{HEAD ~ Such systems} typically also include {TAIL ~ a quasi prepolymer} of an isocyanate and an active hydrogen containing material, and at least one amine resin, and preferably an amine terminated chain extender 
typically include
{ HEAD ~ Such systems } typically also include { TAIL ~ a quasi prepolymer } of an isocyanate and an active hydrogen containing material , and at least one amine resin , and preferably an amine terminated chain extender
HEAD HEAD HEAD HEAD HEAD HEAD REL OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH