Flame retardant (FR) textiles were obtained by surface treatments of polyamide 66 fabrics with microwave (MW) plasma technology in order to reduce the amount of FR involved in the fabric finishing process. More specifically, MW vacuum plasma was employed for polymer surface activation by using a helium/oxygen (He/O 2 ) gas mixture, evaluating the effect of different treatment parameters on the affinity toward thiourea impregnation. Surface fabric modification was investigated both in terms of uniformity and increased thiourea absorption by infrared spectroscopy, wicking properties, and gravimetric characterization to define an operative window for plasma treatment conditions. According to the results obtained, the dry add-on content of thiourea improved up to 38%, thanks to the increase of the fabric surface activation. The effectiveness of plasma treatment resulted in an absolute increase up to 2% in limiting oxygen index (LOI) performance with respect to untreated fabric. As a consequence, a drastic reduction of 50% in thiourea concentration was required to achieve a similar fire retardant performance for plasma-treated fabric. On the basis of these preliminary results, a design of experiment (DoE) methodology was applied to the selected parameters to build a suitable response surface, experimentally validated, and to identify optimized treatment conditions. At the end, a final LOI index up to 43% has been reached.

The development of flame‐retarded polypropylene is carried out with the ultimate goal of obtaining a UL94‐V0 not only halogen‐ but also phosphorus‐free formulation because phosphate rocks, precursors of phosphorus‐based flame retardants, are recognized as critical raw materials within Europe. Different flame retardants (FRs) (melamine, phosphate ester, and radical generator) are used. A statistical approach is applied to predict UL94 behavior and develop optimized formulations in terms of cost, filler or phosphorus content. Models for most common “nondripping” as well as “nonflaming dripping” UL94‐V0 behavior are proposed. The experimental validation has shown the reliability of the models proposed and their usefulness to assist and speed up the development of optimized formulations. The use of the models also gives insight into the interactions between flame retardants, thus suggesting if potential synergies take place, before studying the FRs system in details. Indeed, synergies between melamine and phosphate ester as well as melamine and radical generator are discovered. Thanks to these synergies that V0 rating can be achieved. A UL94‐V0 formulation, comprising melamine and radical generator, is identified as the optimal halogen‐ and phosphorus‐free formulation with a reduced filler content.