What car was the first to have plastic bumpers?
Renault 5 (1971) in plastic (polyester and glass fibre)
Car bumpers are made from reaction injection molded polyurethane plastic or Thermoplastic Olefins. Polypropylene foam is usually found inside bumpers to absorb impact during a collision, while better bumper systems may have hydraulic shock absorbers as well to provide extra protection. Unless you have an old car then it is made of steel.