Investigation of ethylene-propylene-diene monomer (EPDM) ageing behaviour in PMDIs environment by surface NMR

Pressurized Metered Dose Inhalers (PMDIs) are mostly used for the treatment of respiratory diseases. The long-term durability of Pressurized Metered Dose Inhalers heavily depends on the functionality of the elastomeric gaskets they contain. The mechanical, chemical, and morphological stability of those elastomeric gaskets is of a great concern to the overall performance of PMDIs. Elastomers used as sealing materials ethylene-propylene-diene monomer (EPDM), have been investigated in this work, during an accelerated ageing study. The evolution of two formulation of EPDM has been reported via standard characterization techniques. Optical microscopy was used to determine any topographic changes on the surface impacted by chemical or mechanical stress. Attenuated total reflection Fourier transform infrared (ATR-FTIR), swelling tests, and thermogravimetric analysis (TGA) were performed to assess the chemical and structural modification of the materials before and after ageing. Surface NMR measurement were conducted to study the degradation as a function of the thickness of the elastomeric gaskets. In the presence of chemical constraints, degradations were observed compared to mechanical constraints which did not lead to significant changes.