Physicist creates N95-type respirators using cotton candy machine
phys.org
phys.org
I'm always sceptical of these kind upcycling plastic narratives that involve melting them, since apparently a lot of plastics only are labeld safe under the assumption that they don't get heated until the melting point. After that they may start leaking chemicals, a bit like the whole non-stick coating story.
But if the source of plastic is reliable then this sounds pretty good.
> The input polymer is polypropylene or polystyrene, and can include discarded plastic containers of these materials, ...
https://royalsocietypublishing.org/doi/full/10.1098/rspa.202...
Edit: U+2677 and and U+2678. Obviously no one would ever want to write about plastics on HN, so it's totally OK to strip those symbols.
U+2677 is the recycling symbol type 5 (polypropylene/"PP") and U+2678 is recycling material type 6 (polystyrene/"PS").
https://en.wikipedia.org/wiki/Recycling_codes#List_of_resin_...
https://en.wikipedia.org/wiki/Plastic#Thermoplastics_and_the...
Most packaging is thermoplastic.
To be clear: I don't know if the paint in plastic is dangerous, the problem is that I also don't know if they're not. It feels like the kind of area where even without bad intentions/incentives, the people who made the plastics or who set up the regulations for them might have assumed there is no real risk, because nobody planned for this type of plastic recycling.
Pure 'plastic' polymer- be it nylon, polyethylene terephthalate, Acrylonitrile Butadiene, pvc- anything! Is generally a brittle, almost powdery material, that is of no use to anyone. I'd say they range in texture from something like .
What we think of as 'plastic' - what we experience and use as a product or a material, is a cocktail of polymer, 'plasticizers', chain extenders, cross linkers, and other chemicals.
Trying to come up with an analogy, I'd almost say polymers:flour::plastic::cake
I found some other NIOSH N95s recently at a hardware store, but... they seem to be made with a contractor's facial structure in mind.
Just by looking at some masks you can guess which gender the were design by/for, but they are advertised as one size fits all.
Lots of people are in the situation of thinking of an N95 mask as an “upgrade” compared to a surgical or cloth mask for grocery shopping, etc. Early in the pandemic there was this line of thinking as if an N95 mask was 100% useless if it didn’t form a perfect seal. This is obviously untrue, and it’s clearly a step up from a surgical mask even with some minor facial hair! How much of a step up is a totally different question and like you touched on it’s quite possible that it’s not worth the extra hassle and discomfort.
I have a beard. A surgical mask fits only lightly over it, floating a half inch away from my face. That's better than nothing I suppose, but it really is only filtering big droplets. All the air is going in and out that half inch.
An N95, with it's rigid faceplate and strong rubber bands pressing it against my face, crushes the beard and makes breathing more difficult so I can tell some air is being filtered. I'm not getting anywhere near the protection the n95 is designed to provide, it's still much better than what the surgical mask does, which is almost nothing. And I don't use the valve kind, so any filtering the n95 is doing, it's doing it in both directions.
The surgical mask with a beard is kind of like walking around with my hand held a half inch away from my face.
Yeah, but that'd still be better than nothing, too. (As would be a face-shield worn without a mask.) In both cases, the main goal of getting regular people to wear masks isn't to contain exhaled droplets, but to lower the forward velocity of exhaled droplets, so they don't slam right into other people's mucous membranes, but rather have time to get caught in HVAC systems or dispersed into outdoor air.
The faster the droplets are moving when they exit your mouth/nose (e.g. a sneeze or a cough), the less they're going to be able to "turn" to get out the sides of your mask. Masks are very good at stopping sneezes/coughs from contaminating the air, even when badly fit.
That, and masks/face-shields/your own hand/etc. also protect you when someone sneezes or coughs directly "at" your face. Like the sneeze-guard at a buffet. It's not complete protection — the particles, once airborne, can drift "around" the barrier and come in — but it does appreciably lower contamination compared to having nothing there (presuming that people will be sneezing/coughing/breathing directly "at" your face/the buffet. Not a concern for most people; but this is why people in hospitality are wearing the face-shields.)
> All the air is going in and out that half inch.
Out, almost certainly (except for forceful expulsions, as above), but if you're breathing through your nose — and the mask is shaped to surround your nose — then even if it's a half-inch from your nose, at least some of your inhaled air will be coming in through the mask. Even if it feels like all of it's coming in through the gap in the mask. So there will be some fractional protection from that.
