Polymers have been incorporated into paper by (a) solution impregnation, (b) latex impregnation and (c) latex beater addition.
Their effects on the strength properties of the sheet were measured by conventional tests and interpreted in terms of the separate effects of the polymers on bonds and fibres and the distribution of polymer in the sheet. It is noted, however, that the introduction of polymer resulted in time-dependent behaviour that deserves special consideration. Stress relaxation properties were therefore examined and analysed for a variety of polymers and conditions.
A procedure is described in which experimental data relating to relaxation and creep are conveniently obtained and can provide the basis for evaluation and analysis.