Effect of processing variables on the crosslinking of HDPE by peroxide

In this work, the effect of processing variables such as temperature, shear rate, and the content of crosslinking agent on the melt torque behavior in a mixer, the degree of crosslinking, the thermal properties and density of high density polyethylene (HDPE) was investigated. Di-ter-butyl peroxide ( DTBP) was used as a crosslinking agent. It was concluded that the crosslink ing behavior of HDPE by peroxide was an overall function of temperature, sh ear rate in terms of mixer rpm, and the peroxide content. Crosslinking term ination time was shortened on increasing the reaction temperature, regardle ss of the mixer rpm. As the mixer rpm increases, the crosslinking reaction time was shortened by the effect of shear heating. As a result, athough the crosslinking reaction termination time of HDPE depends on both the tempera ture and shear rate at constant peroxide contents the temperature was the m ore dominant. It was found that there is an optimum peroxide content, here 0.6 phr, to crosslink HDPE. In addition, the crosslinking of HDPE gives ris e to a decrease in crystallinity, followed by a decrease in density. (C) 20 00 Elsevier Science Ltd. All rights reserved.