Working with recycled HDPE

This is just draft stuff – sort of so I might remember things I did.  Needs actual rewrite, pictures, more meat.  But at least I have a place to capture some efforts.

It really seems like scrap HDPE – like from milkbottles – should be a wonderful source of material for making stuff – if I could figure out how to work with it.

Some time ago I tried to melt sheets of HDPE from milk bottles into a sheet maybe 6″ square.  A few layers between sheets of silicone parchment on a cookie sheet with a flat piece of metal on top and an anvil to smush it in the over at what – 250? – for half an hour or something.  Results were poor – lots  of voids, poor adhesion.  Needs more pressure (force/in²) to stick.  Or maybe more active smushing/working.  I really thought I took pics of that, too, but can’t find.  Or maybe I just planned to take them.  I’ve seen several videos of people making flat stock from scrap, but most cut it up really fine before melting.  Seems like a lot of work.

Inspired by maybe a youtube of an Indian kid repairing plastic buckets on the street with a torch, scrap plastic and screen?paper clips?, I thought I should try some repairs.  Other videos showed others doing HDPE repairs, like on canoes and water tanks using similar methods.  There’s some skill to it that will come with exposure and familiarity with the materials.

Did a repair of a broken Rubbermaid laundry basket handle with hot air station.  Came out OK.  Some hardware cloth for reinforcement one place, wire in another.  Used milk bottle plastic for welding rod.  Not ideal – seems to have higher working temp and less soft than original.  It was easy to melt thru original, and when I did it was almost liquid.  The Milk Bottle HDPE (MBH) didn’t get that soft.  Made a smoothing tool and a poking tool – both quite useful.  I think cooling/wetting the smoother in water helped.  Thought I took pics, but can’t find.

Did a second almost identical repair with almost identical results.  Again used sheet patches of MBH over the very rough top of the handle.  Made it considerably smoother.  Took several minutes with a new Xacto knife to make it feel fairly nice.  Sanding would have made it smoother more easily, but not left a polished surface.  Maybe I could have flame polished it afterwards?  Meaning hot air probably rather than flame – but should try it with a torch as well.  If that worked, it would be faster and better.

Still looking for softer welding rod, I tried strips of plastic grocery bags.  Finally made a strip maybe 1″ wide, twisted quite tightly, then sort of fused while twisted with hot air.  Didn’t make nearly as nice a rod as I hoped – didn’t stick together well.  Anyway, it didn’t melt any better than the MBH, so nice try but no cigar.  I have an old dish drainer I should try to use for scrap.

I’d really like some softer stuff for welding rods, especially for those laundry baskets.  Maybe Rubbermaid stuff from Goodwill?

I’m considering fusing some MBH together for a bottom bracket for the 1/2″ PVC AA battery trickle charger tube.  Shapelock would work fine, but it’s infinitely more expensive than free MBH.  Actually, what I’m thinking of is using MBH sort of like Shapelock but at higher and harder to manage temps.  Yeah, I could make the whole bracket from wire, but plastic would be nicer.  Maybe just acrylic.  Or maybe shut up Jim, and work on what you’re supposed to be doing.

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3 Responses to Working with recycled HDPE

  1. Jim Harvey says:

    You need a spokeshave.

  2. roy says:

    I have had some success with HDPE milk jugs; I use hot air gun (paint remover) to melt the milk jug; not enough strength to melt it all, but what I do is melt the plastic and pack form the hot clear plastic into a metal rectangular C channel and compress each layer with a cold thin brick, the cool surface does not stick to the plastic, a hot surface wants to bond to the plastic. After letting the newly formed plastic bar cool overnight, it is solid with little air voids. I work with it like wood and wood tools. I square it with a table saw, cut with a miter saw and create clean sharp edges for hand made tools or products. Sanding in OK, but too much pressure will melt the plastic.

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