I've been handling Momentive silicone orders for seven years. In that time I've made 13 documented mistakes—roughly $58,000 in wasted budget. Most were preventable. This FAQ is the checklist I wish I had when I started in 2018.

The questions below are the ones buyers and engineers ask me most. The third one is the one nobody thinks to ask until after they've ordered the wrong material. If you're new to silicone, read them in order. If you're in a hurry, jump to your problem.

1. What is Momentive GE silicone?

Momentive Performance Materials is the company that grew out of GE Silicones. So when you see "Momentive GE silicone" on an old datasheet, it's shorthand for a product line with that heritage. The current trade names are usually something like TSE or Silopren. The GE Silicones formulas didn't disappear—they just moved under the Momentive brand.

Why does this matter? Because if you buy by part number rather than spec, you may end up with a substitute that is "equivalent" on paper but different in cure time, consistency, or temperature resistance. In Q1 2022, I approved a cross-reference without checking the full data sheet. It looked right, passed a basic durometer test, and then failed a 180° heat-air aging test. That cost us half a production run and a lot of uncomfortable meetings.

Read the product name carefully. If a quote says "Momentive GE silicone," ask which current Momentive grade it maps to. As of April 2025, momentive.com is the reference for current datasheets and product revisions.

2. Are Momentive silicone sealants the same as silicone rubber?

Not exactly. Silicone sealants are one category in the silicone rubber family. A typical Momentive silicone sealant is a one-part RTV—room-temperature vulcanizing—made to bond or seal a joint. It cures with moisture in the air. Silicone rubber also covers LSR (liquid silicone rubber), HCR (high-consistency rubber), silicone foam, and brushed-on coatings. They all share a siloxane backbone, but their physical properties are far apart.

Here's a short rule I use: sealants make a joint; rubber makes a part. If you need to seal a seam, you want a sealant. If you need a gasket, a foam pad, or a molded component, you want an elastomer. I've seen someone try to use sealant to mold a flexible part, and the resulting component was too soft, sticky, and failed quickly. (Note to self: always confirm the hardness and modulus before substituting one silicone form for another.)

3. Can I use Momentive silicone sealant to make a silicone lid?

This is the question nobody asks until after the first prototype fails. If you're making a silicone lid for cookware, packaging, or a medical device, don't use construction-grade sealant. You need a food-contact or medical-grade LSR, or—for lower volumes—a platinum-cured RTV with the right compliance marks. A general-purpose Momentive sealant is not designed for repeated heat, abrasion, or leach resistance.

In 2023 I approved a one-part RTV for a lid mold testing project. It looked fine in the mold, but after a 140°C cycle, the lid had an acetic-acid smell and a yellow tint. That was $1,200 and a two-week delay. Looking back, I should have checked the data sheet's migration and temperature ratings before approving. If you're specifying a silicone lid, ask for exact compliance documentation and verify it at the source—don't take a sales rep's word for it.

4. What's the difference between polyurethane liquid rubber and Momentive silicone rubber?

This one comes up constantly. Polyurethane liquid rubber cures into a flexible elastomer. It's usually cheaper than silicone, has good tear strength, and can be excellent for molds or coatings. But polyurethane is moisture-sensitive, and it doesn't handle sustained heat, UV, or extreme cold nearly as well as silicone. Momentive silicone rubber stays flexible across a much wider temperature range and holds up outdoors far longer.

I went back and forth between polyurethane liquid rubber and Momentive silicone for a project that needed a rubber coating on an outdoor aluminum part. On paper, polyurethane had better abrasion resistance and saved about 30%. My gut kept saying the part would sit in direct sunlight for years. We went with a two-part silicone coating. In Q3 2024, after a full summer of UV and rain, the part still looked right. I'm not saying polyurethane is bad—I'm saying it has a window, and silicone has a different window. Match the window to the environment.

One warning: don't assume one "silicone" rating applies to all grades. According to Momentive's product documentation, service-temperature ranges vary by grade. The data sheets at momentive.com are the final reference.

5. How do I choose between silicone foam and solid silicone elastomer?

The short answer is: if you need sealing under compression, use foam; if you need a liquid-tight barrier, use solid elastomer.

Three things to know. First, silicone foam compresses easily and returns to shape—good for gasketing, thermal expansion, and vibration. Second, solid elastomer has lower permeation and is better for pressure or liquid barriers. Third, closed-cell foam resists moisture better than open-cell foam; if the data sheet doesn't say, ask.

I mention this because the search term "silicone rubber" covers all of these. In 2021 we had a 2,000-piece order where every single part absorbed water because the specified foam was open-cell. $4,600 wasted, plus a three-week delivery delay. That mistake taught me to ask about cell structure before the quote, not after delivery.

6. What about PVC vs foam board?

I'll answer this carefully, because it's slightly outside my silicone lane. We're often asked to bond Momentive silicone gaskets to panels and signs, and the substrate affects adhesion. But the structural decision—PVC vs foam board—belongs to the fabricator or structural engineer, not a silicone supplier. If a vendor describes themselves as "the one-stop shop for every material," that's a warning sign.

From field experience: PVC board is denser, stiffer, and holds fasteners better. Foam board is lighter, cheaper, and easier to cut. Neither is universally better. The real question is what load the panel carries, whether it's outdoors, and what the local fire code allows. That's a conversation to have with the fabricator.

My experience is based on industrial sealing and bonding projects. I can't speak to architectural façade systems. But here's the thing: the vendor who says "this isn't our strength—here's who does it better" earns my trust for everything else. I'd rather work with a specialist who knows their limits than a generalist who overpromises.

7. What documentation should I ask for before buying Momentive silicone?

Before you sign a PO, ask for four things: the exact Momentive product name and grade, the data sheet number, lot traceability, and the relevant compliance documents—food contact, UL, USP Class VI, or whatever applies to your sector. If the distributor can't provide them, treat the quote as a guess.

I learned this the hard way. In Q2 2022, I ordered "Momentive silicone sealant" and didn't specify a grade. The warehouse shipped whatever was in stock. It worked for the initial test, but the cure time was twice as long and the adhesion test failed. The replacement cost $2,100 and the project slipped a week. Now I keep a one-line spec checklist in the PO comments: product name, grade, datasheet revision, and lot number. It sounds obvious, but it has caught 47 potential errors in the past 18 months.

This is also where "professional" turns into "trustworthy." A supplier who asks about your application and honestly says what they don't stock is doing you a favor. The order might take longer, but the part will work. That's the kind of relationship that saves money over time—and the one I'm still paying attention to.