High temperature resistant crosslinked phenol, o-chlorophenol and formaldehyde copolymer fiber

Phenolic copolymer fibers which possess clearly distinguishable physical and chemical properties from other synthetic and natural fibers were prepared. Acid catalyzed condensation polymerization of phenol, formaldehyde and o-chiorophenol was carried out by a two-stage polymerization. Initially, phenol-formaldehyde and o-chlorophenol-formaldehyde oligomers were separately prepared by refluxing the corresponding monomers at 100°C under strong agitation. At the second stage, these two oligomers were combined and vacuum-distilled to form a block copolymer which was then melt spinned into fibers and subsequently cured by succinyl chloride in a mineral spirit. Using a flame test and thermogravimetric analysis, it was found that these cured fibers are hard to ignite and self-extingush. They become charred when exposed to a flame for an extended period of time. Based on the oxygen index, this copolymer fiber has a better flame retardancy than that of Du pont\u27s commercial Nomex fiber