How Many Times Can Plastic REALLY Be Recycled?

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In this video, we’re testing the highly debated topic of ‘how many times can plastic be recycled?’. Looking online gives you a whole host of mixed results with a lot of generalisation about ‘plastic’ as a single material. We decided that we were bored of people using this as an excuse as to why ‘recycling doesn’t work’ and decided to test this out for ourselves.
To be super clear about our tests - we’re using recycled HDPE and running it through our machines at 230 degrees celsius. The plastic is only melted for as long as is necessary and doesn’t ever go beyond this temperature. All of our plastic comes from post-consumer waste sources and we are very careful about sorting, separating and cleaning the plastic before we let it enter our material circulation.
We’re fascinated to hear what you think of these results. We absolutely could have gone beyond 30, but we weren’t expecting the plastic to last as well as it did to be completely honest with you! We can also repeat these tests in other materials to see if the results are similar, so let us know if that’s something you’d like to see.
Oh, and here's a link to our carabiners if you fancy one!
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#BrothersMake #HDPE #PreciousPlastic #HDPERecycling #RecycledPlastic #RecycledPlasticBottles #PlasticShredding #InjectionMoulding #PlasticRecycling
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Music by Epidemic Sound

[@BrothersMake]

Go to ground.news/brothers to stay fully informed. Subscribe through our link for as little as $1 a month or get 40% off unlimited access. Supporting our sponsors helps keep us in the workshop and saving more plastic from becoming pollution 🤙🏽

[@EngChagas]

Haven't checked the site yet, and I'm going to just after posting this comment, but seeing all those colored planters had me wondering if you guys have some nicely colored rpg dice sets made of recycled plastic....

[@MegaJERRRRY]

From the injection molding background my self. Poly/HDPE can honestly be recycled loads of times. It’s when you get into your glass filled or carbon filled materials where they can only be recycled 4-5 times typically because of the strength of the material starts to degrade more and more.

[@alexrauber7917]

lol recycling logo... you me resin identification code

[@cezarcatalin1406]

How about chemical recycling? Aka, the plastic is chemically decomposed into smaller molecules, purified and finally re-polymerised.

[@WetDoggo]

definitely try other plastics too. Hdpe is a great plastic already, but there are definitely difficult odes

[@thomascloete2271]

I think the constraint with the amount of times you can recycle plastic is not necessarily from the recycling process itself (as proven in this great video), but from how the product is used between being recycled. For example if the caribiners were used on a daily basis and exposed to lots of UV (someone who works outside alot, construction etc) the plastic may degrade due to UV exposure and lose strength over time. Other factors such as load stress, temperature and exposure to chemicals need to be taken into consideration between each recycle step. The way in which the product is used ends up defining how long the material will last before degrading to a point where it loses it's virgin properties.

[@MJTVideos]

That’s literally exactly what I was gonna say. I think the environmental conditions that each “lifetime” of the plastic is exposed to reduces its recyclability

[@christianfenis1415]

I absolutely agree. I was thinking of the same thing, and while this is a very nice video, I also thought that the way these recycled plastics are to be used for a prolonged period of time before getting recycled again should be a big factor to take into consideration when truly determining the number of times it's actually gonna get recycled before it breaks apart. And that takes waaay more time than what was shown here in the video. But I think it can still be done in a short span of time, by actually intentionally exposing these plastics to harsh conditions or stress before getting recycled again.

[@TheInnerHalo72]

I was thinking this too. I think it's honestly a safe bet that realistically you got maybe half of the amount of times they tested here to work.

[@eugenetswong]

I agree with all that you 4 people have said, except the stress from usage I'm not an expert, but I'm guessing after watching this video that the stress is reset after/during heating. I'm sure that we need proper lab work to confirm what I said, though.

[@eklectiktoni]

@@eugenetswong Exactly, not so much stress, but UV, chemicals, etc - basically anything that reacts with the plastic to change its chemical properties could affect its recyclability. That being said, I don't think the problem is insurmountable because things like steel undergo chemical corrosion as well, yet are infinitely recyclable.

[@db7059]

Australian government should support small plastic recycler businesses instead of exporting plastic to other countries

[@BrothersMake]

Couldn't agree more!

[@TheFiftyQuid]

It should be illegal to export your trash and plastic. You create it, you get to deal with the repercussions.

[@db7059]

@@TheFiftyQuid tell that to the government

[@lawrymccarthy3292]

The CSIRO has been actively researching recycling for at least 3 decades. In Australia pure stream industrial recycling (analogous to the Brothers) is fairly strong but domestic recycling has problems WRT: collection, contamination, sorting, cleaning and UV degradation.

[@2wheelsfinn]

Yup, we are totally thrilled for your trash here in the Philippines..

[@J1P2K]

Maybe you should do a strength test. See how much it can hold before breaking.

[@BrothersMake]

Some friends of ours actually have a tensile testing machine - so we may have to give it a go!

[@patrickbuswell]

I would love to see that!

[@joehorlacher1585]

That would be awesome! @@BrothersMake

[@DyslexicAnaboko]

That's awesome to hear I was going to suggest a tensile strength test. Also compression test. I did expect them to become more brittle, but these results are fantastic and unexpected.

[@harpy9817]

@@BrothersMakeyou could also try giving a few goes on the tensile strength and then recycle them a few times returning to the machine each time. just an idea!

[@rorydickens4379]

You are 100% right about clean and well sorted plastic should have a much higher recycle rate than what is advertised. However the recycling system is broken. With still many items not being cleaned properly, bad labeling and companies creating laminated products containing many materials. The system needs to change! And the only way to do that is through changing our buying habits and supporting the small businesses that make an effort to recycle better, smarter and put in that time! Eg. Brothers Make! However as for the results dont forget that you guys utilised similarly sourced HDPE, with similar properties. However even the category of HDPE in the industrial recycling system can have a wide variety of additives that would affect your success. Also the carabiner is quite a thick object in injection moulding terms. I wonder what the results would have been on a 1-2mm product and what the results would have been with the standard tensile, compression and lateral load tests. Maybe video 2?

