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The use of the melt flow rate method for moisture sensitive materials and an evaluation of the uncertainties in melt flow rate measurement.

Rides, M; Allen, C R G (2007) The use of the melt flow rate method for moisture sensitive materials and an evaluation of the uncertainties in melt flow rate measurement. NPL Report. MAT 3

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Abstract

The current melt flow rate method (ISO 1133) does not adequately cover the measurement of materials that degrade or further polymerise at the melt flow rate test conditions. Materials such as PET, PBT and PA containing absorbed water tend to degrade, sometimes rapidly, at processing temperatures. This will result in poor repeatability and reproducibility of melt flow rate results. The ISO Plastics Melt Rheology committee (TC61/SC5/WG 9) is currently developing a modified melt flow rate method for reliable measurement of moisture sensitive materials, e.g. PBT and PET, thereby providing an alternative to intrinsic viscosity measurements. The modified method controls more tightly the time-temperature history experienced by the material and thus the resultant variability in measured properties due to degradation. Results on a range of moisture sensitive materials are presented, demonstrating the effect of moisture content on measurements. Repeatability of measurements of melt flow rate were up to 10% (1 standard deviation). The need to tightly control the sample preparation (e.g. drying) and sample handing procedures is considered critical to reliable measurements of such materials. Furthermore, an evaluation of the uncertainties in the measurement using the current ISO 1133 is reported and recommendations for improved measurements are made.

Item Type: Report/Guide (NPL Report)
NPL Report No.: MAT 3
Keywords: melt flow rate, moisture, sensitive materials, degradation, polymers, plastics
Subjects: Advanced Materials
Advanced Materials > Polymer Rheology
Last Modified: 02 Feb 2018 13:15
URI: http://eprintspublications.npl.co.uk/id/eprint/3980

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