Elastomer Nanocomposites Based on Organoclay/IIR/EPDM: Microstructure and Mechanical Properties
Nanocomposite samples based on elastomer blends of butyl rubber (IIR) and ethylene propylene diene monomer (EPDM) were prepared using a laboratory scale two-roll mill in order to study the effect of Cloisite 15A organoclay content (i.e., 1, 3, 5 and 7 wt%) on the mechanical and morphological properties of IIR/EPDM/Cloisite 15A nanocomposites compared to the unflled EPDM/IIR blends. Rheometer (RPA), X-ray diffraction (XRD) and scanning electron microscope (SEM) were utilized for relevant characterization of cure behavior and microstructural properties of the prepared samples. Cure characteristics of the prepared compounds including optimum cure time (t90) and scorch time (t5), depicted a decrease in these two parameters with increasing nanoclay content; where the cure time was prolonged with EPDM increasing content. In fact, nanoclay not only acts as a reinforcing agent in nanocomposites but also accelerates the cure process of IIR/EPDM elastomer compounds. Intercalation of elastomer chains into the organoclay silicate layers was determined by d-spacing values calculated according to the results of X-ray diffraction patterns. XRD results of all the nanocomposites samples prepared here showed a leftward shift towards lower diffraction angles in the organoclay characteristic peak, indicating an increase in the d-spacing values compared to the pure organoclay which emphasizes the intercalation of elastomer chains into the clay galleries. This phenomenon was also confrmed according to the direct observation of the cryogenically fracture surfaces of the samples by SEM micrographs depicting a combination of intercalated and exfoliated microstructures. However, there appeared incrementally slowed down rate in higher clay contents. With addition of nanoclay, mechanical properties of the nanocomposite samples including hardness, fatigue strength, tensile modulus and tensile strength were observed to be improved. Elongation-at-break and resilience of the nanocomposites were decreased as expected.