Flame-retardant textiles in the recycling loop

 2 min

In recent years, the topics of recycling, sustainability and circular economy have become increasingly important in the textile industry – including flame-retardant textiles. Several factors are driving this development: EU regulations, economic advantages through raw material savings and increased customer interest. The nonwovens industry in particular offers numerous opportunities to reintroduce residual materials into the production cycle.

The processing of textile by-products such as edge trimmings, quality rejects and cutting residues made of high-quality fibres represents an economically interesting alternative to disposal. Particularly in the case of high-performance materials such as carbon fibres, aramids (meta- and para-), PI, PA 6, PA 6.6, PAN and oxPAN, the high material costs make even more elaborate processing worthwhile. In further development steps, the processes can also be transferred to ‘end-of-life’ products and less expensive fibres such as glass and viscose fibres, PES or PP.

For the processing of the materials, shredding cards are used, sometimes supplemented by upstream cutting processes that reduce the raw material to the required length of 40-80 mm. Alternatively, hammer mill systems also achieve good results. Crucial to the success of the process is a contaminant-free raw material without foreign materials such as plastics, metal parts or wood, which could cause damage to the web forming units.

Reuse of High-performance Fibres – Challenges and Opportunities

One of the main challenges lies in the irregular fibre length of the recycled material. In addition to short fibres and dust, very long fibres also occur, and a large number of unopened parts can arise, especially when processing dense fabrics. The combination of mechanical web formation with needling technology has proven effective for further processing.

The tests show that flame-retardant textiles make it possible to produce fleece. However, highly compressed raw materials from fabrics or MAX non-crimp fabrics are more difficult to process and often do not provide sufficient quality for high-quality products. Short fibres, dust and fabric residues cause problems for the carding rollers and needles during the bonding process, which makes long-term production difficult.

Nevertheless, various products based on recycled materials have already been established. The processing of aramid and carbon fibres is particularly successful. Carbon fibre-based nonwovens from various sources are currently available industrially, both as needle-punched and stitch-bonded materials. In addition, aramid fibres from sustainable sources are used for various products.

Recyclable Textile Floor Coverings with Intrinsic Flame Retardancy

Another innovative approach in the field of sustainable flame-retardant textiles concerns the development of recyclable textile floor coverings. Large quantities of flame-retardant floor coverings are installed in commercial buildings, and recycling them is challenging due to the multilayer structure and the mostly ecologically problematic flame retardants.

A novel concept relies on flame-retardant polyamide 6 (PA6) with intrinsic flame retardancy. In this process, the flame-retardant chemical – a phosphorus compound – is not applied to the fibre surface, but chemically bound to the molecular structure of the PA6. This makes the flame retardancy permanent and prevents it from being washed out or released into the environment.

Although the concept of intrinsic flame retardancy is not new, it has been significantly optimised in recent years. The polyamides have been precisely adjusted in terms of their viscosity and phosphorus content, enabling the two difficult-to-reconcile requirements of spinnability and high flame retardancy to be met simultaneously.

This development enables the production of textile floor coverings that not only contain a reduced proportion of flame retardants but are also optimised for material recycling – an important step towards a sustainable and circular textile industry.

Sources: Online platform ‘scinexx.de’ / Trade journal ‘Technische Textilien’

Photo: ihalilyp