Compression guidlines for compressing LDPE

So using a 100% MacGyver’d wood block compression mold (8″x4″x3″) and c-clamps, I got a block of compressed thermoset after melting some LDPE (melted at 250-270F, no fumes for those concerned) and cranking around on the mold.

A friend is making some steel brick molds and I’m looking into a legit press- possibly hydraulic (any suggestions for NOT the most expensive, will-fit-in-my-workspace, type presses are appreciated). No idea what the molds look like yet and unsure if they will have a overflow well or whatnot.

Question is- what level of compression (PSI?) should I be aiming for to get this LDPE as dense and hard as possible… without breaking anything? I have no idea what sort of pressure I was getting with the C-clamps… as I was unable to measure hahaha.

Also- anyone in Dallas have connects with UTA? I keep hearing about some professor that has been playing with recyclables and I’d like to network with people in the area. Thanks guys! Happy Mad Scientist Monday!!


hi… I love your creations… what happened?

this thread has some of the better compression specs that I’ve come across on here.  He was working in bars – converted to psi there was still a huge range of what’s considered ‘enough pressure’.  We landed somewhere around 5 psi spec, but then when we got to building our little press, I just grabbed a few automotive bottle jacks.  You can get a 20 ton bottle jack (massive pressure) for less than $50.
I’m looking to move towards pressing blocks from dirty agricultural LDPE “mulch” films…  will be following your progress for sure, and will post when we’ve got something to share!  good luck!