking. Silicone will remain flexible. That is why you should not rely on a single 'better rubber' ranking; fluid compatibility comes first.

Polyethylene foam vs polyurethane resin foam

This is where the surprise often happens. Polyethylene foam's closed-cell structure makes it an excellent moisture barrier. It does not absorb water easily, and it is stable against many dilute acids and solvents. Polyurethane resin foam can be open-cell or semi-open, depending on the product. That means it can absorb moisture and hydrolyze in hot, humid service if the formulation is not protected. If you need a waterproof gasket backing, floatation layer, or chemical splash cover, polyethylene foam is usually the safer call.

Compression recovery and the case I got wrong

Silicone has a special advantage when temperatures are extreme: it stays elastic at high heat long after nitrile starts to harden. But in moderate conditions with oil contact, nitrile provides better long-term sealing pressure for the price. I wish more procurement guides said: identify the fluid first, then worry about the temperature chart.

My foam mistake: I specified polyethylene foam for anti-vibration pads under a small industrial fan. The fan was heavy enough that the PE foam took a permanent compression set after about four months. The pads became thin, hard, and started transferring vibration again. A colleague replaced them with polyurethane resin foam pads. The PU pads were still springy two years later.

Cost and total cost of ownership

Nitrile compounds are usually much cheaper than silicone. Polyethylene foam is typically cheaper than polyurethane resin foam per sheet or roll. In my 2024 purchase quotes, a commercial silicone sheet cost roughly two to three times more than an equivalent nitrile sheet. Polyethylene foam ran about one-third cheaper than an equivalent thickness of polyurethane resin foam. Those are illustrative numbers, not price guarantees.

Price differences matter, but they are small compared with the cost of downtime, replacement orders, shipping, and lost credibility. From the outside, picking the cheapest material looks like good cost control. What you do not see is the financial risk hiding in the fine print of the datasheet. If you are uncertain, buy a small sample and test it under your actual load, temperature, and fluid contact.

Momentive, Momentive login, and Momentive support

Why does Momentive appear in a guide about nitrile and foam? Because many of you are searching for Momentive material names. Momentive is primarily a silicone and specialty materials supplier. It is not a nitrile rubber producer, and it does not manufacture standard polyethylene or polyurethane resin foam sheets for commodity cushioning. Understanding that already prevents you from hunting for the wrong datasheet.

If you need help with Momentive silicone product selection, their technical support is genuinely useful. The hard part is access. The Momentive login portal for product registration and technical documents is not the same account you use for the corporate website. Create a free account before you need a datasheet at 5 p.m. I learned that during a rush quote; I spent two days waiting for password reset confirmation emails.

Once you are inside, you can open technical datasheets, processing guides, and compliance documents. If you still have a question, I have received a response from Momentive support members within 24 hours. I contacted them about high-temperature compression set on a specific silicone grade, and the answer changed our design. Use that resource instead of guessing from a supplier's vague secondhand table.

Checklist I use before every material order

Scenario-based recommendation

Silicone is not better than nitrile; it is better where silicone is better. Polyethylene foam is not a cheaper version of polyurethane resin foam; it is a different material. The cheapest choice is only cheap if it survives.

The fundamentals of material selection have not changed: temperature, fluid, load, environment, and price. What has changed is data access. Technical portals like Momentive's make it possible for a plant engineer to check exact values before ordering. The Momentive login may be annoying, but ten minutes of registration costs less than one failed batch. Use the comparisons above as your first filter, then confirm with real data for your real application.