How to Upcycle or Recycle HDPE?

My bad.

I should have defined the problem better.

If I had said something unambiguous like "I want to cold form ..." that clarity would have helped.

Cool video, though.

Without thermal input, you are basically stuck with "plastic deformation" or "shredding".

If you are into hydroponics, then if shredded into adequately small/large particles it would be an OK inert media for nutrient film or maybe trickle provided the particles didn't pack too well but probably not "flood and drain" due to the density being so close to the nutrient solution.

Properly used, a gallon jug as the container would easily manage a single bean plant and potentially produce around 2 pounds of bean for each plant replacement at something less than 10 weeks. Too small for zucchini or normal tomato. Could manage a single corn plant (100 days to get 2 cobs), a single lettuce (5 weeks), 9 carrots (10 weeks), 16 radish (6 weeks) and so on.

Look up "square foot gardening" for the planting methods and some basic hydroponics for the nutrient. Simply thoroughly rinse the media after each crop to eliminate the accumulated salts.

You uses thermal or you ends up with confetti. Got it.

Dang.

Thanks for saving me a drive past the sign that said "Dead End."

If you want to make something YOU can use, you already have heat as ovens. HDPE melts at around 220 F, sticks to itself and is formable at 350 or more, is commercially processed around 400. At these temps, not much pressure is needed. Many areas have city collection of recyclables, and commercial recycling of this plastic (#1) is well developed -- see Trex plastic lumber at most any hardware store, can be used in irrigation pipe, mulch film and more.

Forget solvents for HDPE. They are expensive, dangerous, may need heating.

The environmental benefit of recycling depends on what you're measuring, and if it's energy, you have to use less to collect and recycle than needed to make new. That isn't always the case. But it doesn't matter in real world, as people are so pro-recycling that it is always seen as good. The recyclers hate the pro-degradables as what makes plastics degradable may also weaken and devalue the recycle. It doesn't disappear instantly either, as degradation is a chemical reaction, and we may not want degrading products around.

Any more would be off-topic so I stop here.

Definitely an easy upcycle project in the home.

First, you have to clean the HDPE and remove labels, caps, etc.

Then you need to cut or shred your HDPE pieces into smaller bits for ease, and so on. You can heat HDPE, to soften, without fully melting the plastic.

I see the example of Legacy HDPE (https://legacyhdpe.com/the-temperature-limits-of-hdpe-material/), they do HDPE sheets, pipes and even boats, They said HDPE will not develop significant flow until heated to 80 °C (176 °F) after which it can be molded or reshaped.

Once the HDPE pieces are soft, you can press them into molds, and then cool them back down.

They can be formed into coasters, trays, or other simple parts, and it is better to let them cool slowly so they do not warp when cooling.

People are also mixing it with natural fibers, composites, and other strong recycled materials.

But yeah, HDPE is a great way to recycle regular household plastics!