Simplify the following text for a Grade 8 native English-speaking person.
Original: A polyurethane ( IUPAC abbreviation PUR , but commonly abbreviated PU ) is any polymer consisting of a chain of organic units joined by urethane ( carbamate ) links .
Simplified: Its name is oftened shoredened to PU or PUR . Polyurethane is made of organic units , which are joined by urethane .