Variable porosity irrigation pipe

摘要

Porous pipe having a porosity which varies continuously and controllably with length is produced by extruding a mixture of particles of prevulcanized elastomer such as reclaimed crumb rubber and a thermoplastic binder such as polyethylene with all parameters controlled except for die temperature of pull-off rate. By gradually varying temperature or pull-off rate during extrusion, the porosity of the pipe gradually changes. The leak rate can be controlled in a manner to produce a length of porous pipe in which the leak rate is constant as the pressure drops over the length of the pipe.