He's half man and half machine so he's gotta have a living flesh still in him. But considering he didn't age as time goes by later on in the series. Is he technically immortal then?
Of course he is not immortal. Robocop's body did indeed contain a significant amount of organic material—such as his brain (although not his arm, even though they could have kept it). The unusual environment could certainly change how his organic flesh appeared to age, but the neurons making up his brain simply would not last forever. Eventually, they would succumb (perhaps to Alzheimer's Disease, if nothing else), and he would die.