Regeneration of cellulose by means of a viscose process has been developed and optimized throughout the years for dissolving-pulp sources from special grade wood pulp and cotton linters. However, more recently, the undeniable environmental impact of the textile-industry has caused a growing urge for developing ways to tackle that pollution, such as the reuse of raw materials through several recycling pathways. One of these possible recycling pathways aims to reuse waste-cotton as input for the viscose process instead of new wood-resources. However, previous experiences in industry and research have indicated that waste-cotton pulp performs differently due to differences in chemical and physical properties and morphology. 
This study focused on the first step of the viscose process (‘mercerization’) with the purpose of activating the cellulose-chains in the densely packed crystalline formation (causing poor accessibility and reactivity towards chemicals in its natural form). Hereby, cellulose pulp is steeped in concentrated lye-solution (17-19 wt%) for 20-30 minutes at elevated temperature (45-55°C), creating a swollen alkoxide-derivative. 
The behaviour during mercerization is critical for sufficient reactivity in further process steps and removal of undesirable components in the pulp. However, excessive swelling can complicate removal of excess liquid after the activation of the cellulose, necessary for obtaining optimal dryness and alkali-cellulose ratio in further steps. 
In this study, different input materials including dissolving pulp from softwood, cotton linters and cotton waste were investigated regarding swelling-properties and retention of the liquids in both neutral and alkaline conditions, which was then also connected to the ease of pressing out excess lye after mercerization. The analysis indicates more swelling and retention (and more difficult pressing) in mercerization (alkaline) conditions for cotton-based pulps than dissolving wood pulp. These findings give more insight on the performance of different sources during mercerization, and consequently, in the viscose process.