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Can I densify LDPE + HDPE w/ compression machine?

This topic contains 5 replies, has 5 voices, and was last updated by  mevae 6 months ago.

Stephen Murray phtephen

Can I densify LDPE + HDPE w/ compression machine?

13/09/2018 at 23:38

Hi, new to the forum here, but really like the set up and the community vibe.

I work for a company that makes PE surfboards, the majority of our product is LDPE of various densities, however we do have a bottom layer which is HDPE, they are all heat bonded together so there are no adhesives used throughout the process. What I’m curious about is whether anybody has any experience with densifying LDPE or HDPE, I gather they don’t densifty together very well?

Right now we are focusing on repurposing our offcuts, we do have a recycling company who will take our virgin HDPE but our LDPE is too light and therefore too expensive to ship, so we think densifying it is the best idea, however if anybody knows of another method (or a company who could use it) I’d be really interested.

Ultimately what we would like to do is create recycling program whereby consumers would return our surfboards to us and we would seperate the HDPE layer from the LDPE and then densify and repurpose the output. It would be ideal if we could return it to our manufacturer and create a closed loop for our production.

I’m currently interested in building the compression machine, has anybody tried compressing LDPE or knows if it would or wouldn’t work? And if it wouldn’t why?

TLDR – Does anybody know of a densifier that works for LDPE and/or? And if I built the compression machine would it densify LDPE and/or HDPE?

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07/09/2019 at 17:21

I’m also looking for a way to compress / densify LDPE. I’m dealing with packing material instead of surf boards, but I think the problem is the same. Have you come up with any answer for this?

07/09/2019 at 18:33

I’m not sure what you mean by densify. If it is solid LDPE then its density is not that much lower then HDPE https://www.usplastic.com/knowledgebase/article.aspx?contentkey=508 . If it is in foam form then some experimentation with shred/heat/compress to get the air out, I have not tried this. It may take somewhat higher temperatures to get the viscosity down. Maybe search the forum on recycling foam (there was some Styrofoam activity). It may need the extrusion process to really work the material.
Good question, sorry, not much help.

29/10/2019 at 18:16

Yes, densifiers exist for foam, textiles, and other too light materials. It is not actually densifying the matter (plastics like HD/LDPE are incompressible outside of chemical re-polymerization), but more compacting and clustering it into a sort of plastic nuggets heavier than a flake. you can look at what is generally called cutter-compactor machine.

30/10/2019 at 00:11

Thanks for the replies. I’ve made enough progress in my tinkering that my initial inquiry no longer really applies to my work.  For me the answer came down to making sure the material was ground pretty fine. (Sorry I don’t have a measurement to apply to that term.) Then with heat and pressure on my mold the end product started coming out okay. Hopefully I will have time to publicize more details about my process before too long.

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