I just discovered the Ngram Viewer in Google Books and am having some fun with it. The Viewer creates graphs of the use percentage of a word over time in the books of the Google Books collection. As you might expect, words like "thee", "thy" and "thine" are dying out:
Strangely, "plastic" seems to have peaked:
and it's even worse for "polyethylene" and "polythene":
and worst yet for "rubber":
I have no idea why this would be occurring. It's not as if plastics are losing their place in society, even if many now view them with contempt. I do realize that these are percentages and not actual word counts, so maybe the answer is that more and more books are written that are without these words. But even that is hard to imagine since "plastic" in particular has taken on additional meanings that it never had before. Maybe the answer is in this plot:
If "plastic" is being used less, another word must be being used instead, and it looks like "resin" might be it. It's use is also dropping, but not at the same rate as "plastic". So is "resin" the new "plastic"?