Dilek YAYLALI, Canan URAZ, Esat GÜMÜŞKAYA
These values are less than the ash content in this study (3.5%). These differences can be attributed to the different types of hemp bast fibre sources used. Tutuş et al. [2016] reported that the ash content of wood-based fibre sources ranges between 0.2% to 0.7%, and the ash content ranges between 2% and 7% for non- wood-based sources. Compared to wood-based sources, hemp bast fibres have high ash contents, although it is not as high as some non-wood fibre sources such as sunflower (7% – 10%) and straw (4.9%) fibres [ Gümüşkaya 2002]. The solubility test results of the hemp bast fibres (in this study) and some other fibre sources are presented in Table 4. Table 4. Solubility test results of hemp bast fibers and some other fibre sources Solubility (%) Test type Alcohol-benzene Hot Water %1 NaOH Hemp bast fibers 3.8 9.3 24.1 Wheat straw 5.3 10.5 40.1 Hardwoods 2.3-13.5 1.1-13.8 8-19 Softwoods 0.4-4.7 0.6-12.8 11-22 The cell wall contents of non-wood sources have an impact on the solubility of hemp bast fibres, as do their morphological and structural properties [Gümüşkaya 2002] . Table 4 shows that hemp bast fibres are more soluble than hardwood and softwood fibre sources, but they are less soluble than wheat straw fibres. These aspects allow us to conclude that hemp bast fibre is an appropriate fibre source for the pulp and paper industry. Kraft pulping and beating Figure 1 depicts the colour change of the hemp bast fibres after different treatments. The colour of the hemp bast fibres (size-reduced raw material) was yellowish-brown before pulping. After pulping, the colour became lighter (cream). After beating, the whiteness increased.
Fig. 1. The appearance of hemp bast fibres a) after size reduction, b) after pulping and c) after beating
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