High Performance HDPE Pipe Compound Development [PE]

The development of Marlex" H5 16 high performance HDPE pipe compound progressed over many years resulting in the introduction of Driscopipe 8100 pipe to the United States pipe market in 1997. This product has been extensively evaluated for long-term hydrostatic strength (LTHS). slow crack growth (SCG). environmental stress cracking resistance (ESCR) and rapid crack propagation (RCP). A modified PENT test utilizing a much higher stress has been evaluated for testing high performance products such as H516. Performance of slow crack growth as measured by the modified PENT test is significantly affected by comonomer type with hexene comonomer giving significantly higher results than butene comonomer. This product incorporates hexene comonomer at a density optimized to produce high hoop strength while also providing excellent resistance to slow crack growth. The U.S. Plastics Pipe Institute (PPI) recognizes this material as a PE3408 type with a hydrostatic design basis of 1600 psi ( I l MPa) at 73°F (23°C) and 1000 psi (6.9 MPa) at 140°F (60°C). European laboratories have confirmed long-term hydrostatic strength (LTHS) per IS0 9080 of 10 MPa (1450 psi) minimum required strength (MRS) and very high resistance to rapid crack propagation (RCP). Full scale RCP testing of 12-inch (305 mm) Driscopipe 8100 showed that cracks were arrested at pressures as high as 30 psi (0.2 MPa) at 32'F (0°C). The initial market for H516 is gas distribution pipe generally ranging in size from 112-inch to 12-inch (13 to 305 mm) i11 diameter. although this product offers advantages for many other markets a3 well. For application identification Driscopipe 8100 is a coextruded pipe having a yellow shell over black pipe. Developtnent of a suitably opaque yellow compound with acceptable pipe properties has required extensive testing separate from the H516 black qualification. Driscopipe plant implementation of the shell technology and full production capabilities are expected during 1998.