[@1Kaisermerlin]

Honestly only policy can make manufacturers conform to a shared standard for recycling. Here in germany we have 100% recyclable Pet bottles through a uniform collection and distribution system.

[@speicalkeek4579]

as long as its cheaper for me idc

[@batsy3]

@@speicalkeek4579 the only true way to change buying habits

[@MrFinepixa]

Properly recycling plastic also requires A LOT of consumer knowledge and willingness to recycle. Because there are many different types of plastic and they all have different additive components to regulate their form and function. Its just difficult all around.

[@BornIn1500]

We can agree that the recycling systems aren't perfect, but saying "oUr SyStEm Is bRoKeN" just makes you sound like a petulant child and you insinuate that recycling systems were ever perfect in the first place. It has always been a work in progress and is improving all the time.

[@S1L3NTIGamer]

So I’ve worked in industrial injection molding for 3 years and industrial thermoforming for 5 years. I am quite surprised at the results of this test. Granted I’ve not got a lot of experience with HDPE: mostly with PolyPro, PLA, Nylon (glass-filled and normal), TPE, and TPU. But nonetheless in my current thermoforming job we use our reground material but we mix in %50 virgin material to dilute the degraded plastic. I am curious about the temperature settings for your two machines and how those may have affected the results. If you injected at the lower temperature ranges it would have resulted in somewhat less degradation per run (not sure if the amount is negligible thought). Lastly, those injection and extrusion machines are SO COOL. I’m only used to seeing giant machines with 30ft long barrels, so seeing such small machines is just super awesome to me.

[@redfeather_]

Wait till you see a 3D printer then... jokes aside, there are actually really cool DIY extrusion machines you can build to reuse 3d printing filament and it's just freaking awesome

[@elizabethscribner6365]

This seems to be a good small business opportunity. Or even a chain of businesses. Lots of positive possibilities.

[@notyouraveragegoldenpotato]

I built my own, not as small as all the ones you see online- I wanted to actually be able to make parts with some substance. But I made it all from hand tools, literally molded and cast my own molds, and have been ripping away on it. Pretty neat. Every bit of it from scratch, random metal pipes and an electronic controller with band heater. I use a modified 2 ton jack though instead of a wheel like them

[@jjoo93]

Another thing to think about is that the carabiners and cups are pretty thick plastic (relatively to the thickness of bottles) - and everything is injection molded, not blow molded. I don't know the exact split, but most of the things that you come in contact with are blow molded, not injection molded. Injection molded parts are definitely going to have more strength in general because they're thicker. In addition, you might see a difference in the tensile strength of the carabiners (though I understand why you might be reluctant to do strength testing of them on camera). But if you make a 1L blow molded bottle and try to do a 3' or 6' drop test, you may see differences MUCH earlier than 30x.

[@williambarnes5023]

Plastic degrades over time. The limit to how many times you can recycle it is because it ages and degrades in a way that melting and recasting doesn't fix, leaving you with decayed plastic in a freshly-injected shape. You can grind it and remelt it and reinject it as many times as you want, that doesn't degrade it. You're not really recycling it because it wasn't used until it decayed and broke over time. It's still fresh plastic. It spends years being a bottle and decaying, then you try to melt the decayed bottle into a cliphook, and you get a cliphook made of decayed plastic, and that breaks. You're making cliphooks out of the same fresh plastic, no matter how many times you grind and melt that plastic. It's still only a few days old. The recycling limit is because used products that get recycled are old, and you're mixing together old decayed plastics to make another thing, which continues aging until it too gets recycled, until it's so far decayed anything you make fails.

[@cmac3530]

I would love to see a long-term environmental test followed by recycling to see how the plastic degrades (or doesn't) in different scenarios. Like, put a batch outside for a week, a batch on the window sill getting sun, maybe a batch in and out of the freezer daily to simulate thermal cycling and of course a room temp control group. Shred those batches and re-do the carabiner test to see if any of the plastics are now weaker.

[@Znatnhos]

I think the other thing to consider is that you rarely recycle a product immediately off the production line. It usually spends months on a shelf somewhere, more months or even years being used, and then more months at the end of its life as it's processed, cleaned with harsh chemicals, and finally ground and reformed. All that time likely contributes to the expected degradation of the polymers.

[@harmless6813]

My very first search about the topic gave me a link to a paper the abstract of which reads: "The thermomechanical degradation during processing gives rise to different modifications of the structure depending on the temperature, residence time and applied stress. In general, it is possible to say that if the reprocessing operations are carried out in apparatus with low residence time, the mechanical and rheological properties of the raw materials are only slightly influenced by the recycling operations. Significant degradation phenomena and reduction of some mechanical properties are observed on increasing the number of recycling steps in apparatus with large residence times. By adding antioxidant agents the polymer maintains the initial properties even after several recycling cycles."

[@tzisorey]

That was always my understanding - the change in strength wasnt from the shortening of polymer chains etc, but from the added impurities after each use, recovery, and processing. But that not from work in the industry or anything, just what i was told in school in the 80s

[@TheDeadKingsRaven]

Would love to see this done with other plastics and also think if you threw everything in a room with a UV lamp on for a few days between recycling steps to see if there’s a noticeable difference in strength of the batches. Anyways, cool video and enjoyed watching you test this one out.

[@keithhorning7753]

You do a fine job of keeping the plastic clean, not a good example of post consumer mixed recycling. Maybe that's the point.

[@rainsticklandguitartalk9483]

I'm still stuck on the fact they took all that time to separate the colours...only to throw them all back in the same bin.

[@rachelpatterson9953]

Love that you did this this as a bit of self-researcher, myself. It’s always easier to trust your own results than those someone else has done because you control all the variables that matter to your own things.

[@BrothersMake]

100%! So interesting to find out for yourself for sure - especially when no one can agree on an answer!

