Effect of organoclay modifier structure on the viscoelastic and thermal properties of poly(methyl methacrylate)/organoclay nanocomposites

Abstract

Poly(methyl methacrylate) (PMMA)/clay nanocomposites (NCs) were prepared by suspension polymerization of methyl methacrylate in the presence of two different organoclays (Cloisite 30B, Cloisite 15A) with clay loading ranged from 0.5 to 5 wt%. Increase in molecular weight of the PMMA matrix with addition of the clay was revealed by gel permeation chromatography (GPC) and intrinsic viscosity measurements. As confirmed by X-ray diffraction (XRD), the NCs had an intercalated structure. The organoclays-MMA/PMMA compatibility was investigated by swelling tests and solubility parameter approach. Rheological behavior of PMMA NCs in molten state was analyzed through construction of master curves of complex viscosity, storage, and loss modulus by applying the time-temperature superposition procedure. Melt rheology, scanning electron microscopy (SEM), and UV/Vis spectroscopy results confirmed higher extent of clay dispersion in the NCs with Cloisite 30B. Compared to pure PMMA, all these NCs show increase of glass transition temperature as measured by DSC and improved thermal stability determined by thermogravimetric analysis (TGA). The results obtained by dynamic mechanical analysis showed that the storage modulus of the NCs was higher by incorporation of clay into the PMMA matrix, increasing as the amount of clay increased and that their mechanical performance was significantly enhanced.