Originally Posted by EmailKid

There is United Club in each of the terminals and two in Term C, but if your next flight is on a separate ticket, you may be out of luck, as it would be considered as arrivals lounge. If on the same PNR then Yes, access.

Don't know about SQ (believe) contract lounge in area D (you exit Immigration in E), but if that is no go I would try UA anyway and show SQ and UA boarding passes.

Oh, and welcome to FlyerTalk