Wood pulp can be classified according to a variety of criteria, including raw material source, preparation method, and beating characteristics. Here is a breakdown of the categories and their characteristics:
1. According to the source of raw materials:
• Coniferous wood pulp: derived from coniferous trees, such as pine, spruce, etc. This kind of wood pulp fiber is longer, high strength, suitable for the manufacture of high-strength paper and packaging materials.
Hardwood pulp: from hardwood trees, such as eucalyptus, poplar, etc. This kind of wood pulp fiber is short, but the softness is good, suitable for the manufacture of writing paper and printing paper.
• Depending on the preparation method:
• Chemical pulp: Use chemical solvents to treat wood, dissolve lignin, and separate fibers. Including kraft pulp (also known as kraft pulp), sulfite pulp and so on. The chemical pulp quality is higher and the fiber damage is less.
Mechanical pulp: By grinding wood through mechanical action, more lignin is retained, so the color is yellow, less durable, often used to produce low-cost paper such as newspaper.
Chemical Mechanical pulp (CMP or TMP) : A combination of chemical and mechanical methods, softening wood with chemicals and then grinding it mechanically, can improve the efficiency of fiber separation and reduce energy consumption.
• According to beating characteristics:
Early wood (spring wood) : The part of wood formed at the beginning of the growing season, with a softer texture and longer fibers.
Late wood (fall wood) : The part of wood that forms late in the growing season and has a harder texture and shorter fibers. These two kinds of wood behave differently in the beating process, affecting the nature of the final paper.
In addition, there are some pulp prepared from non-wood raw materials, such as grass pulp, cane pulp, etc., these are often called non-wood fiber pulp, suitable for specific types of paper production.
Different classifications of wood pulp are suitable for different uses, for example high-quality writing paper may require high-quality chemical coniferous wood pulp, while low-cost newsprint may use mechanical hardleaf wood pulp.