Thixotropy and Plasticity in the Rubber Industry

Abstract

Abstract Sole and gels are characteristic colloidal systems. In sole the continuous phase or dispersion medium is a liquid and is in excess; the disperse phase is distributed in this medium in the form of small particles invisible in the ordinary microscope, and having diameters below 0.5 µ. The particles may be liquid or solid or have a more complicated structure. The term colloidal may be used in a somewhat broader sense, to include for instance, latex which contains a certain percentage of larger particles visible in an ordinary microscope, and with diameters up to about 5 µ. It is arbitrary to draw the line of demarcation between colloidal and non-colloidal systems at 0.5 µ most properties of colloidal systems may be found in systems containing larger particles (up to about 6–7 µ) and most methods used in colloid science may be applied to them. The term gel is not so easy to define. The conception favored in the earlier days of colloid chemistry that gels are the counterpart to sols, having a solid medium of dispersion and a disperse phase consisting of small drops of liquid, is not now popular and does not seem probable. It is assumed by many investigators that gels have a structure similar to that of foams or concentrated emulsions, the disperse phase consisting of small solid particles and the dispersion medium being liquid as in the case of sole; but it is present in very thin layers, generally only a few mµ thick, separating the solid particles from each other.