Guys,

I've got a chance of some cheap garden chairs, but one of them has a crack in the corner of the seat base and would not be useable without a repair. They're marked "LDPE" and are thus low density polyethylene. Some googling suggests it won't be easy to plastic weld and the material also seems a bit thin to attempt this. There is however excellent access to the backside of the crack (err.... ;-)).

So; two questions:

1) What would my chances of achieving a solid and lasting repair be if I stuck a bit of fibreglass to it?

2) Is there another way to sort this out?

Thanks!

Would it be possible to wrap the crack in fibreglass? I imagine if you can get a decent bond to the plastic you'd be fine.

As far as I know, LDPE should be weldable in the same way that we do MDPE and HDPE on pipework installations in work. You can even get LDPE welding rods...
Linky
I could be wrong though but it may be worth having a go before you try the fibreglass wrap repair.

I love polyurethane adhesive
I have repaired cracked pots with it and roof flashings.
Try bonding some mesh underneath the crack

Drill a hole at the end of the crack as as crack arrestor no matter what repair method you choose.

soldering iron to melt the bits together...