No, they are actually very different.

Bipolar is a mood disorder. It CAN be triggered, but I don't think our triggers are usually as instanteous.

Like, at least for me... let's use stress for an example. Let's say I have one stressed out part of my day - say I missed the train and was running late. I'll be stressed out, but it'll pass and even then I'll likely still be fine in my actions and thoughts. Someone with BPD will likely have an episode right then and there.

Now, if I was to keep missing that train and keep being stressed out by it, it might trigger an episode. But that's only a might - it might not.

I can have episodes settle in without anything at all to really cause them. They can in fact be triggerless. Like... I've woken up various days and NOTHING in my life has changed.. and I'll be feeling on top of the world because I've just entered into an up phase. That doesn't really happen in BPD, because there would have to be a trigger.

Someone who has both bipolar and BPD have a pretty tough mix - they might be in a manic phase from the bipolar, but then still get triggered by mising that train and then have a depressive (or a mixed episode), right then and there for a few minutes and then go right back into the manic state.