Ocean plastic research
@cymek and I are working in the Precious Plastic & Parley shipping container in the Maldives til May.
While we’re here one of our focuses is learning about ocean plastic, particularly how the extended exposure to saltwater/UV/contamination affects its recyclability with the PP machines.
We’ll share our research below 🙂
@pauldufour , As before great work. The results for the degraded plastic (HDPE?) are very encouraging. I’ve been trying to figure out what to do with crumbly flower pots, etc.
Were the samples on the display board injected? Are those temperatures the body temperatures or the nozzle?
You’ve posted a lot of great results, are you planning on collecting them (along with some detail) in a report of some form?
Thanks again for the update.
@pauldufour this is very valuable work – and great that you have been doing actual experiments, not just relying on preconceived ideas.
Like @donald I found the UV degradation tests puzzling. The usual “received wisdom” is that the UV breaks down bonds, so that the polymer eventually reverts to its monomer. However, UV can definitely have the opposite effect – in that it can promote cross linking, and hence cure (solidify) some liquid polymers. In fact, this is how liquid stereolithography works.
The video showing the brittle and crumbling nature of the (hdpe?) bottles, that have been exposed to sunlight, will be familiar to most of us that have handled “sun degraded” plastic objects.
However, what if the brittleness wasn’t due to breakdown but due to additional (albeit weak) crosslinks? Looking around the web, I found the following paper:
UV effects on the tensile and creep Behaviour of HDPE (Becerra and d’Almeida, 2016)
What it appears to show is that below a certain intensity, the UV is not able to break C-C bonds – and therefore does not actually shorten any of the basic polyethylene chains. However, it can break lower energy C-H bonds, which creates the free radicals necessary for creating additional weak cross links. It seems that this may be what we are seeing during “UV ageing” and associated embrittlement.
If that is the case, heating/melting and re-moulding the HDPE could essentially “recondition” the long chain molecules, restoring “clean” C-H bonds.
If true, the importance of this discovery should not be underestimated. It makes the reprocessing of some “UV degraded” polymers entirely feasible – despite the all the usual negative warnings 😉
(p.s. I’m an engineer, not a polymer chemist, but have had to work with polymers quite a lot over the decades).
Photooxidation is another degredation mechanism that is said to account for a lot of the effects of polymer ageing. In essence, the free radicals, exposed by breaks in the C-H bonds, latch on to atmospheric oxygen.
Materials affected in this way are said to have “perished”. This is predominantly a surface effect – so would tend not to affect the body of the material, unless surface microcracks allow atmospheric penetration (as can be seen on some elastomers that have been exposed to air and sunlight (eg. nitriles and natural rubber).
The above tests on HDPE indicate that if surface oxidation is happening, then it is only happening in the very outer layers of the material, and so it is negligible in volumetric terms. Hence the oxidised molecules are simply lost during remelting.
@frogfall you may not be a chemist, but it sure is pragmatic scientific proof @pauldufour delivered according to your reasoning.
It’s not the (bulk of the) plastic that’s degrading, just the bonds…
In a way making it even more urgent to recycle the Ocean plastics as under the influence of UV they seem to degrade into even more dangerous microplastics (long chains vs short chains).
Or at least how I understand it.
I’m not even an engineer 😉
After @joandarcy mentioned fumes, I had a little search…
Regardess of whether the polymer involved is nylon or polypropylene, fumes should always be treated with caution – and should always be actively extracted. Have a read of this paper (it is open access):
Interstitial lung disease due to fumes from heat-cutting polymer rope (Sharman and Wood-Baker, 2013)
Abstract Interstitial lung disease (ILD) due to inhalation of fume/smoke from heating or burning of synthetic polymers has not been reported previously. A fish farm worker developed ILD after cutting rope (polypropylene and nylon) for about 2 hours per day over an extended period using an electrically heated ‘knife’. This process produced fume/smoke that entered the workers breathing zone. No other likely cause was identified. This case suggests that exposure to airborne contaminants generated by the heating or burning of synthetic polymers has the potential to cause serious lung disease.
I know there are warnings about fume inhalation elsewhere in these forums, but this is a reminder to take those warnings seriously.
Just had a thought…
Has anybody within the community done any traffic analysis on this plastic waste?
If only by ‘scanning’ the packages/waste and mapping where it’s coming from (per location…).
So not just collect and recycle: Record and report!
If most of your ocean/beach trash (plastic, not tourist) comes from X, and you can PROOF this, the UN would be very interested…
I know most of my trash (should I choose to waste my resources) would most likely end up on a certain beach on a certain dutch island, so I do keep it local, but this is mainly because, well, the Netherlands is (yes, a singular plural) an exeption to the rule (like being a singular plural).
