Depends which ABS you are asking,
Albino Blacksheep.
Anti-lock braking system
Abdomen Muscles
Association of Banks in Singapore
OR Acrylonitrile, Butadiene and Styrene.
ABS is a versatile polymer because it eliminates most of the
disadvantages found in the more common plastics like PS, PC, PU,
PE.
Only disadvantage is ABS is considerably more expensive but prices
have been falling but i guess its rising again.
The factors you need to consider for a bumper,
1) High impact resistant
2) non-deteoration
3) easily mouldability
4) heat resistant
5) strong
however you should consider that the bumpers are just a shell, most
cars will have a PS block under it to absorb impact when
collided.