High speed compression properties of textile structures and sheet‐like materials

Abstract

Abstract High speed compression properties of textile structures and sheetlike materials that pass through a set of press rolls are found to be the controlling factor in determining the pressure schedule within the nip region, the loading of the rolls, and the minimum separation of the roll surfaces (nip thickness) of the press. Factors affecting the high speed compression properties of felts (napped textile structures) which are used to carry a wet sheet of paper through the press section of a paper machine are examined. The compressive stress‐strain curves of a single felt design are obtained using the Plastechon High Speed Tester to simulate the strain schedule within the nip region of the press section of the paper machine. Compression curves of new, used and worn felts are obtained at deformation rates from 20 in./sec. to 100 in./sec., equivalent to paper machine speeds ranging from 1000 ft./min. to 5000 ft./min. and at various levels of water content (dry, wet and saturated). The results show that the felt offers more resistance to compression as the strain rate and/or its water content is increased. Similarly, worn felts are found to require more force to achieve a given level of compression than new, napped felts. These compression curves are used to verify a general theory for determining the load versus nip strain relationship of the press section. The results of the experiments conducted on an experimental press section tend to confirm the theory and have thus pointed to the extreme importance of the high speed compression characteristics of the material in the nip region in determining the dynamics of a press.