Reinforcement of acrylonitrile copolymer by polymer blending

Blends of an acrylonitrile copolymer and a reinforcing polymer were formed by polymerization of the second component in a concentrated solution of the first component. The second component, polyureas or polycarbodiimides, precipitated as an intimate dispersion of particulate domains in the liquid medium. Film or fiber formation by coagulation of the solution containing the second component as particulate matter resulted in a distinct two-phase blend. Reinforcement of the acrylonitrile copolymer was evidenced by significant increases in dry and wet moduli above the glass transition temperature of the polyacrylic component. The blends were characterized with dynamic mechanical testing and optical and electron microscopy. The blends exhibited two glass transitions corresponding to those of the individual components. The phase domains were evident over the compositional range examined. The method of blending is illustrative of effective reinforcement by interpenetration of phases in the absence of compatibility of the components at the macromolecular level.