I am researching polymers used in making Ballistic Vests and Zylon, Poly(p-phenylene-2,6-benzobisoxazole), is one of the polymers chosen. Basic Information/ Structure: http://www.matweb.com/search/datasheet.aspx?matguid=140045b4f06c4aea89f8900f4c7bb4fc&ckck=1" http://www.toyobo.co.jp/e/seihin/kc/pbo/gif/structure.jpg PBO is a thermosetting polymers however I cannot figure out how it can form cross-links or hydrogen bonds which make polymers thermosetting. So I was wondering how it forms crosslinks to make it a thermosetting polymer. And I also was wondering why it has such good flame retardancy, high limiting oxygen index and high decomposition temperature (650 C). I know that the oxygen and nitrogen in the oxazoline are partially negative which can act as hydrogen bonds acceptor but there are no positive hydrogen from what I can tell. I thought maybe the compound structure could change to form crosslinks or hydrogen bonds when heat treated but couldn't find information. Thank you.