FUNCTIONAL BINDER SPECIFICATIONS: THE PARTICULAR EXAMPLE OF SOUND INSULATION IN THE CAR INDUSTRY

The present bitumen specifications are mainly tailormade for paving applications and often perceived as insufficient to correctly identify the desired properties and, above all, to define test methods and criteria which reliably reflect them. To reach these objectives, a common approach of the customer and its supplier is highly desirable, if not compulsory. The paper presents an example of such a collaboration between an affiliate of the RIETER group and one of its bitumen suppliers (NYNAS). The bitumen is used in the manufacturing of sound insulation products for the car industry, In the present case, the manufacturer well knows the required performances and how to measure them. But he uses very specific test methods such as the "BLOCKING" test (peeling test which characterizes the non-stickiness of the product when stappled), a "COATING" test (ability of the bitumen to fill-in a certain profile) and, more particularly, a damping test on a vibrating road (OBERST test). These tests are however too heavy and too time consuming to be included in the Quality Assurance procedures of the bitumen supplier. A common investigation program, aiming at the correlation of the above mentioned properties with more easily and rapidly measureable bitumen characteristics (rheological and compositional properties) has thus been launched. Since characteristics such as "Coating ability" can be quite easily related to simple rheological properties such as viscosity, the main emphasis has been laid on the OBERST damping factor. The latter could finally be correlated to an intrinsic rheological parameter and, more surprisingly, to an aromaticity factor (derived from GPC analysis with UV detection at different wavelengths). This example suggests that "smart" bitumen specifications, based on functional analysis, are indeed possible and that the experimental means exist. But it tends also to show that it requires some investigations, on a case per case basis. (A) For the covering abstract see IRRD 885061.