Thereafter, {HEAD ~ the reactor} is charged with {TAIL ~ the polymerization medium} and ingredients in the usual manner and the polymerization reaction commenced 
is charged with
Thereafter , { HEAD ~ the reactor } is charged with { TAIL ~ the polymerization medium } and ingredients in the usual manner and the polymerization reaction commenced
OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH