The inner core can be comprised of cork, kapok, rubber or {HEAD ~ a blend} of {TAIL ~ thermoplastic polymers} and copolymers 
of
The inner core can be comprised of cork , kapok , rubber or { HEAD ~ a blend } of { TAIL ~ thermoplastic polymers } and copolymers
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH