Abstract The objective of this study was to understand the influence of bleaching on % residual lignin, water retention value, brightness and morphological properties of Subabul heartwood and sapwood pulps. The second aim was to compare the properties of unbleached and bleached handsheets with respect to tensile index and fractography. Screened wood chips of Subabul were subjected to kraft cooking (165 °C, 3 hours) followed by ECF bleaching and refining. When unbleached handsheets were compared, higher tensile index was found for sapwood sheets (29.8 N.m/g) than heartwood sheets (12.8 N.m/g). Therefore, it is recommended to use unbleached sapwood sheets for packaging grade applications. The bleached pulps have exhibited negligible residual lignin (0.1 %), higher water retention value (∼21) and higher brightness (88 %) compared to unbleached pulps. Subsequently, the bleached heartwood sheets revealed higher tensile index (∼7 fold) and higher modulus of elasticity (∼2.7 fold) compared to unbleached heartwood sheets. For printing grade applications bleached sapwood and bleached heartwood pulps are equally recommended, because no differences were observed in their pulp and sheet characteristics.

中文翻译：

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Subabul 心材和边材的未漂白和漂白手抄纸特性

摘要 本研究的目的是了解漂白对 Subabul 心材和边材纸浆的残留木质素百分比、保水值、亮度和形态特性的影响。第二个目的是比较未漂白和漂白手抄纸的拉伸指数和断口特性。筛选过的 Subabul 木片经过牛皮纸蒸煮（165°C，3 小时），然后进行 ECF 漂白和精炼。当比较未漂白的手抄纸时，发现边材片材 (29.8 Nm/g) 的拉伸指数高于心材片材 (12.8 Nm/g)。因此，建议在包装级应用中使用未漂白的边材板。与未漂白纸浆相比，漂白纸浆显示出可忽略不计的残留木质素 (0.1%)、更高的保水值 (~21) 和更高的亮度 (88%)。随后，与未漂白的心材板材相比，漂白的心材板材具有更高的拉伸指数（~7 倍）和更高的弹性模量（~2.7 倍）。对于印刷级应用，同样推荐使用漂白边材和漂白心材纸浆，因为它们的纸浆和纸张特性没有差异。