Toughening of ethylene-propylene random copolymer/clay nanocomposites: Comparison of different compatibilizers

Ethylene/propylene-random-copolymer (PPR)/clay nanocomposites were prepared by two-stage melt blending. Four types of compatibilizers, including an ethylene-octene copolymer grafted maleic anhydride (POE-g-MA) and three maleic-anhydride-grafted polypropylenes (PP-g-MA) with different melt flow indexes (MFI), were used to improve the dispersion of organic clay in matrix. On the other hand, the effects of organic montmorillonite (OMMT) content on the nanocomposite structure in terms of clay dispersion in PPR matrix, thermal behavior and tensile properties were also studied. The X-ray diffraction (XRD) and transmission electron microscopy (TEM) results show that the organic clay layers are mainly intercalated and partially exfoliated in the nanocomposites. Moreover, a PP-g-MA compatibilizer (compatibilizer B) having high MFI can greatly increase the interlayer spacing of the clay as compared with other compatibilizers. With the introduction of compatibilizer D (POE-g-MA), most of the clays are dispersed into the POE phase, and the shape of the dispersed OMMT appears elliptic, which differs from the strip of PP-g-MA. Compared with virgin PPR, the Young's modulus of the nanocomposite evidently increases when a compatibilizer C (PP-g-MA) with medium MFI is used. For the nanocomposites with compatibilizer B and C, their crystallinities (X (c)) increase as compared with that of the virgin PPR. Furthermore, the increase of OMMT loadings presents little effect on the melt temperature (T (m)) of the PPR/OMMT nanocomposites, and slight effect on their crystallization temperature (T (c)). Only compatibilizer B can lead to a marked increases in crystallinity and T (c) of the nanocomposite when the OMMT content is 2 wt%.