Materials polyacrylonitrile powder

Freshly distilled 4-VP was mixed with dihaUdes (molar ratio 2 1) in bulk or in solution. The polymerization proceeded to virtual completion in bulk or in solvents (benzene, methanol, dimethylformamide (DMF) or mixtures of DMF with methanol) and in presence of e.g., silica gel, carbon black, sand, porous materials, e.g., paper, cloth, polyacrylonitrile fibers, etc. The rate of polymerization was significantly enhanced in absence of air or by COy irradiation. The mixtures of 4-VP and dihalides were left at room temperature for periods of 5 days during which time the color changed from colorless to pink or red. The resin was isolated by addition of acetone and washing with acetone. After drying it was obtained in the form of a light yellow powder in yields of 70 to 100% of the theoretical amount. 

Particle surface modification could be characterized with the surface energy measurement, ilow the surface energy of dispersed particle affects the ER efiect was systematically addressed by Hao [95]. A set of oxidized polyacrylonitrile (OP) materials of different surface properties were employed for such a purpose. The five kinds of water-free ER fluids composed of oxidized polyacrylonitriles (OP) particle dispersed in a low viscosity silicone oil were used for correlating the ER effect with the particle surface energy. The powdered OP materials with average particle size 0.1-10 pm were treated at 150 C for 8 h, and then dispersed in silicone oil immediately at the particle volume fraction of 35 vol /o. The surface energy was measured by means of the dynamic wicking method [96]. Water and... 

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