A comprehensive study of different types of speck impurities present in bleached eucalypt kraft pulps using Py-GC/MS

Abstract

Analytical pyrolysis in combination with gas chromatography and mass spectrometry (Py-GC/MS) has been used to characterize a wide set of different speck impurities occurring in total chlorine free (TCF) kraft pulps made from eucalypt (Eucalyptus globulus) wood. The specks included pitch, rubber and plastic impurities and were previously classified by mill technicians upon visual checking. Samples of eucalypt wood chloroform extracts, TCF bleached pulps, as well as a large series of rubber and plastic items taken from different parts of the machinery were also selected for this study. The Py-GC/MS evaluation showed that, except for the impurities classified as plastics, the differentiation made between rubber and pitch by visual checking gave erroneous results. Apart from the presence or absence of wood extractives in some samples, most of the impurities analyzed in this work, even those that were unambiguously classified as pitch by mill technicians upon visual checking, showed to contain synthetic rubbers. Finally, the pyrograms of the specks and those of reference rubbers were used as fingerprints to trace the source of contamination.