I'll see what else I can dig out... when you see some of the cracks that welded in kayaks you'd be surprised!
Here's a link
on welding PE plastic from one of the manufacturers
I know of this guy (I recognise his name from the UK kayaking and canoe forums) so trust his advice
, that and the fact he is a high level coach, but it gives you an idea as to what can be welded, and how to do it. (PE again)
With PE there are a couple of different types; there's linear PE and crosslink PE. Linear can be welded easily, crosslink, whilst intially stronger can't be welded.
Not so much easy to find stuff; the ABS is normally a layer in a material called Royalex (which has now gone out of production; it was originally used in aircraft seats)
Here's a good load of links
that might help with plastic welding... I forgot how odd canoeists and kayakers are...