Post #1943: Microplastic, doing a burn test for carpet fiber

Most internet sources assure me that only four fibers are likely to be found in the pile of modern wall-to-wall carpet. A handful of sources add a fifth (acrylic). Perusal of current offerings at Home Depot adds a sixth (triexta).

Wool
Nylon
Polyester
Polyolefin (including polypropylene and polyethylene)
Triexta
Acrylic

I think I can plausibly narrow it down to three, in my case, by eliminating these:

Triexta appears to be new enough that it’s not going to be the fiber in my 20-year-old wall-to-wall carpet.

Acrylic appears rare enough, in wall-to-wall carpeting, that I can’t actually find any roll-type carpet made with acrylic fiber currently offered for sale.

Polyolefin fibers appear to be used only in the cheapest carpet materials. At Home Depot, that’s what their self-stick carpet tiles are made of. That’s not going to be the basis for my well-wearing 20-year-old wall-to-wall.

N.B. 1: SD means solution dyed, that is, that is, the plastic itself is dyed before the fibers are spun from it. As opposed to dying the fibers after-the-fact. This apparently is by far the preferred method for durability in modern carpeting.

N.B. 2: Olefin (a.k.a. polyolefin) is a polymer (long molecule made from simple building blocks) where the basic building blocks are straight-chain alkanes (carbon and hydrogen and nothing else). If you make it out of propane feedstock, you get polypropylene. If you make it out of ethane feedstock, you get polyethylene. I assume they use polyolefin when they make the fiber out of whatever’s handy, or from a mix of feedstocks.

Burn test

The most commonly-suggested way to tell what a carpet is made of is to burn (a bit of) it. Condensing the guidance from this site:

Wool barely burns, extinguishes itself, leaves ash, and smells like burning hair.

Nylon burns well, with a smokeless blue flame, leaves a gray/black blob of melted plastic. And stinks. (I’ve sealed the ends of enough nylon rope to know that. It’s your classic burning plastic smell, but does not stink quite so badly as the smell of burning electronics, which is typically the smell of burning PVC (plastic wire insulation).

Polyester burns well, with a smoky orange flame, sputters and drips as it burns, leaves a shiny plastic bead, and smells “sweet” as it burns. (Really?)

Pretty sure this carpet isn’t wool. So it boils down to burning a bit of it, and seeing if it stinks. If so, it’s nylon. If not, polyester.

What I didn’t realize is that you need a pretty good chunk of fibers to be able to do this test. First time I tried it, I had a fluffy bit of fibers, and they simply shrank away from the flame. Second time I got an entire piece of yarn, twisted it tightly, and got it to burn.

Results: Sputtering flame, no ash, and no stink. I’m pretty sure my carpet is polyester. I could refresh my memory with a bit of nylon cord, or burn a bit of known polyester fabric, but I think this all makes sense. Plus, burning nylon really stinks. Like “don’t do that inside” stinks. And while this did not smell “sweet”, this basically didn’t smell like much at all. Which pretty much rules out nylon.

I may try some different test, if I can find one.

But odds are, given that this is 20-year-old decent-grade grade wall-to-wall carpet, with some worn spots, clearly made of synthetic, and the fiber burns without a stink, this is polyester.