The physical properties of cardboard depend primarily on the type and quantity of fibres used. This criterion applies especially to rigidity, especially if the cardboard consists of several layers. Flexural strength is mainly influenced by the composition of the fibers and the structure of the layers.
What are the types of fiber that make up the cardboard?
For the manufacture of cardboard, two types of fibers are mainly used: mechanically treated or chemically treated. Since the process used for the mechanical or chemical treatment of wood have great differences, the two types of fibers also identify cardboards with different properties.
What are the main differences between mechanical fibers and chemical fibers?
Mechanical fibers are short and rigid, unlike chemical ones that are long and elastic. As a result, a cardboard composed of 100% mechanical wood pulp will be a cardboard with high volume and high rigidity. In contrast, a cardboard composed of 100% chemical pulp will be denser (that is, with a smaller volume) and more durable and elastic.
Products made with 100% chemical pulp have a resistance about 3 times higher than that of 100% mechanical paste products. The elongation values are about 50% higher. This is mainly due to the fact that chemical paste consists of long and well-connected fibers.
What about recycled fibers?
Recycled fibers come from both mechanical and chemical pulp. During the recycling process, the fibers are subject to contamination and high stress, losing resistance.
Depending on the process, the number of recycling steps is between 2 and 4. To ensure the desired quality of recycled products, primary fibres must always be added to the recycling process.
Is there a ProntoPack product composed of different types of fiber?
Among the ProntoPack products there are certainly some cardboards composed of different types of fiber. One of them is the Pronto White: high thickness GC1 cardboard characterized by a double layer of coat on the front and a layer of coat on the back. Its composition includes a bleached thermo-chemical-mechanical pulp, therefore containing both fibers.
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