RECYCLING OF PAPER - CHANGES OF MECHANICAL AND OPTICAL PROPERTIES

11th International Multidisciplinary Scientific GeoConference SGEM2011, www.sgem.org, SGEM2011 Conference Proceedings/ ISSN 1314-2704, June 20-25, 2011, Vol. 3, 867-874 pp

ABSTRACT

The goal of a recycled paper or board manufacturer is to make a product that meets
customers΄ specification and requirements. At the present utilization rate, using recycled
fibres in commodity grades such as newsprint and packaging paper and board has not
caused noticeable deterioration in product quality and performance. The expected
increase in recovery rates of used paper products will require a considerable
consumption increase of recycled fibres in higher quality grades such as office paper
and magazine paper. To promote expanded use of recovered paper, understanding the
fundamental nature of recycled fibres and the differences from virgin fibres is
necessary.

The aim of this work was to follow and qualify the changes at the selected properties of
pulp fibers, made up of soft wood composition, by recycling process.

The experimental conditions, in term of fibers modification, simulated the process of
paper production begun from primary fibers 8-times recycled. The pulp fibers were
drying at the temperatures: 80°C, 100 °C, and 120 °C. After each recycling process
selected properties (strength- breaking length, tear index, optical -brightness, opacity
hand sheets properties) were evaluated.

Following result determination of 8-multiple recycling of bleached kraft pulp, made of
the mixture of soft woods, was shown that the process of repeated defibering, beating
and drying causes irreversible modification in pulp fibres. After the fifth recycling
(sixth beating) faulted changes (extremes) were observable in mechanical and optical
properties. We interpret these changes as ending of outside and more intense of inside
fibrillation and delamination. The influence of recycling number on selected properties
of fibres was evident after every beating degree and this effect was markedly proved in
pulp drying at higher temperature -120 °C.

Keywords: paper recycling, mechanical properties, optical properties, drying temperature, softwood pulp