DOW CORNING Products for Procurement: A Practical Guide for Administrative Buyers

There's No One Right Silicone Material—It Depends on Your Situation

I've been handling purchasing for a mid-sized facilities management company for about four years now. When I first started ordering Dow Corning products, I assumed silicone was silicone. That assumption cost us time and money.

Here's the thing: Dow Corning makes a lot of silicone products. And which one you need depends entirely on what you're doing with it. I've narrowed it down to a few common scenarios based on what I actually see ordered most frequently.

Scenario A: You Need a Long-Lasting Window or Exterior Sealant

This is probably the most common scenario in facilities procurement. Someone needs a seal that can handle expansion, contraction, and temperature swings—for windows, curtain walls, or building panel joints.

What I've learned: A standard silicone sealant might work for a year or two. But if you want a seal that lasts a decade without cracking, you need a Dow Corning 791 or 795 grade sealant (weatherproofing). These cost more upfront—usually 25–40% more per tube than a general-purpose caulk.

In 2023, I ordered a case of general-purpose sealant for a window replacement project (roughly $120). By year two, nearly 20% of the seals had visible cracks. The rework, plus the callbacks from the office manager, cost us around $400 in labor and materials. Now, I specify Dow Corning 795 for any exterior glazing work. It's pricier per unit, but the total cost of ownership is lower because we're not dealing with failures.

A quick note: I'm not a structural engineer, so I can't speak to specific load calculations. What I can tell you from a procurement perspective is that the 700-series sealants meet ASTM C920 Class 25 standards for movement capability (Source: Dow published specifications). For most window-scale installations I've dealt with, that's sufficient.

"The $120 tube of general-purpose sealant turned into $520 after rework costs. The $180 tube of Dow Corning 795 was actually cheaper overall."

Scenario B: You're Looking at Thermoplastic Elastomers for Automotive Components

If you're ordering Dow Corning silicone for automotive applications—say, gaskets, seals, or weatherstripping—you're likely comparing it to thermoplastic elastomers (TPEs). I've been through this comparison a few times.

Here's the insider take: Silicone (including Dow Corning's TPSIV product line) performs better in high-temperature environments (over 120°C sustained) and extreme low-temp flexibility (down to -50°C). TPEs, like Santoprene, are cheaper (often 15–25% less per part) and process faster in injection molding. But if your part gets hot, silicone won't harden and crack the way some TPEs can.

For a recent order (circa mid-2024), we were sourcing gaskets for under-hood components. The TPE quote was roughly $0.80 per unit; Dow Corning silicone was $1.05. On a run of 5,000 units, that's a $1,250 difference. But the silicone parts had a documented 50% longer service life in thermal cycling tests (per internal testing—take this with a grain of salt, as it's case-specific). If your application involves sustained engine heat, the higher initial cost of silicone may justify itself through reduced replacements.

Funny enough, the most important lesson I learned here wasn't about the material—it was about the vendor. I had a supplier who offered an exceptional price on TPE (about 20% below market). The parts arrived on time, but their invoicing was a mess: handwritten receipts, no purchase order numbers, and the accounting department rejected the invoice. That was a $2,400 lesson in why TCO includes vendor capability, not just material cost.

Scenario C: Choosing O-Ring Material—Buna-N vs. Silicone

O-rings are one of those things that seem simple until you need to replace one in a hurry. The most common material question I get is: "Buna-N (Nitrile) or silicone?"

The short answer: For static seals in moderate temperatures (under 100°C), Buna-N is usually the better choice. It's oil-resistant, durable in hydrocarbon environments, and generally cheaper ($0.10–$0.30 per ring, depending on size). But for dynamic seals, high-temperature applications, or where sanitary/high-purity conditions matter, Dow Corning silicone is superior.

Here's something vendors won't tell you: the Durometer (hardness) of an O-ring matters more than the material type in many applications. For example, a 70 Durometer silicone O-ring (mid-softness) handles most sealing jobs. But if you need more compression resistance, a 90 Durometer is better—though it's harder to seat. I always check the Durometer spec first (the Shore A scale), then the material type (Source: industry standards for O-rings per Parker O-Ring Handbook).

Not ideal, but workable: if you're stuck with Buna-N and need high-temp resistance, look for a high-temperature formulation (e.g., Buna-N with enhanced heat stabilizers). But that's a compromise. For long-term reliability, Dow Corning silicone is safer.

Scenario D: PVC Thread Sealant vs. Teflon Tape—Which is Better for Your Application?

This is a classic debate. I've used both and have opinions, but it really depends on what you're sealing.

For potable water or high-pressure plumbing (especially PVC pipes): I prefer a paste thread sealant (like Dow Corning 736 or 737 sealants, though these are more RTV silicone). Actually, for threaded PVC connections, Teflon tape is the standard—but it's not always the best. Here's the issue: Teflon tape can cause over-tightening and cracking of PVC fittings if you're not careful. A pipe dope (thread sealant paste) provides some lubricant properties and can handle slight imperfections better.

For gas connections or high-temp environments (e.g., steam lines), do not use Teflon tape unless it's rated for that (yellow gas-rated tape is acceptable). Silicone-based thread sealants can handle higher temperatures and pressures (up to 300 psi in some cases).

"Pricing note: a roll of Teflon tape costs roughly $2–5. A tube of thread sealant paste runs $8–15. If you're doing 20+ connections, the paste is worth the extra cost for reliability alone."

(Prices as of January 2025; verify current rates.)

How to Decide Which Scenario You're In

If you're still unsure, here's a quick checklist I use:

• Temperature matters: If sustained temperature exceeds 120°C (250°F), lean toward silicone over Buna-N or TPE. If it's below -30°C, silicone also wins.
• Chemical exposure: Hydrocarbons (oils, fuels) → choose Buna-N or a specialty TPE. For general moisture or mild chemicals → silicone is fine.
• Lifetime expectations: If the seal needs to last 10+ years (e.g., building windows), invest in Dow Corning high-performance sealant rather than general-purpose.
• Cost of failure: What happens if the material fails—a small leak, or a system shutdown? If failure is expensive, spend more upfront.

After going through these scenarios myself, I'd say: most procurement decisions for silicone products come down to a trade-off between initial cost and long-term TCO. If you're buying for a critical application, the higher upfront cost of Dow Corning often pays for itself within a year or two.

(Note: I'm not a materials scientist. This is all based on my experience managing roughly $150K annually in silicone and elastomer orders across about 60–80 line items per year. Your mileage may vary.)