Rn: The Effects on Fibres from Multiple Recycles, 1993 Recycling Symposium Proceedings

Loreen D. Ferguson

The effects of recycling on chemical pulp fibers are quite well documented in the literature. Until recently, there has been little work on the effect of recycling on mechanical pulp fibers. This paper is a review of the recent work reported in the literature to assess the effects that recycling has on the physical properties of mechanical pulp based paper. Researchers have examined the effects of: the original pulping process, for example, TMP and CTMP; papermaking processes like repulping and calendering; the effects of the chemicals; the effects of a mixed ONP/OMG type furnish, and final

printability.

The researchers have shown that, surprisingly, mechanical Pulp furnishes suffer minor effects from repeated

recycling. Sheet density and scattering coefficient are reduced, but physical

properties such as burst, tensile and fold are increased. The typical furnish for a recycled newsprint mill will

contain some fraction of kraft fibers. The physical properties of a blended furnish will exhibit changes relevant

to both kraft and mechanical pulp fibers. As the rate of change in physical properties with recycling is

different for chemical and mechanical pulp fibers, the effects are the net result of the different rates.