Comparison of Softwood Pulp and Hardwood Pulp

softwood pulp and hardwood pulp

Wood is the main resource of fiber materials for paper and pulp making. Nowadays, wood provides about 93% of fibers of pulp making, the rest of the fiber materials include wheat straw, sugarcane bagasse, bamboo, reed, jute and other non-wood fibers.

According to types of tree, wood can be divided into two types: softwood and hardwood. Generally, gymnospermae is called needle wood or softwood; angiosperm is called broadleaf wood or hardwood. Hardwood and softwood is just a habitual way to distinguish them, although hardwood is harder than softwood, there are always exceptions to the rule, as one kind of hardwood, poplar is softer than some softwood. In the world, wood fibers are made up of 35% softwood and 65% hardwood.

Both softwood and hardwood can be applied to paper and pulp making. Correspondingly, the wood pulp can be classified into softwood pulp and hardwood pulp. How much do you know about softwood and hardwood? What is the difference between softwood pulp and hardwood pulp? We’ll figure it out today.

Softwood and softwood pulp

softwood and softwood pulp

As the name suggested, softwood is soft and strong, contains more resin. Softwood has obvious feature of seasonal growth. Softwood generally grows at an altitude of 100 to 1500 meters, with economic and ornamental value. Common softwood includes pinus massoniana, larch, red pine, spruce, and etc. Most of the softwood grow in the high altitude area, Finland, Canada, Sweden are the main softwood pulp production of place worldwide.

The vertical structure of softwood is almost made up of conical cells. Some kinds of softwood contain resin canal. The horizontal system consists of narrow ray cells.

Hardwood and hardwood pulp

hardwood and hardwood pulp

Hardwood consists of 43-70% wood cellulose, 20-40% duct, 10-20% wood ray and 2-13% parenchymal cell. Hardwood generally has large size and weight, it is easy to warp, crack, and hard to process. Common hardwood includes birch, poplar, basswood, eucalyptus, maple, and etc. hardwood fiber is short, the length is usually about 1mm and length-width ratio mostly less than 60 times. Hardwood contains a large number of parenchyma cell, the paper made from hardwood pulp has low strength, loose paper quality, strong absorptivity, high opaqueness, hardwood is so applicable for printing paper manufacture.

The relative density of hardwood range from 9%-23%, deflective hardwood and branches will grow tension wood. Although tension wood has high chemical pulp yield, tension wood fiber is not easy to beat, low binding force between fibers.

Differences between softwood pulp and hardwood pulp

Softwood pulp and hardwood pulp are two classifications of wood pulp. There are a lot of differences between softwood and hardwood, such as fiber characters, price, applications, etc.

  • Fibers: softwood fiber is long, thin, and pure, contains fewer impurities; hardwood fiber is short and thick, contains more impurities.
  • Lignin content: lignin content of hardwood is less than softwood, about 20-40%, so hardwood is easier to make pulp and bleached, less alkaline consumption required.
  • Density: the density of wood has the close connection with paper pulp quality, for example, paper yield per unit volume is proportional to density, and high-density wood pulp has slower beating rate, bigger bulk, and tensile strength. In general, hardwood has the higher density than softwood.
  • Paper character: The softwood pulp paper has good flexibility, high folding strength, good tensile strength, and printability. The hardwood pulp paper is loose, with strong absorptivity and high opaqueness, high thickness, high stiffness.
  • Price: under the same condition, softwood pulp is more expensive than hardwood pulp.
  • Application: softwood pulp is excellent material for papermaking, generally apply for text paper, coated paper, map paper, offset paper and other industrial and technical paper manufacture. Compared to softwood pulp, hardwood pulp is worse, but still belong to good paper pulp, mainly mix with softwood pulp and apply for manufacturing coated paper, lightweight coated paper, offset paper, also apply for printing paper and writing paper solely.

Except for wood pulp, there are other fiber materials for paper and pulp making, such as bagasse pulp making, bamboo pulp making, reed pulp making, wheat straw pulp making, cotton pulp making, jute pulp making and wastepaper pulp making, etc.



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