Exploring rheological responses to uniaxial stretching of various entangled polyisoprene melts

Abstract

The present study is carried out to determine whether marginally entangled melts behave differently in both startup uniaxial extension and stepwise extension and how entangled solutions and melts with a comparable number of entanglements per chain behave similarly or differently. It is found that there is still a yield-to-rupture transition in the weakly entangled polyisoprene (PI) melts. Specifically, even a PI melt with fewer than five entanglements per chain was found to undergo melt rupture as if there was chain crosslinking. On the other hand, such weakly entangled melts were unable to show a type of strain localization called tensile decohesion. Moreover, the PI melts with the relatively low molecular weights were observed to remain essentially intact after stepwise extension of a magnitude for which well-entangled PI melts of high molecular weight undergo elastic breakup. Finally, it was demonstrated that an entangled solution shows a stronger elastic response than entangled melt of comparable degree of entanglement.The present study is carried out to determine whether marginally entangled melts behave differently in both startup uniaxial extension and stepwise extension and how entangled solutions and melts with a comparable number of entanglements per chain behave similarly or differently. It is found that there is still a yield-to-rupture transition in the weakly entangled polyisoprene (PI) melts. Specifically, even a PI melt with fewer than five entanglements per chain was found to undergo melt rupture as if there was chain crosslinking. On the other hand, such weakly entangled melts were unable to show a type of strain localization called tensile decohesion. Moreover, the PI melts with the relatively low molecular weights were observed to remain essentially intact after stepwise extension of a magnitude for which well-entangled PI melts of high molecular weight undergo elastic breakup. Finally, it was demonstrated that an entangled solution shows a stronger elastic response than entangled melt of comparable degr...