... "DO NOT use Oxiclean on plastic."
Not something I've heard of either, but I use "generic" (unbranded) Sodium Percarbonate so it won't have such warnings.
I imagine it's a warning for the general public? We (as brewers) generally use only
"thermoplastics" "softer" plastic, e.g. PVC pipes, will not "glue" together, which would be unaffected. There is also
"thermo-setting" "harder" plastics, e.g. ABS pipes, are "glued" together, plastics that could perhaps be damaged? When dealing with the "general public" you don't recite such "complicated" differences, just say "plastic" and let people think "all plastic".
Here's an illustration! The UK discourages oil based paints (because of environmentally damaging fumes). So, paints are usually water-based containing PVA plastic. Water-based paint is a pain in the bum 'cos you can't easily strip it with the paint strippers we're used to. I wash my brewing kit upstairs (including plastic), using an "oxy" cleaner (Sodium Percarbonate), run up-and-down stairs with wet hands (wet with "oxy" cleaner), and ...
... paint-stripper!
The handrail fittings are factory-painted in oil-based/"enamel" paints. And totally resistant.
Conclusion: Don't worry about "oxy" cleaners damaging your plastic bucket!
Oxiclean free (unscented version) is just sodium percarbonate and sodium carbonate plus a surfactant and inert polymer. PBW contains sodium percarbonate, sodium carbonate, sodium metasilicate, sodium bicarbonate, tetrasodium pyrophosphate, and possibly a surfactant. ...
There go ... for the worried PBW users. Sodium Metasilicate is a powerful degreaser BTW, that is used instead of the environmentally disasterous Trisodium Phosphate ... but
Tetrasodium Pyrophosphate!!!!!
Okay? It's for something different and perhaps isn't Trisodium Phosphate on steroids! Still, it doesn't half make "Trisodium Phosphate" sound a bit pathetic.
Interesting (?) side fact (brewing related ... roughly!) that I came across very recently: "Phosphate" and "Silicate" (think "sand") seem worlds apart? I didn't even think "silicate" could be soluble. But they are both anions that contribute
Alkalinity! ("Carbonate/Bicarbonate" is just the commonest by far). Perhaps everyone here knows and I'm showing my ignorance? Just an "interesting" fact to share ... I do NOT recommend using "water glass" or toothpaste to adjust alkalinity in your mash!
[EDIT: Another "side-fact": Don't clean you "Tilt" hydrometer in "oxy" type cleaner. Or most other floaty hydrometer thingies. The "oxy" can damage the shell. Except for RAPT "Pills", and they gloat that their hydrometer is made of better stuff (they're just not as good for other reasons
)]