A typical textile sample does not flare up suddenly as usual, but only hesitantly begins to melt. At first, the fabric only contracts and dark polymer droplets fall off very late … An excellent result for flame retardancy, which was made possible by a new development by the “Deutschen Institute für Textil- und Faserforschung [German Institutes for Textile and Fibre Research]” (DITF). As the trade journal “Melliand Textilberichte” reports, it was possible to achieve a kind of intrinsic flame resistance for the first time, because the properties are directly part of the polymer chains of the material.
Flame retardant phosphorus compounds are usually added to the polymers as additives. However, large quantities of phosphorus compounds are required to achieve a good fire protection effect. And this is usually done at the expense of the physical and physiological properties of the textiles.
Contrary to the usual methods of adding flame-retardant properties to the polymer using phosphorus compounds as an additive, the researchers from Denkendorf with this new method were able to incorporate these directly into the polymer chains at low concentrations. This takes place directly during polycondensation, i.e. the synthesis of the plastic in reactor vessels.
In general, the aim here is to produce molecules with as long a chain as possible in order to guarantee good properties for later spin ability of the polymer granulate into textile fibres.
Fewer Phosphate Compounds With The Same Properties
One problem of traditional manufacturing processes is that when larger amounts of phosphorus compounds are added as additives, they prevent the formation of long molecular chains – they thus act as chain breakers. The resulting plastic is very difficult to process into fibres, and in addition, due to ageing and washing processes, the additive emerges from the fibre over time.
The new process allows compounds to be chemically coupled to the molecular chains and thus achieves a much stronger bond to the polymer – more than would be possible with additive blends.
The reduction of the required flame retardants makes it much easier to control the achievable molecular weight during synthesis, according to the journal. In this way, the viscosities can be precisely adjusted to guarantee the optimum spin ability of the polymer into fibres.
In addition, the chemical bonding of the flame retardants to the polymers prevents migration and leaking from the fibres due to ageing, which is common with the use of additives.
In their application, such textiles made of intrinsically flame-retardant polyamides show their advantages, especially where high flame-retardant requirements are placed on the materials. This is usually the case in home textiles like carpets, upholstery and seat covers or curtains.