Introduction: Recycle Plastic Into Giant Lego

Picture of Recycle Plastic Into Giant Lego

Hello, and welcome to my instructable about plastic recycling. This project is the result of a course I studied at university called "Architectural Technology Research". The brief was to investigate any part of architectural technology that interested you and produce a research document. I chose to look at citizen lead plastic recycling and how it might empower self builders, particularly in countries where low-cost housing is required and there is widespread poverty.

The process is inspired by a really amazing design studio called Studio Swine and in particular their project Sea Chair. In this project plastic is recovered from the sea, melted and moulded into simple pieces that are assembled to make a beautiful piece of furniture whilst raising the issue of marine pollution. Sea Chair is an open source project, the information required to replicate the project is freely available, from how to build your own furnace safely to the sizing of the mould pieces to make the stool.

I decided to take their method and apply it to my own project. This project was very much an experiment into the possibility of whether citizen lead plastic recycling is viable in developing countries where perhaps recycling is not yet a priority. My project was also influenced by the work of Conceptos Plásticos, a company in Columbia currently building low-cost housing, from waste plastic, for those most in need.

I thought I would share the results not necessarily so that someone might recreate this project like for like. If you are wanting to make enough giant lego from recycled plastic to make anything think again! It is intended more as reference material, to share my research into the behaviour and scope of the material.

Step 1: The Mould: Design

Picture of The Mould: Design

To begin with I thought about how I would shape the molten plastic into a brick shape. I also of course had to think about the shape of the brick, the Lego shape was preferable in the context of the research project since it enables quick and easy assembly without the need of mortar.

The mould I designed is a simple press that comes apart to allow the brick, once cooled, to be freed. It was also intended that no specialist equipment or materials were used in the process to enable it to be replicated regardless of location.

The brick's dimensions match that of a standard British brick: 65 x 102.5 x 215 mm

Step 2: The Mould: Fabrication

Picture of The Mould: Fabrication

The tools I used in the fabrication of the mould:

  • Donkey saw
  • Pillar drill
  • Drill bit 6mmØ
  • Hole saw 50mmØCu
  • MIG welder
  • Panel saw
  • Metal Guillotine

The material used in the fabrication of the mould:

  • 2.4m of 20 x 20mm steel square section
  • 220 x 300mm of 18mm plywood
  • 400mm x 300mm of 2mm thick steel plate
  • 200mm of 20 x 20mm steel L profile
  • 100mm of 50mmØ steel pipe
  • M6 nuts and bolts
  • Black spray paint
  • Red spray paint

Step 3: The Furnace

Picture of The Furnace

The furnace I used was based on the Studio Swine method. It is simply a large cooking pan with a tin filled with charcoal bolted to the lid. Holes are drilled through the tin and the lid to allow the noxious fumes to pass up through the charcoal, this works as a basic filter. A hole is also drilled in the lid for a thermometer to be placed. The furnace should then be wrapped in fibre glass insulation and a layer of aluminium foil.

Step 4: Collect Your Material

Picture of Collect Your Material

To make just one brick I collected a lot of plastic, 1.3kg of clean recyclable plastic chopped up into 1 x 1 cm squares. It is important to use particular plastic types, not all are suitable for this process. I collected High Density Polyethylene (HDPE #2) and Polypropylene (PP #5). The reason for this is their lower melting point of around 130ºC. This makes it a little safer and easier.

I collected the vast majority of what I melted at home and it took about 3 weeks to collect what I needed. I also put a bag in my communal stairwell with a sign asking for my neighbours plastic.

The Sea Chair project appeals for people to go out to the beach and collect plastic that has been washed up. Whilst I like the sentiment it would take an incredible amount of time to collect 1.3kg, also it would be difficult to identify which plastic types were collected.

Step 5: Melt Your Plastic

Picture of Melt Your Plastic

***Important!***

Melting plastic is potentially very dangerous. You are dealing with high temperatures and nasty fumes. If molten plastic gets onto your skin it will be very painful and difficult to get off. Make sure to cover all skin, wear safety goggles and a respirator. Also it is essential to do this outside. I went to the beach.

The process is pretty self explanatory. Heat the plastic pieces over a camping stove until you reach 130ºC, be careful not to burn the plastic an occasional stir should help with this.

I imagined the plastic would flow a bit when heated to melting point but I found it to be more the consistency of dough (perhaps I should have heated it to a higher temperature) As such I had to scoop the plastic out of the pan and into the mould.

Once the mould was filled I clamped it shut and pushed more plastic in through the top and pressed it in with the handle. This all has to be done very quickly, before the plastic cools.

Step 6: Results

Picture of Results

Once the plastic has cooled you should be able to remove the brick from the mould. Easier said than done! It took considerable force to remove the brick and I actually had to cut the mould apart to release it.

I am pretty pleased with the result though. The brick is very tough and I like the aesthetic of the swirling plastic colours, although not sure I would want a whole house built from these bricks!

The conclusion of my project was that it would in fact not be a suitable process at a citizen level, this kind of recycling needs to be done at scale because of the quantities of plastic needed.

I really enjoyed the project and I think recycling your own plastic waste is something that can work, just not for building giant lego bricks. Precious Plastic is a dutch designer who has built a series of open source machines that enable home recycling and the results are amazing, the machines however require serious metal working skills and quite a bit of money to build.

I hope you have found this instructable to be interesting. If you have any questions please leave a comment. Happy making!

