Extruder

An extruder for extruding a composition comprising polypropylene and an organic peroxide, the extruder comprising:

• a housing having a first end and a second end longitudinally opposite the first end, the housing having an inlet hopper proximate the first end, an outlet die at the second end, and an inlet zone within the housing, the inlet zone extending from the first end of the housing,
• at least one extruder screw disposed within the housing, the at least one extruder screw having a length extending from the first end of the housing and configured to convey the composition from the inlet to the outlet die, and
• a plurality of heating devices configured to generate a plurality of heating zones within the housing between the first end and the second end,
• wherein a first heating device is disposed adjacent to the inlet hopper and is configured to generate a first heating zone adjacent to the inlet zone, the first heating zone having a first temperature of from about 110° C. to less than about 160° C.,
• wherein the inlet zone and the first heating zone together extend from the first end of the housing to from about 25 to about 45% of the length of the at least one extruder screw,
• wherein said at least one extruder screw does not comprise a reverse screw element within the inlet zone and the first heating zone, and
• wherein the extruder is configured to have maximum internal pressure of about 500 bar or less.