Abstract: A mixer for mixing and processing materials comprises a mixing chamber with an inner space configured for receiving material to be mixed. An elongated rotatable mixing shaft extends through the chamber inner space and has a stub end and a drive end positioned proximate opposing ends of the mixing chamber. A non-rotatable stub shaft extends through an opening in the end of the mixing chamber and is coupled to the chamber end for linear translation therethrough. The stub shaft is generally prevented from rotating in the chamber end. The stub end of the mixing shaft is rotatably coupled to the stub shaft within the inner space for rotating in the mixing chamber without extending through the end of the chamber. A static seal structure is coupled between the stub shaft and the end of the mixing chamber for sealing the chamber inner space from the environment outside of the mixing chamber.