Also, I believe high-grade masks are somewhat adsorbant — airborne droplets just like sticking to them if they rub up against them, rather than staying airborne. So a good mask can "passively" scrub the air you're breathing in, even if that air is coming in "around" the mask instead of "through" it! (This is only a small effect, though, and shouldn't be relied on. I'm trying to list the reasons mask-wearing is better than nothing, not trying to justify intentionally wearing your mask less-well-fitted than you could.)
I have an FFP3 (~N99) one from some DIY pre-pandemic (so cheap, good luck even finding it now! I do wonder what tradesmen who need them for workplace safety, but their work isn't medical, are doing at the moment) - it isn't rigid and fits well.
It is used and 'not reusable', but I'm hanging on to it. If I 'have to' travel or something at some point I figure used FFP3 beats piece of loose-fitting cloth.
Almost every N95 is made from meltblown materials (thermoplastics) with a polymer that holds electrostatic charge after production.
>>>sci-hub.se uses an invalid security certificate.
>>>The certificate is not trusted because it is self-signed.
>>>Error code: MOZILLA_PKIX_ERROR_SELF_SIGNED_CERT
I accepted the risks and proceeded:
>>>The requested URL /10.1098/rspa.2020.0469 was not found on this server.
I hacked the URL to reach the home page of that site and was greeted with this message:
>>>The website you want to visit is blocked! The block is a claim from the Patent and Market Court. It is the result of a lawsuit initiated by the Dutch scientific publisher Elsevier, in a lawsuit against Bahnhof and six other Swedish internet operators.
You could try the sci-hub.st or sci-hub.do domains instead; according to Sci-Hub’s Twitter account¹, those are also official domains where Sci-Hub can be located.
Unfortunately, http://scihub22266oqcxt.onion/ seems to be inaccessible at the moment, as is https://whereisscihub.now.sh/ which used to show at what site Sci-Hub was currently readable.
(Also, changing the URL is not, IMHO, “hacking”.)
Oh dear. Thx for letting me know.
>> Also, changing the URL is not, IMHO, “hacking”.
URL hacking: https://www.google.com/search?q=url+hacking+definition
As a volunteer firefighter I'm fortunate to have access to N95 masks. As an engineer, I'm frustrated the world hasn't managed to scale production enough for everyone to get them. As a hacker I want to do something about that, and love how creative inspiration like this might provide something better than the same cloth coverings used since the early 1900's.
The paper (https://sci-hub.se/10.1098/rspa.2020.0469) is refreshingly approachable. It explains the basic engineering theory and tests a range of fabrication methods using readily available parts. My favorite example sprayed heated plastic out of a soda can perforated with small holes mounted on the end of a drill.
Feedstock was commercial polypropylene (PP) and polystyrene (PS) pellets, but the author suggests raw material could alternatively be sourced from discarded plastic containers sanitized in a domestic pressure cooker then pulverized with a blender. Spun media was pressed between electrodes of a home ionizer to impart an improved electrostatic charge.
The study conducts detailed characterization of the self-manufactured masks, compared to baselines obtained from N95 and surgical masks. Scanning electron microscopy imaging of the resultant fiber mesh bore close resemblance to conventional N95 fabric.
Some of the filtration tests were improvised - one involved a piezoelectric atomizer, modified mannequin and commodity PM2.5 detectors. Another aerosolized fluorescent-tagged nanoparticles to simulate SARS-Cov-2 virions.
Within the given constraints, their results indicated the homespun PP fabric achieved effectiveness bordering on N95 thresholds, and suggested the PP+PS blend might easily meet N95 criteria for up to 17 hours of use.
One interesting, ancillary finding reinforced how the effectiveness of surgical masks is highly dependent on fit - particle penetration dropped from 50% to 12% after establishing a taped seal.
I'd be really interested to see the results of more rigorous, independent testing conducted using the same equipment as NIOSH certification facilities, including oscillatory respiratory air flow (to simulate the dynamics of inhalation and exhalation).
Some alternate links to the paper in case the one above becomes unavailable:
https://web.archive.org/web/20201128172100/https://sci-hub.s...