Compatibility of hydrazine and EPDM rubber containing polybutadiene coagent

Histogram analyses of atomic force microscopy (AFM) phase images demonstrated changes in the surface composition of ethylene propylene diene–modified (EPDM) elastomeric formulations containing polybutadiene after exposure to hydrazine. It was determined by Fourier-transform infrared (FT-IR) spectroscopic analysis that the change in the surface composition is caused by hydrogenation of the vinylic double bonds of the polybutadiene coagent, stemming from diimide generation from hydrazine. The diffusion and subsequent reaction of hydrazine with two cured EPDM elastomeric formulations were investigated by mapping FT-IR spectroscopy. The depth of diffusion and reaction was determined by monitoring changes in the intensity of the vinyl group signal from the polybutadiene in the FT-IR spectra. The FT-IR analysis of horizontal microtome specimens and vertical ‘cross section’ of the EPDM samples showed that hydrazine diffused less than 200 μm into the elastomeric materials over a period of 40 weeks. Sequential proton nuclear magnetic resonance spectroscopy of the polybutadiene coagent showed that the vinyl groups in polybutadiene were hydrogenated when mixed with hydrazine at room temperature. The reaction of hydrazine with the polybutadiene coagent of the EPDM elastomeric material was corroborated by matrix-assisted laser desorption/ionization time of flight mass spectrometry as well. A model compound, 4-vinyl cyclohexene, was used to assess the relative hydrogenation rate of primary and secondary double bonds using gas chromatography/mass spectrometry.