Comments

Boingo (author)2017-04-21

Please try again. I am certain you will have more success the next time.

Watch this video:

I suspect it will be useful to you in coming up with your next design.

You said:
"I imagined the plastic would flow a bit when heated to melting point but
I found it to be more the consistency of dough (perhaps I should have
heated it to a higher temperature) As such I had to scoop the plastic
out of the pan and into the mould."

I must inform you that HDPE used in bottles and jugs remains in a putty like consistancy, even at higher temperatures, due to the fact they are blow molded. A blow molding machine produces a continuous hollow sleeve of plastic that is then pinched between two halves of a mold and inflated to produce the final part. To keep the sleeve from falling apart under its own weight as the machine produces it, the HDPE contains additives to make it more viscous.

On the contrary, HDPE used in injection molded items, such as bottle caps or plastic buckets contain additives to make it more plastic and easier to push into molds, giving it a more runny consistancy, like syrup, when heated.

A higher temperature (190ºC) and a longer melt time may help (Beware! The HDPE will have a tendancy to scorch if left uncovered.). Higher pressure compressing the plastic inside the mold should also make it conform more closely to the shape of the mold.

I encourage you to continue with your experiments. Creating low cost housing material from waste plastic is a worthy endevour to pursue.

Here is a video of a plant in Ukraine that is producing roof tiles by mixing waste plastic with sand that you might find useful:

And a video of another plant, also producing roof tiles, in Uganda:

Good luck!

rogernewman10 (author)2017-02-04

this is interesting Hen. A few thoughts:

- if one did want to make these on a commercial scale, one would need a name for them; can't use Lego due to copyright. So, Jaki and I have a couple of suggestions for you, and the world, to share: PLOCKS (plastic blocks), IntraBlocks (it's what's inside that matters) or IntraPlocks of course...

- did you use any kind of release agent in your mould? Such a shame you had to cut the mould apart.

- what rating of MIG welder did you use for this? One you can plug into 240v 13A supply? Quite tempted, but don't tell Jaki!

- we have a donkey saw at school (didn't know it was called that!) but not sure it has the 45degree mitre vice; will have to check. Does yours look like it came with it or is it a custom addition?

- if you had made 3 you would have been able to test their inter-connectivity, which would have been great to see.

- in terms of actually building with them, it would be drafty without some kind of mortar. But George did a uni project of heating pieces of plastic (HIPS possibly) with an ironing iron, under greaseproof paper and that made thin flat sheets which could be an inner or outer membrane layer...?

Good stuff Hen, thanks for sharing. Roger

Hi Roger, thanks for the comment. In answer to your questions:

- I hadn't really thought of what I would call them, I like plocks though; better than putting the words plastic and bricks together!

- I didn't use any release agent, I guess that is where I went wrong. I still have all the mould pieces and could weld them back together.

- I don't remember the rating of the welder at uni, I'm pretty sure though that it takes a 110v supply, most stuff in their workshop does. My one at home is a 240v job though. It is a Clarke 90:

https://www.machinemart.co.uk/p/pro-90-mig-welder/...

Got it second hand for £100 off Gumtree.

- I believe the donkey saw has been customised to achieve a 45º angle yes. Will take a picture when I'm next in of how it was done.

- I really wish I had made the brick 3 times smaller and made three, I had to collect soooo much plastic to make just the one large brick. I had originally intended to have the brick tested in the engineering department against a conventional brick so I thought for a fair test I should make the plastic one the same size.

- Conceptos Plásticos have a very successful plastic brick system (http://i1.wp.com/ecoinventos.com/wp-content/uploads/2016/06/Conceptos-plasticos.jpg?resize=960%2C960) which is so precisely engineered the draft issue would not be a problem. Their extruded profile also has an overlapping joint which would prevent this. In my research I also found other projects where an adobe skin was applied to plastic brick walls. This is a good fire retardant too and would eliminate drafts. What did George use his thin HIPS for?

I hope that answers your questions. Looking forward to your debut instructable!

Henri.Lacoste (author)2017-02-04

Hi Roger, thanks for the comment. In answer to your questions:

- I hadn't really thought of what I would call them, I like plocks though; better than putting the words plastic and bricks together!

- I didn't use any release agent, I guess that is where I went wrong. I still have all the mould pieces and could weld them back together.

- I don't remember the rating of the welder at uni, I'm pretty sure though that it takes a 110v supply, most stuff in their workshop does. My one at home is a 240v job though. It is a Clarke 90:

https://www.machinemart.co.uk/p/pro-90-mig-welder/...

Got it second hand for £100 off Gumtree.

- I believe the donkey saw has been customised to achieve a 45º angle yes. Will take a picture when I'm next in of how it was done.

- I really wish I had made the brick 3 times smaller and made three, I had to collect soooo much plastic to make just the one large brick. I had originally intended to have the brick tested in the engineering department against a conventional brick so I thought for a fair test I should make the plastic one the same size.

- Conceptos Plásticos have a very successful plastic brick system (see attached image) which is so precisely engineered the draft issue would not be a problem. Their extruded profile also has an overlapping joint which would prevent this. In my research I also found other projects where an adobe skin was applied to plastic brick walls. This is a good fire retardant too and would eliminate drafts. What did George use his thin HIPS for?

I hope that answers your questions. Looking forward to your debut instructable!

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Bio: Hey! I'm Henri and I love making things. I'm currently studying to become an architect
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