#butylene__butene  any of three isomeric hydrocarbons C4H8; all used in making synthetic rubbers
  supertype:  #gas  a fluid in the gaseous state having neither independent shape nor volume and being able to expand indefinitely
  subtype:  #isobutylene  used also in making gasoline components
  subtype:  #polybutylene__polybutene  a polymer of butylene; used in lubricants and synthetic rubber

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