STRUCTURE-PROPERTIES RELATIONSHIP IN TERNARY PP/MWCNT/OC NANOCOMPOSITES

Among the most versatile polymers are polyolefin matrices, such as polypropylene (PP), because of their good balance between properties and cost, low density and ease in processability. Also isotactic polypropylene (iPP) is one of the most important commodity thermoplastics, accounting for about 20% of the world polyolefin production. On the other hand, carbon nanotubes (CNTs) have been considered as unique reinforcements for different polymer materials due to their exceptional physical, thermal and mechanical properties. The tensile strength, tensile modulus and Poisson ratio for CNTs have been reported to be in the range of37-100 GPa, 640 GPa to 1-2 TPa and 0.14-0.28, respectively. Dispersion of clay nanolayers in polymer matrices usually results to exfoliated and/or intercalated polymer/clay nanocomposite, that combine the properties of ingredients and these hybrids often result to improved mechanical and thermal properties. So far, two-phase composite materials of polypropylene/clay and polypropylene/MWCNTs have been widely investigated. However, hybrid materials that combine two nanofillers particles in a polymer matrix are seldom researched. Researchers reported on extraordinary property enhancement in the case of hybrid nanocomposites incorporating two different nanophases. Only few attempts have been made to compare the mechanical properties of the conventional binary nanocomposite to a ternary nanocomposite, which combines carbon nanotubes and nanoclay as reinforcement in polypropylene matrix. Also several processing methods are available for the production of polymer/CNT composites, such as melt mixing, solution casting and in situ polymerization. Among them, melt mixing is particular desirable as it combines simplicity with speed. Among several melt mixing processes, extrusion process has captured considerable interest due to its industrial importance and its ability to disperse the CNTs in a polymer matrix. In this study the effect of the three-phase combinations on the structure, rheological, thermal and mechanical properties of the PP/MWCNT/OC nanocomposites is investigated and compared with those of the neat polymer and the two-phase blends.