Morphology and Mechanical Properties of an Elastomeric Poly(HIPE) Nanocomposite Foam Prepared via an Emulsion Template

Open-cellular elastomeric nanocomposite foams were obtained by polymerization of water-in-oil high internal phase emulsions (HIPEs) containing 2- ethylhexylacrylate, styrene, divinylbenzene, and organo-modified montmorillonite (org-MMT)s. The effects of various org-MMT contents on the emulsion viscosity and microcellular structure and mechanical properties of the resulting elastomeric foams were investigated. The results showed that the incorporation of modified clay (organoclay) led to lower emulsion torque value, approximately to a characteristic value of the emulsion viscosity. Scanning electron microscopy (SEM) micrographs revealed that the presence of modified clays, 1-5% (by weight), considerably influenced the microstructure of the copolymer solid foam. For instance, the introduction of 1% (by weight) organoclay (Cloisite® 15A) decreased the mean void diameter from 5.47 to 4.45 μm and the intercellular pore size from 1.39 to 0.86 μm. At above this content of organoclay, the mean void diameter and intercellular pore size increased. The presence of organoclay may influence the separation phase behaviour within the polymerizing monomeric organic phase and it may act as a co-surfactant to vary the sizes of voids and intercellular pores. X-Ray diffraction (XRD) patterns and transmission electron microscopy (TEM) micrographs showed an intercalated nanocomposite structure for the elastomeric composite foams containing Cloisite® 30B organoclay. TEM Micrographs showed that less hydrophobic Cloisite® 30B organoclay tends to be located at the interface between aqueous and organic phases of emulsion, while in case of more hydrophobic organoclay, i.e., Cloisite® 15A, it finds its position away from the interface; inside the continuous organic phase of concentrated emulsion. Surprisingly, adding the organoclays to the emulsions lowers the compressive mechanical properties of the reinforced solid rubbery foams compared with the copolymer foam without any reinforcement. On the whole significant improvement on the compression set was observed.