[@vinny5915]

Interest video. HDPE actually performed much better than what I expected. I will just add some more information here. The problem with giving you an exact number of times plastic can be recycled is not that there is some sort of agenda to keep that information from you. It is genuinely complex, as there are so many variables involved. To name a few: 1. What plastic are you using? - obviously 2. How well can you clean them? - In a small operation like in your workshop, and regrinding the material immediately after extruded, your samples are very cleaner. 3. What is the thermal history distribution of the mix? - basically, what if you mixed batch with different heat cycle counts. You actually did this to some extend, I think, by puting everything in the same extrusion moulding machine. 4. what is the shape of the object you are making? - The thinner the wall of the object the harder it is to make via recycled plastic. For example, recycled plastic bags (which you can buy in the ) are noticeably easier to tear than virgin plastic ones. 5. etc. All of this make plastic recycling extremely unapealling. As anyone want to try it on an industrial scale must always invest tons of money up from to even know if the final product is even viable. This is compounded by the lack of recycling policies (in sorting trash) and consumer awareness (e.i. remove the lit/warping off your food-packaging/soda-bottle and give everything a rinse before binning. - this make a world of different, btw).

[@Mikemk_]

Chemistry student here. There's two main categories of plastic, thermoplastic and thermoset. Thermoplastics melt when heated and are much easier to recycle as a result. Sometimes, as in the case of PE [includes HDPE, LDPE], infinitely recyclable barring contamination. Thermosets harden when heated, making them difficult to recycle. You can't melt them down, so you have to use chemical means of breaking them back apart into their monomers, which isn't always possible. Also, you got the terminology wrong here. You were saying the carabiners were strong because they weren't breaking, but that's the opposite of the truth. Their elasticity is what allowed them to not break. Strong materials are brittle. When too much force is applied, they snap. Weak materials are elastic. When too much force is applied, they bend. Nothing is perfectly strong or perfectly elastic; real materials exist on a spectrum between the two. Plastic actually gets stronger when heated or exposed to UV light or ozone. Specifically, the long polymer chains will get cross-linked began two side to side chains. This forms small off color, typically white, thermoset dots in the product. The more you recycle the plastic, the slightly larger these dots become. Because they no longer melt, if you recycle enough times, they'll clog your extruder nozzles. They're also stronger than the original plastic, which makes the plastic less elastic and more brittle. If you've read this far, you should make an update video looking closely through a magnifying glass and microscope for those dots.

[@keithezard]

Great video - boring to do but of such value to the community. I had exactly this question. Thanks very much for your effort!

[@BrothersMake]

Thanks Keith! Fortunately the boredom was easily fixed with a fair few Podcasts 😅 glad we could help.

[@guybrush20X6]

Good on you for seeing a lot of conflicting information and deciding to put it to the test so there's more real world data.

[@BrothersMake]

Ah thank you so much, it was a super interesting video to make!

[@richardokeeffe8375]

Brilliant video. You’re definitely right about recycling centres getting a mixed bag of quality but this shows what COULD be done!

[@jdniedner]

The big recyclers don't clean thoroughly. I heard that one teaspoon of peanut butter in a not cleaned peanut butter jar can ruin a Dozen kilograms of recycling. Well duh.

[@rolfbjorn9937]

This is a great thing you guys are doing. Your test uses clean, on-site, premium post process material. Post consumer material is...glorified trash. The efficiency goes down and so does the $$$$ incentive. In the industry, enforcing any rules all grinds down : $$. In Metal Fab for example, the most efficient subcontractor wins, whether it's cutting corners, better processes or material costs. In my region of Canada, recycling and garbage are hard to distinguish, even for educated people, judging by the sheer amount of recyclable matter in the garbage and vice versa. Glass contaminates the fibrous materials and the plastics, the plastics contaminate the glass and fibrous materials... And since it's expensive to process, the stuff is sent overseas or buried. Ironically, clean sorted materials are worth $$$, cardboard bales have companies that pay you to pick them up! It's also a pain to bring back cans and bottles to stores for refund...I wish we could have a local system where it's actually easy to just shove plastics/glass/ferrous/etc down a specific drain where it gets shredded/compacted and picked up by the appropriate industry. Polystyrene Foam should be easy to recycle, but the very low density makes it a pain. I have the equivalent of a solid cubic meter of accumulated polystyrene packaging dissolved in half a liter of acetone in a couple jars. No kidding.

[@jellesmith]

I did a literature review on this (or recycling PLA into new fillament for FDM printing to be more specific), and one of the most interesting findings was that adding around 1/3 virgin material when recycling would always give a very usable result with relatively good realogical properties, even when the other 2/3 had been recycled many times.

[@edeniaAJ]

Very surprised to see that HDPE can be recycled at least 30 times! Although that doesnm't come close to the potential of Polystyrene. With PS, you don't even need to melt it down, you can just thermally depolymerise it, recover the styrene, and heat it with Benzoyl peroxide to turn it back into Polystyrene. Alternatively you can perform the latter step using something like benzophenone (radical photoinitiator) and blast the styrene monomer with UV to the same effect.

[@SianaGearz]

"recover the styrene" is the yucky part. I would not want to be around this monomer at home or in a normal workshop. Fume hood please.

[@josephtwilley7187]

It looks like the marbling evened out and became a solid color over time. Great experiment.

[@BrothersMake]

For sure - by round 4 all marbling had pretty much gone! Was nice to see that when we cut it with white again at the end, the marbling came back in full effect though! Thank you Joseph 🤙🏼

[@josephtwilley7187]

@@BrothersMake Thank you for making content like this. It's going to inspire people to recycle more and reuse materials as much as the can. I'm trying to reuse the tires I just replaced on my car. Any ideas?

[@WeebotTheRobot]

A better measurement in material change after each round of recycling would be to put all of the sampled carabiners in a tensile testing machine and seeing how much the yield strength changes over time. It would require more than one of each round's sample to get an accurate average yield strength though.

[@LilyLewis771]

It would be so cool if we could have neighborhood plastic recycling centers like we have post offices and drug stores- they'd take and sort the plastics from people's and businesses' recycling bins, and recycle it to create new things that people can buy- household items like storage bins, clothes hangers, food containers, reusable grocery bags, toys, etc. or create larger orders of items for businesses.

