Rides, M; Allen, C R G (2002) Low rate extensional rheometry of polymer melts. NPL Report. MATC(A)114

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Abstract

The NPL extensional rheometer has been developed further to test polymer melts at low strain rates. Results of extensional viscosity measurements are reported for various polyethylene melts at strain rates down to 0.001 s-1 and at 150 ­ºC.
Three polyethylene materials, a HDPE, JDPE and LLDPE, exhibited significant differences in their extensional behaviour, particularly in their additional strain hardening to failure which was greatest at the lowest strain rate. Comparison of four similar HDPEs used for thick-walled pipe extrusion revealed differences of up to a factor of x2 in their transient extensional viscosity values.
Measurements of extrudate draw-down using a melt flow rate instrument and a hand-held micrometer, and interpreted as approximate extensional viscosity values, yielded results that were consistent with the data obtained using the more elaborate NPL extensional rheometer. An analysis of the uncertainties in measurement of transient extensional viscosity values at low strain rates is briefly reported.

Item Type:	Report/Guide (NPL Report)
NPL Report No.:	MATC(A)114
Subjects:	Advanced Materials Advanced Materials > Polymer Rheology
Last Modified:	02 Feb 2018 13:17
URI:	http://eprintspublications.npl.co.uk/id/eprint/2485

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