Development of silane-modified EP(D)M formulations for use as coating material for medical devices
The modification of synthetic rubbers with organosilane functional groups offers considerable potential for the development of new medical technology products. Ethylene-propylene rubber (EPR) is characterized by the fact that it is resistant to many external influences due to its saturated main chain. By modifying commercially available rubbers, crosslinking and interaction properties can be controlled selectively. By means of peroxide-initiated free radical grafting of alkoxy-terminated silanes, the materials are usually optimized to be condensation-crosslinkable. In addition, the functionalization serves as a compatibilizer between inorganic fillers and non-polar polymer matrix by increasing interfacial adhesion.
In our study a commercially available ethylene-propylene liquid rubber is modified with an alkoxysilane. This grafted functional unit serves as a coupling site, which allows to connect an azide linker in the second step. This gives the opportunity to bind natural products to the polymer via a copper(I)-activated azide-alkyne cycloaddition (CuAAC) in a further step. This “Click”- reaction can be carried out under mild conditions and does not give any byproducts. Natural products are, for example, antibiotic polypeptides which have propargyl functionalization. The aim of this approach is to produce polymers that have antibiotic properties and are thus ideally suited for medical applications.
This study demonstrates the successful peroxide-initiated grafting reaction of vinyltrimethoxysilane (VTMS) on a rubber via reactive extrusion in a twin-screw extruder. The effect of some of the process parameters like VTMS and peroxide concentration as well as screw speed and temperature on the degree of grafting is determined by a two-level factorial experimental design (DoE). Successful grafting is demonstrated by 1H-NMR spectroscopy and FTIR spectroscopy.
/ T. Bäuerle, S. Ulitzsch1, J. Saur, S. Grond, G. Lorenz /