[@OkOhYeah]

Again, proving something we have been taught being absolute nonsense. Cheers for testing this in such an honest way. Placing my order for a carabineer right now!! 😁

[@BrothersMake]

You are far too kind, sir! 🪄

[@wwiiinplastic4712]

I'm glad you put in the rock-climbing disclaimer as I was thinking I wouldn't even let an Action Man doll rappel using recycled plastic carabiners.

[@simon10000]

Great work guys. Thanks for investing the time to find out the truth. You say your setup is not controlled, but you are underestimating the care you put into your processes. I love the addition of the first time recycled white to add the colour differences back in. Keep up the great content.

[@sebastianwalder2498]

It'll be interesting to see it with a tensile testing machine.

[@BrothersMake]

It would be! Some friends of ours actually have one so we'll have to try it out.

[@EngChagas]

​@@BrothersMakecan't wait to see that test results....

[@projectrebuild908]

Great video. It would be fantastic to see further videos of different plastics.

[@BrothersMake]

Thanks so much - noted!

[@projectrebuild908]

@BrothersMake I really appreciate the work yous put in to making products, content and challenging plastic norms.

[@CTCTraining1]

Excellent research video guys, pushing the boundaries of plastic. Keep up the great work😀👍

[@dewainanderson8088]

I work in a plastic factory and the two things that limit the recyclability of the plastic is degradation from heat which happens during melting and molding and degradation from time and weather, you can't really say that plastic can only be recycled a specific number of times

[@moth.monster]

A lot of it depends on the material. PET and PE will recycle practically indefinitely, but PLA (of 3d printing fame) shows significant degradation after a single pass through a recycling setup. (It can still be practically recycled if mixed in with about half virgin pellets, though.) Love to see a practical experiment though! P.S. You guys should totally make an "S-hook" style carabiner with two spots, one for your bag's strap and one for your keys.

[@logicalfundy]

I'd actually be interested in knowing which properties are affected by repeated attempts at recycling - how does the degradation manifest itself?

[@semibiotic]

Easy degradation is a feature of PLA. It isn't even intended for long-lived application.

[@Yoyocreative]

I think you can recycle plastic a LOT more! As long as it's use changes too. The first (maybe second time too) recycle could pretty much be used as anything. After a certain amount of recycled, the hygiene/waterproof/durability level becomes too low for general use, it could still be recycled into outdoor tiles, counterweights or anything that doesn't have to hold big weights. I think there's a lot more possibilities, but it's just not researched well enough at this point. If there's a generalized standard we could follow, that'll be a possibility. For example: if we know a certain type of plastic is safe to be used in food/drink storage up until two recycles after initial production, these plastics could be sent to a factory that produces recycled plant pots. If it's no longer good to use it in hollow/open structures, it could then be sent to factories making bricks and so on. We're nowhere near that level of recycling, but it would save a lot of trash in my opinion!

[@Squibbleses]

Interesting. I remember seeing a bit of a similar test with recycling 3d printing filament. I think it may have been with ABS and they definitely started to have problems with 3d printing it after a few rounds of grinding/melting. I think the issue they had was dust and moisture inclusion that was causing bubbling/popping as they tried to extrude it while printing.

[@BrainSlugs83]

You forgot to do the most important part. This plastic is all from the same batch and doesn't mimic real world recycling. In real world recycling, the plastic is all from different batches each round. That's where the weakness is introduced.

[@BrothersMake]

This is the key point we were trying to make at the end - that weaknesses are introduced when different types of plastics are incorporated. But if the time is taken to clean and separate into plastic types, then it will be fine as long as 100% HDPE is used (for example. You can see at the end where we cut the 30x blue recycled plastic with the 1x white recycled plastic - the result is perfect ♻️

[@jimysk8er]

the problem with putting a number on the amount of times something is recycled is that they limit it to being the same product that remains within acceptable margins of quality. I absolutely hate that they choose not to publish the possibility or transitioning to products with increasingly more lax margins. Just because some plastic is no longer good for a water bottle or carabiner why can't they just make starter plant pots or packaging or those little pedestals for holding rebar 3 inches off the ground or components that aren't seen anywhere like the underside of electronics buttons or the bulk of the inside of tools like a mallet or screwdriver or the little wheels under furniture that aren't good for ten years anyways or even lastly asphalt or pavers or just general aggregate or filler. Also worth noting that when a company says 5% recycled material it usually means they reuse the rejected products and or the little tabs that get cut off a molded part like the injection point.

[@TrashPandaDiscGolf]

Historic / Legendary video gentleman 👏 (Been wanting to try this for months with TPU on our discs.)

[@BrothersMake]

Ah thanks so much man, it has been on our list for a fair while too! Was super interesting to try out. Hope you're keeping well, brother 🤙🏼

[@Super1275gt]

This was fab, I'd love to see this repeated with another material.

[@eugenetswong]

Yeah, like another plastic.

[@PhoenixtheII]

Step 1, sort your HDPE by color Step 2, just shred it all together. Genius.

[@roswoodhead-colombia8493]

Fascinating. Thanks for doing this. Just shows what can be done with a little effort. Yes, I would be interested in seeing what happens to other sorts of plastic.

[@BrothersMake]

Glad you found it interesting! Noted, we're definitely keen to try out another so we'll get on it ♻️

[@kharmachaos667]

Two of the biggest things that limit plastic recyclabilty (look ma, new word) is 1. Weathering of the plastic which can consist of but is not limited to UV breaking down the plastic into weaker breakdown products, heat doing the same thing, even acidic rain- and 2. Contaminates. In order to recycle, you have to prewash the plastics- and many things don't just wash off with the commonly used solvents. It only takes one person using a plastic bin as an emergency oil container to contaminate a batch. This also has something to do with differing plastic types getting into the batch and even the colorants mixing together at percentages that weaken the mixed plastics.

[@KatharsisTF2]

That overdub was clean af and I don't think I would have noticed if you hadn't said it was.

