1 1/2 hrs is tight (doable but tight) so hopefully your flight departs JFK on time and arrive early in PVG to give you extra time. 2 hours should be the minimum if you want to feel at ease. Anyway, many domestic flights in china especially those departing from big hubs like PVG and PEK are almost always delayed. You will need to pass immigration and retrieve your luggage and check it in again. the processes itself are pretty fast, it's just a lot of repetition