Hemicelluloses number changes

Filter Paper with Hemicellulosic Fractions Added On. Hemicellu-lose fractions were isolated from unaged and thermally aged papers by extraction with LiOH, following the procedure described by Giertz and McPherson (6). The changes in postcolor number [100(K/S) — (K/S)0] (7) for various test sheets during exposure to visible and UV radiation and to heat are shown in Figures la, lb, and lc for material extracted from... [Pg.372]

Figure 1. Changes in postcolor number of filter-paper sheets with 15% add-on of hemicellulose fractions derived from various pulps. For comparison, the thermal discoloration of a test sheet of groundwood pulp, gp, is shown. The initial postcolor number represents the increase in color over that of the untreated filter paper a, daylight fluorescent lamps b, black-light fluorescent lamps c, heat (90 °C and 50% rh). Key O, blank filter paper , BP A, GP V, UBP 0, chlorited UBP.

$Figure 1. Changes in postcolor number of filter-paper sheets with 15% add-on of hemicellulose fractions derived from various pulps. For comparison, the thermal discoloration of a test sheet of groundwood pulp, gp, is shown. The initial postcolor number represents the increase in color over that of the untreated filter paper a, daylight fluorescent lamps b, black-light fluorescent lamps c, heat (90 °C and 50% rh). Key O, blank filter paper , BP A, GP V, UBP 0, chlorited UBP.$

Such autocatalytic effect caused by the change of the hemicellulose conformation as the chain length diminishes can be interpreted as an increasing rate constant, with conversion X defined through the number of glycosidic bonds in the beginning of the reaction o when < = 0 and after some reaction time n ... [Pg.712]

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