What type pf pulp is the
best?
This is a question that we are often asked, and our
answer is that “it depends”.
Different papermaking applications place different
demands on their fibre components. The properties of
the component pulps, especially their length, coarseness
and collapsibility, strongly influence their papermaking
potential and the quality of the final paper. Some papers
require very high tensile strength properties while
others require a very bulky porous structure. Other
paper grades need folding endurance, while still others
must be strong while light in weight. The skill of the
papermaker produces papers in a very diverse range of
grades and types and does so on a wide variety of machines.
No one fibre type could possibly be ideal for all of
these circumstances.
So let us start by considering the properties that
contribute to Tensile strength. As before we will concentrate
here on softwood fibres. Tensile strength has often
been described as the most fundamental property of paper,
and this is probably no exaggeration. In simple terms,
tensile strength is controlled by the intrinsic strength
of the fibres and the strength and area of the hydrogen
bonds formed between the fibres. For a given fibre strength,
increasing the sheet consolidation by wet-pressing,
or increasing the strength of the bonds through hemicellulose
retention, are common ways to achieve higher tensile
strengths. But the most commonly used way of achieving
high tensile strength in paper is through using fine,
low coarseness, collapsed fibres in the paper furnish.
Paper made from flat, ribbon like fibres will exhibit
far higher tensile breaking length properties than paper
made from cylindrical fibres (for a more detailed description
click here to view our Morphology
presentation. The graph shown here of data from recent
testing done at the Canfor R&D Centre, demonstrates
the effect of coarseness on the potential to develop
tensile strength. Fine fibres have a low coarseness,
while coarse fibres have a high coarseness.
| Porosity/Bulk
Click on graph for larger image |
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| Reinforcement |
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