• Title/Summary/Keyword: rheology behavior

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Rheological properties of branched polycarbonate prepared by an ultrasound-assisted intensive mixer

  • Kim, Hyung-Su;Lee, Hoo-Seok;Lee, Jae-Wook
    • Korea-Australia Rheology Journal
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    • v.19 no.1
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    • pp.1-5
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    • 2007

  • By combining ultrasonic energy which is essential for the chain scission of polymer molecules and a multifunctional agent (MFA) having double bonds at its ends, we were able to modify the molecular structure of polycarbonate (PC) from linear to a branched structure during melt processing. The three double bonds in chain ends of MFA were expected to act as sites for trapping macroradicals of PC during the course of ultrasound-assisted mixing process. The transformation of molecular structure of PC was confirmed by the measurements of rheological properties of the modified PC. After the ultrasonic irradiation of PC together with MFA, increase in complex viscosities and shear-thinning behavior were observed. The Cole-Cole plot and measurement of extensional viscosities revealed the characteristic features of branched structure with well-defined extensional behavior which is comparable to that of a commercial branched PC.

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Strain hardening behavior of linear polymer melts

  • Hong Joung Sook;Ahn Kyung Hyun;Lee Seung Jong
    • Korea-Australia Rheology Journal
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    • v.16 no.4
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    • pp.213-218
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    • 2004

  • Linear high-density polyethylene (PE) was controlled to induce strain-hardening behavior by introducing a small amount of second component with an anisotropic structure. In order to form an anisotropic structure in the PE matrix, the polymer was extruded through a twin-screw extruder, and the structure was controlled by varying the extrusion conditions. Depending on conditions, the second component formed a film, thread and droplet structure. If the second component was kept rigid, the morphology evolution could be delayed and the second component could maintain its film or thread structure without further relaxation. In par­ticular, the second component of the thread structure made a physical network and gave rise to remarkable strain hardening behavior under high extension. This study suggests a new method that induces strain hard­ening behavior by introducing a physically networked second component into the linear polymer melt. This result is anticipated to improve the processibility of linear polymers especially when extensional flow is dominant, and to contribute to our understanding of strain hardening behavior.

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