polyether vs polyethylene

polyether

noun
  • a polymer, such as an elastomer, in which carbon atoms of the repeating units are joined by a single oxygen atom 

polyethylene

noun
  • A polymer consisting of many ethylene monomers bonded together; used for kitchenware, containers etc. 

How often have the words polyether and polyethylene occurred in a corpus of books? (source: Google Ngram Viewer )