Investigation and analysis of the impact of fibre mixing on the strength of nonwoven fabrics produced using double-drum carding machines

Viscose-polyester nonwovens are now widely used. The desired performance properties of these nonwovens, such as quality and strength, depend to a large extent on the carding process, in which homogenised layers of properly mixed fibres are formed. In this article, a comparative analysis of two different designs of modern, double-drum carders and their impact on the quality of fibre mixing and on the strength of the final nonwoven fabric is presented, based on research and tests carried out in an industrial production line. To this end, mathematical models were developed for the relevant indicators (fibre delay time and the average fibre circulation path length in the carding machine) that characterise the carding process. Based on numerical calculations, these indicators were determined for the actual geometry of the carding elements and the process parameters applied in the tests. A discussion is provided to interpret the values of these indicators and their correlation with the strength of the nonwoven fabric produced, taking into account the different design of the carders used in the tests. The results showed that the average fibre delay time ranged from 1.40 s to 1.99 s, while the corresponding fibre delay length varied between 4.42 m and 6.30 m. Moreover, the mean fibre circulation path length was greater in the second carding machine (20.5-26.4 m) than in the first (16.9-17.0 m), indicating more intensive longitudinal fibre mixing.