In principle there are two ways to find differentiate between ABS and PLA. Here you should be careful. The experiment is subject to your responsibility:
– Use a lighter to burn parts of your filament. But be careful! ABS filament burns very quickly, while it emits black smoke and strong smells of plastic. PLA can difficult to ignite, it produces less smoke and smells more sweetly.
– Immerse your filament in boiling water, with ABS no change will occur whereas PLA filament behaves like a spaghetti and loses its shape after a short time in hot water.