Structure and Mechanical Behavior of Carbon Yarns Impregnated with Polypropylene and Ethylene-Vinyl Acetate

A co-extrusion system, consisting of two sequential impregnation modules equipped with two heating systems, has been developed aimed at forming carbon yarns impregnated with thermoplastics. It has been shown that to ensure complete impregnation of the formed yarn, it is necessary to maintain the temperature in the extruders at 60-80 °C above the melting temperature of the polymer used. The highest strength achieved in the impregnated yarns was 3.3 GPa, which is 67% of the strength of raw carbon fiber. The degree of strength attained is determined primarily by the viscosity of the polymer melt; the minimum strength of 2.3 GPa and the greatest damage to the carbon fiber during impregnation was observed with the most viscous polymer. For all the studied samples, the elastic modulus is 210-220 GPa, which indicates good orientation and uniform drawing, allowing the rigidity of the raw carbon fiber to be almost completely realized.