Melt-Spinning of an Intrinsically Flame-Retardant Polyacrylonitrile Copolymer

Abstract

Poly(acrylonitrile) (PAN) fibers have two essential drawbacks: they are usually processed by solution-spinning, which is inferior to melt spinning in terms of productivity and costs, and they are flammable in air. Here, we report on the synthesis and melt-spinning of an intrinsically flame-retardant PAN-copolymer with phosphorus-containing dimethylphosphonomethyl acrylate (DPA) as primary comonomer. Furthermore, the copolymerization parameters of the aqueous suspension polymerization of acrylonitrile (AN) and DPA were determined applying both the Fineman and Ross and Kelen and Tüdõs methods. For flame retardancy and melt-spinning tests, multiple PAN copolymers with different amounts of DPA and, in some cases, methyl acrylate (MA) have been synthesized. One of the synthesized PAN-copolymers has been melt-spun with propylene carbonate (PC) as plasticizer; the resulting PAN-fibers had a tenacity of 195 ± 40 MPa and a Young’s modulus of 5.2 ± 0.7 GPa. The flame-retardant properties have been determined by Limiting Oxygen Index (LOI) flame tests. The LOI value of the melt-spinnable PAN was 25.1; it therefore meets the flame retardancy criteria for many applications. In short, the reported method shows that the disadvantage of high comonomer content necessary for flame retardation can be turned into an advantage by enabling melt spinning.

Novel In Situ-Cross-Linked Electrospun Gelatin/Hydroxyapatite Nonwoven Scaffolds Prove Suitable for Periodontal Tissue Engineering

“…However, exact determination of pore structure and size is difficult in electrospinning, since it varies with fiber diameter [112]. Exemplarily, alternative current biomaterial fabrication methods include 3D bioprinting or melt spinning [113][114][115][116]. While oral applications of melt spinning have been scarcely reported in the literature, 3D bioprinting has been successfully applied to periodontal ligament cells [117].…”

Melt-Spinnable Polyacrylonitrile—An Alternative Carbon Fiber Precursor

“…The combination of the molding ability and an increase in the limiting oxygen index of the copolymer was achieved in [ 78 ] by using a phosphorus-containing comonomer-dimethylphosphonomethyl acrylate (5–7%). Its precipitation copolymerization with AN and terpolymerization with AN and MA have resulted in the binary and ternary copolymers with M n ~35–55 kg⋅mol −1 , Đ~5, and the limiting oxygen index 22–26 instead of 17–18, typical for PAN [ 79 ].…”

Transformation of Specific Dispersion Interactions between Cellulose and Polyacrylonitrile in Solutions into Covalent Interactions in Fibers

“…[8][9][10]. However, the main method for producing PAN fibers is a solution (wet and dry-jet wet spinning), while the melt spinning method is still under development [11][12][13]. The main difficulties in obtaining melts of PAN copolymers lie in the polarity of the PAN nitrile groups, which have a high dipole moment equal to 3.9 D [14].…”