Abstract
Several problems were discussed on fractionation of polyacrylonitrile through use of dimethylsulfoxide-toluene and dimethyl formamide-heptane systems. The following facts were revealed:
1) Addition of acids to the fractionation system prevents the discolouration of polyacrylonitrile in the fractionation process. In the case of the fractionation at high temperature, however, caution must be taken for the degradation of the polymer chains induced by the action of the acids.
2) The efficiency of fractionation is lowered by addition of acids in to the fractionation system.
3) Such systems as dimethyl formamide-toluene cannot be used for fractionation of polyacrylonitrile, in which the concentrated phase becomes colloidal.
4) The efficiency of fractionation is depressed by adhesion of the gel particles on the glass wall.
5) The efficiency of fractionation is lowered by the stirring of the solution for an unnecessary long time in the process of the separation of the gel phase.
