metastable disentangled state evolves to a fully entangled state [3]. In order to gain a better ... model was employed in its modulus representation as follows [5]:.
[5]
Nocita, D., Forte, G., Drakopoulos, S., X., Visco, A., Gianporcaro, A., Ronca S., submitted to Polymer (2017).
P19. An Experimental and Theoretical Analysis of the Dielectric and Rheological Spectra of nascent disentangled UHMWPE in the Melt State S X Drakopoulos1, G Forte1, G C Psarras2 and S Ronca1 1
Loughborough University, UK, 2University of Patras, Greece
The wide range of possible applications arising from the unique properties of ultra-high molecular weight polyethylene (UHMWPE) [1] calls for a deeper understanding of the structure-property relationship using advanced techniques. In certain reaction conditions, UHMWPE with a reduced number of entanglements can be synthesised [2], having the advantage of improved processability. This material also offers an interesting melt behaviour, as the metastable disentangled state evolves to a fully entangled state [3]. In order to gain a better understanding of the relaxation processes involved in this metastable melt state, Broadband Dielectric Spectroscopy and Rheology will be combined, taking into consideration the analogous phenomena they refer to and that they are described by similar formalisms [4]. Disentangled UHMWPE was prepared in house according to [2]. Prior to testing, the UHMWPE specimens were annealed under vacuum in a nitrogen environment in powder form followed by the compression moulding, both at 160oC. Rheological measurements were made at 160oC in the frequency range between 10-2 to 102 Hz. The dielectric measurements were conducted by means of Broadband Dielectric Spectroscopy at 160oC in the frequency range of 100 to 105 Hz. A TA Instruments ARES-G2 Rheometer using plate-plate geometry and a Novocontrol Technologies Aplha-N Frequency Response Analyzer with a Novotherm system using a gold-plated parallel-plate capacitor in a BDS-1200 dielectric cell, were employed respectively. For the theoretical interpretation of rheological data the Cole-Cole model was employed in its modulus representation as follows [5]: πΊ β = πΊπ +
(πΊβ βπΊπ )(πππ)π½π 1+(πππ)π½π
= πΊ β² + ππΊ β²β²
(1)
To theoretically understand the recorded relaxations and processes in the dielectric measurements again the ColeCole model function was employed in its electric modulus form as developed by Tsangaris et al., [6]: πβ =
[1] [2] [3] [4] [5] [6]
44
ππ πβ οΏ½1+(πππ)π½π οΏ½
ππ οΏ½1+(πππ)π½π οΏ½+(πβ βππ )
= πβ² + ππβ²β²
(2)
Kurtz, S. M. UHMWPE Biomaterials Handbook. Oxford: Elsevier, 2016. Forte, G., Ronca, S. International Journal of Polymer Science (2017), doi:10.1155/2017/7431419. Pandey, A., Champouret, Y., Rastogi, S. Macromolecules (2011), 44, 4952-4960. Pakula, T. (2003). Dielectric and Mechanical Spectroscopy β a Comparison. In F. Kremer & A. SchΓΆnhals (Eds.), Broadband Dielectric Spectroscopy (pp. 597-624). New York, NY: Springer Berlin Heidelberg. Pritz, T. Journal of Sound and Vibration (1996), 195, 103-115. Tsangaris, G. M., Psarras, G. C., Kouloumbi, N. Journal of Materials Science (1998), 33, 2027-2037.
Physical Aspects of Polymer Science 2017
