Flame Retardants

A review of the wash durable flame retards used in textiles, identify them, explain methods of application, and what problems do they present to nonwovens.

There is an increasing interest for Flame Retardant (FR) nonwovens, especially due to recent legislations and market trends wherein the upholstered furniture and bedding products are required to pass the standard open flame test. Presently this standard is active in California, and there is a proposal to extend across the country soon.  In this regard, we are developing cotton based nonwovens for bedding products with flame retardant properties by blending cotton with other commercially available fibers, binders, followed by chemical treatments, offering a cost-effective way to meet the upcoming federal mattress flammability standard. This research explores the opportunities to take advantage of possible synergistic effects to achieve maximum performance.

Nonwoven composites were prepared from bagasse and cotton fibers in blends with a series of biobased polymers, such as cellulose (in-house made lyocell), commercial poly(lactic acid) and poly(hydroxy butyrate). Citrate esters were used to plasticize and lower the processing temperature of bio-polyesters. Depending on the ratio between the fibers and mechanical stabilizers the materials were classified as polymer-stabilized nonwoven composites or fiber-reinforced polymer boards. Durable and non-durable fire retardant (FR) formulations were applied to compositions containing bioderived polyesters. Fire retarding efficiency was evaluated from the value of the oxygen index. Anaerobic degradation of composite nonwovens was assessed based on the evolution of methane and carbon dioxide gases, spectral (FTIR) and thermal data (DSC, TGA), morphology (microscopy) and mechanical strength at different time periods after submission to bio-degradative conditions.

Intumescent foaming action is achieved in cotton fabrics, using A-B paired, emulsified topical applications containing fire retardant components.  The A emulsion holds an acid, the B emulsion a base, which after applying, will react and foam when exposure to flame temperatures.  In a further embodiment, the A portion may be able to utilize water-soluble flame retardants such as Boric Acid and still result in a system semi-durable to home laundering.  Different architectures are used to meet differing FR needs in a cost-effective manner.

Chemical reaction mechanisms for various classes of flame retardants are presented and their uses relative to nonwoven fibers and fabrics are discussed along with an overview of regulations and standards.  A flame retardant’s action upon the burning combustion cycle generally requires the interruption of some aspect of the chemical reaction mechanism involved.  These mechanisms can be in the solid or gaseous phase or have an endothermic (cooling) effect on the system by absorbing or consuming heat during the pyrolytic decomposition.  Flame retardants do not generally improve material properties, but ensure high fire safety levels.  Fire safety is required in many applications. Products used for building/construction, transportation, electrical/electronics, textiles and furniture all have specific requirements for fire control.  In particular, it is apparent there is a significant overlap with respect to the broad use of textiles and nonwovens as components in these other applications.  Fire regulations and tests are increasingly international and more stringent.  Notable US standards have been developed by the US Consumer Product Safety Commission (CPSC) and California as regulations and Technical Bulletins, the National Fire Protection  Association (NFPA), Underwriters Laboratory (UL), and American Society of Testing and Materials (ASTM).  Internationally, the various members of the European Union harmonized their regulations under the auspices of the EC Commission in 2005 and reissued new EN standards for products and the International Organization for Standardization (ISO) for testing.  In the rest of the world, many nations assure their testing procedures and standards are in compliance with the EN and ISO standards.