[@Sobou]

Wonderful video, love this kind of methodical testing. Just recently did a series of tests with a bunch of waste plastic from a warehouse: multiple jars containing water, vegetable oil, and a 50/50 IPA 70% to water mix to determine "good or bad" -> "PP or HDPE/LDPE" -> "HDPE or LDPE". Messy, took a bunch of time, but cemented for sure what I could use and what was functionally worthless for these projects.

[@eight7934]

I think the reason its hard to put a number on how many times you can recycle them is the age of the plastic determines its degradation from oxidation, uv light etc

[@smokeduv]

Most of the time, the problem is the use case and not that it can't be recycled, but how many times can it be recycled before it doesn't meet with their quality control, which can be for something simple like color, for example, Coca Cola was hesitant to use recycled HDPE because in their tests it wasn't completely transparent, but then they figured it out how to make it work (and with collection centers specific for PET it was easier because they are a lot cleaner so they don't need extra steps) so they now use recycled PET, which is great news, but yeah, it depends. For things that are not so picky in terms of color (for example if you use pantone), most plastics can be recycled many many times if you're careful not to overheat them

[@piafinch7537]

I would love to see you do this with the other types of plastic as well.

[@BrothersMake]

We certainly will!

[@lindawolffkashmir2768]

Polyethylene is a pretty good durable recyclable plastic. Usually the process when being remolded is to add a percentage of virgin to the regrind to help with its integrity. However, if you’re running something like ABS or a stiffer or glass filled plastic, something that requires a hotter mold with thermolaters, or the machine temperature to be exceptionally high, that plastic can degenerate a lot quicker. There were times when we were running low on a plastic, and had to use 100% regrind to try to complete the order, but the resulting product caused more scrap than running it was worth. Depending on the plastic, you’d either get shorts, or it would get too viscous and flash out. It was a real crapshoot during those times. Poly is usually forgiving, though, as long as it doesn’t get overly contaminated.

[@liag5894]

Absolutely amazing work as always

[@lornacy]

Yes!!

[@vuaeco]

There's a problem with this test. Plastic doesn't change its chemical property with the heat used in injection molding. That means you can recycle it indefinitely. I think what people really means when they say "plastic can be recycle X times" is that over time, especially when exposed to UV light, it changes its chemical property due to UV damage. Plastic can only be recycled up to so many times before it is too chemically damaged it loses its intended purposes. Ultraviolet light breaks down covalent bonds in plastic hence changes its chemical and physical property. You can only recycle it up to a certain amount of times before its chemical property is changed enough to alter its physical property. Put a one gallon bottle of milk in the sun for some time and it will start losing its flexibility. Pick it up, try to bend the bottle, it will break and crumble in small pieces instead of flexing when it was new. You should experiment on milk bottles that are exposed in the sun for different periods of time (like 1, 2, 3, 4... months interval) and recycle them to see if they still retain their physical properties.

[@fillman86]

what an incredibly useful video to call out companies that are against our 10c return on plastic bottles

[@TheBestestKitty]

This comes down to the different properties of different plastics, their volatilities and how they react to heat. A large chunk of plastics aren't actually plastic injections, but rather resin casts and resin is entirely impossible to recycle. it can only be shredded and burned. Different kinds of injected plastics, like you use here, have different heat tolerances and baking preferences; some ask to be baked for long periods and others not, however, so long as material is not lost they are theoretically infinitely recyclable for the exact same reason why metals can be recycled indefinitely and it's for a few key points: Let's start with environmental damage. These plastics don't have the same level of volatility, eg, they're more stable compounds and as a result, are very resistant to UV, water, etc., damaging them. They don't rot, and remain for the most part static. A piece of plastic like this could have been sitting out in the elements for decades, and be in the same condition it was when first cast. This is not the case for plastics created from resins, like PVC, polyethylene, epoxy, etc., which all degrade rapidly when exposed to UV light (they turn yellow and brittle.) These are by far the most commonly used plastics, for example many vehicles outer shells are created entirely from this, headlight lenses are made from this, fibreglass is universally made from this, etc., and they're used because they are sturdy, light and resistant against physical damage and deformation. They usually have a high ignition point, and can handle lots of pressure and heat before degrading. This is not the case for plastics used here, which will melt when exposed to high heats. They're also, rather importantly, food safe as they do not contain any catylists such as polystyrene, which is used almost universally in other plastics like polyethylene or, the plastic named for it, styrofoam. To summarize, the plastic used here is infinitely recyclable, so long as it's cleaned and treated properly; usually with some chemicals and lots of water. Resin-based plastics, formed by chemical reactions, are entirely unrecyclable. That's why every single plastic object should have a label saying what kind of plastic it is, and whether it's recyclable (though I'd prefer it be banned entirely and we go back to good old glass).

[@IoannisOuzounis]

I really like youtubers that annihilate misinformation in practice.

[@gordonwiley2006]

Probably the fragility of a given design is probably just as important. Something with real tiny fiddly bits to snap and such would probably be better for "fresh" plastic just to be safe, whereas stuff with no moving parts at all you can probably be way more willy nilly with the usage. At the end of the day, if it's something important enough to matter, it probably deserves its own set of tests.

[@zero-waste]

The general perception of how many times plastic can be recycled is not based on how many times a single type of plastic can be molded, shredded, and then shredded and molded again. Obviously, this can be done many times; maybe even hundreds of times as long as the temperature during the molding process doesn't significantly exceed the melting point of the plastic. The general rule of plastic being able to be recycled maximum ten times is based on several factors. A few can be mentioned here: Even commercial plastic recyclers with machinery worth millions cannot reach a purity rate of more than 98 to 99% when mixed used plastic is sorted. It means that small amounts of other plastic types slowly but surely will be mixed into the plastic type they're sorting out, every single time it's recycled, i.e. an accumulation of contaminants. Another problem is that not all foreign particles can be fully removed when used dirty plastic is cleaned in the washing channel. Sand, dirt or metal particles embedded in the surface is impossible to remove completely. Further, the plastic items to be recycled may have been used for many years, causing wear and tear of the molecular structure. If used outdoor for prolonged time all plastic will be more or less degraded due to UV in the sunlight. indefinitely by chemical recycling. Well, some may argue it's not genuine recycling, but at least it keeps plastic out of landfills and especially the environment. Yes, it requires more energi to process waste plastic this way and perhaps it also releases a few more toxic components, but it's still a lesser evil than plastic garbage in the oceans and the increasing amount of micro plastic in all animals and humans.

