The appearance of polyacrylonitrile is white powder, and the density is 1.14-1.15g/cm3. It is softened and decomposed when heated to 220-230. Due to the role of side group cyanide group, the main chain of polyacrylonitrile macromolecule has a spiral spatial three-dimensional conformation. After introducing second monomers and third monomers into acrylonitrile homopolymers, the macromolecular side groups have great changes, which increase their structural and conformational irregularities.
It is generally believed that acrylonitrile homopolymers have two glass transition temperatures, 80-100 for low order region and 140-150 for high order region, while two for glass acrylonitrile three copolymers.
The chemical stability of polyacrylonitrile is much lower than that of polyvinyl chloride. Under the action of acid or alkali, the cyanide group of polyacrylonitrile will turn into amide group, and the amide group can further hydrolyze to produce carboxyl group and release NH3. The higher the temperature, the more intense the reaction is. The NH3 released from alkaline hydrolysis produces amid based on the cyanide of unhydrolyzed polyacrylonitrile, making the color of the polymer and fiber yellow.
Pan cyano, triple bond between carbon and nitrogen atoms (a key and two keys) can absorb the strong energy such as photon entangles the external light, and converted into heat, the polymer is not degraded, so that the final polyacrylonitrile fiber has excellent light fastness. Polyacrylonitrile has good thermal stability. It is generally not changed when polyacrylonitrile is heated to 170-180 C for fiber formation. As in polyacrylonitrile, there are impurities, such as thermal decomposition of Polyacrylonitrile and the change of its color.
At 100 DEG C for long time heating pan solution, ring phenomena of molecular chains of polyacrylonitrile in air or oxygen in the presence of long time heating, can make the polymer dark first into yellow brown, finally, the polymer will lose dissolution properties, such as the pan is heated to 250-300 DEG C then, the occurrence of thermal cracking and decomposition of atmosphere of hydrogen and nitrogen, bladder, amines and unsaturated compounds. Polyacrylonitrile is stable to various alcohols, organic acids (except formic acid), hydrocarbons, oils, ketones, esters and other substances, but it can be dissolved in concentrated sulfuric acid, amide and sulfoxide solvents.
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