A transfer method and system (8) to discharge overflow slurry from a polymerization reactor (10) to a tank (14). The method includes thermally isolating a conduit extension (28) at a distal end of a transfer line (20) from a quench fluid inlet (42) to a quench chamber (12). The transfer system (8) is characterized by an annular thermal barrier around the conduit extension (28) that can include insulation (34) and/or thermally resistant support ring (36), and a trap-free conduit (20) in fluid communication between the reactor (10) and the conduit extension (28). The transfer method and system can reduce or eliminate incidents of transfer line (20) plugging in the manufacture of isoolefin polymers and copolymers.