[@FaZuQ]

It’s a pity that they limited themselves to plastic tests - it was possible to conduct deformation tests (under different conditions), tests for resistance to abrasion and chemicals, tests for the structure of the material, a test for aging of plastic

[@darrenosborne8252]

I've always been curious what would happen if you added some propylene glycol. I've added it to soap to make it easier to melt. I know plastic and soap are WAY different. I'd be curious if it helped flow or soften the plastic. Just food for thought. I love the channel.

[@SianaGearz]

I don't think propylene glycol should be added to HDPE, I think it will just weaken it immediately because propylenes and ethylenes are not miscible in each other. Try ethylene glycol instead. But yeah worth an experiment because I don't really know for certain. Beware of long term effects. Both can help plastic draw humidity from the air and might act as plastifiers. But the water can then be catalysed by UV light and heat to perform hydrolysis on the plastic, causing it to fail sooner in use. How susceptible plastic is to this, varies a lot, and I don't know the details. Many plastics derive strength specifically from absorbing water into the matrix though, nylon being a prime example but this can also be observed with some others. I think ultimately this is why it's great for soap, because it's a water based product essentially, just mostly dehydrated. And PG helps it hold onto a little bit of water, not too much not too little. Also it's pretty remarkably safe, MEG less so.

[@darrenosborne8252]

@@SianaGearz You definitely understand the principles behind it better than I do. But I'm glad you could see my point and improve upon it.

[@newolde1]

​@@SianaGearzso essentially what I hear you saying is that we can make millions of gumby toys! In all seriousness, thanks for sharing!

[@isunembizsu]

To add to this discussion: while the degradation in the case of this material and this specimen is limited, an important point (at least in case of PET and recycled bottles) is that the reused material loses it's work-ability - reaching the same wall thickness in a hot-blow operation (e.g.: bottles) is impossible after 2-3 cycles due to the shortening of the polymer chains, and as noted: contamination is the killer when it comes to plastics, not to mention the mixing of degradable plastics into the same container as the "non-degradable" versions...

[@MrMartinSchou]

If you repeat this experiment, you should use a strain gauge tester to get some quantifiable numbers on the force needed to break them.

[@Lzzeecrkrs]

What this tells me is that the pieces you have to cut off the finished product can be reused with no fear. This video answers that question for me. What you said at the end makes sense. I do notice that every plastic you use looks very clean and you have everything exact. I think if you were to collect some of the items you have made after a few years of normal use and recycle again, there may be a noticeable difference from factors such as UV light as others have commented. It always makes me happy to see how people reuse and recycle items. Answering questions like this video does are also enjoyable. Thank you.

[@HappyJackington]

I've done a lot of work with plastics in a former job and I can definitely say that HDPE is one of the most recyclable plastics you can run across. PP definitely will give you different results if you try it out. Honestly, it surprised me how different plastics can be. Another thing that can help your search into recylability is to look up a term called re-grind. It is an industry term for including shredded waste parts with virgin material in making parts.

[@KozelPraiseGOELRO]

In a research I did years ago (for a school project), I concluded: Even with recycling reaching higher levels, plastic is more contaminant than reusable matherials such as ceramics and metals. Adding to that, most (and I mean >90% of plastics) isn't even recycled once.

[@maxlosergor]

I work at a plastic company and recycled plastic is often added to new material to cut down on the overall cost

[@maxlosergor]

Also PLASTIC REGRIND IS MY NEMESIS

[@iggysixx]

One of the main 'issues' is that plastic being colored will be an important factor. Brands will want to remove that color (i.e. a 'blank slate') in order to imprint colors that match their brand identity. It's likely that the removal of colour (which is likely a fairly destructive process) is taken into the equation. And it's likely that colored plastic is NOT considered 'recyclable' if removing color is too costly (e.g. 'Only blank (white / transparent) plastic is considered a valuable resource'

[@TechMobileReal]

One thing we have to consider is that we recycle plastics that already have served its purpose For example A Pot will be used in sunlight, rain and it greatly changes its strength and when we recycle it again , we use it again under the same conditions that results in a decrease in strength more and more. But i highly appreciated your efforts ❤❤

[@sainteins]

If you made test pieces and used lab equipment to test the material, you will see some degradation because the polymer does degrade with heat cycling and such. Another factor that drives degradation is if you have glass filled polymer and you end up with shorter and shorter fibers. That would definitely also show up in testing.

[@EdmansTube2008]

As mentioned by others, here some grains of salt (from sb who worked for a company that produces plastic granules with high concentration of additives, called a master batch). The reason why there are so many different answers (if any at all) to "how many times can plastics be recycled" is simply because the topic is really, really broad and complicated. The answer depends on SO many factors. What additives are in the recycled material? Do you KNOW? If you can't be sure you allready run into trouble, depending on your use case. You don't want the UV stabilisers of agricultural foils in an item you store food or beverages in. You don't want additives, that accelerate the degrading process, in items that are supposed to be long lasting. Just to name 2 examples. Then there is the mixing of types. It is common practice to mix different layers of different types (like LDPE and PP) in one foil to get the barrier effect of both materials (one is really good at blocking oxygen, one is really good at blocking water from defusing in). There is also the mixing of 2 different types in one layer, like HDPE with PP to get a mat finish (if you ever had a none-shiny bag of chips, that's the stuff. The outer 5 micrometers are a mat-compound) ). It's common to have more than 3 layers (though for most everyday packaging you either have just LDPE or a 3 layer foil), sometimes even metalised bags, to really keep it dry. What I'm getting at with all that is, the stuff recycling companies get is a hot mess of mixed polymers (aka plastics), it's not easy nor cheap to get it all sorted, and a lot of the material can't be properly sorted, cause it's fused together. Mixing different types of polymer, containing different additives, severely limits the reusability of the material, regarding physical properties and food savety. And that before I even start about processing and in-use-degradation. The processing these guys did was about as gentle as you can go. In industrial machines you will encounter processing, that puts way more strain on the material, to get it homogeneous. That's one of the key benefits of plastics, it can be made homogeneous at a low cost, it doesn't rot and it is very versatile. So, there is no easy answer. If they mixed in some other plastics with every cycle and had a longer extrusion machine it could have been a much more realistic test. Talking about pushing someones agenda... Don't get me wrong, we HAVE TO RECYCLE PLASTICS. But you got to understand it doesn't work irl like in this experiment. The only way to save the planet is to produce less waste, consume less.

