ANALYSIS OF PAPER MANUFACTURING
An analysis of how paper is created will help to understand the properties that I have discovered through research and testing. Paper is a felt of highly compressed cellulose fibres which are formed into a flat sheet through the addition of water and heat. The fibres are suspended in water after being chemically broken down. This pulp which is constructed of 90% water is then sprayed onto a conveyer belt and successively compressed and drained to its final thickness and a water content which is usually 6 - 8%. As a result of this process 70% of the fibres are aligned to the machine direction, 20% in the opposite direction and 10% in the paper thickness. This creates an anisotrophic material whereby properties are different in the three orthogonal directions, with the bonding of fibres primarily dependent on hydrogen bonds. As most of the fibres are laid in compression the paper has a greater structural strength in compression. This process method has a 5mm thickness limit due to the ability of the drying process to dry the paper to a sufficient moisture content. To increase the thickness of the material PVA can be used to glue layers together. To create cardboard tubes multiple layers of spirally wound paper plies are glued together with a starch or a PVA glue, with up to 22 plies being combined to create a tube of 16mm thickness. It is through the lines of the spiral that the tubes failed in compression as they are the weak points of the material.
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