Exfoliation Of OMMT Research Articles

Exfoliation of organic montmorillonite in iPP free of compatibilizer through the multistage stretching extrusion

Polypropylene (PP)/organic montmorillonite (OMMT) nanocomposites were first prepared through twin-screw extruder and then subjected to multistage stretching extrusion with an assembly of laminating-multiplying elements (LMEs, which divide and recombine polymer melts). The exfoliated efficiency of LMEs on OMMT dispersed in PP matrix was investigated by optical microscopy, scanning electron microscope, transmission electron microscopy and X-ray diffraction. Because of the absence of compatibilizer, molecular chains of PP were not intercalated into the galleries of OMMT during the multistage stretching extrusion. The exfoliation of OMMT was induced by the strong force occurred in LMEs, which can destruct van der Waal’s interaction between the laminate OMMT platelets. The exfoliation degree of OMMT has been improved with the increase of number of LMEs used. The dispersion morphology of OMMT was thermodynamically stable after secondary melt processing. As a result, the mechanical properties of composites have been enhanced with increasing LME number. We realized the exfoliation of OMMT by the function of strong shear field without the incorporation of compatibilizer.

Polyolefin-based nanocomposites: the effect of organosilane on organoclay dispersion

This work dealt with the morphology and properties of polypropylene/organoclay (PP/OMMt) nanocomposites prepared using maleic anhydride-grafted polypropylene (PP-g-MA) or organosilane (OTMS) as a compatibilizing agent. The content of OMMt was 2 wt%, and different concentrations of OTMS were used to obtain OTMS/OMMt mass ratios of 0/1, 1/1, 0.5/1 or 0.25/1. The results of wide-angle X-ray scattering and transmission electron microscopy investigations showed that the OTMS promoted the total exfoliation of OMMt in the PP matrix, while the OMMt yielded a micrometer-scale dispersion when PP-g-MA was used. In general, the OTMS satisfactorily compatibilized the PP/OMMt nanocomposites, increasing the modulus of the PP matrix. When a hybrid compatibilizer of OTMS/PP-g-MA was used, better thermal and mechanical properties were achieved.

Preparation, Properties, and Mechanism of Novel Polyurethane Adhesive/Organic Montmorillonite Nanocomposites

Novel polyurethane adhesives (PUA) were prepared by the incorporation of organic montmorillonite (OMMT). The structure of the PUA/OMMT adhesives was analyzed by wide angle X-ray diffraction, Fourier transform infrared spectroscopy, and transmission electron microscopy. It was observed that the OMMT layers in the PUA were of nanometer dimensions and the molecular structure of PUA was perturbed by the presence of OMMT. This was due to the reaction between the monomers and the intercalation agent. Physico-mechanical properties such as adhesion and thermal stability were investigated. Results showed that the PUA system with 3 phr OMMT has the best physical and mechanical properties due to the exfoliation of OMMT. The nano-reinforcing effect caused by the exfoliated silicate layers may reduce the amount and size of voids during peeling, which can increase the length of the crack path in their vicinity, leading to improved adhesive properties. This is postulated as the mechanism for improved adhesion in the PUA/OMMT adhesive.

Effects of ultrasonic oscillations on structure and properties of HDPE/montmorillonite nanocomposites

In this paper, high density polyethylene (HDPE)/montmorillonite nanocomposites (HDPECNs) were prepared via conventional and ultrasonic extrusion technology developed in the authors' laboratory. X-ray diffraction analysis, scanning and transmission electron microscopy results show that ultrasonic oscillations can effectively improve the dispersion of organic montmorillonite (OMMT) particles in HDPE matrix with some exfoliation of OMMT. The yield strength, elongation at break and Young's modulus of ultrasonicated HDPECNs with the ultrasonic intensity of 200 W are thus respectively improved by 11·1, 30·2 and 12·3% compared to those of conventional HDPECNs. The crystalline behaviour and spherulite morphology of HDPE in HDPECNs were also investigated by differential scanning calorimetry and polarising light microscopy. The results show that the OMMT particles and ultrasonic oscillations play important roles in the nucleation rate, crystallisation temperature and spherulite size of HDPE. Ultrasonic oscillations can improve the crystallinity and reduce the spherulite size of HDPE matrix in nanocomposites.

Water absorption of epoxy/glass fiber/organo-montmorillonite nanocomposites

The epoxy/glass fiber/organo-montmorillonite (OMMT) nanocomposites were prepared by hand lay up method. In the previous work, the flexural and morphological properties of the epoxy/glass fiber/OMMT were studied. In this work, the epoxy nanocomposites were characterized by X-ray diffraction (XRD), differential scanning calorimetry (DSC) and water absorption tests. The exfoliation of OMMT in epoxy/glass fiber nanocomposites was detected by XRD. DSC results showed that the glass transition temperature (Tg) of epoxy was increased slightly in the presence of OMMT. Water uptake of epoxy was reduced by the addition of glass fiber and OMMT. The decrease of water absorption in epoxy is attributed to the increasing of tortuosity path for water penetration in the epoxy composites by the hybrid of glass fiber and OMMT.