Characterization of Melt Flow Index of Commercial Polystyrene Using Data from Interlaboratory Comparison

The melt flow index (MFI) of commercial polystyrene samples has been investigated throughout an interlaboratory comparison study. The homogeneity samples have been assessed prior to the distribution over the participants. The one-factor analysis of variance model has been applied to separate and evaluate the uncertainty components arising from the analytical method and the heterogeneity of the samples. It has been shown that the samples are sufficiently homogenous. The stability of the samples has been monitored over 6 months. The stability and the uncertainty arising from the instability of the samples have been evaluated throughout the linear regression analysis. No significant trend could be detected over the stability assessment period. The results reported by the participants have been investigated. An almost normal distribution shape has been obtained with no evidence for outlier or systematic bias. The MFI value has been evaluated as consensus value from the results reported by the participants with a standard combined uncertainty of ~ 2.2%.