Influence of stem morphology on pulp and paper properties of Arundo donax L. reed

Abstract

The response on pulping of the two main botanically distinct parts of the stem of Arundo donax L. reed (nodes and internodes) has been studied using kraft pulping as the predominant process for pulp production. Different access to kraft pulping of nodes and internodes was established in accordance to difference in chemical composition and anatomical characteristics. Pulps with higher screened yield (44.5 vs. 38.6%) and lower content of residual lignin (Kappa number 25 vs. 33) were produced from internodes, compared to nodes. Papermaking properties as well as brightness of unbeaten kraft pulps from internodes were also higher (burst index 0.7 vs. 0.2 kPa m 2 g −1, tensile index 25.2 vs. 5.2 N m g −1, tear index 13.3 vs. 4.4 mN m 2 g −1 and brightness 23.9 vs. 21.2% ISO for pulps from internodes and nodes, respectively). Freeness of the unbeaten pulps was 10 and 11°SR, respectively for internodes and nodes. Fast response on beating connected with increase in drainage resistance was found for both pulps. Dewatering problems were more pronounced for pulps from nodes, which was attributed to higher content of hemicelluloses and parenchyma cells. PFI beating improves more significantly the strength properties of pulps from internodes (burst index 7.0 vs. 4.5 kPa m 2 g −1, tensile index 85 vs. 45 N m g −1, and tear index 11.0 vs. 7.0 mN m 2 g −1 for pulps from internodes and nodes, respectively, at freeness about 45°SR). The strength properties of the beaten as well as unbeaten whole stem kraft pulps were similar or lower to those from internodes, reflecting, as with the pulping results, the mass proportion of nodes and internodes in the stem of A. donax.