Abstract: The present invention relates to a method of fabricating a yarn constituted by a multi-filament core coated in a polymer sheath. The sheath is made by depositing a miscible mixture of molten polymers on the multi-filament core, the mixture comprising: at least one flame-retarding agent; and at least two polymers that, in the molten state, do not establish mutual permanent chemical bonds, with one of the polymers, referred to as the co-flame-retarding polymer, presenting both a glass transition temperature that is significantly lower than the glass transition temperature of the other polymer, referred to as the base polymer, and also a melting temperature that is likewise significantly lower than the melting temperature of the base polymer; said deposition being followed by a cooling step during which the base polymer freezes first and the co-flame-retarding polymer migrates outwards entraining at least a fraction of the flame-retarding agent therewith.

Abstract: The present invention relates to a method of fabricating a yarn constituted by a multi-filament core coated in a polymer sheath. The sheath is made by depositing a miscible mixture of molten polymers on the multi-filament core, the mixture comprising: at least one flame-retarding agent; and at least two polymers that, in the molten state, do not establish mutual permanent chemical bonds, with one of the polymers, referred to as the co-flame-retarding polymer, presenting both a glass transition temperature that is significantly lower than the glass transition temperature of the other polymer, referred to as the base polymer, and also a melting temperature that is likewise significantly lower than the melting temperature of the base polymer; said deposition being followed by a cooling step during which the base polymer freezes first and the co-flame-retarding polymer migrates outwards entraining at least a fraction of the flame-retarding agent therewith.