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I Forge Iron

HDPE handles.

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The heat would concern me for sure. Melting point is in the mid *200f but extrusion is in the *350f-*500f range. If the tool Is quenchable, then no biggie. 

The slickness from sweat is a great point. Not sure if added texture would help. Maybe a type of tape for extra grip? Tennis racket tape? 

It will be a fun experiment. I'm trying to find ways to recycle all the plastic coffee containers from work and other pieces that I see floating around on a daily.

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I used to use polyethylene for closed cell foam mats that were turned into the floor grip on jet skis at the rubber refinery. It would become malleable in the Banbury at about 180f. I don't remember if it was high density though. Just little PE balls. We added lots of chemicals to it so that may have played a part in it's plasticity also. Iirc we would dump the batch between 265f and 285f onto the mixing mill and sheet it off on a secondary mill.  It's been years though so don't pay too much attention to me. 



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I am not quite getting a notion of how you want to use the HDPE but I manufacture plastic sprockets in many plastic materials and HDPE is too brittle for that.  HDPE for those who need a comparison is what is usually used for plastic screw caps on things--as well as cutting boards.  It becomes useless at about 190 degrees F.  LDPE is what one usually sees as the body of plastic milk jugs.  UHMWPE is the next step up..and it's a big step..from a molecular weight of roughly 200,000 for HDPE vs UHMW with a molecular weight of about 6,000,000.  LDPE runs 30,000 to 50,000 in molecular weight.  UHMW is almost impossible to break;  LDPE is so soft it's mostly bendable;  HDPE is flexible but can crack, especially if it was even slightly over-heated in processing.

None can be glued effectively using normal procedures--to glue you must do a special etch of the material and use semi-specialized adhesives.  LDPE and HDPE can be plastic welded.  I've seen UHMW plastic welded but it isn't as strong as the parent material.

And there is one more issue:  Cold flow.  As an example, imagine a bar of the material spanning between supports.  Over time, that bar will sag as the molecular chains slide relative to each other.  The bow is effectively permanent and can only be removed by causing flow the opposite way.  

The stuff HATES UV light and will degrade--so this material isn't what you want for things left in sunlight.  Carbon black is usually added as a UV blocker so UV resistant material will generally be black in color.  

But it has been used and some people like it.  I wouldn't usually though--at least not without some sort of structurally stable member like a steel core to provide the actual stability.  Many commercial kitchen knives (the ones for the generic "slice and dice" staff who don't need expensive knives) use it--those are in the $ 15 range in cost as semi-disposable.

Compression molding does work for the material and is the likely choice for forming short of really expensive dies and procedures.

To put it into perspective, the whole class of plastics is just variations in lengths of chains of ethylene molecules--starting with propane and butane at the low molecular weight end, turning into paraffin wax when the chains get a little longer, and plastics when they get quite long.  If you heat an unknown plastic (burn a little such as with a hot pin) and it smells like a wax candle, it's one of the polyethylenes.

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