The effect of additives on the mechanical properties of dry-formed fibre networks

The effects of thermal bonding and friction-changing additives on the mechanical properties of dry-formed cellulosic networks have been evaluated. Calcium carbonate particles and a cationic surface active agent were used to change the coefficient of friction of cellulose (Chemothermo mechanical pulps; (CTMP) and rayon fibres. The parameters used to describe the networks were the storage modulus G'(o) (measured at low strain amplitudes) and the critical strain gamma(c) (at which the network yields) obtained from the dynamic-mechanical measurements and the maximum force F-max measured with a shear tester. The mechanical properties of the networks were improved as a result of the thermal bonding, which promotes stress transfer through the network structure. The friction-changing additives changed the ability of the fibres in the network to disentangle before the network ruptures. This change was, in the first place, reflected in corresponding changes in the critical strain gamma(c) and the maximum strength F-max of thd dry-formed networks. (C) 1998 Chapman & Hall.