WHAT KIND OF PLANT FIBRE IS USED TO MAKE PAPER?

Nowadays most paper is made from specially grown trees. These trees are usually softwoods, grown in the cooler parts of the world where little else can thrive. Fir, pine, spruce, larch and cedar trees are all used. The trees do not have to be very tall or straight, as they do for timber. Almost all parts of the tree, except the bark, can be ground up into fibres for papermaking.

Most plant materials also contain nonfibrous elements or cells, and these also are found in pulp and paper. The nonfibrous cells are less desirable for papermaking than fibres but, mixed with fibre, are of value in filling in the sheet. It is probably true that paper of a sort can be produced from any natural plant. The requirements of paper quality and economic considerations, however, limit the sources of supply.

Pulped forest tree trunks (boles) are by far the predominant source of papermaking fibre. The bole of a tree consists essentially of fibres with a minimum of nonfibrous elements, such as pith and parenchyma cells.

Forests of the world contain a great number of species, which may be divided into two groups: coniferous trees, usually called softwoods, and deciduous trees, or hardwoods. Softwood cellulose fibres measure from about 2 to 4 millimetres (0.08 to 0.16 inch) in length, and hardwood fibres range from about 0.5 to 1.5 millimetres (0.02 to 0.06 inch). The greater length of softwood fibres contributes strength to paper; the shorter hardwood fibres fill in the sheet and give it opacity and a smooth surface.

Since cellulose fibre is a major constituent of the stems of plants, a vast number of plants represent potential sources of paper; many of these have been pulped experimentally. A rather substantial number of plant sources have been used commercially, at least on a small scale and at various times and places. Indeed, the use of cereal straws for paper predates the use of wood pulp and is widely practiced today throughout the world, although on a relatively small scale of production. Because many parts of the world are deficient in forests, the development of the paper industry in these areas appears to depend to a considerable degree upon the use of annual plants and agricultural fibres.

Nonwoody plant stems differ from wood in containing less total cellulose, less lignin, and more of other materials. This means that pulps of high cellulose content (high purity) are produced in relatively low yield, whereas pulps of high yield contain high proportions of other materials. Papers made from these pulps without admixture of other fibre tend to be dense and stiff, with low tear resistance and low opacity.

The morphology (form and structure) of the cells of annual plants also differs considerably from wood. Whereas the nonfibrous (parenchyma) cells of coniferous wood constitute a minor proportion of the wood substance, in annual plants this cell type is a major constituent. As hardwoods also often contain considerable amounts of nonfibrous cells, there is a closer resemblance between hardwood pulps and pulps from annual plants.

Picture Credit : Google