Charakterizace degradace celulózy v průběhu urychleného stárnutí pomocí GPC-MALS, GPC-DAD a A4F-MALS

In this work, we compared three methods of analysis of cellulose in paper subjected to accelerated ageing: size exclusion chromatography in combination with multiangle light scattering (SEC-MALS) detection, size exclusion chromatography in combination with diode-array detector and calibration using polystyrene standards (SEC-DAD), and asymmetric flow field–flow fractionation in combination with multiangle light scattering (A4F-MALS). Prior to separation, cellulose sample were derivatized with phenyl isocyanate to CTC and dissolved in tetrahydrofuran.Práce porovnává tři metody analýzy celulózy vystavené urychlenému stárnutí: gelová permeační chromatografie v kombinaci s víceúhlovým rozptylem světla (GPC-MALS), gelovou permeační chromatografii v kombinaci s detektorem diodového pole a kalibrací na polystyrenové standardy (GPC-DAD) a frakcionaci tokem v asymetrickém tokovém poli (A4F-MALS). Před separací byly vzorky derivatizovány fenyl izokyanátem na CTC a rozpuštěny v tetrahydrofuranu

Oxidative degradation of non-recycled and recycled paper

AbstractThe degradation of paper-based materials involves several and complex mechanisms, such as hydrolysis and oxidation. The behaviour of different types of pulps can be very variable. In this study, the difference upon oxidation of contemporary non-recycled and recycled papers, which now constitute a considerable fibre source, is investigated. A 0.015 M potassium periodate solution is used to oxidise five types of paper, two non-recycled and three recycled, for 0.5, 1, 2 and 4 h. The effects of such oxidation treatments are evaluated in terms of carbonyl content and degree of polymerisation (DP). A modified procedure of the Szabolcs's method and viscometry are used to measure the carbonyl content and DP, respectively. The carbonyl groups are found to increase more rapidly in the recycled papers than in the non-recycled ones. On the contrary, oxidation causes a larger decrease of the DP values in the non-recycled papers, the paper made of pure cellulose being the most sensitive in terms of depolymerisation. The DP values measured for pure cellulose paper are in line with previously reported data. Moreover, in accordance with the Ekenstam equation, the plots of the reciprocal of DP as a function of oxidation time show good linear correlations for all types of paper investigated. Pseudo rate constants are thus calculated from the slopes of these plots, those of the non-recycled papers being found to be higher than those of the recycled papers. Graphic abstrac