WATERPROOFING MEMBRANES: COMPATIBILITY PREDICTION BETWEEN BITUMEN AND POLYMER

In the industrial sector, main utilization of bitumen is for water proofing membranes: modern process technology is based on mixtures of bitumen, polymer and mineral filler, which are used to impregnate a rigid support, so to have a resulting elastic structure, shock resistant and capable of withstanding cold weather and atmospheric agent actions. It is essential to have the best compatibility between bitumen and polymer, in order to obtain mixtures with low polymer concentration, therefore at lower cost, yet maintaining high elasticity and resistance performances. While for the choice of the polymers manufacturers are mainly oriented toward two types of product (polypropylene and styrene-butadiene-styrene), as far as bitumen is concerned, market offers numerous produce types, different both for parental crudes and for refining production technologies. In this paper the authors proposed a correlation between chemical characteristics of bitumen, defined through the Colloidal Instability Index, as measured by the Iatroscan device, and the minimum polypropylene concentration sufficient to obtain phase inversion of the bitumen-polymer's mixture, inversion defined as the condition of polymeric matrix containing bitumen particles. As a result, through the proposed correlation, with a simple bitumen compositional analysis, it is possible to predict its performance when mixed with polypropylene. In the paper, besides the description of the Iatroscan device utilization procedure the operational steps for determining phase inversion are also presented: from the formulation of the bitumen-polymer mixture, to the subsequent optical observation with fluorescence microscopy. (A) For the covering abstract see IRRD 885061.