Plastic is cheap, durable and endlessly shaped, so it is read as convenience, artifice and something that lasts longer than it should. Dream books also link it to feeling fake or out of touch with what is natural.
When this appeared in your dream, what were you feeling?
My Cosmic Code has a private dream journal. Write a dream down and the app picks out the symbols in it, shows what dream books say about them and, over time, which words recur across your entries. The journal is stored on your device only.