Alright, so, the "soft" plastic bottles of a reo are generally speaking either HDPE or LDPE depending on manufacturer and the like these are extremely chemically stable, and mildly heat stable (they tend to have a low enough melting point that you can create your own molds for these plastics). So, basically not much to worry about in terms of "cracking."
Polycarbonate however, while is heat stable and tends to be mostly chemically stable, it's attacked by acid and certain other chemicals. The easiest thing to tell with Polycarbonate is that they are /clear/ and rigid.
There are other rigid plastics that are more chemically stable, but they generally less optically clear.