[@wooddavid8293]

Very nice demo of engineering and testing!

[@lornacy]

Thank you for empowering and educational content 😊

[@BrothersMake]

Our pleasure! Thank you 😊

[@Green.Country.Agroforestry]

Guys, if you can make stackable planters, there is a huge market for them - my viewers love the things, but they sell out at the dollar stores so fast in the spring, they find getting them challenging.

[@xcoder1122]

Keep in mind that plastic isn't plastic. There are all sorts of plastic and what applies to one kind doesn't have to apply to another kind. Also your way of recycling is to just shred and melt the plastic again but plastic beverage bottles for example are not recycled that way anymore. They are shredded and then added to a solution that will completely dissolve the plastic. From the solution the plastic can be extracted again and guess what, this process creates new plastic that is almost indistinguishable from brand new one and there is no degradation whatsoever as you are basically rebuilding the plastic on molecular level. That's why it is possible today to create new plastic drinking bottles from 100% old ones without adding even a tiny bit of new plastic to to the process and this process can repeat forever. This is how beverage bottles in Germany are recycled and that's why there is a deposit on those bottles, to ensure that people will actually bring back their empty bottles as if they don't, they won't get their deposit back and thus have to re-pay it every time they buy beverages again. You don't have to bring them back to the store you bought them, every store selling plastic bottles also must take back plastic bottles. And the best part of this new process: It's not more expensive than making bottles out of new plastic, actually when done correctly and in masses, it is less expensive.

[@danaharrington6561]

Fantastic work, guys! I hope you’ll get around to testing this same thing with a variety of other plastics. I’d love to see how many cycles common 3d printing filaments can go through.

[@VeritasAbsoluta]

UV is a major part of plastic decomposition. If you were to measure the UV intensity in daylight in the winter/summer, then construct a chamber with UV lights and measure the intensity in the chamber, you could potentially subject your test samples to a years worth of UV in a much shorter amount of time and then test the affect this has on how recyclable the plastic is.

[@jhsevs]

I’m having real struggles finding good ways to clean (really dirty) plastic, without having to spend so much time, do you guys have any tips?

[@josephtwilley7187]

They put their stuff in a mesh bag and put it in a washer.

[@BrothersMake]

This is really the hardest part! So all plastic that we get that hasn't been cleaned already is ran through our washing machine on a cold wash inside mesh bags. This cleans 95% of the plastic - however those that are more stubborn we clean by hand. Unfortunately we haven't found a quicker solution than that to date!

[@eugenetswong]

What kind of cleaning do you need to do? Garden soil is different from solid animal fat, which is different from vegetable oil. Also, the shape of the container matters. If it is large and open, then it can be cleaned in the dish washer.

[@andrewledford3865]

You got these results, definitely because of the type of plastic you used. HDPE, LDPE, and Polypropylene will give you these type results, although the polypro will show degradation more than the High and Low density Polyethylene. If you want to show degradation as it would be in another application, use something like polycarbonate, or acrylic. Those acrystaline plastics show degrade through heat quicker than an amorphous compound like PP or HDPE.

[@scarsdale7186]

Recycling isn't just reusing the same plastic, it's blending the old plastic with new at about 30-50% mixture, that reduces any degradation the plastic or any other recycled material that is used. Doing it at home really isn't practical however, too much equipment is needed. A grinder, a heated mixer with an extruder screw, and a cutter to cut short, grind-able pieces (or pellets, since you are injection molding), and a filament extruder for FMD printers if that's what your using. (like myself)

[@andymanaus1077]

Hi guys! Thanks for another great video. I'd like to put forward an idea for another video on this topic. There is a major factor which you didn't address in this video which could affect the ability the recycling of plastics: how does UV damage affect HDPE's ability to be recycled? UV degradation is a major cause of microplastics in the environment but of particular interest to us here, is that UV damage might also be a significant problem in the recycling industry. I wonder if you guys would like to expose some granulated HDPE to a controlled ultraviolet light source for varying periods of time (days to months) before processing and testing it. Does the melting process repair the UV damage? Does mixing unexposed plastic to the UV damaged plastic improve its qualities? If UV damage is irreversible, what options for recycling are available? UV degradation might help to explain why plastics can have a limited recycling capability in real world situations and why estimates of recycling capacities vary so wildly between sources. Your results could also inform people on how to store and use their plastics to maximise their ability to be recycled and help them decide the best products to buy if they are to be exposed to direct sunlight.

[@swarlyy]

Great video. I learned something new today. I do send your videos to my students sometimes. Many of them are quite sensitive/interested in this kind of content. Keep it up.

[@BrothersMake]

Ah that's great to hear - thanks for sharing!

[@freakygardener8033]

I have ALWAYS been a strong supporter for recycling. I have personally recycled aluminum drink cans for about 50 years, BUT I have to wonder about expenses, vs. final value. Even if you write off all the start off expenses, (molds and other equipment), just the cleaning, sorting, heating/injecting, I would think what you are doing would be cost prohibited! If you spend $50 to produce something only worth $15, it just can't work out. Could you please expand on some of your actual expenses? I hope this doesn't sound rude or anything, I honestly love the concept, and would like to try it out for myself!!!

[@ku8721]

1 You guys ARE the reliable source for plastic recycling!!! At l;east on a home/shop scale!!! 2 You need Need NEED to do a crossover with CNC Kitchen!!!

