The Question That Came Up Every Time We Reviewed Components

I'm the office administrator for a 150-person industrial equipment company. I've handled purchasing since 2020—roughly $1.2 million a year across eight vendors, with orders covering everything from sealing compounds to rubber wheels.

A question I kept hearing from our engineers was: is rubber thermoset or thermoplastic? The short answer: both. The long answer is more useful for someone who has to write purchase orders. If you're choosing a material for molded parts, gaskets, or wheels, the real difference is where and how long the part will perform.

This is not an exhaustive chemical comparison. It's a buyer's comparison between a thermoset material—Momentive GE silicone—and a typical thermoplastic rubber (TPE), based on what I've observed from ordering both.

Thermoset vs. Thermoplastic: A Buyer's Version

Thermoplastics melt when heated and solidify when cooled. That makes them easy to process and, in theory, easy to recycle. Thermosets, on the other hand, form crosslinks during curing. Heat them again and they won't melt; they degrade.

Most people assume the meltable option is better because it’s easier to recycle. That’s true for some applications. But the counterintuitive part: for a stressed rubber part—think a wheel rolling under a hot oven—thermoplastic can soften and take a set, while thermoset holds its shape.

I remember a vendor warning me about this when we were ordering wheels for a conveyor that ran near ovens. I didn't listen. I ordered cheaper TPE wheels to save $600. Within five weeks they had flat spots, and the production line was down twice. The replacement silicone wheels from Momentive are still running. That was my reverse lesson.

Heat and Chemical Resistance: Where Silicone Pulls Ahead

For our oven line, the performance spec was straightforward: the wheels needed to handle continuous contact with a 150°C surface and not deform. The TPE datasheet looked okay on paper, but the actual test failed. The silicone wheel handled it easily.

I want to say Momentive's data sheets for many GE silicone grades list continuous service around 200°C, but don't quote me on that—grades differ. The point is the headroom. A TPE might be rated at 110°C, while thermoset silicone has a wider window. If your process has spikes above 120°C, a thermoplastic wheel can suddenly become a permanent oval.

Momentive Support: The Invisible Procurement Factor

One thing that never appears on a spec sheet is supplier responsiveness. With Momentive support, I could get a human who actually understood silicone additives and processing conditions. When we needed to adjust a cure profile, they sent compatibility data within a day.

Contrast that with a TPE supplier we used once. Every question required three emails and a call-back. The documentation was sparse. For an administrative buyer who is not a chemist, that friction is real. If I can't answer an engineer's question about a material, I look inefficient. If I order the wrong material because the supplier didn't clarify a handling issue, that's worse.

This is where momentive support matters. They also helped us with silicone additives—not just the base elastomer. We source additives for flame retardance and mold release, and their recommended dosages made a difference in consistency. Buying an additive without a supplier who explains interactions is guessing.

Price vs. Cost: What the Comparison Actually Shows

Here's where the tables turn, at least superficially. The TPE wheel was $14. The Momentive silicone wheel was $28. On a purchase order, the TPE looks better.

But we replaced TPE wheels about every five months, while silicone wheels lasted around twenty months. My rough math on cost per month:

That's before labor and downtime. I'm not 100% sure of the exact counts, but the order of magnitude is right. The lesson stuck: cheaper components can be the expensive choice if they fail in a high-stress application.

I want to emphasize that I do not mean TPE is always bad. If you need a rubber wheel for a small cart in an air-conditioned warehouse, the TPE option is fine—and probably the right call. The comparison changes with service conditions.

Silicone Additives and the Recycling Question

When I hear people say thermoplastic rubber is "recyclable" and therefore the greener option, I'm a bit careful. Per the FTC's Green Guides, environmental claims should be substantiated—what exactly gets recycled, and where? We found TPE could be recycled in theory, but no local facility accepted the specific compound we ordered.

So the practical environmental argument collapsed. A long-lasting thermoset silicone part that doesn't need replacing is arguably better than a short-lived "recyclable" part that ends up in the same landfill. This is one of those moments where the simplistic conclusion—thermoplastic = recyclable = good—doesn't survive contact with procurement reality.

Silicone additives can also improve the life of the final product. For our molded components, additives helped with mold release and cure stability, which meant fewer rejected parts. Fewer rejected parts is good for cost and for the customer's perception of our product quality.

Which Should You Buy?

Here's how I make the call now:

Choose thermoset silicone—Momentive GE silicone—if the part faces high heat, heavy load, chemicals, or any situation where failure would stop production. It costs more upfront, but the reliability and longevity buy back the difference.

Choose thermoplastic rubber if the application is conventional, the temperature is low, and you need quick or inexpensive parts.

The material you choose is part of your company's reputation. When our line stopped because of a failed wheel, the operations manager wasn't mad at the TPE—he was mad at the person who ordered it. That was me. I've never forgotten that.

So if someone asks you is rubber thermoset or thermoplastic?, the answer is either. The real question is which failure mode you're willing to accept. I'd rather pay for quality than explain a production stoppage.