Cellulose fibre

Cellulose is a natural polymer that makes up the majority of plant cell walls and vegetable fibres. It is typically locked in with lignin and hemicellulose, except in the case of cotton which is virtually pure cellulose. In the production of cellulose fibres, it is extracted from wood and other plants with chemicals or by mechanical means in much the same way as paper pulp.

Chemically produced cellulose, called regenerated cellulose, is semi-synthetic, combining renewable ingredients with polymer chemistry. Some types of cellulose acetate use some pretty toxic chemicals in production and result in significant volatile organic compounds (VOC). This is being addressed with modern production techniques that help to reduce, but do not eliminate, by-products such as sulphur, metal salts (copper and zinc) and ammonia, which are potentially harmful to people and the environment if not properly managed. Lyocell has taken a novel approach, using a different chemical system – N-methylmorpholine-N-oxide (a form of amine oxide known as NMMO) and water – which allows a virtually closed-loop production system.

They may be biodegradable and compostable. To be certified compostable, the product must break down into water, CO2, and biomass at a rate consistent with other biomaterials. Also, there must be no negative chemical effects on the final compost, which is ensured through eco-toxicity testing – for example, dyes and finishes must be compatible. Thermoplastic types are recyclable.

Cellulose fibre – viscose, lyocell, modal, acetate other types of regenerated fibres – may be produced from recycled cotton and other cellulose rich fibres. The waste material is shredded, de-buttoned, de-zipped, de-coloured and turned into a slurry. Contaminants and other non-cellulosic content are separated from the slurry. The slurry is dried to produce dissolving pulp, which is used to make new cellulose fibres, such as viscose, lyocell, modal and acetate. Another example is Infinna, who take mixed textile waste with high cotton (or cellulose) content and chemically recycle it with urea to produce new regenerated cellulose carbamate fibre.

The type of plastic depends on the degree of substitution of hydroxyl groups with acetyl types. During the manufacture of triacetate (TAC) the cellulose is completely acetylated (>92%), whereas in regular cellulose acetate or cellulose diacetate, it is only partially acetylated. Partially acetylated types are used in fibre, textiles, filters, films, drug delivery, membranes and moulded products. Triacetate, used in film and fibre, is significantly more heat resistant than acetate and diacetate types – with increasing acetyl content, the permeability to gas and moisture decreases whereas the chemical resistance, heat resistance and stiffness increases.

Spinnova is an innovate fibre development that has removed the need for chemicals during production. Using a process similar to paper making, cellulose materials such as wood and cotton are mechanical refined to produce micro fibrillated cellulose (MFC). Suspended in water, the mix is passed through a nozzle where the MFC become oriented and entangled as a strong yarn.