Whenever someone asks me to compare materials, the first thing I do is kill the phrase 'Which is better?' Because better doesn't mean anything until you define the service conditions. I manage materials sourcing at a 40-person manufacturing company. Over the past six years, I've signed off on somewhere around 300 purchase orders for rubber, plastic, and silicone parts. Maybe 280, I'd have to check our ERP. The question I hear most often is 'silicone or [fill in the blank]?' My honest answer: it depends. But I can make that answer useful by comparing four things: temperature, compression set, cure chemistry, and total cost.
Most of the Dow Corning silicones I buy are not exotic. They're standard grades used for seals, watch straps, bakeware, and building joints. Dow Corning is now mostly folded into Dow, but the old product numbers still live in our system, so I still search 'dow-corning' when I need a datasheet.
Temperature: Silicone vs. Organic Rubber
Silicone is known for a wide operating range. A typical silicone compound can stay flexible down to -60°C and handle continuous heat around 200°C. Organic rubber like NBR is usually limited to about 100°C continuous, and EPDM's ceiling depends on the formulation. If the application is below 80°C and there's oil, NBR is often a better value. I say that as someone who has bought a lot of silicone.
Here's a concrete example. I once specified a square o-ring for a steam valve in a food plant. The original EPDM ring hardened and leaked within 11 months. Silicone was the replacement, and the same square o-ring is still seating properly after three years (as of January 2025, at least). The field data was unambiguous.
But there's a boundary. For a dynamic seal—something that rotates or sees sliding motion—silicone's low tear strength hurts. A fluorocarbon (FKM) will outperform it in hot oil and high-pressure movement. The uncomfortable truth is that choosing silicone just because it handles high temperature can be wrong if the seal also has to handle friction.
That's also why silicone watches work for straps. A watch strap doesn't need to hold pressure. It needs to flex, resist sweat and UV, and feel okay on skin. Those are silicone's strengths. A silicone watch can spend all summer in the sun without becoming brittle. That's not true for every rubber I've tested.
Compression Set and the Square O-Ring Question
Compression set is the percentage of deformation that remains after a seal is squeezed and released. Lower is better. A low compression set means the material tends to return to shape instead of taking a permanent flat spot.
If you specify a square o-ring, the cross-section geometry helps keep the seal stable in the gland and reduces the chance of twisting. But the geometry only works if the material itself has good compression set at the actual service temperature. I've seen buyers pick a square-profile ring thinking it solves everything, then complain about sealing when the compound was never right in the first place.
My rule of thumb: for a static seal—a flat flange, a stationary cover—silicone is often the best material in the comparison. For a dynamic seal, I reach for FKM. The anti-intuitive part is that a silicone square o-ring can cost less and still outlast a standard round o-ring in a static application. The round ring might be cheaper per piece, but the square ring's stability can reduce emissions, leaks, and warranty calls.
Cure Chemistry and the Dow Corning 795 Sealant
Sealants are one of those product categories where I tell people not to autopilot on price. The Dow Corning 795 silicone building sealant is a specific product that has shown up in our renovation specs more than once. It is a neutral-cure silicone, which means it doesn't release the strong acetic-acid smell you get with some acetoxy silicone sealants. That matters when you're sealing inside a building and don't want to evacuate.
According to the Dow technical data sheet I keep in our spec folder, the 795 has a joint movement capability of ±50%. I won't quote the full adhesion list from memory—I'd have to check the current TDS before sharing it with a contractor. What I remember from the field is that 795 cured predictably and stuck to the substrates we tested.
I compared it to a polyurethane sealant for a south-facing expansion joint. Polyurethane was less expensive and paint friendly, which made it tempting. But silicone's UV history is the reason I specified 795 for the exterior. And before you think I'm anti-polyurethane, I'm not. I bought polyurethane for the interior painted joints and it worked fine. The surprise was not that one material won. It's that both were the right answer in different places.
Food Contact and 'Can You Bake with Silicone Molds?'
Let's answer the baking question directly. Can you bake with silicone molds? Yes, if the mold is made from a silicone compound that meets the relevant food-contact standards. The distinction matters because 'silicone' covers a huge range of formulations, and only some are intended for food.
In the U.S., the FDA regulates rubber articles intended for repeated food contact through 21 CFR 177.2600. Many silicone bakeware suppliers will provide a compliance letter if you ask. Per FTC guidelines (ftc.gov), a marketing claim like 'food-grade' needs to be substantiated. So if a supplier says 'it's food grade' but can't produce test documentation, I don't buy it.
The same logic applies to silicone watches. The strap sits against your skin all day, every day. Skin-contact certification is not a luxury requirement; it is as important as the durometer. But I'm not a regulatory specialist. If you need legal certainty for a product claim, verify the current rules at the FDA or FTC before you write your spec.
Total Cost: What Procurement Actually Tracks
Now for the part that keeps me up at night. It's tempting to think you can compare two silicone products by unit price and durometer. That's fundamentally wrong. Identical-looking specifications from different suppliers can have completely different performance in a hot, oily, or UV-exposed environment. The cheapest quote only wins if the part works.
I went back and forth between two silicone o-ring suppliers for a 100,000-piece order. Supplier A quoted 18% lower. Supplier B had a better warranty, a documented QC process, and a place in my spreadsheet from previous orders. I knew B was the right choice, but I'm a cost controller, so I hated the 18% difference. Even after I approved B, I kept second-guessing. What if A was fine and I just wasted money? The first production batch from B arrived with a defect rate of 0.2%, ten times better than our typical tolerance for that part. I relaxed. The 18% premium paid for itself in fewer field failures.
I don't have a neat formula for every decision. But I do have a spreadsheet with hundreds of line items, and the pattern is clear: silicone is worth it when the operating environment includes temperature swings, UV, moisture, or a need for long-term flexibility. It is not always worth it when you need extreme oil resistance, high abrasion resistance, or a dynamic seal under heavy load. That's not a criticism. That's a boundary, and respecting it is what makes a procurement decision defensible.
Choosing What to Buy
My selection advice is boring: match the material to the application. For a static square o-ring, an outdoor building sealant, a watch strap, or a bakeware mold, silicone is a strong candidate. For a dynamic oil seal at high pressure, I'd look at FKM or polyurethane first.
One last thing. I'm not a chemist, and I don't sell silicone. I buy it. The material supplier who tells me 'this is not where our product works' earns more trust than the one who promises a custom compound for everything. The 'we can do anything' vendor gets checked last, not first.
So, can you bake with silicone molds? Yes, if you check the certification. Should you choose silicone for your square o-ring? Only if your application matches silicone's strengths. And if someone tells you 'silicone is better,' ask them to define the temperature, the pressure, and the cost of failure. Comparison is the only honest way to buy.