Development of an intermediate layer for multilayer hoses used in turbo lines of motor vehicles

DEVELOPMENT OF AN INTERMEDIATE LAYER FOR MULTILAYER HOSES USED IN TURBO LINES OF MOTOR VEHICLES SUMMARY Multilayer rubber hoses for turbo charger systems are expected to meet the requirements of specifications used in automotive industry. They are expected to be stable for a long time at service temperature with high oil resistivity and flexibility. In this study, new blend systems were developed and optimized to offer potential for using as an intermediate bonding layer for multilayer hoses. Multilayer comprises an intermediate layer in between an amine-curable ethylene acrylic (AEM) based inner layer and a peroxide-curable ethylene propylene diene (EPDM) terpolymer based outer layer. AEM and EPDM containing blends are promising candidates since it shows high temperature and oil resistivity and also low temperature flexibility having the properties of AEM and EPDM rubbers, respectively. Different compositions of dipolymer AEM/EPDM and terpolymer AEM/EPDM blends were successfully prepared and their mechanical properties, thermal resistivities and swelling ratios after oil immersion were investigated. Effects of homogenizer and compatibilizer on the properties of the blends were also investigated. For this purpose, blends were prepared using a homogenizer named Struktol 60NS in different phr values (5 phr and 10 phr). According to the results, addition of 5 phr homogenizer decreased both the scorch time and the curing time of the dipolymer AEM containing rubber blends. However, addition of a 10 phr homogenizer instead of 5 phr acted inversely and increased the scorch time and the curing time. In order to see the compatibilizer effect, maleic anhydride grafted EPDM (Ma-g-EPDM), which acts as an interfacial agent between AEM and EPDM phases, was introduced into the blends. Results showed that, the higher increase in the viscosity values and better improvement in the morphology and also higher adhesion values to the inner layer were observed when terpolymer AEM used in the blends instead of dipolymer AEM. In terms of thermal resistivity, the type of the rubber is much more effective than the compatibilizer addition into the blend system. Results showed that rubber blends prepared from both dipolymer AEM and terpolymer AEM with AEM/EPDM ratio of 60/40 are suitable for the intermediate binding layer applications. The effect of the compatibilizer addition was also explored by dynamic mechanical analysis (DMA) and DeMattia tests. Ma-g-EPDM addition into the rubber blends caused to decrease the crack propagation especially in the terpolymer AEM containing blends. The effect of the compatibilizer addition was also explored by scanning electron microscope. Results show that the curing systems used in the intermediate layers are quite effective in dynamical point of view. The blends having AEM/EPDM ratio of 60/40 (specifically DE6040N, DE6040M10, AE6040M10 samples) were produced and applied as an intermediate binding layer in a multilayer hose manufacturing system. Corresponding hoses have AEM based inner layer, EPDM based outer layer and developed intermediate layers. One more hose structure containing only AEM based rubber compounds in its both inner and outer layers was also manufactured for comparison. The produced hoses were subjected to the real life testing conditions. Cyclic pressure testing and also functional tests with two different fitting configuration were performed. At the end of these tests, all hoses did not showed any leaks or tears. At the end of this study, 3 different blend formulation were successfully developed and applied in a multilayer hose which is suitable in turbocharger systems. Moreover, a multilayer hose with an intermediate bonding layer of AEM/EPDM mixture, which can be cured by amine and peroxide based vulcanization system for use in charge air lines of motor vehicles was for the first time produced and patented.