Mass-suspension Polymerization Process as an Efficient Tool to Produce Polymer/Clay Nanocomposites

Abstract

Background: This work presents the preparation and characterization of the polymeric nanocomposites based on methyl methacrylate (MMA), ethyl acrylate (EA), and natural and modified clays. The clays used to prepare the composite were natural green bentonite (GBC-N) and organophilic clays modified with ammonium quaternary salts: Praepagen (GCB-P), Dodigen (GCB-D) and Praepagen/Dodigen mixture 1:1 in weight (GCB-P/D). Objective: The experimental studies focused on the evaluation of the effect of clays (in nature and chemically modified) on the final quality of the polymeric nanocomposites containing around 3 wt%. of clay nanocharges in association with MMA to produce poly(methyl methacrylate)/clays, and MMA/EA to form poly(methyl methacrylate-co-ethyl acrylate)/clays. Methods: The poly(methyl methacrylate)/clay and poly(methyl methacrylate-co-ethyl acrylate)/- clay materials were synthesized through mass-suspension polymerization process. The natural and modified green bentonite clays were characterized by X-ray powder diffraction (XRD), infrared spectroscopy (IR), Differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) analyses to understand its effect on the basal spacing, d001 (compared to the pure clay), as a result of cation exchange step, which also improved the thermal efficiency of the final nanocomposites. Results: The proper incorporation of MMA and MMA/EA monomers between the layers of natural and modified clays occurred through in situ mass-suspension polymerization, leading to a successful exfoliation of clay layers during the growth of the polymer chains. Conclusion: The IR, SEM, TGA and DSC analyses confirmed the improvement in the thermal property of the composites compared to polymers formed in the absence of clays. The experimental results are very promising, indicating that the experimental protocol based on the in situ formation of polymer nanocomposites by using sequential mass-suspension polymerization consisting of an interesting tool.