Chemical analysis applied to the development of a model for the determination of quality of PE pipes

The aim of this work is expanding the base of data on which a previous developed method of predicting polyethylene (PE) quality was based. The refined method will provide water companies with a simple way of assessing chemical differences that may occur among PE pipes due to different manufacturers or different batches of virgin polymer. A number of samples, taken from PE water-ducts, were pyrolysed (triplicate analyses) at 700 ◦C in N2 atmosphere using a platinum coil pyrolyser inside a tube cooled in liquid nitrogen. The volatile and non-volatile products were identified and quantified by gas chromatography/mass spectrometry, and subjected to discriminant analysis. The same samples were also pyrolysed at 900 ◦C in order to analyse high molecular weight pyrolysis products. Moreover, polycyclic aromatic hydrocarbons and volatile organic compounds leaching from PE tubes into drinking water were determined. Data acquired were matched up with results obtained using physical methods of polymer characterisation, namely density, oxidative induction time, melt flow rate and carbon black dispersion.