anyone know how to differentiate plastics?

TrueBlueGT

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I have a hairline split in a fuel tank on a tractor. It is a two piece 300 gallon total capacity tank. The split is in the left side saddle tank and it needs repaired. A replacement saddle tank is $1400 through John Deere not counting labor. I got a plastic welder after several tank repair putty attempts failed. The manual with the plastic welder is decent and I've determined this tank is either polyethylene or polypropylene but I don't know which. The repair requires a different rod for the two types of plastic but I don't know how to determine which I have. Anybody know anything about this stuff?
Thanks,
TBGT
 

Teethy

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EDIT: It may be HDPE, or High Density Polyethylene which is a common material for automotive gas tanks.
 
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oldmodman

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65x2

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Like oldmodman said, it should have a designation somewhere on it.

They also make a uni-weld rod that you can use in the instance you can't distinguish. But I've never had much luck with it.

Have you read through the instructions with your welder? Some will tell you if plastic starts smoking or turns X color then the wrong heat/rod choice was made.

You can always try and if it adheres, then you made the right choice, if it pulls back away, then you're up for round 2.
 

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