A Buyer's FAQ: Dow Corning 111 Silicone Grease, Black Teflon, and Other Material Questions

I took over purchasing in 2020 for a mid-sized manufacturing company—about $400,000 a year in purchase orders across eight vendors. I don't have a chemistry degree. What I have is a filing cabinet of spec sheets and a habit of asking questions before I order materials.

This FAQ is not an engineering guide. It's the stuff I've needed to know as the buyer who gets asked 'what's this material?' and 'can we use X instead of Y?'. If you're in a similar seat, these answers will save you some of the tabs I have open.

Why do I need to know the difference between Dow and Dow Corning?

Dow Corning was a joint venture between Dow Chemical and Corning, and it's the name a lot of older specs still use. In 2016, Dow bought out Corning's share, so the silicones business now sits under Dow. Many product names have moved to the DOWSIL label, but you'll still find references to Dow Corning in legacy catalogs and maintenance manuals.

From a purchasing perspective, this matters when you're matching an old product number to a current one. I've had suppliers tell me the product is 'the same'; I still ask them to put the current name and old name on the quote. (Most do. The ones who hesitate are usually the second source trying to substitute.)

When should I order Dow Corning 111 silicone grease?

Dow Corning 111 silicone grease is one of those products that shows up whenever a maintenance spec talks about valve O-rings, pumps, or water systems. According to the current technical data sheet, it's a silicone grease designed to lubricate and seal rubber and plastic parts while staying where you put it. It's not a penetrating oil, and it isn't meant to be a food product.

I first ordered it because a valve vendor said 'use Dow Corning 111' in the manual. When I started comparing, I found that silicone grease comes in several variants, each with different temperature ranges and approvals. If your application touches drinking water, you need the NSF listing. If it's for incidental food contact, check the FDA rule. I once ordered another silicone grease that looked almost the same—the tube was even similar—and maintenance caught it only because the part number didn't match their approved list. That was a cheap lesson compared to a system shutdown.

Is the search phrase 'Dow Corning silicone breast implants' relevant to an industrial buyer?

Search for silicone history long enough and you will land on that phrase. Dow Corning did make silicone breast implants years ago, and the company eventually stopped selling them in the mid-1990s after litigation and regulatory pressure. That history is why 'Dow Corning silicone' can surface results that have nothing to do with an O-ring, a grease, or a sealant.

For procurement, the better lesson is grade separation. The silicone grease we buy for maintenance is not in the same regulatory class as medical-grade silicones. If an internal customer says 'we need medical grade,' they need a clearly defined material specification, not a verbal description. I've had vendors respond to 'medical grade' with a first-aid kit. That's why I ask for an application and a spec sheet before I trust a category label.

Can oil polyurethane be used as a substitute for silicone?

Only in narrow cases, and usually the answer is no. Oil polyurethane, as most suppliers use the phrase, is an oil-based finish for wood or floors. It cures into a hard film. That film has different flexibility, temperature resistance, and adhesion properties than a silicone elastomer.

I got pulled into this when our facilities person asked for 'oil polyurethane to seal a joint.' Part of the job was a coating; another part needed a flexible sealant. They are not the same material. If you order oil polyurethane when you meant silicone, you will be buying a product that can't stretch or absorb vibration the way silicone sealant can. My rule for substitutions is simple: any proposed material swap has to include a datasheet and the end use. If they won't provide both, it's not an approved substitute.

What is black Teflon and should I choose it over silicone?

Black Teflon is the common name for black PTFE, a fluoropolymer with carbon filler. Teflon itself is a brand name for PTFE; in industrial supply lists, people use 'Teflon' generically. It's usually supplied as sheets, strips, or bars for low-friction wear applications.

Why compare it to silicone? Both can be used as seals, but they don't share the same mechanical properties. Silicone rubber compresses and recovers. Black PTFE is stiffer, has a low friction surface, and resists chemicals well. If a part drawing says 'black Teflon,' order PTFE. If it says 'silicone gasket,' don't swap in PTFE just because both are high-temp materials. I am not an engineer, so whenever a part is critical I send the drawing to the supplier. A quick confirmation has saved me from ordering the wrong material more than once.

Is polystyrene thermoplastic or thermosetting?

Polystyrene is a thermoplastic. It softens when it gets hot, so it can be molded, recycled, and remelted—but only under the right conditions. Expanded polystyrene foam cups, clear disposable labware, and some packaging trays are all thermoplastic polystyrene.

Thermosetting plastics are different: once they cure, they stay cured. Epoxy and phenolic are examples. For a buyer, the distinction matters because replacement parts, cleaning solvents, and waste disposal all treat the two classes differently. If a request simply says 'polystyrene', the material family is clear. The question is which grade and form—solid sheet, foam, or resin—since that affects the actual part.

How did I stop getting lost in material specs?

Three years and one expensive mistake later, I set up a simple request form. It asks three things: application, temperature range, and the chemical or fluid the material will touch. If the requester can't answer, I send it back to engineering before searching for a product.

That small process cut our sourcing time from five days to about two. It also means we're no longer relying on someone remembering whether the last order was silicone, PTFE, or polyurethane. We didn't have a formal process before; the third time we ordered the wrong plastic sheet, I finally created a checklist. Should have done it after the first time.