I am trying to select a LDPE for the production of an irrigation tube 12mm OD 10.4mm ID through pipe extrusion. I have no experience in selecting polymers. The manufacturer wants the tube to be ldpe.

I am looking for some general guidelines to determine an ldpe as I don't currently know specifics of the extrusion line (such as pump size or dimensions of the screw). Because of the lack of information I have about the process I have been trying to select a polymer for testing based mostly on the melt flow. I know for extrusion melt flows are usually near or lower than 1, but I've also been told that for LDPE I should use a melt flow of near 2.

Some of the information I do have is that during the initial test phase the line will be running much slower than production speeds so the screw RPM will be low and residence times will be longer.

I tried to be descriptive as possible but since I don't have all the necessary information I don't need a specific polymer just some basic guidance. Any help would be appreciated.

Thanks

It seems you're on the right track. Extrusion does use polymers with MFI of less than 1. It should be fine to run your line slower as PE is resistant to thermal degradation. If for some reason it does degrade just as a touch more antioxidant, e.g. Irganox B225 or similar.

Chris DeArmitt
Plastic Training Webinars since 2003
visit: www.plastictraining.com

I would seek advice from the guy who runs the extrusion plant and your raw material supplier about specific grades, but an MFI of about 1 sounds correct. It may vary a little or even take some minor experimentation to fine tune, depending on your equipment and finished product requirements.

Regards
Pat
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