3330318 PVOH polyvinyl alcohol 99 3330324 PVOH poly(vinyl)alcohol 3 3330323 PVOH poly-(vinyl alcohol) 3 3330322 PVOH starch-polyvinyl alcohol 2 3330319 PVOH bio-polyester-polyvinyl alcohol 1 3330320 PVOH chitosan-polyvinyl alcohol 1 3330321 PVOH properties of polyvinyl alcohol 1