Dresden 2003 – wissenschaftliches Programm
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CPP: Chemische Physik und Polymerphysik
CPP 1: Polymerschmelzen
CPP 1.7: Vortrag
Montag, 24. März 2003, 11:30–11:45, ZEU/160
On the Mechanical α-Process in Polyethylene — •Yongfeng Men and Jens Rieger — BASF Aktiengesellschaft, Polymer Physics, 67056 Ludwigshafen, Germany
We clarified the existence and the assignment of two high temperature mechanical α-processes (αI and αII in the order of increasing temperature) in polyethylene by studying three selected samples with similar crystallinity, melting behavior and long period but with different branch content or branch length. The results support the original assignment of Takayanagi that the αI process is due to crystalline mosaic block grain boundary slips within lamellae and that the αII process is caused by the diffusion-like motion of the chains within crystals. Moreover, we showed that the high temperature peak in G” corresponds to the αI process which appears as a shoulder in the tanδ curves. The value of the activation energy of the αI process, as derived from G”, is similar to those obtained by NMR and dielectric spectroscopy measurements, although they have a different physical origin - as will be discussed. This often leads to a misconstruction of results deduced by different techniques in literature.