A Method has been devised for staining with aqueous KMnO4 solution on one surface of any thick sample of rubber blends in which one or both consisting of unsaturated hydrocarbons for effective visualization of its morphology under the microscope. Experiments showed that the method is sensitive for incompatible blends such as NBR with EPDM

BR with LDPE or EVA/SBR/PE

and is applicable to compatible blends when mutual blending is not yet completed or dispersion is not satisfactory. The advantage of this method lies in its simple preparation

ease of operation

low cost and freedom from morphological distortion. The strongly contrasting pictures resulting from this method can be used for examining thick samples without the use of the phase-contrast microscope or the microtome. This method is thus expected to provide an effective means of quality control for mixing operations and of rapid measurement of homogeneity of dispersion.