InFlameTex - Development of a circular economy capable textile floor covering for the commercial sector based on bicomponent fibers made from flame-retardant and conventional polyamide 6

Textile floor coverings with flame retardants reduce the risk of fire and the spread of fire. Such floor coverings are installed in large quantities in commercial buildings. However, recycling these materials is difficult to implement because the floor coverings consist of several interconnected layers and the established flame retardants are usually ecologically problematic.

The basis of the newly designed carpet yarn is polyamide 6 (PA6), which has intrinsic flame retardancy. This means that the flame retardant is permanent and can neither be washed out nor emitted into the environment. The viscosity of the polyamides and their phosphorus content could be precisely adjusted.

The new material was spun into fibers on a Biko spinning system. So-called bicomponent fibers are created in it. These have a core made of conventional polyamide and a shell made of PA6 with highly concentrated flame retardant. The core and sheath components of the fibers complement each other perfectly: the fiber core ensures technically good spinnability and sufficient strength of the fibers. The fiber cover, on the other hand, has flame protection exactly where temperature and flames attack: on the surface of the fiber.

The second aspect of the research project deals with the recyclability of the textile floor covering. This is about separating the flame-retardant top layer of the floor covering from the textile backing. The polymers and Biko yarns produced at the DITF are used to develop textile floor coverings with a top layer made of flame-retardant modified multifilament yarn and the textile backing. The back coating is designed in such a way that thermal separation of the back from the flame-retardant top layer is possible. Hot melt adhesives are used for this, whose flammability is also taken into account. For this purpose, the fire properties of the textile floor coverings are determined. The separability of the top layer and back is verified in laboratory tests.

Results:

To produce textile floor coverings from bicomponent fibers (core-shell), commercial polyamide 6 was used for the core (Ultramid B24N03) and polyamide 6 polymers were synthesized for the flame-retardant sheath. Various flame retardants were used for this purpose. Three selected candidates were successfully integrated into polyamide 6. The syntheses could be scaled to 25 kg batches.

The spun bicomponent yarns were false-twist-textured in preliminary tests to imitate the BCF character. These fine textured yarns (

Using a statistical series of tests, a hot melt adhesive (Co. Abifor) was selected that enables the wear layer and backing to be separated. Measurements of the pole knob pull-out forces confirmed good integration of the knobs in the carrier. The top was successfully tested in accordance with the specifications. Based on the knowledge acquired here, a demonstrator was built and installed on a test track. After a three-month inspection period, no change in appearance or delamination of the back could be detected. A second demonstrator was produced using the same hot melt adhesive. This was applied to a hot calender, where the wear layer and backing could be successfully separated.

The final report can be obtained from the research institution.

Figure: Bicomponent fibres (cross section) - core with flame retardants and sheath without flame retardants

Funding program and project number

IGF 21736 N

Duration

01.04.2021 – 31.03.2023