Dilek YAYLALI, Canan URAZ, Esat GÜMÜŞKAYA
virgin pulp due to cycles of reuse. These fines block inter-fibre vacancies, and the hornification of the fibres causes the internal pore structure to collapse [Kumar et al. 2020]. The low extent of fibrillation of the hemp bast fibres after beating is also beneficial in this decrease since there are large pores between the fibres as they are not fibrillated at the desired level, allowing free flow of air to pass through the paper. Conclusions The conclusions for each examination topic are as follows: x Hemp bast fibre is an appropriate fibre source for the pulping and papermaking industries in terms of holocellulose, cellulose, lignin content, ash and solubility. x Hemp bast fibres are initially yellowish-brown in colour, but they become lighter (cream) after cooking and even lighter after beating. x When compared to wood-based sources, the yield of kraft cooking is determined to be 70.8%, which is a high yield value. x The low hemicellulose content and highly stable crystalline structure of hemp bast fibres reduce external fibrillation. Since it takes too long to process to reach the desired degree of fibrillation, it consumes a lot of energy to beat. x With the use of a fine cutting mill, the desired average length of hemp bast fibres was successfully obtained. Alternative size reduction methods can be considered for better precision. The diameter and cell wall thickness of the hemp bast fibres used in this work were consistent with those in other studies. Cooking did not affect the fibrillation of the fibres; however, applied beating had some fibrillation effect on the cooked hemp bast fibres, but it was less than that of wood sources. x According to XRD results, the degree of crystallinity of hemp bast fibres increases after cooking owing to degradation in the amorphous domains of cellulose. The unexpected increase in crystallinity indicates that the applied beating did not affect the fibrillation of the fibres, as supported by the OM results. x FTIR results confirm the removal of lignin and small amounts of hemicellulose from the raw material after treatment. x During the preparation of wastepaper pulp, some impurities/contaminants were observed. There were some apparent brown and white speckles on the handsheets made from wastepaper pulp and hemp bast fibre pulp, especially on the handsheets with 40%, 60% and 80% hemp bast fibre, due to a disintegration problem with wastepaper. This problem was due to low water absorption of the corrugated medium and white top face plies
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