The Properties of Melt-Blended Compatibilized Metallocene Polyethylene/Clay Nanocomposites

摘要

Although it is well known to employ compatibilizer to assist clay dispersion in thermoplastic/clay systems, the properties of compatibilizers have often been neglected. Metallocene polyethylene (mPE)/clay nanocomposites were prepared via a melt-blending approach to further investigate this compatibilization effect. Maleated mPE (mPE-g-MA) was also prepared as a compatibilizer to improve the dispersion of commercial organoclay. The mPE/mPE-g-MA/clay compatibilized systems showed good dispersion of clay or swollen tactoids through X-ray diffraction (XRD) and transmission electron microscopy (TEM) assessments. The compatibilized cases showed slightly higher crystallization temperatures at higher clay contents than their counterparts without any compatibilizer. The mechanical properties of the investigated systems were rather complex and unusual. The Young's modulus of compatibilized nanocomposites showed slightly higher values in all investigated cases, stemming from the more effective interfacial interaction. The tensile strength of mPE/clay systems increased with increasing clay content; however, that of mPE/mPE-g-MA/clay systems decreased with increasing clay content due to possible heterogeneous microgel (bound polymer) formation in the compatibilized clay. Lower tear strength for compatibilized cases was found, which was attributed to the low tear strength of the compatibilizer and microgel formation, along with the clay moiety serving as inorganic crosslinks to give less energy dissipation during deformation. The results indicated that high dispersion of clay did not guarantee high strength, and the mechanical properties should be carefully evaluated to exploit the reinforcement of nanocomposites.