The influence of the preparation metod of asphalt-isotactic polypropylene compositions
on their structure and mechanical properties
On the basis of the results obtained by benzene extraction, optical microscopy, particle size analysis, bendig strength and microhardness, the effect of the method of homogenization (in the molten state or in p-xylene solution) and conditions of cooling (rapid, slow, repeated melting with slow cooling) on the structure and some properties of asphalt-isotactic polypropylene compositions has been investigated. It has been found that isotactic polypropylene forms in the asphalt either dispersions of isolated particles (macrohomogeneous compositions) or dispersions of aggregated particles (macroheterogeneous compositions) and that particie size of these dispersions depends both on the preparation method and fraction of components. Asphalt is accumulated at the interface of spherulites. Bending strength of compositions with predomination of asphalt is higher than that of pure asphalt and of composition with predomination of isotactic polypropylene high er than that of pure polypropylene. It depends also on the metod of cooling. Microhardness of composition homogenized in solution was lower and had broader distribution of values than that of compositions homogenized in the molten state.
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