JEC COMPOSITES MAGAZINE - Issue #81 - May/June 2013 - 53

Fig. 2: Board layering technique

achieved by piling two or three separately formed mattresses and
then hot-pressing them. This enables the manufacturer to optimize
the different layers, e.g. achieve enhanced surface smoothness or
mechanical resistance. The study includes the development of two
multi-layering methods to produce novel types of hardboard.

Fibre sorting by size
The first optimization method investigated consists in improving
hardboard properties via fibre size sorting. According to the experimental data obtained within the study, fibre size has a significant
effect on hardboard bending properties (Figure 3). Contrary to
initial expectations and existing opinion, reducing the large fibre (i.e.
> 2.32 mm) content increases the modulus of rupture (Mor), while
increasing the small fibre (< 0.105 mm) content improves it. Therefore, hardboard made as three layers with small fibres on the surface
would have smoother surfaces and enhanced bending properties.

multi-layered panel. Thus keeping the board faces pristine.
According to the results obtained so far, up to 10% of virgin wood
fibres can be substituted by rejects without affecting panel performance. reducing wood fibre consumption by 10% would provide
significant annual savings in wood and energy at the industrial scale.
In addition, the use of paper recycling wastes to make fibreboard will
reduce the environmental impacts of both the paper recycling and
panel board industries.

Recyclability of the new boards
Paper recycling wastes contain high amounts of non-fibrous inorganic matter. This may affect the recyclability of the panels, so a short
study was conducted. A number of multi-layer panels containing
20% paper recycling wastes were repulped and their fibres mixed
with virgin fibres and made into new multi-layer hardboard panels.

Fig. 4: Specimen dimensions and artificial crack positions

Figure 4 shows the Mor of the new boards as a function of their
recycled fibre content. It appears quite clearly that the Mor is not
negatively affected, quite the reverse in fact. This is because the average fibre size is reduced in the panel, thus improving its properties.

Conclusion
Fig. 3: Effect of fibre size on hardboard resistance to bending

Inclusion of rejects from the paper industry into the
boards
The second optimization method focuses on both energy and wood
savings via partial substitution of virgin wood fibres with waste
materials generated during paper recycling processes within one or
more of the fibreboard layers. These reject materials often represent
about 30% of paper recycling volumes which, in spite of their high
wood fibre content, are currently incinerated or disposed in sanitary
landfills. This study investigates the potential of mixing paper wastes
with virgin fibres and then concealing them in the core layer of a

The multi-layering technique could improve the properties and
reduce the manufacturing costs of hardboard panels. Properties can
be improved by sorting fibres by size and placing the smallest fibres
in the outer layers of the panel. Manufacturing costs can be reduced
by substituting some of the virgin fibres with wastes from the paper
recycling industry. boards made this way can still be recycled at the
end of their first useful life. n
More information:
www.fcba.fr; www.ecoledubois.fr
Acknowledgements
Financial support for the present research work was provided by the
BoostEff European 7th Framework programme project (FP7-NMP2009-LARGE-3).

No81 May - June 2013 /

jec composites magazine 53

http://www.fcba.fr http://www.ecoledubois.fr

JEC COMPOSITES MAGAZINE - Issue #81 - May/June 2013

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