Arrive at PVG from United Airlines flight Chicago then to a Vietnam Airlines flight to Hanoi.

Since these airlines are not allied, I will have to buy separate tickets, and I understand that I will not be able to have baggage checked through.
I am therefore planning travel without checked baggage. My question is: Will I be able to go directly between these flights or will I have to go through Chinese immigration to get from one flight to the other?
Both flights appear to arrive/depart from Terminal 2.