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The Role of Water in Papermaking, H Bonds |
"The more one knows about the fundamental nature of a material or a process, the more likely it is that some improvement can be effected."
-James d'A Clark.
"Basically the pulp and paper industry is concerned with taking vegetable matter apart, then bonding selected portions with the aid of water. Thus it is important to have some concepts of the nature of cellulose, water, and other materials, and of the forces that apply to the constituent parts. weaker and non chemical bonds between particles are so important with respect to paper." -James d'A Clark.
The Role of Water in Papermaking
Cellulose is found in reeds, cotton, linin, esparto, straw and wood, which are all used to make paper. When water is added to these materials, water adheres to open surfaces because cellulose is extremely hydrophyllic.The free surfaces of the water droplets create internal negative pressure, and this holds the fibers together. As the pulp dries, the droplets shrink, and their negative pressure increases, pulling the fibers closer together. Finally, hydroxyl groups of the adjacent cellulose surfaces create linkages called hydrogen bondswhich holds the fibers together permanently, to make strong paper.
Binding in paper
After water (H2O) is removed from a paper sample, several types of binds can occur:
Hydrogen bonds are an integral part of papermaking. Strength in the plane of the paper is from H bonds and van der Waals forces from where fibers dried together. For a Hydrogen bond to occur, there must be Hydrogen attached to Nitrogen, Oxygen, or Fluorine with an electron pair to share.
Surfaces of like material 'stick' together without any cementing substance.
This property is called 
cohesion,
from the Latin root co-, which means together. Coherence of cellulose fibers
is largely from H bonds. Another form of 'stick' is called mechanical binding,
or the entanglement of fibrils on surfaces of fibers important in papermaking.
Another type of binding is called frictional binding. Frictional binding occurs when the direction of the fibers makes it difficult to separate the fibers. For instance, at the torn edge of a sheet of paper, it is hard to pull a fiber out in the direction of the plane of the sheet. Conversely, it is easier to lift off a fiber lying on and protruding from the surface of the sheet
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