Synthesis and characterization of acrylonitrile methyl acrylate statistical copolymers as melt processable carbon fiber precursors

Statistical (random) copolymers of acrylonitrile (AN) and methyl acrylate (MA) have been synthesized by free radical homogeneous (solution) and heterogeneous (suspension) methods. Selected compositions can be fabricated by environment friendly, solvent-free melt spinning and are of interest as precursors for carbon fibers. The dynamic and steady state melt viscosities of these copolymers were studied as a function of molecular weight and copolymer composition. Melt processability at 200-220 degreesC depends on the copolymer composition, and also on the molecular weight, which was controlled by chain transfer agent concentration and reaction temperature. Copolymers of controlled molecular weight containing 10 or more mol% of methyl acrylate show good melt processability, which can be further enhanced by stabilizers. This thermoplastic behavior is supported by a significant increase in temperature by the cyclization exotherm. Thermal analysis (differential scanning calorimetry, dynamic mechanical analysis) further illustrates that the comonomers retarded the cyclization, which permits thermoplastic processing. (C) 2002 Elsevier Science Ltd. All rights reserved.