Transparent HDPE for injection machines

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Transparent HDPE for injection machines

Postby japetus on Thu Apr 17, 2008 4:29 pm

I am searching for a totally transparent HD polyethylene material that can be used at an injection moulding machine... Any clues on how to search for it? Type, brand etc.. MFI is not an issue, though a high one (around 7) would be preferred..
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Re: Transparent HDPE for injection machines

Postby DwightDixon on Thu Apr 17, 2008 5:17 pm

HDPE is a semicrystaline material. That is why the density is higher than LDPE. The crystaline diffuses the light so you can not make a clear HDPE. Maybe you are thinking of Copolymer PP which can be quite clear. To be really clear you need something that is amorphous like polycarbonate. You specified HDPE. What are the properties that would make HDPE your choise for the particular application?
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Re: Transparent HDPE for injection machines

Postby japetus on Thu Apr 17, 2008 5:43 pm

No, an appropriate copolymer would be just fine.. It is just that in the products we produce we only use HDPE and in some cases PP. I haven't worked with another material so I don't know how it would behave... I need this transparent material for an advertising item that we want to produce, a [chopped] box with edges of about 4 inches on a 150tn machine.
Any advice of an appropriate glass-clear material would be greatly appreciated.
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Re: Transparent HDPE for injection machines

Postby Jim on Thu Apr 17, 2008 6:12 pm

There are a wide variety of Acrylic resins that should suit your application. Acrylic is widely used for car lenses, and other products that require good clarity. Hope this helps....

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Re: Transparent HDPE for injection machines

Postby japetus on Thu Apr 17, 2008 6:25 pm

Acrylic would be ok but I would prefer a material with more elasticity and not that easy to break..
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Re: Transparent HDPE for injection machines

Postby DwightDixon on Thu Apr 17, 2008 6:43 pm

There are rubber modified acrylics that have better impact resistance. Plexaglass DR comes to mind. Polycrbonate is much more impact resistant but much higher cost. Lexan is one of the big Tradename polycarbonates. You might also consider something like Eastman PETG which is very impact resistant and moldable at 390 to 420 F. The copolymer PP would likely be the cheapest and fairly good clarity and impact resistance for a display box. Proprionate is clear and high impact at a higher price and some grades have low flex modulus. A impact grade rigid PVC might also be cost effective and have any flex modulus you want. The PVC should use stainless steel tooling.
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Re: Transparent HDPE for injection machines

Postby Jim on Thu Apr 17, 2008 8:24 pm

Dwight mentioned acrylics that are impact modified; another material that comes to mind is crystal styrene, which has excellent clarity and is reasonably impact resistant. I have molded display cases for models out of crystal styrene and have had good results. Most display cases don't get tossed around too much, so I would think that whatever material you choose, it should be the most cost effective. I would definitely not recommend polycarbonate, as it is quite expensive.

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Re: Transparent HDPE for injection machines

Postby Tom on Thu Apr 17, 2008 8:25 pm

Cellulose acetate butyrate is often used in this type of application. Not sure if it can be injected in thin walls. A lot of the time it is thermoformed.
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Re: Transparent HDPE for injection machines

Postby japetus on Fri Apr 18, 2008 3:45 am

Thank you all! Although the container to be produced is not a display case, I think I'll try to find an appropriate copolymer PP to run a test production.
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Re: Transparent HDPE for injection machines

Postby Underdog on Fri Apr 18, 2008 10:00 am

Basell Metacene random coPP will do the job for you. It isnt quite water clear but very close. Then of course there is always PET which is tough as nails and water clear. There is even clarified ABS out there.

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Re: Transparent HDPE for injection machines

Postby rickbatey on Fri Apr 18, 2008 3:08 pm

SAN could be used, clear ABS, but crystal PS is easy to mold and inexpensive. Milliken makes an excellent clarifying agent for PP also. Rick.
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