For most people, wood is the hard material you find when you remove the bark from a log of wood. Even though it can be shaped with a saw or a knife, it is quite hard and predictable. Seen from a chemical perspective, wood is however a highly flexible building block. The components of wood can be combined with other substances and even formed to create completely new substances or material.
Some 45 per cent of the wood truck is fibre. When a fibre is fully formed it dies. This means that nearly all the cells in wood are dead and cannot be changed. Wood fibres consist primarily of cellulose, hemicellulose and lignin.
 
Wood from spruce is comprised of 41 per cent cellulose, 26 per cent hemicellulose, 29 per cent lignin and three per cent extractive matter. Cellulose and hemicellulose are both built up from polysaccharides. In contrast to cellulose, the structure of hemicellulose is forked with much shorter chains and is built up from other saccharides.

Pulp is still the most common application of cellulose, but composite materials such as WPC (Wood Plastic Composite) and FRC (Fibre Reinforced Composite) are rapidly growing application areas.

In WPC, wood is mixed with plastic, pigments and other substances to a product that can be formed and handled with woodworking tools, but remains extremely resistant to moisture and rot.

FRC is a fibre-reinforced composite material. The fibres, which can be both cellulose and carbon, are cross-linked in the composite and thus reinforce the strength of the material. There are many different types of FRC depending on which composites are used, and the applications are many including thermoplastics and construction material.

But cellulose can, in addition to being mixed with other substances, even be chemically reshaped into completely new substances with unique properties. One example is rayon – the world’s oldest artificial fibre. Greve Hilair de Bernigaud, after 29 years of research, was able to take out a patent on the world’s first artificial fibre in 1889 for a fibre called Chardonnay silk. This fibre, which had its shortcomings and ultimately disappeared from the market, was the origin of the rayon fibre that has been used in textiles since 1926. Cellulose as a raw material is thus nothing new in chemistry, but as the world’s oil supplies dwindle the interest in cellulose is once again growing as a renewable replacement for oil in plastics and other chemical products.

At Södra we are working on projects to add new properties to wood fibre, such as making it water resistant. Another project is to use the hemicellulose which already exists in wood and which has properties that should enable it be used in gels or thickening agents, or as a barrier film for liquid paperboard that would be more ecofriendly and easier to recycle. Read more about our projects here.