No I didn't. I said it is not glued, not that it cannot be glued, if somebody is crazy enough to do that. Even teflon can be glued is you have the right kit. Right across the street from my office was an industrial pipe supplier that had just about every plastic part you could think of in stock, including noryl pipe, micropipette tubing for medical and university R&D, teflon ball valves over $5000 apiece, chemically resistant drain pipe up to 8 ft in diameter. But heat shaping and heat welding of thick sheets of Polypropylene, like I had done, is routine, and does not involve any hazardous chemicals. Your hypothetical method of trying to chemically glue polypropylene would be far less reliable, given its significant coefficient of expansion and contraction in an application like a sink.
Torch welding, in my case in conjunction with polypropylene corner fillets, forms a single continuous mass of plastic, just like metal welding. It was done by an acquaintance who welded lead nuclear reactor core linings for a living, heavy work - his arms and neck were like tree trunks. But my 3ft by10 ft sink itself was so light that it was made in his shop, and we just hand carried it into my darkroom.
Chemically resistant hypalon roofing is done the same way, whereas liquid hypalon roofing was so damn noxious it could not be even used on a Naval ship deck within US waters - and now not at all. Prior to that, I sold it for paint-on industrial bath linings containing concentrated acids - a far more demanding application than any darkroom sink.
Oh yeah, tiny parts ... not a typical application of polypropylene. It doesn't machine well.