While almost any diisocyanate may be used, TDI and {HEAD ~ MDI} are preferred because of {TAIL ~ their low cost} 
preferred because of
While almost any diisocyanate may be used , TDI and { HEAD ~ MDI } are preferred because of { TAIL ~ their low cost }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL