Characterization of strain bursts in high density polyethylene by means of a novel nano creep test

Author(s)
H. Wilhelm, F. Spieckermann, C. Fischer, G. Polt, M. Zehetbauer
Abstract

Recent nanoindentation experiments have shown that in semi-crystalline polymers, strain bursts emerge during creep experiments. A shortcome of nanoindentation is that due to the in-homogeneous stress field, a critical stress for the onset of strain bursts cannot be determined, and the resolution of the method seems to be limited. Since the strain bursts in polymers are in the nm range, an extremely high resolution in deformation measurement is necessary. Such a resolution is provided by modern solid state rheometers having a resolution <10(-6) rad. With such a facility, in this work single strain bursts in PE-HD have been investigated in creep mode at stresses as low as <0.5 MPa. As the strain bursts only occur rarely, hundreds of creep experiments were carried out and evaluated statistically. Through variation of the temperature and the stress, the activation energy for the strain bursts was determined as 0.65 ( +/- 0.06) eV. In addition, negative strain bursts (contrary to the direction of deformation) with an activation energy of 0.49 ( +/- 0.08) eV and post-oscillations after strain bursts could be observed for the first time. In summary the new method represents a powerful tool for a quantitative characterization of strain bursts and gives a new insight to dislocation kinetics in semi-crystalline polymers.

Organisation(s)
Physics of Nanostructured Materials
External organisation(s)
Lab Polymer Engn LKT TGM, Montanuniversit├Ąt Leoben, Isosport
Journal
International Journal of Plasticity
Volume
116
Pages
297-313
No. of pages
17
ISSN
0749-6419
DOI
https://doi.org/10.1016/j.ijplas.2019.01.010
Publication date
05-2019
Peer reviewed
Yes
Austrian Fields of Science 2012
Materials physics
Keywords
Portal url
https://ucris.univie.ac.at/portal/en/publications/characterization-of-strain-bursts-in-high-density-polyethylene-by-means-of-a-novel-nano-creep-test(e3b4224b-e663-4e41-a396-853961ec1eb8).html