**5. Conclusion**

The unique feature of cellulosic substrates to absorb moisture from the air or absorption of water or other solution, for example sodium hydroxide, causes swelling of this substrate. Then expansion of the fibre, yarn, or fabric occurs due to the swelling in liquid media. By continuous growth of fibre, yarn, or fabric, the accessibility becomes restricted as the porosity or the inter- and intra-yarn pores and/or inter-spaces diminish. Hence, NaOH treatment influences physical properties such as stiffness, shrinkage, water retention value and wet pick-up, mechanical properties such as tension, break force, elongation, crease recovery angle and mass loss.

Also, it was shown and discussed herein that alkalization and release during wash-off are governed by fabric structure and alkali concentration. This finding is of particular relevance for an optimized processing of fabrics from regenerated cellulose fibres. While in technical processing, materials consisting from the same type of fibre and with similar mass per area are considered to behave identical during alkalization the present results show the need for individual process adaptation.

It is obvious that the cellulose is very complex material and there is still limited knowledge available in this field rather containing more questions and uncertainties. A representative example is alkali treatment of this substrate with ongoing research more than 160 years and always some gaps within this area are recognised. In recent years, it can be seen that the field of cellulose, cellulose derivatives, or polysaccharides is expanding largely due its recognised wide potential and also its environmental benefit. Therefore, the long-term task for present and future research in cellulose is the development of novel processes which yield no or minimal ecologically harmful by-products. If these efforts are successful, cellulose will maintain and strengthen its position as a renewable and environmentally beneficial, industrially important raw material competing with synthetically produced polymers.
