Is it a single (already blended) fiber, or is it something else (perhaps individual components?)
My guess was that it would be the already blended fiber, and this site seems to suggest that this is the case. They say that, in the first step
the raw materials (polyester and polyamide) are mixed together, in the proper proportions to achieve the desired final yarn composition. The mix is then heated to their melting point.
The process of producing microfiber fabrics begins by melting down polyester and polyamide pellets in separate vats. At this stage the liquid polyester and polyamide vats are pushed or extruded simultaneously through jet moldings that contain seventy-two pie-shaped segments. Each pie shape contains eight segments of polyester and eight segments of polyamide with trace amounts of oil separating the two polymers so they do not mix. (See figure 1.) The seventy-two pie shapes combine to create one filament.
which sounds to me like the polyester and polyamide are extruded separately.
Perhaps these two sources are using different production techniques (there are many techniques developed) but it doesn’t seem like they are to me. (it seems to me like they are both “melt spinning”?).
Also, just a (non-essential) follow up question: is the answer dependent on the type of microfiber we are thinking about (shape/components, etc)
My reading of that is that a single fiber that comes out of the spinneret contains multiple sub-fibers that don’t stick very well to each other and they separate. Similarly:
The cloth is made by forcing the plastics through a tiny pipe and heating them so they weave together. These fused fibers are then split apart into microfibers 10–20 times smaller.
I don’t see the two explanations you found as necessarily all that different. If the two polymers are immiscible, they’ll stay as separate phases, which may mechanically separate after cooling. Or you can pipe 72 (in this case) separate feeds through the same spinneret, which will then separate after spinning and cooling.
It could be that they are separated after coming out of the spinneret. Indeed, your second link seems to say that.
Normally, I would leave it at that, but the second quote I posted explicitly says 72 segments are combined (I think after leaving the spinneret). This doesn’t make sense to me, and implies to me that what comes out of the spinneret may not be a fiber, but a sub-component, which seems to contradict the source you posted (and my first source).
Also, if you google images for the cross section of a microfiber, it looks kind of like pie-shapes glued together, which lends support to the second quote of my original post. But if this is the case, how do they get pie shapes from the spinneret holes? (the quote references a figure 1, which I did not include, but I don’t see any pie shaped openings for extrusions in the image, just circle…)
I realize they might “split” it into pie shapes, but i don’t understand how they could do so and still get the specific arrangement of stars/wedges for the polyester and polyamide.
Also, welcome!
Thanks! Although I must admit I am not new around here. Its just that most of my time is spent reading and not logged in.
I know you know the difference because you were talking about PET earlier, but lest someone wander by and get confused, polyethylene terephthalate is a polyester, whereas polyethylene is a polyolefin.
I see 21 “spinnerets” there. I’m assuming the full circle gives us 72. For a single spinneret, I’m assuming the polyamide comes out the center and spokes, and the polyester comes out the hole in each of the 8 slices. As long as the mass flow is matched, it’s ok that the hole in the pie slice is small; it should fill in the gap between spokes. How the plumbing works on the other end, I have no idea.
Now I would call what comes out of a single spinneret a filament, but they’re calling the combined output of the entire 72-spinneret bushing a filament. Whereas I might call that a yarn. But I’m not a fiber guy. I do know one though and will consider pestering him.
I started replying to your first try at the thread, which had a “hasn’t posted in a while!” message. By the time I responded here, I had forgotten and assumed it was a new poster message. Regardless, you should ask more because it makes us learn stuff.
Ah, I think something just clicked in my brain, but let me make sure I understood properly.
Lets say there are 8 spokes and 8 holes. I am also assuming that the polyamide comes out the spokes and the polyester the holes. Before, when i looked at the figure (in your post) my brain said “that can’t be right, the polyester (from the holes) won’t be touching the polyamide!”. But you’re saying that the polyester (or I guess polyamide) can expand and will end up making contact? (assuming flow and everything is correct).
If that is what you’re saying, that makes a lot of sense to me. (If its not what you’re saying, i apologize). However, the other thing my brain says is “if the polyester and polyamide expand to make contact, that would be really wide!”, which is a problem since microfiber is supposed to be thin.
Maybe it isn’t so wide though. I have been thinking that each spinneret is like 1/3 a finger wide, since it looks like thats a persons finger in that picture, but in this other picture from the same website (see below) I cannot see the spinnerets at all, so I think they’re much smaller than 1/3 of a finger.
I am with you 100% here.
I did not read it like that, and but now I think that may in fact be the correct way to read it.
So I did some reading, and I still don’t understand well, but I think I understand well enough now.
I guess the key thing to note – at least for me – is that the diameter of a thread does not seem to be the diameter of whatever is formed by the spinneret. I don’t know why this is exactly, but it might be the result of the “thread” possibly being in a solution, as in this paper which says
It is worth noting that the diameter of the fiber is 30 – 40 times smaller than that of the spinneret, which is probably caused by the low concentration of PEDOT/PSS (0.72 – 1.14%) or no additional pressure driving the solution through the spinneret. We should emphasize here that the fiber spun under the conditions of C 1⁄4 0.72% and f 1⁄4 180 mm has a diameter of 4.6 mm
Another possibility for why the diameter of the thread is less than that of the spinneret is simply how a thread is defined (I am just not realizing I never looked up how a thread is defined, and just assumed a thread is as wide or wider than a spinneret…). This patent application
says
the conjugated textured yarn thus obtained having a titer in the range 300 to 450 d and a filament count in the range 12 to 128 , with the titer per filament in the range 0.01 to 0.5d (Process 1)
Chopping said dried conjugated fiber into .5 to 5d conjugated staple fibers with a length in the range 32 to 102 mm; and spinning the conjugated staple fibers into 20 and 45’s spun yarn, with the titer per filament in the range 0.01 to 0.5d
And some sources I look at make me think that it also might be the result of stretching the filament/yarn after coming out of the filament (and maybe processing it). I don’t know when stretching is used though, so I am only mentioning it in passing here.
Also, It’s confusing what is a fiber vs filament vs yarn…but I think its pretty likely that the website I cited in my original post is incorrect when it says “The seventy-two pie shapes combine to create one filament.”.
