Preparation and morphological evolution of heterophasic PP-EP/EVA/organoclay nanocomposites: Effect of the nanoclay organic modifier
Valera-Zaragoza, M. | Ramírez-Vargas, E. | Medellín-Rodríguez, F.J.
A study is presented on the morphological effects caused by the nanoclay organic modifier and the nanoclay concentration. This was made under previously determined compatibility conditions of heterophasic polypropylene copolymers (PP-EP)/poly(ethylene vinyl acetate) (EVA)/organoclay nanocomposites. The nanocomposites were prepared using the fluidity of the EVA phase to disperse the nanoclay platelets. Therefore, no additional compatibilizer was used to achieve the clay dispersion. Two organoclays were used with different characteristics and polarity of the substituent groups. Transmission electron microscopy and X-ray diffraction results first indicated that two hydrogenated tallow modifiers are more effective than one to enhance nanoclay exfoliation. Thermogravimetric studies indicated a low probability of thermal degradation of the nanoclay modifiers and as a consequence of their effect on the layer-layer exfoliation. Molecular simulations were made with the purpose to study additional factors affecting exfoliation. The introduction of nanoclay, within the compatibility conditions of the PP-EP/EVA system, was also studied. It was determined that the system preserved its original morphology and that the silicate layers were hosted by the EVA domains. The crystallization characteristics of the PP-EP/EVA mixtures indicated a gradual evolution of the overall crystalline structures depending on the EVA content. In the case of the ternary nanocomposites PP-EP/EVA/nanoclay, the β crystalline structure was partially formed, although it decreased with increasing nanoclay content.Show more [+] Less [-]