Wood chemistry fundamentals and applications pdf

Many kinds of paper are made wood chemistry fundamentals and applications pdf wood with nothing else mixed into them. This includes newspaper, magazines and even toilet paper.

Pulp is one of the most abundant raw materials worldwide. By the 6th century, the mulberry tree was domesticated by farmers in China specifically for the purpose of producing pulp to be used in the papermaking process. In addition to mulberry, pulp was also made from bamboo, hibiscus bark, blue sandalwood, straw, and cotton. By 1900, sulfite pulping had become the dominant means of producing wood pulp, surpassing mechanical pulping methods. Canada being the largest source at 21 percent of the total, followed by the United States at 16 percent. Chemical pulp made up 93 percent of market pulp. The finished product may be either bleached or non-bleached, depending on the customer requirements.

The aim of pulping is to break down the bulk structure of the fibre source, be it chips, stems or other plant parts, into the constituent fibres. Much of the lignin remains adhering to the fibres. Strength is impaired because the fibres may be cut. There are a number of related hybrid pulping methods that use a combination of chemical and thermal treatment to begin an abbreviated chemical pulping process, followed immediately by a mechanical treatment to separate the fibres. These hybrid methods include thermomechanical pulping, also known as TMP, and chemithermomechanical pulping, also known as CTMP.

The chemical and thermal treatments reduce the amount of energy subsequently required by the mechanical treatment, and also reduce the amount of strength loss suffered by the fibres. 9 percent, and second- and third- and more generation forests account for the rest. The number of trees consumed depends on whether mechanical processes or chemical processes are used. 24 trees to produce 0.

Mechanical pulping is about twice as efficient in using trees, since almost all of the wood is used to make fibre, therefore it takes about 12 trees to make 0. Most pulping processes require that the wood be chipped and screened to provide uniform sized chips. Most modern mills use chips rather than logs and ridged metal discs called refiner plates instead of grindstones. The pulp is then screened and cleaned, any clumps of fibre are reprocessed. Chemical pulp is used for materials that need to be stronger or combined with mechanical pulps to give a product different characteristics.