Effect of Carbon Black Content on Curing Behavior of Polysulfide Coatings

Polysulfide is well known elastomer for use in aerospace applications due to providing flexible coating and chemically resistant sealants. In this work, the effects of carbon black content on curing behavior of polysulfide elastomer were investigated and Rheological properties for samples with different filler content 15, 20 and 25 phr were evaluated by rheometric mechanical spectrometer RMS. According to RMS analysis, sample with 20 phr carbon black had minimum gel point temperature and loss factor and highest elasticity. Also, the time sweep test for the optimal sample resulted from temperature and frequency sweep at 90°C was done and gel time obtained less than a few minutes. From the dynamic differential scanning calorimetry DSC diagram for polysulfide with 20 phr carbon black observed two exothermic peaks in heat flow for uncured sample. The first peak indicated the curing of polysulfide elastomer and second peak may be attributed the curing of resole resin and formation of methylene linkage.