Of course the “origin” results might be strangely affected by the years of “waste export” across the world. See (BBC) Recycling: Where is the plastic waste mountain?
But some waste can be very traceable – such as on this image from a beach on the Scottish island of Eigg – as the fish processing company named is located on the west coast of Ireland. Although, I guess, the people dumping the box ties could be customers of the fish packers – located in another country.
Our group [email protected] started out researching the flux of plastic in North West Scotland. We set up a beach clean bin at our local beach, cleaned the beach weekly and counted and surveyed our finding. A very simple method to get some good empirical data.
Please see our website https://www.plasticatbay.org/category/resource/
We have got some funding so now we employ a Beach Ranger to help. We have also started doing microplastic surveys, we are getting involved with a study to monitor the incorporation of plastic in seabird nests and we have sent off nurdles for toxicology reports
We got into the recycling side of things as 80% of what we collect is fishing ropes and nets and we were sick of putting them in landfill and we need money to do more research.
Do you know someone to contact in the UN, we would be happy to pass on what we know so far….
Thanks for the link.
If more local initiatives would do similar tracing, we could really build some momentum.
Gapminder might be a good tool for this (for origin and landing stats of the plastic waste).
I’m afraid ‘1 beach’ will be considered a local issue, but let’s see it as the first step. A global network of data is harder to ignore (even ‘Europe’ only would be a local issue).
I’ll reach out to my EU contacts for more info to find an ‘in’ at he UN (open invitation, PM me if you (somebody) already has more information).
Do you have a spreadsheet you could share?
I’ll try to formulate a simple data structure for collecting data, so anybody can join in. You can help me determine if collecting such data is feasible.
Indeed, if only all data was this obvious!
But even EANs (barcodes) can give valuable information and would be easy to trace as often they are also region bound (there is an international database).
Or languages of the ingredients, or…
to be continued…
Makes you wonder what happens to the plastic waste the world exports to southeast Asia for recycling that does not have enough value.
Maybe it’s time for a reminder of this thread from last year:
And yes – a large portion of the waste plastic being inadvertently pushed into rivers, during informal manual sorting/scavenging in underdeveloped countries, has come from Europe and North America.
And if this waste washes up somewhere, in quantities, this can actually be proven and cut of at the source.
Making international dumping more trouble than it’s worth by outing these practices AND offering a local alternative (give US al your waste plastic) is actually something we could do.
The proof is in the pudding(packaging)!
@pauldufour great work. Here is an article on hdpe arctic ocean plastic
but they did NOT melt the plastic, just compared the strength etc of new plastic and ocean plastic. Their only goal was to use ocean plastic to reinforce concrete and they concluded it was viable. Your research is much more important because it shows remelted ocean plastic is STRONG. Thank you.
@joandarcy great work at the tippy top of Scotland! some resources on nylon fishing gear:
an Italian company Aquafil makes high-end designer wear and carpet from ocean nylon nets in a factory in Slovenia [ghost nets are usually nylon]:
they cater to upscale market because (I deduce) their product is more expensive than virgin nylon. That’s because nylon is hard to work with:
https://www.patagonia.com/recycled-nylon.html “For some reason locked deep in polymer chemistry, nylon is more difficult to recycle than polyester.”
“The economics of recycling nylon are not very appealing, however. Stephen Johnston, an associate professor in plastic engineering at the Univ of Massachusetts Lowell, ran a research program on recycled fishing nets for Bureo. Nylon, he says, is not an easy or cheap material to recycle. “
for those wanting to research nylon more, it is polyamide plastic and the most common form is PA6.
@joandarcy fumes are certainly something to be mindful of – my most simple recommendations would be to do experiments to see what the lowest possible melting temp for the rope is in your oven and use that.
if fumes are still an issue, a respiration mask will filter out most of the VOCs being released in the process.
@irismongolia is a chemical engineer on the V4 team working specifically with fumes – I’m sure she’d also be able to provide some insight (and maybe double check that i recommended the correct mask 😉 ) hope this helps.
@suzereuse very interesting research – while using plastic as an alternative aggregate for concrete might give us somewhere to put the material for a few decades, i find myself wondering if ultimately it just complicates things. hopefully we can continue experiments to learn more about the viability of recycling UV degraded plastic 🙂
From my research about the fumes, mostly PS has the most issues concerning with toxic fume production, because melting can create styrene and similar aromatic compounds in the air. PE and PP creates much less fume when heated because it is essentially a refined wax. Fortunately, we have some masks available commercially which is 3M ABEK filter respirator which filters organic vapours above 65C, inorganic gases, acid gases and ammonia. These filters need to be changed after 40 hours of use (around 15USD for a pair).
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