acrylamide and 0 3 mohr salt in the solution the ph was maintained at 1 5 after agitation during 30 minutes at 50 u00b0 c the cellulose sample was washed and weighed the material contained 500 polyacrylic acid this amount of polyacrylic acid means that the fibre material has increased its weight 5 times through the addition of grafted polyacrylic acid accordingly the fibres treated in this way contain a covalent bound grafted polymer which in water forms a hydro gel and creates accordingly a swelling of the material moreover the swelling is promoted when the fibre material is aftertreated with alkali and or acid non woven fibre of polypropene was placed in an ozone reactor and exposed during 45 minutes as described in example 1 the ozoned fibre was thereafter grafted in a solution of 30 acrylic acid 10 edma and 0 3 weight of mohr salt based on the monomer after 25 minutes the grafting was visible after 100 minutes the material contained 1800 polyacrylic acid this means that the fibre material had increased its weight by 18 times the fibres were thereafter treated with 1m naoh at 80 u00b0 c during 3 hours and were dried when the fibres were placed in water.