Lignocellulosic fibres, sources

In order to use models to estimate composite properties, it is necessary to know the properties of the fibres, which vary widely depending on the source, age, separating techniques, moisture content, speed of testing, history of the fibre, etc. The properties of the individual fibres are therefore very difficult to measure. Moreover, in a natural fibre-polymer composite, the lignocellulosic phase is present in a wide range of diameters and lengths, some in the form of short filaments and others in forms that seem closer to the individual fibre. 

Agro-based lignocellulosics suitable for composites come from two main sources. The first is agricultural residues and the second is those lignocellulosics grown specifically for their fibre. The first source includes rice husks or cereal straws, which are by-products of food or feed crops and can be used for everyday purposes such as animal bedding or fuel or alternatively are simply left on the field or burnt to reduce mass. Two examples of the second source are jute and kenaf. These plants also have residues, which are often used for bedding or fuel as well. 

None of the vegetable and animcil fibres are of major importance as additives for polymers, although cotton yams were extensively used in flexible composites, including tyre cords, before the development of manufactured fibres to replace them. Cellulosic fibres, derived from cotton or cheaper lignocellulosic sources such as jute and hemp, are used to some extent in gaskets and in other thermosets, and despite their low char temperatures are sometimes added to thermoplastic polymers. 

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