I've never tried welding PE or PP with hot air. The supplier who sold me the plastic sheets said it was best to use nitrogen on the polypropylene sheets I purchased from them. The only plastic material I've ever welded using hot air was PVC.
When using hot air to weld PVC it's easy to scorch the plastic if you're not careful. This problem is greatly reduced or eliminated when using nitrogen since the gas displaces any oxygen in the weld zone. I only use hot air welding for minor PVC repairs otherwise I use nitrogen for all plastic welding.
I put a micro switch on the torch holder so when the torch is laying on the holder it switches a valve that idles the torch on compressed air. When the torch is lifted from the holder the valve switches over to nitrogen. Air or gas must flow when the heating element is powered up or it will burn out. I learned that the hard (and expensive) way. Always have a spare heating element on hand!
--- In Homebrew_PCBs@yahoogroups.com, Simao Cardoso <simaocardoso@...> wrote:
>
> twb8899 wrote:
> >
> > The easiest tanks to fabricate were those made from PVC since it can
> > be welded using a hot air welder.
> > When welding PE and PP I always use nitrogen as the welding gas.
>
> I was strongly advised towards PVC because the easier welding. I am
> reconsidering PE because the price only. And since it as superior specs
> for the application...
>
> According to your description I may probably end with solder burns or
> poor joint by welding PE with an hot air welder?
>
> My little experience was a few ABS and PP repairs in vehicle plastics,
> never with PVC or PE.
>
> Thanks,
> Simao
>