Synthesis of AN-g-casein copolymer in concentrated aqueous solution of sodium thiocyanate and AN-g-casein fiber's structure and property

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The main products of graft copolymerization of acrylonitrile (AN) onto casein in concentrated aqueous solution of sodium thiocyanate in homogeneous phase were characterized as a graft copolymer (AN-g-casein) by Fourier transform infrared. The effects of the monomer concentration, initiator concentration, reaction temperature and reaction time on copolymerization were investigated. The result of WAXD showed that the major part of casein in graft copolymer is amorphous. The SDSC determination showed that the lateral order of PAN, the side chain of copolymer, decreases and the lateral order distribution becomes wider with the increase of the casein component in copolymer. It revealed that the two systems of AN-g-casein copolymer are incompatible by an investigation of DMTA, SEM. The two systems of AN-g-casein exist in separating phases, but tie up each other. So the phenomena of characteristic boundary relaxation occur. Direct spinning of graft copolymer in concentrated aqueous solution of sodium thiocyanate in homogeneous phase was successfully carried out. The skin-core layer structure of AN-g-casein fiber cross-section was observed by scanning electron microscope (SEM). In the core layer, the dimension of phase domain of casein is about from 20 to 60 nm. When the fiber was drawn into broken, microfibrillation occurs, the fiber skin layer is compact, and its broken section is flat. Many long and thin casein strips are formed in the surface of the fiber, respective crystalline grade of two components is scarcely effected by the change of the content of casein. AN-g-casein fibers have good hygroscopicity and dyeability, and more, they can be dyed by acidic dyestuff and cationic dyestuff. AN-g-casein fiber still has good mechanical properties, so AN-g-casein fiber is a new type modified “silk-like” fiber for wide application.