[@CreativeUsernameHere-r1k]

Hey, it's super cool, and maybe we could put these recyvled plastics into those bits that get used in buildings like the plastic casings for screw we use when attaching picture frames or other built in bits...

[@amandasnider2644]

The biggest factors i imagine are these: how clean the plastics are when they are remelted (zero residue whatsoever) and environmental factors like UV light and freezing temperatures. Some plastics become brittle when repeatedly frozen.

[@matthias7534]

Amazing video! So basically the big plastic companies don't want you to know that plastic can be infinitely recycled. They don't want you to attempt to do it yourself, because they would lose profits. I can't say it's unexpected of them 🤣

[@jedih8526]

Okay, bit of a question. Why did you sort all the plastic into their colours, just to then immediately throw it all in the same machine and shred it into one big pile?

[@cufsedfox98]

0:58 This is why I feel manufacturing company's miss the point. They use old plastic to make new plastic but when it gets too thin they inject new "stronger" plastic to keep it going. As plastic gets recycled I believe more and more micro plastics start peeling off or dissolve into whatever we use. It's not a good solution but go back to the big and durable washable straws.1:48 plus the shredding and melt? Process reminds me of Crayola creation. Making your own crayons.

[@johnbradford9235]

Bloody love you guys 😊😊😊 !!! Thank you for sharing the experiment with us and the learning 🙏🙏🙏. 😎

[@BrothersMake]

Thanks John! 🙌🏼♻️

[@essmene]

Treating a Thermoplast (a polymer formable under heat - a subset of all polymers) like Aluminium or steel (a metal) might not get the full scope of recycling plastic. In the same manner you could say that glass recycling does not work - just by throwing in a bit of stonework, car and window glas. Glass bottle recycling is very dependant on the glass sorting prior to remelting. In a similar fashion there are recycling processins that break down polymers in their monomers, purify them and then create new polymers that are just as strong. If you promote downcycling - e.g. by mixing many different thermopasts - you can get some material, but the mix does not have something in common with the original material.

[@Briflyguy87]

this trial has provided tremendous amount of info for me. thank you

[@michaelhenderson9399]

I would love to see a video where you test each generation to the point of failure. Great video. Made me subscribe.

[@SianaGearz]

Someone tried to teach me that ABS is "infinitely recyclable" while i have first hand experience that keeping it for half an hour to an hour in a molten state absolutely murders it, it becomes discoloured and brittle enough to crimble in your hand. You definitely need to keep supplying virgin material to that. Of course every polymer has a different degree of thermal stability and i expect HDPE to actually be the most stable of the things you can handle at humane temperatures. PVC the least and ABS the second to least. Then there's a lot in between with many fairly stable ones.

[@BrothersMake]

For sure - they will certainly all have different variables. That's why we're surprised when so much research groups all plastics together. But we're very keen to try out different ones. We don't really work with ABS, but are keen to try PP, LDPE and PLA.

[@chainsawz5618]

my first thoughts about this was that just shredding and reheating isn't exactly "recycling" it's just reprocessing, it's not been made into an actual product to then be recycled it's just been heated and cooled, then heated again, functionally these are all really just slightly longer melted plastics being compared, not recycled

[@thibaud1330]

I think the biggest problem with recycling plastic is how it behaves chemically when used to store sensitive stuff such as food or cleaning products, which may in turn make it less recyclable if it starts leeching chemicals in the thing it is supposed to contains This is also the reason why although more than 50% of the water present on earth predates our solar system we still have expiry dates on plastic water bottles.

[@kskollections2142]

Totally fascinating! Y’all are total legends!

[@BrothersMake]

Far too kind, thank you!

[@JoelReid]

Commercially they need very specific parameters to ensure quality and compatibility with their machines. The values online and in research are likely based upon the commercial mass manufacturing situation with high QA parameters. For example. A scientific study, for example, may be looking for how many times before the parameters change by 0.05%, which would usually be the basis for QA testing, which likely would be about 3-10 times. Obviously for a plant pot made in your situation for a casual consumer, it wouldnt be a problem.

[@DrWakey]

Amazing! Now i am really hyped to see how different kinds of plastics perform! How about PET next?

[@AndrewHelgeCox]

The short cycle time meant the material stayed dry between heating. Leaving it to cool down and sit in humid conditions to pick up moisture from the air for a day between cycles may have caused each cycle to do more damage to the polymers.

[@OvhanDevos]

Asking if "plastic" can be recycled is like asking if "wood" can be made into plates. Yes it can, except the ones that are poisonous! Not that plastic is poisonous, but the point is, plastic is a large variety of materials. Each with different cahracteristics. And this just happens to be testing the most recyclable one. But it does not take into consideration the age of plastic that is reused. Plastic degrades over time, from use, UV, heat, etc. And once you start recycling plastic, you have no idea how old the plastic you're working with is. Has it been recycled before? How much of it is new and how much of it is old? IMO the best option is just to not use plastic period unless you absolutely need to. And then we need to find a better way of handling our plastic trash, reusing it like this isn't going to last in the long run. And many plastics cannot be reused to begin with.

[@theflashjaxx]

I have some experience in plastic injection molding using natural acetal, pellet colored abs, and pellet colored polystyrene so I will just give my thoughts. Acetal being an engineered plastic would be heavily reliant on the oils for bonding so I would assume there would be a much bigger difference between 1 to 30 times recycled. ABS has so much off gassing I have to imagine there would be something lost after all those cycles. Polystyrene on the other had can be recycled quite a bit but with some drawbacks such as splay on the surface finish which isn't acceptable in some applications, also welding of small joints becoming an issue depending on mold temperature. With pellet colored plastic you can start to see a difference in the color as it "burns" the color out with each additional heat cycle. I have never tried 30 times recycled but after 2 or 3 times recycled with styrene and abs it wasn't cost effective with our process as we only have one regrinder so it was a long job to clean out the regrinder between acetal and abs as mixing those cause toxic fumes when heated.