Better barrier screws emerge.

Two new barrier screw designs surfaced at NPE. Robert Barr Inc., Virginia Beach, Va., unveiled a new variable-barrier version of its ET (energy transfer) screw designs at NPE. The VBET screw has a 30% to 60% longer melting section and also eliminates the distinct barrier flight. It reportedly achieves higher throughput rates, lower melt temperatures, and better mixing than the standard ET design. Barr has been selling the new design quietly for two years but didn't publicly exhibit it until the patent was issued two weeks before the show.

American Kuhne Corp., Norwich, Conn., launched its HP2 barrier screw, which has deep roots designed to process stiff resins like fractional-melt HDPE. It increases throughput as much as 15% with backpressures of 3500 psi, Kuhne says. The first application was on a blow molding machine six months ago. Now it also used commercially in pipe and profile extrusion.